Tech: Sunn Model T (reissue) schematics and discussion

I've had a broken Sunn Model T reissue head since 2007. I got it from the (then) bass player of Battlefields in Fargo, ND. It has a hole the size of a quarter burnt through the main PCB near where the power transformer primaries are connected. I took it to a shop about a year ago, hoping to have some sort of point-to-point workaround, but the amp has been sitting there for all that time with no work done.

So I'm taking it back home. Thinking that I might now have the chops to repair it myself, I've pulled out my schematic and started looking at the area in question. Turns out, it might actually be simple.

When I initially examined the amp, I noticed that no fuses were blown. The burnt area of the PCB is on the primary side of the PT --- it's like a little 'patch bay' with terminals (CP2-CP9) for converting the amp to run on 240, 230, 120, or 100V mains. The problem may have simply been caused by a piece of dust or other contaminant flashing over between adjacent terminals. While I understand the utility of using this little corner of the PCB this way, it seems silly to put a bunch of spade connectors carrying the full mains supply only millimeters away from each other. If you're going to do this, at least put the whole thing on its own PCB and spread things out. Anyway, if the PT is ok (the tech in the shop says it is), then I can just lose the conversion flexibility (and the liability), splice the wires together in the 120V configuration, and go to town. It probably isn't actually that simple, but I'm hopeful...



The schematic for this amp floating around the internet is only one page, so I mail-ordered one from Fender. I've posted both pages below, and as high-res PDFs here.

For the record, I know that this amp is absolutely nothing like the 60s-70s Model T. I happen to think that both are excellent amps in their own ways. It's a shame that Fender discontinued the Sunn reissues line, especially given all the mediocre solid-state stuff they make now.

I'll post more as the project continues; it promises to be pretty interesting...



Update 11/30/09:
FIXED. It really was that simple. I hooked up the power transformer primary leads with wire nuts and taped them up, replaced TH-1 on a terminal strip, and moved P31 and P32 away from the charring, to C46. C46's replacement got moved to a terminal strip near the standby switch. Everything works! No other repairs required.

I do think I'd like to try KT66 power tubes in it. I hear that they have a greater midrange presence than 6L6s, and that's something I like. Tung Sol preamp tubes are doing the trick nicely right now.

Update 12/4/09:
I tried some JJ KT66s in here and they sound fantastic. I don't know how "authentic" a KT66 sound this really is, but it's vastly better than the Groove Tubes 6L6Ss that were in there before. They might have been tired, or just years-old Chinese stuff that wasn't very good to begin with. They sounded compressed, fizzy, and dark, somehow all at the same time. The KT66s sound more open, midrange-y, and smooth; a little more like an EL-34. Being that most of my stuff tends toward "British" (tonally speaking), that's great. They really flatter this particular amp; it's got this awesome "spank" sound on the drive channel when you dig in with the gain around 5. Sponge-y!

I did have to dial the bias way down to get them stable at 30mA per tube. Right now there are only two tubes in the amp, running at half power. I'm also using the 1/4 power switch... which means in total I'm running the equivalent of about 12-15 watts right now. It's still way way too loud to play at home.

Update 12/14/09:
I used the amp as a slave head with Rosetta at Saturday night's show in NYC, with the 4x 6L6 back in it. It performed admirably (much nicer than my Marshall 3210) except for some cutting out at high volumes. I later traced the problem to cold/cracked solder joints on the FX loop PCB. It's good to go now. When it's used as a slave amp (power amp only), the 6L6 tubes do very nicely, especially when combined with my EL34-based Marshall master head. Playing through the Sunn's own preamp, though, I still like the KT66s better.

I couldn't resist --- in the preamp, I've added a small coupling cap between the gain control and V1B. This blocks some low bass (below 60Hz) and tightens up the gain channel with downtuned guitars. Not a lot, just a tiny bit -- too much lowcut before this triode makes the amp sound like a Marshall. I already have one and don't need another. I also added 147pf across the gain channel's volume pot to cut some of the fizz -- again, not too much. This one's a keeper!

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Notes about the design:
Tube V2 is used exclusively by the clean channel. It sits between the volume control and the tone stack (V2B is a cathode follower that drives the tone stack). You can swap this tube out for a different type without affecting the sound of the drive channel --- one good option would be a lower-gain tube like a 12AT7 (I use a JJ ECC81 here). With a 12AX7 the channel tends to break up fast, though not at low volume, because there's no "quiet" part of the volume control's range. It goes from "off" to "loud" between 1 and 1.5. Looking at the schematic, it appears that Fender was doing their own spin on a Marshall Plexi preamp. The sound is still Fender-y when it's clean, but there's a lot of filtering going on that will keep the breakup tight if you run it all-out. Cathode bypass caps in this channel are more typical of a Marshall than a Fender. If you were to sub a 12AT7 and go lower-gain + more clean, you could also get more bass response out of the channel by increasing the value of C7. If you intend to run it crunchy at high volume, it's best to leave it as-is, to avoid farty distortion.

V3 is used exclusively by the drive channel, so this can be swapped out without affecting the clean channel. It has less of an effect on distortion than V1, though. V1A is the first gain stage for both channels, then V1B is used by the drive channel as its first distortion stage. The drive channel's gain control is in between V1A and V1B, which then feeds V3A and B, then V4A and the tone stack and channel volume.

V4B is used by both channels and provides either drive to the phase inverter --- when the FX loop is off --- or a small amount of gain to the send controls for the FX loop. V5A is the FX send buffer (an AC-coupled cathode follower), V5B the FX return buffer. V6 forms the phase inverter, a standard long-tailed pair.

In sum --- as far as preamp tubes, you'll get the most bang for your buck swapping out V1 (changes both channels), V2 (changes clean channel), and V3 (changes drive channel).

The power amp is a very standard Fender 6L6 push-pull design. It's no different from myriad other amps. I happen to think it sounds great with KT66s. One thing to watch here is that Fender recommends a bias setting of 60mV per side at the test points, or 30mA idle current per tube. For a decent 6L6GC (I like the JJs, they are TOUGH), this is a really cold setting --- less than 50% of rated plate dissipation. You usually want to be at 60-70% for a good middle range. I'm sure Fender did it to be on the safe side, but a more reasonable value for 6L6GCs at this plate voltage (489V) would be 35-42 mA per tube. 37mA gets you 60% of rated dissipation, 43mA is 70% (pretty warm for class AB operation). So try the bias at 75 or 80mV per side instead of 60, I found it sounded better.

KT66s will need to be kept right at 60mV per side, though. They are rated for 25W plate dissipation (not 30), so running them at 30mA per tube is just about right --- in this case, stick to the 60mV per side recommendation.

Remember that if you pull two power tubes to cut the power by half, you'll also need to set the bias for HALF of what it would be with 4 tubes... so 37-40mV per side for a pair of 6L6GCs, 30mV per side for a pair of KT66s. You'll also need to move the speaker impedance switch to HALF of the speaker impedance you're actually connecting to --- so for example, set it at 8 ohms if you have a 16-ohm cabinet.

