How about a high gain amp kit?

Necrovore · Post by **Necrovore** » Sat Jan 14, 2006 5:00 pm

George, the only ime I think you will get a cease and desist letter is when you get to the point where you are affecting Marshall's bottom line, or that you start selling products that the less than honorable would be able to clone an exact replication and start selling them AS actual vintage Marshalls with counterfiet serial numbers etc... Much like the way Ed Roman has counterfieted BC Rich's in the past.

Post by **VelvetGeorge** » Sat Jan 14, 2006 5:16 pm

I feel the same way. Maybe if I printed Superlead on the panels or made a Metropoulos script logo in white plastic. Obvious stuff.

I'll be happy selling (2) amps a week myself. That's all I have time to build.

I did get (2) 12 series done this week.....finally! There was a wait for the steel in the dual voltage PT's.

George

Bainzy · Post by **Bainzy** » Sat Jan 14, 2006 7:09 pm

594Life wrote:The amp used on the appetite for destruction album was supposedly a 1959T that was modded. The trem was converted to an extra gain stage.

I think there is a market for a 1959T model. You could offer that amp kit and simply add mod info on the CD. What do you think?

I've done a complete layout diagram of the 1959T in a thread in the Marshall board here, but me and Dan seemed to be the only ones actually remotely interested in developing it. I don't think George added it to the CD as I think I was planning on making a neater version before sending him it to put on there.

The 4th preamp tube mod I consequently worked out that was mentioned in this thread was pretty much just like the Caswell mod, the only difference is I've been experimenting with using my own cathode values and not the Caswell ones. I don't know what values the Caswell one uses but I've got a good guess it produces a frequency around 800Hz, and in the picture I have of the mod, the cathode bypass cap appears to be 2.2uF (it's hard to make out). Using George's provided RC time constants, that would mean:

1 / (2pi * 0.0000022 x r) = 800Hz (approx)

so working out that r value will give you a resistor value reasonably close to what Caswell used if the value I see in the pic is right. If it works out to 9.4k, he probably used 10k resistors as they are pretty common. If r = 90-100k, it was probably a 100k resistor etc etc. I'll let you guys work that out for yourselves.

Bainzy · Post by **Bainzy** » Sat Jan 14, 2006 7:28 pm

Necrovore wrote:
bmf5150 wrote:
Bainzy wrote:Yeah I put in an extra preamp tube in my 1959slp that with a DPDT switch is totally switchable between plexi and JCM800 spec (and even more gain with another DPDT switch if I used the other half of the extra tube). Sounds great for metal and is an easy mod.
do you have a schematic for this mod,sounds cool!
Yeah this sounds pretty interesting. Is it switchable on the fly?

Totally switchable on the fly. I don't have a schematic, but I've got a modified diagram that I did where I took Dan's 1959 diagram and I added the extra circuitry onto that. The mod totally transforms the amp into a different amp, basically it runs on channel 1 but leaves it stock tonally when taken out. The gain control for the mod is channel 2's volume control, because when using channel 1 you won't be needing that, so by changing the single pot to a dual pot for channel 2's volume, the pot changes it's function when used with the mod but keeps everything stock tonally. It's pretty neat if I don't say so myself

With the mod disengaged the amp looks and sounds normal, with the exception of the DPDT switch I've fitted. However, if you change one of the other pots at the front to one with the same value BUT that has a DPDT push-pull switch in it, you could have the amp 100% stock looking from the outside!

With the mod engaged and the Rk=2.7k, Ck=.68k, mids on 0-5 and G12T-75's, the amp is PERFECT for heavy metal in the vein of Slayer to Megadeth. Bump up the mids more and you're into Dokken territory, 80s hair metal. The sound of the amp still depends on the rest of the stock circuit (I've used it with a 12000 series circuit but it'd be closer to 80s hair metal if you used a '69+ circuit).

