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

[R_ADKINS80]

nevermind....i'm stupid lol

 

[R_ADKINS80]

It would make mine clise to that even though it's a 3ch and yours is a 2ch?

The cathodes on 3ch Rectifiers have 100 ohm resistors (think that's what you meant) to simulate the LDRs. I'd remove and jump them. The 2M || 82pF circuit is not something you should change if you're strictly looking for Pre500 tone. If you want to mod further, then sure, but otherwise this circuit is equivalent.

I found the resistors.....but the color code on them is brn-blk-blk-blk-brn......pretty sure that is a ten ohm color code.....wtf? my amp had 100k gain pots and now 10 ohm cathode resistors when the schematic says 250k and 100....it's like my amp was built last on a thursday afternoon by a guy ready to start a weekend of binge drinking.

 

[Anonymous]

I found the resistors.....but the color code on them is brn-blk-blk-blk-brn......pretty sure that is a ten ohm color code.....wtf? my amp had 100k gain pots and now 10 ohm cathode resistors when the schematic says 250k and 100....it's like my amp was built last on a thursday afternoon by a guy ready to start a weekend of binge drinking.

Hmm...are you sure one of those brown stripes isn't actually gold? One of them should be a tolerance, which makes that correct for 100 ohms.

 

[R_ADKINS80]

no they were 100.....i tried it, definately made it sound more vintage....didn't really like it....seemed to cut down on the gain and lost clarity to my ears. going to put those resistors back in.

 

[R_ADKINS80]

Do you have a hi res gut shot photo? I might be able to point it out...

Ha, you read my mind. :lol:

You can also remove the 82pf cap and then remove and jump the 2m resistor below that 82pf cap near V1A and replace the 680k resistor with a 470k below that.
You can also remove and jump the 100k resistors on all the cathodes, this is what I did to my Triple and I think it would make your Triple nearly identical in tone to mine, if not exact.

I wish I had been able to record better clips while I was borrowing the SM57... I didn't have the chance to really crank it, it doesn't do my amp justice at all., it sounds much better in the room

what does removing that 82pf cap and swapping that resistor do?

 

[Anonymous]

no they were 100.....i tried it, definately made it sound more vintage....didn't really like it....seemed to cut down on the gain and lost clarity to my ears. going to put those resistors back in.

Wait, did you jump them, or just remove?

 

[R_ADKINS80]

no they were 100.....i tried it, definately made it sound more vintage....didn't really like it....seemed to cut down on the gain and lost clarity to my ears. going to put those resistors back in.

Wait, did you jump them, or just remove?

I jumped them.

 

[JCDenton6]

Swapping the 680k for a 470k cuts back on some of the total resistance, the 470k was used in the Rev C/D amps and removing the 82pf cap jumping the 2m resistor below it seemed to give the amp even more attack and crunch.

 

[R_ADKINS80]

Swapping the 680k for a 470k cuts back on some of the total resistance, the 470k was used in the Rev C/D amps and removing the 82pf cap jumping the 2m resistor below it seemed to give the amp even more attack and crunch.

ooooooh that sounds like it would be right up my alley. after some tweaking i do really like those two 100 ohm resistors jumped......i am thinking about putting them back in a putting a mini switch in parallel to make this mod switchable....along with that cap i removed....so i can have 2ch and 3ch tones in one head whenever i want i can switch on the fly.

 

[R_ADKINS80]

Found the 82pf cap and 2.2M resistor....clipped the cap and heating up the solder iron as we speak. I love modding stuff!!! It really give a player a chance to make his gear his own, ya know. To have something different than everyone else that just goes to the store and buys an amp to just play it as is.

 

[JCDenton6]

no they were 100.....i tried it, definately made it sound more vintage....didn't really like it....seemed to cut down on the gain and lost clarity to my ears. going to put those resistors back in.

You should've gotten more gain and clarity. :?
Crazy, guess there are more differences between the 2 ch and 3 ch amps then I had originally imagined.

I hear you on modding and tweaking amps though, I really like this configuration, I couldn't go back to the stock Rev G setup.
I wish you guys could hear my amp in person, makes me want to break stuff, might have the same effect on you :twisted:

 

[Anonymous]

ooooooh that sounds like it would be right up my alley. after some tweaking i do really like those two 100 ohm resistors jumped......i am thinking about putting them back in a putting a mini switch in parallel to make this mod switchable....along with that cap i removed....so i can have 2ch and 3ch tones in one head whenever i want i can switch on the fly.

That's a cool idea! Sometimes it's tough because the differences are pretty subtle in these circuits. I get the impression that most players want a big change when they flip a switch, but really, small changes are sometimes all that's necessary to get a different vibe. That's what I tend to like in my amps, at least.

Swapping the 680k for a 470k cuts back on some of the total resistance, the 470k was used in the Rev C/D amps and removing the 82pf cap jumping the 2m resistor below it seemed to give the amp even more attack and crunch.

Here's how everything was configured (for clarity's sake).

Pre 500:
Orange clean = totally different circuit
Orange gain = 470k parallel .002uF
Red gain = 470k parallel .002uF

Rev. G:
Orange clean = 2.2M parallel 82pF
Orange gain = 2.2M parallel 82pF parallel 680k parallel .002uF
Red gain = 2.2M parallel 82pF parallel 680k parallel .002uF

Doing the math, you'll see that the stock Rev. G configuration is equivalent to the Pre 500 configuration, 470k parallel .002uF (82pF is insignificant, since this value is well within the .002uF cap's tolerance). So modding that circuit further provides no advantage if you're after Pre 500 tone.