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Discussion (read: ultra nerd-out):

It's strange how the 70s Model T and the Fender-made reissue are enormously different --- and yet they're both uniquely suited to similar sludge-y/doom-y styles and tones.

In the 70s model, you have a kind of Marshall MKII amp on steroids: a Plexi preamp circuit with a bit of added bass, master volume, and a hugely overpowered 6550/KT88-based power amp which is ultralinear with a massive transformer. The result is a Marshall-ish circuit that actually stays tonefully clean at thunderous volume levels (in fact it's very much like the 200W Marshall Major). A full stack running full throttle with a nasty fuzz or distortion in front creates a truly "sinister" tone... very doomy indeed.

In the case of the reissue model that I've been working on, it's really just a Fender amp. It's not a "doom amp" made by Fender, it's actually quite literally a Fender amp. The power amp design is a very standard Fender 6L6 stage, and nearly a part-for-part replica of the power amp in the red-knob "The Twin" from the early 90s. It just runs at higher voltage. The Model T reissue's output transformer is the same as used in the red-knob Twin, the Tone Master, and the current-issue Pro Tube "Evil Twin" (though the XLR line-out tap on the secondary is sometimes not used). The Model T reissue's power transformer is used in the Evil Twin too (same part number), and an almost-identical power transformer is used in a number of Fender amps (see: Tone Master PT, Vibro King PT) --- even though the part numbers don't match, the measurements and specs are all the same, including the separate 56V bias supply winding. The Model T reissue's tube-driven FX loop and 1/4-power switch (voltage reduction in the power supply) are standard Fender designs, which are used in all the current Pro Tube series amps.

The case I'm trying to make here is that the reissue Model T is basically a souped-up Fender Twin with an additional high-gain preamp channel. It's clean channel is really clean --- some would argue here, but I think that's because the volume pot lets it get too loud too quickly. It's a typical Fender clean, nice to have. The drive channel is the real show-stealer. It's loose, throaty, fuzzy, higher-gain than Fender was ever known for... and with the amp cranked, it's doom-y as anything. At low gain it's got an apocalyptic crunch, at high gain it's stoner-fuzz-metal heaven. The amp is LOUD (though the 6L6 output section isn't a match for the old Model T's 6550s), mean-sounding, out of control. You've heard this specific amp on Isis, Khanate, Sunn 0))), Russian Circles, and Cave In recordings, just to name a few.

Weird thing is... that not-so-Fender drive channel didn't die when the Model T reissue went out of production. It too got dumped into the 2-channel Pro Tube Evil Twin. I can't really express how weird this is --- an amp known as a power tool of doom, sludge, and "post-metal" was remade in a combo format with reverb/tremolo and is selling as the new Fender Twin!! The controls are identical. The current Twin circuit is 90% the same, right down to the alternating hot/cold biased preamp triodes in the drive channel (they just took out the cathode follower that drives the tone stack... who knows why). Look at the Twin schematic and compare it to what I posted above. Sure there are some component differences (e.g. look at the 250pf cap they added across the volume pot... so they cut back the fuzziness just a tad), but the topology is all there. Weird weird weird!

If I had to guess, I'd say that the Model T reissue was essentially a test platform for Fender to develop some new, more diverse and versatile sounds to add to their next generation of amps. The Model T reissue is the missing link between the early 90s red-knob Twin and the current Pro Tube Evil Twin.

So why isn't the Pro Tube series Evil Twin the doom amp du jour? I think I might have seen Mono playing through them. But this does reinforce two points: 1. that marketing hype and prejudice have as much to do with what people choose to play as features and sound, and 2. that if there is a significant difference in sound, it has to do with speakers and cabinet design. There's a pretty big difference between two 12" Jensens in an open back enclosure and a closed 4x12 with G12Ts. Changing speakers matters a lot more than changing tubes.

I would welcome thoughts that other amp nerds and Model T Reissue fans have. Though I would love to eventually own a 70s Model T, I have always loved the reissue model. It's unique (or at least I thought it was). Like a lot of people my age, it was my first introduction to the Sunn name (right about the time the same-named band began making demo recordings). Now I'm beginning to understand why Fender ended their production with the Sunn name. There were only two amps "reissued," and both the Model T's and 300T's circuits were destined for a top-of-the-line Fender guitar and bass amps, respectively. Before now, the 300T's continuation as the Bassman 300 was obvious, but only now do I realize that the Model T was reincarnated as the Evil Twin.

Tech: Thoughts on cabs

Speakers and other mods

Along with amp and instrument mods, I've experimented a lot with different speakers over the years. I had more or less settled on a combo of Celestion V30s with G12T75s, until I recently tried some Eminence Red Coat speakers and was very impressed. I'm now using their Governor model in place of the V30s. V30s are 60W speakers and should have been fine with my amp, but I push them hard and they kept blowing up periodically. The Governors are louder (102 dB sensitivity instead of 100dB) and handle 75W. They have better bass and a less harsh upper mid --- basically everything I wished I could change about the V30. I still have V30s in my 1960A, but both of the cabs I use in Rosetta now have 2 Governors and 2 G12Ts. Given how impressed I am with Eminence and how the 97dB G12Ts get drowned out by the Governors, I may swap in some Wizards for the G12Ts. With the Eminences, I've turned the Deep switch off on the amp and get a clearer bass response.

Beyond speakers, though, you can make other improvements. This video talks about cleaning out your cab with a hose (terrible idea), tightening the screws (good idea), and caulking its seams (decent idea). I skipped the hose section, but have done some of these things, along with others, to my 1960A and B cabs.

The B cab is the one that tours with Rosetta, and it has two Eminence speakers in it that are insanely efficient (i.e. louder at the same wattage: 102 dB @ 1W/1m) --- meaning that since it's driven singly by a 100W amp cranked up, the cab is constantly trying to tear itself apart. As a result it occasionally develops loose screws and weird buzzes, so most of the cab mods I've done have been experiments in trying to improve tightness and clarity under extreme SPLs with low tunings, but have often resulted in greater durability too.

In my experience, the most important thing is getting the center brace set up so that it's stiff, tight, and actually centered. Lots of cabs don't even have these, and the ones that do rarely have them installed properly. On a Marshall, you can take out the two screws that hold the brace to the baffle, then get rid of the tiny staples that hold the T-shape together. Replace them with a combination of strong glue and a wood screw. Spread glue on the baffle-side surface of the T and then screw it back in, tightly. When the glue dries, it should be 99% immovable. You can see the Gorilla Glue foaming in the picture as it dries. If you use it, be careful that it doesn't foam and drip on your speakers. You'll also notice in the picture that in the stock assembly, the brace had wobbled enough that the screw from the back of the cab went in off-center, reducing the strength and effectiveness of the brace. After gluing and tightening the baffle end, the screw from the cab back now goes straight into the middle of the brace.