I'll refer to the mod as the 'Bainzy Mod' in future so you guys know what I'm talking about. I think it's wired quite differently to the Caswell mod (on that you can't control the gain of the mod stage), so I'll try figure out still what he was doing aswell so you guys can have more options. I've been pretty reluctant to give this mod out as it took tons of research/trial and error/blueprinting/building/testing etc to design, but after seeing the way Mark gets blasted on PP for asking somebody just one component value in their amp, I'd hate to be like them.

Here's a picture of the Caswell mod, interesting to see it uses a Mustard cap for the signal cap for the mod. My guess is that will be a .0022uF because of the way that amp on AFD sounds.

Bainzy · Post by **Bainzy** » Sat Jan 14, 2006 7:31 pm

Here's a clip of the 'Bainzy mod' doing lead guitar, back when my amp had the stock Marshall RI OT, Mallory 150's, awful stock Marshall chinese preamp tubes and was running all G12T-75's. Oh, and it's on triode mode.

http://www.bareknucklepickups.co.uk/for ... php?t=2083

The Bainzy mod can be wired up so amp actually acts as a JCM800 when engaged, and remains a plexi 100% when disengaged. I'd have to do a separate diagram for that as volume for channel 2 would thus act as a preamp master - although it'd be interesting to hear how a JCM800 would sound if both gain stages had gain controls.

One cool thing about the Bainzy mod is you can add it again and again and again to get as many gain stages (2 for each extra tube you add) as you want if you use 470k resistors instead of a gain control and you can still revert it all back to a stock plexi if you flick all the switches off. The only problem you might run into is noise issues without enough lead dress detail, so if you're adding 2 or more stages I'd recommend heavily insulating the wires you add (and some stock ones too).

I'll be up for fitting this mod to people's amps for you if you're in the UK later on this year. For the tube for the mod I'd recommend a JJ ECC83S, that's what I used to prototype the mod.

594Life · Post by **594Life** » Sat Jan 14, 2006 10:06 pm

Brainzy that's awesome! I've wanted to do the Caswell mod but didn't want to pay the $400.00 for it. I'm really interested in doing the mod, especially with the push/pull volume pot method. Do you have a layout for it?

Flames1950 · Post by **Flames1950** » Sat Jan 14, 2006 11:17 pm

VelvetGeorge wrote:I feel the same way. Maybe if I printed Superlead on the panels or made a Metropoulos script logo in white plastic. Obvious stuff.

I'm surprised you're getting away with the "JTM45" designation on those panels, as well as the "Super Amplifier" on the JTM45/100 clones panels........I thought that would get you noticed in a quick way for sure.........but at least there are so many precedents for selling the general styling that I think you're safe. Not only Blockhead, Germino, et al. but old amps like HiWatt and Sound City are very close in cosmetic styling as well......

Bainzy · Post by **Bainzy** » Sun Jan 15, 2006 11:05 am

594Life wrote:Brainzy that's awesome! I've wanted to do the Caswell mod but didn't want to pay the $400.00 for it. I'm really interested in doing the mod, especially with the push/pull volume pot method. Do you have a layout for it?

Yep PM me your email address and I'll send a Bainzy mod diagram to that address. I didn't know he was actually doing them yet, $400 seems pretty damn steep for what the mod consists of (even if he's added effects loops n stuff).

Billy Batz · Post by **Billy Batz** » Sun Jan 15, 2006 12:20 pm

Flames1950 wrote:I mean, I have a lotta fun with the 100-watters I've built but the fact is: THEY'RE TOO LOUD FOR MOST GIGS. At least that most guys are playing. My Weber MASS can only run in parallel with a cab since it can't handle either of the 100's on its own, which means at best 3dB of reduction in volume. I guess there's ******'s trick of simply turning your cab to face the back wall........even with my fifty's I had to shoot at the side wall most gigs........

Correct me if Im wrong but couldnt you safely attenuate your 100W down in the -12db range without dissapating more then its max rating? You just couldnt attenuate all the way down to load.

