Want Pre500 tone? Here's how to get it!

[Jorn218]

Ok, Went out for a little bit to dial in the amp post gain knob swap. I very much like both changes. While yes the 1M pot in ch.3 gets very wooly after 12:00, it is still usable, though not for what I am wanting it for. Right now I have it set to about 11:30 which gives tremolo picking decent compression enough to create the proper smear while still retaining clarity. Curious to hear what the addition of the cap @D rail adds.

500K in ch.2? All I can say is WOW!!!! I still hate what the 25K presence pot does to this channel, but I am starting to wonder what say using a 100K pot with a 25K resistor across it would liven it up a bit while not making it as in your face as ch.3

Changing the tone controls all at noon and diming the mids helps tremendously. Also one thing I noticed was as I turned up to stage volume with this setup, I did not get a mid bump that I got when tones were set how I normally set them at stage volume. The amp just got louder. There was no amp sounds good, then mid bump where up close the amp sounded ok, but great further away. The gain control mods really do open up the amp by themselves. I noticed no parasitic oscillation noise when diming ch.3's gain all the way up, the amp just got really compressed, while this I think would work for rock and regular metal, it won't work for stuff that has a lot of tremolo picking.

Whoever said the mod adds thump, you are correct. While tonally the amp is the same. There is a huge amount of punch in the feel of the amp. I guess the gain pot increases allows the amp to track a little better? I am definitely wanting to hear what she sounds like with my pedal board connected to the signal chain with the noise suppressor before the amp. This is going to be godly once done.

 

[R_ADKINS80]

ok now imagine that....done to a triple rec that has 6550 power tubes biased up in it....there is your godly, right there!!!

 

[Jorn218]

Yeah 6550's would give good headroom.

Another thing I wondered. Does anyone know what Henry the chokes have been through the various revisions? I know in Marshalls using different valued chokes affect the stiffness or looseness of the amp overall. Has anyone researched this? Looking at the schematic for my 3ch. It notes the choke in the power supply section, but does not give the value. Looking at my Marshall schematics, they do not either. In a Marshall a lot of people like a 3H choke for the old non master volume amps vs. a 5H choke which they say starts being too stiff/bright. I wonder if the older amps used greater value chokes and decreased them towards newer revisions, which might be a reason why some say the newer amps sound loose. My Marshall 2203 that I have loaded with KT88's I use a 7H choke which makes the amp very stiff and percussive, which does what I want it to for the music I play.

 

[JCDenton6]

@JCDenton - I will take some more gut shots either tomorrow, or Monday. I have a gig tonight and today is going to be spent tailoring my amp to the pot swaps I have done to get through the show tonight.
Yes I do believe it is the shellac used to cover the transformer windings as you mentioned. I just wondered if this was something I should be concerned about? It is dry, but should the leaking stop, or is this something that will continue?

The shellac used to coat the windings most likely dripped down a little after installation and burn in, I think the transformer is fine.
Another thing that will give you more tightness and clear gain/mid boost is removing the 2m/20pf circuit that's in parallel with the 680k/.002uf right before V1, along with removing and jumping the 100 ohm resistors on the cathodes of V1, V2 and V3.

 

[R_ADKINS80]

@JCDenton - I will take some more gut shots either tomorrow, or Monday. I have a gig tonight and today is going to be spent tailoring my amp to the pot swaps I have done to get through the show tonight.
Yes I do believe it is the shellac used to cover the transformer windings as you mentioned. I just wondered if this was something I should be concerned about? It is dry, but should the leaking stop, or is this something that will continue?

Another thing that will give you more tightness and clear gain/mid boost is removing the 2m/20pf circuit that's in parallel with the 680k/.002uf right before V1, along with removing and jumping the 100k resistors on the cathodes of V1, V2 and V3.

This right here was the happy ending at the massage parlor of tone in my amp. This thing is the most beastly rectifier I have ever heard or had the pleasure to play, and I've played quite a few.

 

[Jorn218]

@JCDenton, I think I will try that before the cap in the D power rail. Thanks guys for all the time and bigtime effort directed towards unlocking these amps. I loved my tone tonight from the little I heard of it. Never fails in this city. FOH always sounds nice. Stage always I mean always sounds like crap. What good are having monitors if the venue isnt using them. Not to mention the soundguy disappeared as soon as we started. Everything was tight until the last song when it unravelled. Oh well march on........ Night, Gent's.


Bjorn

 

[JCDenton6]

I had time last night to swap out my presence pots from the stock values for a Rev G (25k for orange ch and 100k for red ch) to 250k for both...
**** I love the result, more overall brightness and sizzle/openess in the top end while tightening the amp further.