I'm a skeptic when it comes to speaker cable hype. Still, I don't like all that 18-gauge wiring inside the cab. It's cheap to improve it, so just replace it with something larger than 16-gauge. My 1960B has 14-gauge wiring inside (nothing special, just zip cord from the hardware store), and my 1960A has doubled 16-gauge since I had a lot of it laying around. I just used the 2-conductor cable as a single conductor by twisting the ends together, yielding an equivalent 10-gauge connection. I soldered these to the jack plate board and speaker terminals. Keep the lengths short and they won't rattle around inside the cab.

Per the above video, I tried caulking the edge of the baffle after tightening the screws down. This makes no apparent difference above about 250 Hz, as far as I can tell. There are several before and after videos on YouTube that make this point. However, I thought that the low end seemed more present and I felt more attack at the bottom of the speakers' frequency response. Caulking gets criticized and dismissed a lot, but it certainly can't hurt to try it, and hi-fi speakers are almost always sealed in a similar manner.

With the B cab (the one that tours), I went further. Its baffle has worked itself loose enough to buzz on a couple of occasions, just as a result of the volume and beating it gets regularly. Needing a more permanent fix than just continuing to tighten the screws, I removed the baffle entirely and ran a bead of Liquid Nails along the inside cabinet edge where it mounts. I used wider, longer screws on the reinstallation. For good measure I caulked the back of the seam and installed steel L-brackets at spots where the baffle most often loosens. The cab's handles had cracked in a few places from touring wear, so it didn't hurt to replace them with metal ones. You can caulk the handles or gasket them to seal air leaks. I gasketed them so they'd be easy to remove later.

(The B cab also has tape on the inside of the grill cloth [similar to this] in front of the G12Ts, to cut down on high-frequency "beaming" in their very spiky treble range. You can see the tape in this picture.)

Both cabs are now lined with foam. This gets done to bass cabs and hi-fi speakers to help break up standing-wave resonance that can create strange peaks in response. Generally these peaks are "part of the sound" in the upper registers, but in the lower registers of detuned instruments they are objectionable. Foam helps to control that, and with both cabs I liked the additional clarity, especially when using an octave pedal or the 8-string. The difference isn't very noticeable except in percussive riffing or high volume sludge. I didn't find that it took anything away from the tone in the upper registers.


Cabinet marketing voodoo

An awful lot of people say that the Bogner Uberschall 4x12 cabinet is the best they've heard. I've heard them (and thought they were decent) but never seen one opened up. I read that they have damping foam or insulation on the inside, as well as heavy gauge wiring (probably 14 AWG or thereabouts, where Marshalls usually come with 18 AWG stock). Given that Bogner cabs are not made by Bogner, but come from a third-party supplier, consider this:

Bogner 2x12 open back / $789-ish
Avatar 2x12 open back / $389

Bogner Uberschall 4x12 / $1200-ish
Avatar Vintage 4x12 / $529

As far as I can tell, these cabinets are actually made by the same third-party cabinet maker, and loaded with the same speakers. The woodworking and specs are identical in each case. There are two possibilities here to explain the difference in both price and acclaim. One is that the brand name psychology works and is causing people to hear a placebo effect that's not there, and pay more as a result. The other is that Bogner buys these cabs in bulk and then does some extra modification before they're sold, where Avatar doesn't.

I've never seen any of these models open (though I do own some other Avatar cabs and like them very much). If anyone has them, I'd love to know what the insides look like --- it seems that the Bogner cabs have insulation or foam dampening material lining the insides, where I'm pretty sure that the Avatars don't. They may also have heavier gauge wiring (which shouldn't matter that much if it's above 16 AWG). I don't think these "value-added" bonuses are enough to explain the price difference, even if they're all done by hand.

However, based on my experience with modding Marshall cabinets, sealing and dampening can make an audible difference in the clarity of the low end, especially with drop tunings. Let's assume for the sake of argument that the Bogner cabs do have additional touches compared with other brands or models. Hi-fi nuts know the importance of eliminating air-leaks in sealed enclosures: a tiny crack with air escaping does NOT constitute a "port" (that's stupid --- ports are tuned with specific diameters and depths, to produce a certain cabinet Q and frequency rolloff), it simply lowers the cab's efficiency and hurts its transient response. It really can't hurt to eliminate the leaks. Likewise, foam is used in Hi-fi and PA system speakers to help break up standing waves inside a cab. It really won't take away from the "sound" of the wood or the size of the enclosure --- if anything, stuffing a cabinet has the effect of virtually increasing the enclosure size. What it does is help clear up the super-low end, where certain notes on the guitar can cause rattling or unpleasant boomy-ness.

Given that most people playing through Bogner 4x12s are playing metal, the combination of lots of small improvements --- particularly to the low end character --- probably makes enough difference from a Mesa or Marshall cab that they feel they've found something special. That magic is psychologically amplified by the price tag. Still, the reality is that you could buy the Avatar equivalent and add in whatever extra touches the Bogner has --- even buy a Bogner logo on Ebay --- and still have spent several hundred less than you would have otherwise, for an identical cabinet. In this case, it really pays to do it yourself.

Furthermore, it's simple and cheap to do that extra work on any cab. That was my thinking in trying out these different processes on my Marshalls. I'm happy with the results, though it's barely noticeable at all with a regular 6-string. The biggest difference is with the 8-string on the bottom end. Palm-muting sounds more dynamic and percussive, and there's less boom when stopping a note. The biggest improvement you can make is still changing the speakers themselves.

Tech: Home setup

Someone asked in the pedal post what I have on my other board. This is the setup I keep at home -- all the stuff that doesn't get used for Rosetta (except the Marshall head, which comes and goes because I like to play it every day).

The board has a EH LPB2ube, Boss RV-3 Delay/Reverb, MXR GEQ-10, Ernie Ball stereo volume pedal, Boss BF-2 Flanger, and Ibanez WD-7 wah. There are also an Ibanez Thrashmetal and Phaser that I know next to nothing about and are not hooked up.

This 1960A has 3 Vintage 30s and 1 G12H30. I am now using a mix of Eminence (4 Governors) and Celestion (4 G12T75s, possibly to be replaced with Eminence Wizards) in my live cabinets. After break-in, Eminence sound better to my ears at the insane volumes we use live, are more reliable (I was blowing up V30s constantly), and louder at the same wattage.

You can also see the two Valve Juniors, a Randall backup slave head, the Frankencaster, and my Agile 8-string (post forthcoming).

Edit 10/18/09: This post is completely outdated now. The Valve Junior setup is still the same, but that's about it. I have a PODxt/FBV Express MKII > power amp > 1960A setup now for practicing at home, so I can leave the TSL at the practice studio. I sold the Randall and several of the pedals, keeping only the RV-3, LPB2ube, and Volume pedal for the VJs. The MXR EQ is used for 8-string only, mostly at practice. With the POD, it's much easier to record demos cleanly at home. No mic'ing, and I use cabinet impulses in the DAW -- super fast, and means I spend more time practicing and making demos, instead of hooking things up and fiddling with knobs.

You can see the updated setup here.

Tech: Pedals (update)

An update on pedals, since the last time I posted my layout was in December 2006. The Ibanez WD-7 wah pedal from my previous setup is now for sale ($45, contact me if you're interested).