Flames1950 · Post by **Flames1950** » Sun Jan 15, 2006 3:13 pm

Billy Batz wrote:
Flames1950 wrote:I mean, I have a lotta fun with the 100-watters I've built but the fact is: THEY'RE TOO LOUD FOR MOST GIGS. At least that most guys are playing. My Weber MASS can only run in parallel with a cab since it can't handle either of the 100's on its own, which means at best 3dB of reduction in volume. I guess there's ******'s trick of simply turning your cab to face the back wall........even with my fifty's I had to shoot at the side wall most gigs........
Correct me if Im wrong but couldnt you safely attenuate your 100W down in the -12db range without dissapating more then its max rating? You just couldnt attenuate all the way down to load.

I wouldn't try it with my MASS, it's gotten hot enough to smell really bad before as a parallel load.........the Power Brake I used to have could only get to about -6dB before the tone absolutely stunk the room up.......maybe the HotPlate would do that better, but I'm not buying one right now.......

joshwilson3 · Post by **joshwilson3** » Sun Jan 15, 2006 6:07 pm

Bainzy,

What do you think of this mod with a 100w Master Volume?

Does this mod add resistors and/or caps to the circuit?

I know a tube has two gain stages. Do you think using both sides of the tube would be too much for a 100w Master Volume? Cause I remember you talking about having two switches, one turned the extra tube on, and the other switch turned on both sides of the tube.

Billy Batz · Post by **Billy Batz** » Sun Jan 15, 2006 6:10 pm

joshwilson3 wrote: I know a tube has two gain stages. Do you think using both sides of the tube would be too much for a 100w Master Volume? Cause I remember you talking about having two switches, one turned the extra tube on, and the other switch turned on both sides of the tube.

You can add as many tubes as you want provided you adjust the circuitry correctly. But to keep the stock circuitry as is and add that much gain without having issues its going to be tough.

joshwilson3 · Post by **joshwilson3** » Mon Jan 16, 2006 1:21 am

Billy Batz wrote:
joshwilson3 wrote: I know a tube has two gain stages. Do you think using both sides of the tube would be too much for a 100w Master Volume? Cause I remember you talking about having two switches, one turned the extra tube on, and the other switch turned on both sides of the tube.
You can add as many tubes as you want provided you adjust the circuitry correctly. But to keep the stock circuitry as is and add that much gain without having issues its going to be tough.

What would you change in the circuit?

Do you think more than 4 gain stages would be needed?

Billy Batz · Post by **Billy Batz** » Mon Jan 16, 2006 1:41 am

It may not be but your adding a lot of gain before a 2203 preamp and you have a limited amount of the circuit you can modify to make it work if you want to keep the other part of the amp stock. What I would change is what I would have to to get the sound I want and have it work without oscillation and noise. Im just saying if you want it switchable so that the rest of the 2203 is stock when off, then your limited to just modifying the added stages to get what you want and make it work which is potentially difficult. Just a general assesment. I havent done much 2203 modding. Brentsp has but he doesnt post anymore. Larry has but maybe he doesnt want to give away any secrets

joshwilson3 · Post by **joshwilson3** » Mon Jan 16, 2006 3:10 am

Billy Batz wrote:It may not be but your adding a lot of gain before a 2203 preamp and you have a limited amount of the circuit you can modify to make it work if you want to keep the other part of the amp stock. What I would change is what I would have to to get the sound I want and have it work without oscillation and noise. Im just saying if you want it switchable so that the rest of the 2203 is stock when off, then your limited to just modifying the added stages to get what you want and make it work which is potentially difficult. Just a general assesment. I havent done much 2203 modding. Brentsp has but he doesnt post anymore. Larry has but maybe he doesnt want to give away any secrets

Have you looked at the Bainzy mod? I'll have to have him send me a diagram. But I figure it would work for a 2203 as well as a 1959.