I think 250k pots are correct for Rev C brightness (in theory from experimenting and recording clips to compare with Rev C clips) while you can use 220k pots for Rev D brightness, I think this (250k pots vs 220k pots) was the difference between the 2 revisions since I recall reading that you turn the presence pot up 45 degrees for the Rev D to match the brightness of the Rev C.

 

[R_ADKINS80]

I had time last night to swap out my presence pots from the stock values for a Rev G (25k for orange ch and 100k for red ch) to 250k for both...
**** I love the result, more overall brightness and sizzle/openess in the top end while tightening the amp further.

I think 250k pots are correct for Rev C brightness (in theory from experimenting and recording clips to compare with Rev C clips) while you can use 220k pots for Rev D brightness, I think this (250k pots vs 220k pots) was the difference between the 2 revisions since I recall reading that you turn the presence pot up 45 degrees for the Rev D to match the brightness of the Rev C.

I put the 250k pot in my orange channel of my 3ch triple and it didn't do anything......not a bit of difference.
pretty amazing considering stock was 25k. So much for the channel cloning by switching out the presence pots comment in the manual.

 

[JCDenton6]

That sucks man, I guess the layout/signal path changes in the 3 ch heads maybe account for this :?

 

[R_ADKINS80]

Well, it even states in the 3ch manual that if you like one channel then you can simply swap the presence pot on the other channel and make it sound like the one you like more. I did the red channel presence pot cloning it to the orange channel before and it worked perfect...not so trying to donit the other way around.

 

[Anonymous]

I put the 250k pot in my orange channel of my 3ch triple and it didn't do anything......not a bit of difference.
pretty amazing considering stock was 25k. So much for the channel cloning by switching out the presence pots comment in the manual.

I wouldn't expect it to on Raw or Vintage modes, but what about Modern?

IIRC, when a negative feedback loop is used (as it is on Raw and Vintage and not on Red Modern), a 5k pot is the best value because it gives you a far more even taper than 25k. At least, this holds true for older Marshalls.

 

[R_ADKINS80]

I put the 250k pot in my orange channel of my 3ch triple and it didn't do anything......not a bit of difference.
pretty amazing considering stock was 25k. So much for the channel cloning by switching out the presence pots comment in the manual.

I wouldn't expect it to on Raw or Vintage modes, but what about Modern?

IIRC, when a negative feedback loop is used (as it is on Raw and Vintage and not on Red Modern), a 5k pot is the best value because it gives you a far more even taper than 25k. At least, this holds true for older Marshalls.

I only use modern mode....the presence knob is a "do nothing" knob lol. 250k pot sounds no different than a 25k pot.

 

[Anonymous]

I put the 250k pot in my orange channel of my 3ch triple and it didn't do anything......not a bit of difference.
pretty amazing considering stock was 25k. So much for the channel cloning by switching out the presence pots comment in the manual.

I wouldn't expect it to on Raw or Vintage modes, but what about Modern?

IIRC, when a negative feedback loop is used (as it is on Raw and Vintage and not on Red Modern), a 5k pot is the best value because it gives you a far more even taper than 25k. At least, this holds true for older Marshalls.

I only use modern mode....the presence knob is a "do nothing" knob lol. 250k pot sounds no different than a 25k pot.

Ah....looking at the schematic that makes sense. On ch. 2, you should notice the difference 250k vs 25k in Raw mode only.

 

[APEMAN]

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[Third Age Amps]

The Mark III tranny was used up to somewhere around serial number 2200, so Rev C, D, E and F.

Is there any way to tell a difference between Mark III transformers and the others? I have schumacher transformers in mine, but how to tell if they are regular Recto tranny's or Mark version?

JCDenton - Awesome job on the mods BTW. Are you considering a written tutorial besides the pics/instructions you've posted here?

 

[JCDenton6]

I'm more convinced now that the mark 3 OT's don't influence the tone at all and it's the circuit differences that do, but would need to confirm it with playing my amp next to a rev C to put it to rest (since I'm going off of comparisons)
The PT's are mark 4 PT's as was shown earlier in the thread but they differ from the later version used in the rest of the 2 channel heads, It doesn't quite have as much juice as the later version. The B+ runs about 20 vDC less. They are all schumacher trannies anywho, so there isn't really a drop in the quality of the iron in the 2 channel amps.

I have listened to and compared my clips (playing the same riffs, using the same mic) with those of a fellow boogie board forumites clips (Nikevist1) back and forth and have found they sound identical, but my amp is tighter and perhaps a little bit more aggresive (could be the EL34's or the higher voltage) but I really want to go back to 6L6's, TAD's are what I'm looking at, I miss that 6L6 grind and open top end, and the low mids as well.