Over time this has started to look more and more like a Boss product display. That's mainly because of a subconscious feeling that Boss pedals "sound better" --- which is in fact because they play well together. Tone suckage is minimized when all the pedals have the same output impedance and line level characteristics --- which generally only happens when they're all from the same manufacturer. "True bypass" minimizes this problem and lets you mix and match. None of these are "true bypass," but there are no impedance mismatches, so it doesn't matter. All the non-Boss stuff is on loop A of the Line Selector. I had tried an MXR 10-band EQ to get more control than the GE-7, but it didn't play well with the Boss gear. It is now on my other board.

EDIT 11/16/09:
A few things have changed since the European tour. I got tired of patching the MidiVerb into the loop for the fade-in delay, so I am using an EH Memory Toy (9.6v, wall wart #1) in that spot now. Lots more character, a lot less flexibility --- more in this in another post. The patchbay is still hooked up so I can throw other things in that loop. The MidiVerb is hooked up between my master and slave heads, running a short delay and a little reverb, so that the live sound is now true stereo. The tremolo unit went to my other board for use with Valve Juniors (I haven't used it in Rosetta since TGS), and the MXR EQ (18v, wall wart #2) is now on board for use with the 8-string --- as a low-cut and boost.

This is also technically a new board, since I had to warranty the previous one after Europe (the handle broke off). Furman was really cool about replacing it. Notice the upgraded industrial velcro for the mat... big plus.

Tech: "The red guitar"

This has been my main stage instrument since Spring of 2007, and I used it to record all tracks on Wake/Lift except Temet Nosce. It's a 2005 Gibson Les Paul Studio, finished in wine red. It had gold/black hardware when I got it, which I swapped for cream almost immediately. Originally it had EMGs in it --- taken from the destroyed cream Les Paul that I used to record Galilean Satellites --- but after having been off the active-pickup kool aid for almost a year in Spring '07, I got tired of the sound quickly.

I went hunting for something that would sound closer to the Velvet Brick pickup in my Sonex-180 (used to record Au Pays Natal and Absent... more on this guitar in another post), but higher output. Since the Sonex is made of "resinwood", the Velvet Brick sounds much less thrilling (more compressed and middy) when moved to a mahogany Les Paul. The closest thing I could find to what I was looking for was the Gibson Dirty Fingers bridge pickup, which I combined with an uncovered 490R in the neck position. I recorded Wake/Lift with this configuration, and the guitar served this way until this past Winter.

I'm now using a Bare Knuckle Pickups Painkiller set. On strong recommendations, I got in touch with Tim Mills from BKP and picked his brain about what I was looking for, and he recommended this. It's the closest I've ever heard to the open tonal character of the Velvet Brick, but with even less compression, more volume, and vastly more clarity in the low end. It's extremely flattering to downtuned mahogany guitars, especially with really heavy strings. My bridge pickup is F-spaced, since this is one of the few guitars where Gibson used a 53mm string spacing at the bridge instead of 50mm. The saddle cuts look strange this way, since the replacement Tune-o-matic bridge I installed is a standard 50mm spacing, but the stock pickup on the guitar was 53mm and the saddles were cut accordingly off-center on the original bridge. In practice it makes no difference, but it's nice to have the polepieces lined up properly.

The guitar is tuned Bb F Bb Eb G C, or four semitones detuned with a dropped low string. The gauges used are .013/.017/.026/.036/.046/.062. The overall tension here is actually higher than in standard tuning with a set of .010-.046 strings. Even with the large jump from the F to Bb strings, the lowest string is still lower tension than the others. I also had to flip the bridge backwards to get extra intonation adjustment to compensate for the low tuning, regardless of the different core/wrap ratios I tried. The nut is now a Graphtec Trem-nut, which helps make tuning slicker with big strings.

All controls except the neck pickup volume pot are disconnected. I have no need for tone controls, and rather than waste time trying to find a 1-megohm long-shaft pot for a Les Paul, I opted to hardwire the bridge pickup directly to the switch. I love running pickups wide-open (see the post on the Frankencaster). I can still roll back the neck pickup volume for more mellow tones.

After playing an 8-string for a while, this guitar feels like a miniature. But it's still the instrument I use the most often, and it has the most reliably-good tone in the widest variety of situations. It's also the easiest to play, which is why I generally don't use it to practice with at home. I haven't toured with anything else since early 2007.

Tech: The Frankencaster (a.k.a. the Telesmashter)

Nobody asks about this guitar because I haven't recorded anything "serious" with it apart from (Temet Nosce). But it's probably my favorite because it's so weird, and it's one of a kind.

It started as a standard MIM Fender '72 Telecaster Deluxe reissue, made in 2006. I bought it to replace my '87 Les Paul, which had been destroyed by heat and botched neck repairs. '72 Tele Deluxes are electrically identical to Les Pauls -- two humbuckers with two volumes, two tones, and a 3-way switch -- but sound radically different because of the traditionally-Fender materials and construction. The reissue pickups, while oversized, are in fact average humbuckers that have been sized up to look like the original Seth Lover-designed Wide Range humbuckers. The original '72 Deluxes had 1MΩ pots, but the reissue uses 250kΩ, presumably as a cost-cutting measure. Replacing the 250ks with 1Ms makes a substantial sound improvement to the instrument. I used the guitar this way with Rosetta in Fall of 2006.

The first things to go were the pickups. I initially swapped in two EMGs which I had previously used in a Les Paul, but quickly removed them because they weren't wide enough for the huge 2-1/4" string spacing -- a result of the "vintage style" Strat hardtail bridge -- and the outside strings had a noticeably lower volume. After realizing that the spacing is so weird that appropriate aftermarket pickups would be vanishingly rare, I gambled on the only other drop-in option I had: Rio Grande's '72 Big Bottom Humbucking set. This set is their Vintage Tallboy humbucker for the neck and Muy Grande humbucker for the bridge, rebuilt specifically for the '72 Tele. The nicest part about these units is the 4-conductor wiring for coil splitting. These models are single-coil-specific designs that have simply been doubled into humbuckers. I replaced the two tone controls with push/pull pots to switch between single-coil and humbucking mode on each pickup. The guitar did duty this way in Rosetta in Winter/Spring of 2007, but I went back to the stock neck pickup because I only used the bridge pickup in Rosetta and the weaker Fender reissue pickup caused less sonic interference ("stratitis").

I was surprised and pleased at the versatility and sweet sound, but eventually decided the bridge humbucking wasn't really suitable for Rosetta. The Muy Grande output was huge but the combination of AlNiCo magnets and high DC resistance didn't allow enough treble attack, and I felt the guitar was being misused and undervalued in that context. So it gave way for yet another Les Paul (the red guitar) and became my home experimentation instrument. At this point I set it up as a straight baritone guitar, tuned B E A D F# B, and set about trying to maximize its potential for new sounds.

The main change was a custom pickguard from Warmoth, routed for the full-size 4-bolt pickup at the bridge and a standard 2-bolt Gibson humbucker at the neck (where the string spacing is not a problem). I opted for only two control holes --- one for a volume pot and one for a switch.