Of course if you should want to get something different, that's another story. However, every high gain amp I've come across has used some sort of tone shaping circuit to prevent everything from getting too mushy, and jumping the 2.2M resistor (or any other component in this stage) will bypass everything. Stock is what I like so far.

 

[R_ADKINS80]

After tweaking the settings extensively i really like these mods and plan on keeping them. Really gunna sit down and draw out how I want to make all these switchable and hide the switches on the back panel. after it's all said and done I will dub this amp the Mesa Boogie 2ch/3ch Triple Rich-Tifier..... after my first name lol.

 

[JCDenton6]

Pre 500:
Orange clean = totally different circuit
Orange gain = 470k parallel .002uF
Red gain = 470k parallel .002uF

Rev. G:
Orange clean = 2.2M parallel 82pF
Orange gain = 2.2M parallel 82pF parallel 680k parallel .002uF
Red gain = 2.2M parallel 82pF parallel 680k parallel .002uF

Doing the math, you'll see that the stock Rev. G configuration is equivalent to the Pre 500 configuration, 470k parallel .002uF (82pF is insignificant, since this value is well within the .002uF cap's tolerance). So modding that circuit further provides no advantage if you're after Pre 500 tone.

Of course if you should want to get something different, that's another story. However, every high gain amp I've come across has used some sort of tone shaping circuit to prevent everything from getting too mushy, and jumping the 2.2M resistor (or any other component in this stage) will bypass everything. Stock is what I like so far.

Ah, I understand this now, sorry if I confused you guys on this.

 

[JCDenton6]

After tweaking the settings extensively i really like these mods and plan on keeping them. Really gunna sit down and draw out how I want to make all these switchable and hide the switches on the back panel. after it's all said and done I will dub this amp the Mesa Boogie 2ch/3ch Triple Rich-Tifier..... after my first name lol.

Sweet, glad it's working out for you.

 

[R_ADKINS80]

Humor me for a moment, if you will. What I have noticed in the clips posted here, and now through my own experience modding my own 3ch head, is that these "pre-500 2ch mods" make this amp have a smoother tone with more growl and crunch with less buzzsaw tone than a stock 3ch. If someone wanted, say, an in between sound you could only remove one cathode resistor or possibly just raise/lower the values to tweak the tone to the player's liking? And also mess with the value of the 20pf cap removed from the v2 section. This theory seems sound enough to really come up with some unique recto circuits able to be tailored infinitely. One could also use small trim pots to make these mods readily adjustable. Just so you know, magiceight and JCDenton, you have created a monster here......audiences beware.

Rich Recto s/n 0001 complete and ready to thoroughly rape your ear holes.

 

[Anonymous]

Humor me for a moment, if you will. What I have noticed in the clips posted here, and now through my own experience modding my own 3ch head, is that these "pre-500 2ch mods" make this amp have a smoother tone with more growl and crunch with less buzzsaw tone than a stock 3ch. If someone wanted, say, an in between sound you could only remove one cathode resistor or possibly just raise/lower the values to tweak the tone to the player's liking? And also mess with the value of the 20pf cap removed from the v2 section. This theory seems sound enough to really come up with some unique recto circuits able to be tailored infinitely. One could also use small trim pots to make these mods readily adjustable. Just so you know, magiceight and JCDenton, you have created a monster here......audiences beware.

Rich Recto s/n 0001 complete and ready to thoroughly rape your ear holes.

:twisted:

I'd say the difference is in the 20pF cap a bit more than the 100 ohm resistors. The thing that gets tough with this stuff is doing it without adding noise or parasitic oscillation. For the cathode resistors, it shouldn't be a big deal, but the cap might be more difficult because of its location at the V2a grid.

As for your questions, absolutely! The possibilities are infinite, as you say, which makes it difficult sometimes when everything is a variable! After spending a lot of time tweaking, it seems more of your tone comes from later stages, where more of your feel comes from the first and second gain stages. If you want an in-between sound, you could use 50 ohm resistors for all three stages, but I think it would sound better to put the 100 resistor back in for V3a and maybe V2a, leaving it out of V1a. This would give you a slightly tighter response earlier on, but with the same tone later.

 

[JCDenton6]

How far did you get with your mods Rich?

 

[msi]

If anyone wants help figuring out what needs to be done to a three channel recto and lives in the Minneapolis area I could help. Of if someone wanted to send me photo's of the area around the tube sockets for V1, V2, and V3 and then do some simple probing to figure out the specifics we can do that as well.

The basic approach is remove three 100 ohm resistors and short the attached capacitor to ground. The 1.8k resistors should be left alone.

 

[Third Age Amps]

This isn't Pre500 tone specific but, if you want to get an interesting mid/high-mid boost in your tone wire a .01uf/600V cap in parallel with R242. You can just hook the leads right under the resistors leads and solder. Even wire a SPST switch in with it to take it back to stock.

It's a basic Treble-Peak circuit but it's farther down the signal chain and adds some neat harmonics and a bit of chime.