@ThirdAgeAmps, I will most likely type out a more in-depth tutorial in the near future and have though about a video as well when I have another 2-channel up for modding.
As for the tranny codes, I don't remember all of them off the top of my head, but there was a thread on the board that had them all listed.

 

[Jorn218]

I'de like to chime in on something brought up earlier regarding the changing of the gain pots. I tried using the 1meg pots in my red and orange channels. While yes, it vastly increases the gain on tap you can send to the preamp, it has also introduced a ton of white noise, that I am finding unacceptable. It is almost as if I have a dimed metalzone on n the background while playing nothing(I am not talking about distortion). I am talking that unending pshhhhhhhhh. I am going to go back to the stock configuration, and find another work around.

I have also stopped boosting my amp since this mod. I guess what I am after now, more than early 2 channel cloning is trying to get the volume matched between the Orange and Red channels. I love the Orange channel for lead tones, but the amount of volume drop between the two channels, is in my humble opinion, unacceptable for this expensive of an amp. I can understand drastic volume changes between channel 1 vs. 2 & 3, but channels 2 & 3, should be identical with a noticeable voicing difference the two. Mesa says that Channel 3 is more aggressive than channel 2, I agree with that, but to me its because channel 3 sounds twice as loud than channel 2.

 

[Anonymous]

I'de like to chime in on something brought up earlier regarding the changing of the gain pots. I tried using the 1meg pots in my red and orange channels. While yes, it vastly increases the gain on tap you can send to the preamp, it has also introduced a ton of white noise, that I am finding unacceptable. It is almost as if I have a dimed metalzone on n the background while playing nothing(I am not talking about distortion). I am talking that unending pshhhhhhhhh. I am going to go back to the stock configuration, and find another work around.

I have also stopped boosting my amp since this mod. I guess what I am after now, more than early 2 channel cloning is trying to get the volume matched between the Orange and Red channels. I love the Orange channel for lead tones, but the amount of volume drop between the two channels, is in my humble opinion, unacceptable for this expensive of an amp. I can understand drastic volume changes between channel 1 vs. 2 & 3, but channels 2 & 3, should be identical with a noticeable voicing difference the two. Mesa says that Channel 3 is more aggressive than channel 2, I agree with that, but to me its because channel 3 sounds twice as loud than channel 2.

Channel 3 doesn't have a negative feedback loop in modern mode, so it's going to be louder. Why not just turn up the channel volume on 2 and 1?

As for the white noise, it's going to be there for any amp with that much gain (Ecstasy, 5150, etc.). You could always put a noise suppressor in the loop.

 

[Jorn218]

Channel 3 doesn't have a negative feedback loop in modern mode, so it's going to be louder. Why not just turn up the channel volume on 2 and 1?

As for the white noise, it's going to be there for any amp with that much gain (Ecstasy, 5150, etc.). You could always put a noise suppressor in the loop.

So channel 2 has neg feedback in the modern mode? I thought only the vintage and raw modes had that. hmmm learn something new every day.

No, the white noise I am talking about is drastic. High gain amps have white noise and is part of the deal... This sounds like a distortion box is on. I would understand this much if the pot were up all the way, but it doesn't matter where in the sweep it is. It is not a Mesa pot, but actually a CTS, so the construction of the pot is better(shaft is metal vs. plastic), it isn't bad solder joints. I have never had an anomaly like this from modding amps. Are the Mesa pots internally shielded?

Explain using a noise suppressor in the loop please? Can I use my NS2 directly in the loop? I don't have enough cables right now to try that 4 wire method.

 

[Anonymous]

So channel 2 has neg feedback in the modern mode? I thought only the vintage and raw modes had that. hmmm learn something new every day.

I would assume so because you're implying a volume drop from 2 modern to 3 modern? I don't see anything else in the schematic that could cause a volume drop.

No, the white noise I am talking about is drastic. High gain amps have white noise and is part of the deal... This sounds like a distortion box is on. I would understand this much if the pot were up all the way, but it doesn't matter where in the sweep it is. It is not a Mesa pot, but actually a CTS, so the construction of the pot is better(shaft is metal vs. plastic), it isn't bad solder joints. I have never had an anomaly like this from modding amps. Are the Mesa pots internally shielded?

More than a 5150?? Something is wrong. I get noise but not as much as a 5150, and the pot I'm using is nothing special.

Explain using a noise suppressor in the loop please? Can I use my NS2 directly in the loop? I don't have enough cables right now to try that 4 wire method.

Just hook it up through your FX loop. I'd imagine it would work in parallel, but it'd probably be better in series. As long as your guitar is louder than the noise, you're good to go.