The current neck pickup is a Gibson Dirty Fingers 4-conductor humbucker (I added a nickel cover from an old 490R, it helps with hum in split-coil mode). This is one of the only ceramic pickups I find tolerable for the neck position, and it seems to flatter this guitar and its low tuning, more so than the Gibson 490R I tried first. I previously had the Dirty Fingers in the bridge of my Les Paul before swapping in a Bare Knuckle Painkiller there. I don't know of anyone else using the DF in the neck position, and certainly not on a Tele. Gibson claims it is "bridge only," but in fact its spacing is the same as Gibson's "neck" models (50mm), narrower than their other "bridge" models (53mm) like the 498T.

The bridge pickup is hardwired to the switch and output, with no volume/tone controls. With zero loading from any pots, this gives maximum output and attack, mitigating the Muy Grande's overly-warm tendency. The silver toggle switch shorts the middle wires to the hot wire, bypassing the lower coil and running the upper coil by itself. The neck pickup is wired to a 500k volume pot with a DPDT pull-switch. This switch shorts the middle wires to ground, running the lower coil by itself. When blending both pickups in single-coil mode, using "opposite" coils like this results in hum cancellation (this is called "RWRP"), just like switch positions 2 and 4 on later model Strats. With the Dirty Fingers at lower height, plus the cover, and with the pot loading, it matches up just perfectly with the Muy Grande in terms of output and blending. See below for a schematic.

This guitar is also fully shielded internally, using copper foil. Shielding doesn't completely eliminate hum from single-coils, but makes a noticeable difference. I tried shielding the pickup coils themselves, but hum was still present and it dulled the sound.

Tuning the guitar baritone B to B presents some challenges -- both in the accuracy of tuning and with staying in tune. It also requires higher-than-usual action to accomodate heavier strings, more slack, or both. I use a 14-18-28w-38-48-58 set for this guitar. To give a finer tuning ratio, I installed Steinberger gearless tuners. These use screw shafts to pull the string into the headstock, without gears, at a 40:1 ratio. They work well. You won't need to enlarge the existing mounting holes, but the Steinbergers require a small (1/16") auxiliary hole pointing in the direction of the nut. Getting the Fender tuners out is also a pain, since the topside inserts are wedged tightly in the mounting holes and can take the finish off as they come out, if not tapped out carefully.

To reduce friction and increase sustain, I replaced the high string tree, nut, and saddles with Graph Tech lubricated models. The lower string tree is a roller model, which worked better with the tuning machines so close to it. Replacing the nut required that I re-profile it, which also allowed me to fine-tune the setup for baritone tuning and larger strings. This is an absolutely necessary procedure if you're going to drastically change tuning or string gauge. I don't use needle files -- instead, I use the folded edge of a piece of 620-grit sandpaper. It's slower, but works well.

Obviously, the guitar is quite versatile. I have not found the absence of tone controls or a second volume knob to be a practical limitation. The amp isn't "covering the deficiency" either, since I primarily use this guitar with two Valve Juniors that have no tone controls themselves.

As far as tone, single-coil mode on either pickup is excellent and very characteristic of a Telecaster, and the blended sound between them is actually much better than most other Telecasters I've heard played that way. In addition to canceling hum, it has broad harmonic response without being harsh or spitty. Being able to fade the neck pickup in and out without changing the bridge pickup's output is an excellent way to tweak for tone. In humbucking mode, both pickups have extraordinarily high output, but different character. The DF in the neck position is very deep, but retains a lot of treble clarity, far better than the 490R. The Muy Grande in the bridge has the most mids I've ever heard, period. I don't use it for clean sounds except when blended with the neck pickup and a bright switch on the amp engaged --- but it sounds incredible for high gain, very smooth and responsive.

EDIT 4/2009: I'm now tuning this guitar A to A, or sometimes drop-G, using string gauges .014, .018, .028W, .038, .050, and .070. I have also removed the lower string tree, since I found that it gets in the way of the Steinberger tuners.

Tech: Valve Junior head mods

These are the two Valve Junior heads that you hear on Rosetta's track (Temet Nosce). I run them in stereo, each through a 2x12 closed-back cabinet with one Vintage 30 and one G12H30 (made by Avatar, who I highly recommend). On (Temet Nosce), I played my mutant '72 Telecaster through a stereo delay pedal, with each amp/cab set up and mic'ed in a different room. We just panned the tracks left/right and that was it. The outro to Monument was also recorded with these heads, but in 4 takes with my Gibson Sonex-180.

The amps sound significantly better now than they did then, due to further modding. At that time, the only changed components were R1, R2, R6-9, and 10uF cathode bypass caps on the preamp triodes. That circuit was a huge improvement over the stock sound, but I think the current version is vastly superior.

The schematic below (based on stock schematics from SEWATT.com) shows all of my changes in red. You can find an excellent explanation of different components in S2 Amps' upgrade kit instructions. Whether or not you buy their kit (I did not, and doubt it is still available), the instructions are full of useful info. Loads more info can be found in the SEWATT Octal Mod file, even if you have no interest in adding another power tube. The complete repository of Valve Junior info is here.

My 390pf "bright switch" around R6 (switched via large toggle on the black amp, push/pull volume knob on the white amp) is very helpful for humbucking pickups. It's very "Marshall-y" sounding. I prefer it off with single coils. The 47pf bright cap on the volume pot only adds a tiny bit of shimmer or chime when playing clean. As you turn up the volume, the effect gets smaller, which is great because it's not needed once the amp starts to break up --- around 11 o'clock on these heads.

Both amps have Hammond 125ESE output transformers. These are far larger than needed for a nominally 5-watt amp, but the greater dynamics and bass extension are worth it, particularly since I most often play a baritone-tuned telecaster (my '72 Frankencaster) through the VJs.

Not noted on the schematic is that the rectifier on the high-voltage power tap is discrete 1n4007 diodes, in the stock amp. I replaced these with UF4007 diodes and the switching noise was reduced.

For recording purposes, the black amp has a second, smaller 3-way toggle that switches R15 from 10k to 5.6k or 1.5k, for a kind of presence or power amp voicing control. Most of the time it stays on 10k, to match the white amp.

Tubes: both of these amps use a JJ ECC803S (long plate) in the preamp, and a JJ EL84 in the power amp. I specifically asked for power tubes graded for maximum clean headroom.

Final notes: these amps are LOUD -- much louder than the 5-watt rating would suggest. I can't get anywhere near breakup at "bedroom" levels. If you're interested in controllable preamp gain, I don't recommend adding a master volume. I've tried it and it sounds crappy. The best solution is to use a tube overdrive pedal in front of the amp. The closest thing I've found to adding extra gain stages is the EH LPB2ube, which works in either stereo two-stage or ganged-mono four-stage. I use it in stereo to front end both amps, with a stereo volume pedal. Getting a small amount of distortion from each tube in the overall chain adds up and sounds incredible.

