Thoughts on my Seal Modded Marshall

[Luke Duke]

As some of you may, or may not, know I sent my 1981 Marshall 2204 to Jeff Seal. I had been experiencing a very loud grounding out noise and being that the tube heaters were on I figured that I must have a bad component somewhere. I sent the amp to Jeff Seal to give a going over. He figured out it was just the tube in V2 that was going out. after that, no more problems. I gave Bob a Eurotubes a call and told him what happened and he sent me out a new tube. Jeff gave me a call and we talked about some mods I had in mind. He told me that the amp was so clean he would rather build up a whole new turret board that mess with the PCB.

So, after telling him some tones I really liked and wanted to be in the vicinity of I gave him creative liberties.

Luke was after what quite a few people are after, not tons of gain like a Mesa, but more of a "Marshall on steroids" type tone. SO..... the circuit you see is a combination of a 1959(super lead) 2204, 2210 and a 2555. The basic premise was to create a 2204 with a PPIMV but without the "drawbacks" the new MV create's. (that is a discussion within itself!) The layout is gain, gain, gain, tone stack(plate driven) MV then another gain stage.
Besides being incredibly loud, the amp now has twice as much gain, but with the ability to clean up nicely at all levels. Single handedly the coolest thing is that little trimpot located to the bottom about halfway through the board. It allows the rate of which OD is achieved to accomodate playing styles by either increasing or decreasing the onset of OD while simultaneously "boosting" the level proportionately. Basically all the way down is standard 2204 gain structure, up is closer to TSL. This allows the use of the guitar's volume control to further dictate the amp's OD amount. (if that made any sense at all!)

Here are the pics again. Christian thought Jeff had been looking inside an old Sound City or Hiwatt.

My particular 2204 started its life with 6550s. Upon receiving the amp I ordered some new tubes. I had a RCA 6550, and a Magnavox 6550, and 3 burned up Groove tubes in the preamp slots. I order some JJ KT88s (having heard they have even sweeter mids and thumping lows (they did not disappoint), and high gain graded JJ 12AX7s. That is the current tube compliment, the JJ 12AX7s might be a bit too dark for some folks taste with this mod, it all comes down to personal preference. This is all pumped into the cab bought with it, loaded with (30's) I threw in this blurb where folks could identify the differences in my particular set up and figure out how their setups might differ.

<to be continued>

 

[Luke Duke]

Re: My Seal modded Marshall thoughts

Re: My Seal modded Marshall thoughts

<continued>

Tonally it sounds exactly what Jeff describes; a Marshall on steroids. There is at least twice as much gain on tap, and even at low levels it sounds pretty good. The interesting thing is regardless how much you turn up the amp the tone doesn't change a whole lot. The big thing I DO notice is that the mids and lows boost get boosted the higher you turn it up. Obviously your ear responds differently as you turn it, but the core tone doesn't change a whole lot. I've played all my guitars through i (with the exception of my Godin) with great results. The amp really eats up those hotter pups too, which really blew me away. I can get a sweet sound with vintage style buckers, and lots of crunch and articulation from higher output buckers, WITHOUT sounding super small, which is my main complaint about high output humbuckers. The Brobucker sounds sweet and warm, but I'll keep my final thoughts on that on under my hat till I pull the cover. My strat is quacky sounding, yet full and warm. The tele has bite on the top end, creme in the middle, and crunch on the low end. The 330 has bite and bounce throughout the tonal spectrum. The amp is definitely warmer and more controllable than it was. The 88's sound really large, and the girth of the mids and bass is huge, I would be interested in A/Bing a set 88s and EL34, and or E34Ls.

One of the big things I told Jeff I had to be able to do was to control the amp with the guitar's volume knob. I wanted to be able to still get useful clean tones when I needed them, being this is a one channel amp. Even with the gain dimed I can still get some cleans. Now the cleans are proprotional to how high you have the actual volume too. If the volume is real low and you turn down the guitar your clean sound is going to be pretty low dB-wise, but I expected that being used to dealing with single channel amps.

Jeff also moved where the tone stack is in relation to the rest of the circuit, it is now plate loaded. This makes it what some people would call an "active" tone circuit. It really isn't though it doesn't boost or cut frequencies with 12 o'clock being zero. The tone stack operates in the same manner as it did but there is much MUCH more use in the tone stack. The bass control actually WORKS!! Right now I've got everything on about 9-11 o'clock. As I turn up the amp I can cut back the mids and bass quite a bit. In fact as you turn it up the amp gets unbelievably fat. Some people might not like that you'll have to re-EQ your amp at higher levels, but to me it's not a big deal. To get an idea of what kind of tone stacks I'm talking about compare a BF or SF Fender or Mesa tone stack to a Marshall tone stack.

I have yet to pull the chassis and noodle with the internal gain structure pot that Jeff added. But plan to, just where I can say I know what it does, and how it affects the tone.

For me this is probably THE Marshall. I'll probably never get another Marshall or similiar, and if I ever decided to sell the amp it would only be for a channel switching amp, and then I'd have the regular PC board, in one nice, neat piece, and the turret board. So somone could decide which voicing they preferred, stock or modded. I'll be sticking with the modded board.

Luke

 

[B2D]

Re: Thoughts on my Seal Modded Marshall

Daaaaaaaaamn.

That tears it. Next time I buy an amp it's gonna be a 2205 and it's going to Jeff Seal first thing.

 

[Gearjoneser]

Re: Thoughts on my Seal Modded Marshall

Sounds great. I can't believe how clean that Marshall is. It's like it was under a cover for 20 years. Too bad Marshall doesn't experiment enough with their vintage designs. They either give you a PC board copy of a vintage amp or a modern amp with too many bells and whistles and a thin tone. They need to learn from guys like Jeff how to take their basic platform and improve on it.

 

[ErikH]

Re: Thoughts on my Seal Modded Marshall

Very nice, Luke that is one clean looking amp, even before the change. Keep in mind, Marshalls are like Pringles, you can't have just one. My 2nd one is on the way (Lead 12).

 

[JacksonMIA]

Re: Thoughts on my Seal Modded Marshall

I've tested this in person and can vouch for everything he says. This amp is a BEAST, yet it's quite controlable. I was blown away by how useful the EQ was throughout it's entire range.

 

[BluesGuyJ]

Re: Thoughts on my Seal Modded Marshall

Sounds killer man. Nothing beats a well modded Marshall, hands down.

 

[Jeff Seal]

Re: Thoughts on my Seal Modded Marshall

.....!

Js

 

[Luke Duke]

Re: Thoughts on my Seal Modded Marshall

<Bump> for posterity's sake