Tech: Amp guts - complete Marshall TSL mods

How to make the TSL-100 good at almost everything
(but especially sludge/doom)

This post is Google bait, so that someone else won't have to do all the searching I did in researching these mods. All of them require some experience soldering components on PCBs. They are presented in the order I did them.

Schematics here, with links throughout. Before doing these mods, please be sure you know about the voltage hazard inside the amp from the supply caps. The TSL (at least my 2005-made model) has bleeder resistors, so you can leave the amp unplugged for an hour and the caps will discharge themselves --- but ALWAYS CHECK WITH A VOLTMETER before diving in. A quick web search should yield whatever info you need here.


1. Get rid of the fizz
Cost: ~$1
Perceived sonic change: large and immediately obvious

These amps have a reputation for being "fizzy" or "buzzy" in the lead channel. You can easily and cheaply get rid of this without making the amp sound dull. This will NOT affect the sound of the crunch or clean channels. This is from a thread on MEF.

Use two silver mica capacitors to create a 12dB/octave low pass filter at around 7.5kHz, in the preamp. This not only kills fizz in the preamp, it saves some headroom in the power amp and the power tubes break up more smoothly when they saturate. The treble you do keep is more pleasing.

Put a 390pf cap across R1 on the main circuit board (the one the tube sockets are on), and a 47pf cap across the lead channel volume pot -- VR2 on the lead channel panel PCB. Note that the pots used have 4 terminals; one of these is part of the pot case, for grouding/shielding. Counting from the side toward the gain pot, use terminals 1 and 3. There should be only one pin (pin 2) between the two pins connected to the cap, and one pin on the side toward the treble pot. You will have to remove the chassis, tubes, aluminum top plate, and panel PCBs to do this mod --- that includes all the knobs and pot washers. You will want to put pieces of tape on each of the wires you disconnect, labeling what they connect to.

If you want to do the same thing to the crunch channel, just add another 47pf cap to the outer terminals of the volume pot (VR2) on that channel's panel PCB. I tried this and didn't like it, so I removed it -- the crunch channel's voicing seems ok to me.

EDIT 3/30/09: I have since changed the VR2 cap to a 68pf, to remove even more fizz and increase smoothness. I left the 390pf cap alone, since I know now that it affects all channels ever so slightly. So now the filter on the OD channel starts at a lower frequency, and maintains a 6dB/octave slope up until 7.5 kHz, where it steepens to 12dB/octave.

EDIT 4/4/09: Upped the VR2 cap to 100pf, which brings the corner frequency down to about 3.5 kHz. I don't recommend this unless you are a) using the MMOT (see #7 below) and b) you love midrange crunch. I used to keep the treble at 1 even with the 47pf cap, now it's at 4 or 5. It sounds very British -- more like a JCM800 running close to meltdown.


2. Change the tubes
Cost: $100ish for complete re-tube
Perceived sonic change: medium

This is inevitably a taste issue. If you want more raunch and a warmer sound, JJ tubes do nicely. This is what I use --- ECC83s preamp tubes, and E34L power tubes. Eurotubes offers a full re-tube kit for the TSL with a variety of options. I used the high-gain preamp tubes (I love gain). I have tried JJ's KT77 power tubes and found them to be muddy/farty and fizzy compared to JJ's E34L tubes when playing downtuned or sludgier material. There are applications where they are appropriate for adding roundness to the sound, but the bass is too loose for full-on gutteral roar. JJ's straight EL34 is a good option for a more traditional Marshall sound, more like the stock Svetlanas but better. The E34L type seems to improve both low-end extension (without mud) and headroom -- great for more rumble without fartiness.

EDIT 1/12/09: For E34Ls to sound best, they need to be biased on the high side, at about 90mV per side, or higher if you don't mind decreased life. 90mV per side is Marshall's spec for the amp, but most agree that this is high, and anything in the 80-90mV range is ok. I found that below 90, the E34Ls sounded a little fizzy and cold at lower volumes. There is good info on how to bias the TSL/DSL here.

EDIT 4/4/09: The high-biasing advice above really only applies if you replace the OT (see #7 below!). If you don't, most settings between 80-90mV per side will sound similar.

EDIT 6/15/09: On the other hand, since the MMOT handles more power cleanly, you can bias lower and get actual usable headroom --- with the same nice warmth at a higher volume level. Biasing low, to 70-80mV per side or so, gets you noticeably more volume before things start to break up --- by "noticeably" I mean that it feels like the speaker cabinet is going to fall apart. For Rosetta's European tour, I converted the voltage and ran the amp at ~80mV per side, and turned it a notch louder to compensate for a less efficient speaker cab.


3. Clean up the rectifier
Cost: ~$40, or ~$1
Perceived sonic change: marginal/unpredictable

D3 through D10 (8 adjacent 1N4007 diodes) form the rectifier portion of the power supply. These are crappy, cheap diodes. Recently, using ultra-fast (low recovery time) diodes in guitar amp supplies has gotten really popular, with people saying they sound "less harsh" and "more tube-like." These claims may be spurious -- since ultra-fast diodes have nothing remotely like the occasionally desirable voltage sag in tube rectifiers -- but you can clean up hash and switching noise, and improve reliability, by replacing the diodes with faster ones.

There are two options: FREDs (Fast Recovery Epitaxial Diodes) or UF4007s. FREDs are the parts that are getting all the attention. They are huge, look like two-legged transistors, and have the lowest possible recovery time (40ns) at extremely high voltages and currents. They also cost $5-7 a piece, and you need 8 of them. The other option is just the ultra-fast version of the stock diodes -- UF4007s instead of 1N4007s. They cost about 25 cents a piece, with 75ns recovery time.

I went all-out with the FREDs, to see what it would do. They eliminated the supply switching noise, and as far as I could tell, they did change the tone slightly -- but not in the way I expected. Instead of being "smoother", I found the tone had more crunch and sounded more aggressive. Perceived headroom improved slightly. It was not objectionable, so I have kept this mod. The 1200V/16A FREDs I put in will probably be more reliable than the original diodes anyway.

To change the rectifier, replace D3 through D10 (8 diodes) on the main circuit board, but be absolutely sure to observe polarity -- connecting a diode backwards will pretty much blow up your amp. If using FREDs, cover any exposed metal with electrical tape so they don't accidentally short.


4. Add a choke
Cost: $35
Perceived sonic change: medium

A choke is an inductor that helps to filter ripple out of the power supply. Inductors in series act as a lowpass filter -- like in a crossover network -- so one that is large enough to filter out everything down to DC can smooth out the 60Hz ripple after the rectifier (it doesn't matter if you didn't understand that). They were often used in older amps back when large-value supply capacitors weren't as readily available. Now, large caps are easy to come by and cheaper than filter chokes, so they are used by themselves. However, with high inductance, chokes also seem to be able to store a certain amount of current, making that available to the power tubes in high-demand situations. I installed a Mercury Magnetics MC10H choke, and found that the amp became more responsive in high gain situations with a lot of low end in the sound --- palm-muting, octave pedal stoner riffs, etc. It had more attack in the bass and seemingly some more volume.

To install a choke, desolder R71 on the main circuit board. Mount the choke to the chassis next to the power transformer and run the wires through a small hole in the aluminum top plate. Solder them where R71 used to be.

EDIT 10/23/09: I notice that Mercury now has a 25H choke from the Axiom line. I'd be interested to hear people's experiences with that... might be even better for this application than the 10H.


5. Misc. cap value changes
Cost: less than $1
Perceived sonic change: medium

Comparing the TSL with its earlier cousin, the DSL, some find the DSL to have a slightly darker, bassier sound, though the amps are nearly identical. One reason for this may be the coupling cap C16 on the main circuit board. In the TSL, it's a 2.2nF ceramic, in the DSL, it's 4.7nF. I replaced C16 with a 4.7nF Orange Drop cap (nicer than ceramic anyway). The 4.7nF value rolls off frequencies below about 35Hz, which should be pretty insignificant unless you're playing an 8-string or hybrid guitar/bass. The TSL's normal 2.2nF rolls off frequencies below about 72Hz, which shouldn't be terribly noticeable with a 6-string tuned standard. But when you get below that, it certainly does make a difference. The preceding triode (V1B) is not run full-range anyway, so the coupling cap is adding to an existing lowcut.

I eventually found that the 4.7nF cap wasn't great with downtuning -- it didn't add anything I like, and made the amp muddier at high gain. 2.2nF sounds tighter to my ears, so I switched back.

EDIT 4/4/09: I recently noticed another (much more important) component value difference between the DSL and TSL -- C18 on the main circuit board is designed to bleed treble frequencies to ground coming off the V1AA triode. Since this triode is not used by the clean channel, this area is crucial to distortion voicing. In the DSL, the cap is a 470pf cap, but in the TSL, it's only 100pf. This means that more treble passes through to the next stage in the TSL than in the DSL. I have replaced the 100pf ceramic cap C18 with a silver mica 470pf cap, and this is a bigger and better change than the coupling cap swap. The tonality change between stages makes breakup in the later preamp triodes smoother and more mid-centric, but without altering the clean channel. I think this is probably a key source of the perceived difference between DSL and TSL.

Another cap to change is C9 (a 470pf ceramic cap) on the Lead channel circuit board -- this cap bleeds treble past the gain pot on the lead channel. It has no effect when the gain is maxed out (so I didn't notice it while playing with Rosetta), but makes the tone brighter when you turn down the gain. I happen to think it makes the channel sound "quacky". You can reduce the value to 100pf to move the corner frequency higher, or just clip it entirely. I clipped it and find the sound to be much more predictable at different gain points.


6. Fix undersized cap
Cost: less than $1
Perceived sonic change: none

C46, a 22pf/500V ceramic cap on the main circuit board, has been known to fail in the TSL. If it shorts, it can destroy all the power tubes and the output transformer. There is absolutely no reason a 16-cent part should be allowed to cause $300 worth of damage. I replaced this cap with another of the same value, but rated for 3150V.


7. Replace output transformer
Cost: $250
Perceived sonic change: substantial, but not necessarily better

The stock output transformer on the TSL is a Dagnall general purpose model, part #C3070, TXOP 00001. Mercury Magnetics makes a drop-in replacement -- the MAR100-OM -- that is bigger, more reliable, and is supposed to sound better. It's pricey. This mod requires no soldering and no drilling, just reconnecting the 7 wires to the right spade terminals on the new transformer. Mercury includes a diagram.

The new OT has wider bandwidth (read: deeper and higher), so it perceptibly improves clarity and attack. The lead channel seems fizzier at low volumes, but maybe a touch smoother at really high volumes. The "improvement" becomes more audible as you turn up the amp, which is to say, the breakup of the power section comes in more slowly, and there's more consistency from low to high volume. You may or may not consider this a good thing. There is quite a bit more bass available in the tone network, no doubt due to the extended low-end response of the MM. However, this can make the tone sound "tubby" at higher volumes with very low tunings.

I now realize that while this transformer is undoubtedly more reliable and cleaner than the stock model, it may be a little too polished (i.e. linear), lacking some of the "gravel" in the old one. The added bass also makes it initially sound less "tight" with high gain detuning. It's hard to say whether I became attached to the "imperfections" in the old OT, or had gotten so used to compensating for them that it's hard to make the MM work for me. The MM model may be suited to a more traditional style of playing, where the Dagnall seems to be (accidentally?) tighter and smoother for more extreme gain and tuning. I would say the Dagnall has a more (gasp!) "vintage" sound, and the MM is more modern. It may all be a matter of taste, and $250 is a lot to spend on something that subjective.

EDIT 4/2/09: I switched back and forth between the Dagnall and MMOT a couple of times, and found that even though the "tone" of the Dagnall was more pleasing, it was no substitute for the greater volume and bass response of the MMOT. The MM transformer opens up a lot of possibilities.

The real issue is that it was one of the later mods I did, so the earlier component and settings choices had been made unconsciously to accommodate or to flatter the Dagnall's limitations -- after I tweaked some of my existing mods (pulled even more treble out of the lead channel, most importantly) and started over from scratch with all the controls at 5, I found I could get what I was looking for. I can now hear a much bigger difference between different bias settings, and the tone network's behavior actually makes sense. I now have to pull the bass back a lot --- but doing so gets back a good deal of the "tightness" I missed from the old setup, and reveals some lower frequencies (below the center frequency of the bass control) that were never there at all before.

However, make no mistake: the MMOT will not get rid of the "fizz" in the amp, contrary to some other opinions I've seen, and will probably make it even more noticeable. There are advantages to it, but less fizz isn't one of them. To put it succinctly: if you think the amp is fizzy, and you hate that you have to turn it up too loud to get a good sound, don't get the MMOT. If you are modding out the fizz (or you like it as-is) and you wish the amp was louder and had more "oomph," then by all means go for it.

EDIT 4/6/09: On further reflection, I think that the undersizing of the Dagnall is mostly responsible for the "tonal qualities" I was hearing --- it is highly likely that its core was saturating when I pushed the amp hard. I say this because with the Dagnall in the amp, I would hit a wall at about 6 on the lead channel's volume knob, beyond which the amp would not get louder --- but would start to sound dramatically different, losing bass response and tightness. With the MMOT, that wall was removed. I had assumed before that I was hitting power tube distortion, but if that were the case, the limit onset would have changed with different bias settings (it didn't) and would not have changed with a new OT (it did).

Furthermore, the Dagnall OT would get very warm while playing loud, while the MMOT remains the same temperature as the surrounding chassis, even at extreme volume. I can only assume the extra heat from the Dagnall was output power that was lost due to inefficiency, core saturation, or both. This would also explain why there are so many stories of the Dagnall OT blowing up when people try to run the TSL on the clean channel with all the knobs at 10 (Plexi-style). The amp is in fact capable of much more volume and bass response than its stock transformer allows, at least from a perceptual (standing in front of the amp) standpoint.

This added power could be good or bad depending on your needs -- if the amp only sounds good at enormously high power levels which you could never use, then it's not an upgrade. For my purposes though, it's a great thing, although I never expected I would think an amp was "too loud" (yikes!). Eventually I may be able to eliminate my Marshall 3210 slave head and drive both of my 280W 4x12s into speaker breakup with only this amp. I couldn't do that before.

Digression: I have heard that Mesa apparently uses deliberately undersized OTs in their Rectifier heads (but NOT in their other models) to get an effect similar to what I describe above. Maybe that's more integral to the "Mesa tone" of "pleasing compression" than their much-vaunted tube rectifiers...? But then again, "cheap, small output transformers" doesn't make for good marketing copy, so who knows?

---

At this point, I wouldn't trade this amp for one 5 times as expensive. You can hear it on every track on Wake/Lift except (Temet Nosce), using all three channels. At the time of that recording, the amp had mods #1-4 above, with the 390pf/47pf version of #1. The other mods hadn't been done yet. I used some EQ on the Wake/Lift guitar tracks, mostly to compensate for the microphone's non-linearities, but also to get a sound closer to what I imagined in my head. The amp is closer to that sound now, by itself. It is a very good-sounding amp now, one of the best I've ever played through, as far as the qualities I prize most: smoothness, bass transient power that maintains tightness, bell-like cleans, enormous gain, and of course sheer volume. I doubt that --- short of a custom design --- I could find anything else that would be as satisfying, in stock form.

As far as comparisons, I suppose it has a Bogner-ish and/or hot-rodded JCM800 kind of character, but deeper and with a more Fender-y clean channel. It is very much a Marshall, though, maybe more than in its original form. The gain on the lead channel is outrageous but stays focused at high volumes (I have the gain at ten, volume at the edge of power tube & speaker breakup). Crunch is nicely versatile. The VPR circuit actually sounds decent now, too, and whether it's on or not, the amp sounds steadily better as you turn it up. I would characterize the sound as the "next logical step" if Marshall had continued producing amps with the philosophy and quality of the JCM800s, but with modern levels of gain.


Some thoughts:

+ The most effective mods are not necessarily the most expensive. I've tried to be as objective as possible here, balancing what I've heard (NOT properly/scientifically ABX tested, obviously) with what I know about electrical engineering and amp design.

+ No mod will improve an amp for everyone. Different tastes have different requirements. I don't see these changes as "fixing" the amp; instead it's more about keeping the things I liked and refining the things I didn't. Since so much of the tweaking of this amp involves controlling the treble: before you get out the soldering iron, put an EQ in the effects loop and see what you like and don't like in the voicing. Try an EQ in front of the amp, too.

+ Mercury Magnetics has quite a hype machine, but for the most part their products live up to it, and they are helpful to talk to. I would buy from them again.

+ As a taste issue, I also swapped the reverb tank on the amp. The stock one is very good, just not as dense as I'd like. EDIT 8/28/09: I had Accutronics make me a custom Type-9 reverb tank and it's even better than the one I had swapped in before. Nice and rich --- the part number is 9BB3C1D.

EDIT 8/17/09:
"Tightness" vs. "looseness" -- while a lot of this has to do with what kind of cab you're using, I've found that the modded TSL is WAY tighter sounding than any Mesa. Even A/B'ed against a VHT (Sig:X) or Engl (Fireball), it holds its own. You can boost the input, roll back the gain, and get amazingly percussive tones without fizz. It's crunchy but VERY controlled. It's the closest thing I've ever gotten to a Meshuggah tone without a POD. My 8-string sounds incredible (even on the low E-flat string!), with the tone controls all at 12 o'clock and the lead channel gain at 4, and a 6-8 dB boost in front of the amp (a little "frown curve" EQ helps too).

This is all quite opposite of what I originally intended the mods to do --- give me a thicker, smoother saturation for enormously high-gain sludge riffing. It really speaks to the true versatility of the basic design (as opposed to its initially compromised realization) as well as the retention of a lot of buried "Marshall tone" that only came out after modification.

Tech: Long-awaited amp post

Gear nerds, at long last: AMPS.


This is the live setup I've been using since about early 2005. The only change in all that time is that I now use a Marshall TSL-100 for a master head, instead of an AVT150H. The AVT150 + 1960B was what I used recording TGS and Project Mercury. The TSL wasn't a huge improvement right out of the box, but afforded MUCH more opportunity for tinkering, so it is currently being used with the same old 1960B to record the new Rosetta full-length, "Wake/Lift" (which will be out 9/28/07 on Translation Loss).

The pedal setup was posted before. I use no distortion pedals, everything on the board front-ends the amp, and all the drive comes from the master amp. Each guitar head drives a single 4x12, and the bass head drives a 4x10. The bass head is useful because our tuning (Bb F Bb Eb G C) is low enough that a guitar cabinet can't reproduce the fundamental frequency of the lowest string. Having the low end reinforcement means the 4x12s don't have to be driven as hard.

Nearly every component listed has been modified in some way (though the old AVT head was completely stock, no modifications). All of my guitars are also electrically modified, so the "Rosetta sound" or whatever you want to call it is not really created by any one piece of equipment. It's more the result of a laborious process of matching different components to each other, and when it doesn't fly, breaking out the soldering iron and making it work better.

TSL-100:
- JJ EL-34L + ECC83s hi-gain tubes from Eurotubes (noticeable improvement, + more headroom)
- 1 390pF cap in V3 and 2 47pF caps on volume pots for treble roll-off on Lead/Crunch channels, per this thread (huge improvement)
- FRED rectifiers to replace stock 1N4007 diodes [some info here] (jury's still out)
- 10H Choke from Mercury Magnetics (noticeable improvement)

3210 MOSFET:
- Stock Hitachi MOSFETs burned out, replaced with Magnatec BUZ900/905, +25W power gain

Hartke HA3500:
- JJ ECC83s tube swap

1960B:
Replaced two stock G12Ts with Vintage 30s. Now has 2 G12s and 2 V30s. We mic the V30s for recording.

Homebrew cab:
Was once a Crate 80W 4x12 (?). Now 300W with 4 G12Ts like a stock Marshall, but with its larger size, sound resembles a Sunn0))) 4x12. Rewired with switching jacks for selectable 4/16 ohm impedance (like a Marshall).

--- ---

Eventually I'm going to put up a permanent page on here for amp/guitar mod stuff that I do, with as many of the associated hard-to-find links as I can dig up. I have also been working extensively on two Valve Junior heads lately which have been doing stereo duty with my Frankenstein-like Telecaster and a delay pedal in Temet Nosce. This setup will also make a brief appearance on the new Rosetta.

Tech: Pedals

It occurred to me that a few of you who read this might be interested in some more mundane tech stuff. People ask about pedals more than they ask about amps and guitars. This is the effects setup I use touring with Rosetta. I just rebuilt it to accommodate some new components.



This is completely nerdy but I like talking about gear. Usually when we tour with other bands, one of the early friendly connections is gear talk. It's like shop talk, or book talk, or hey-you-like-Twin-Peaks-too talk.