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

[Jorn218]

Well isolated my noise problem. Can we say ground loop children? I feel like a dunce for not figuring it out earlier. Im getting a ground loop between my pedalboard and the amp. I wasnt hearing the hum due to the gain of the amp. It was coming across as white noise.
Figured it out by trying to isolate which gain stage the noise was coming from and when i removed the pedalboard the noise went away. Plugged pedalboard back in noise came back. moved board power to seaparate circuit no noise. at least i found the problem.

 

[kramerxxx]

JCDenton6

What caps do you put on the gain pots?

What value, and ceramic or metal film?

 

[Third Age Amps]

Depends on the tone you want. I always use film caps in the signal path, but I like a pretty even EQ spectrum. Ceramic is supposed to be a bit brighter or metallic. You can't go wrong with Orange Drops.

While you're at it, change the tantalum cathode bypass caps (little yellow arrow looking ones) to film as well. It definitely helps tighten up the tone.

 

[Third Age Amps]

While I'm at it, I'll be completing the Pre500 mod this week on my RevG, and changing pickups in the Les Paul so I'll get a recording done soon!

 

[JCDenton6]

@ kramerxxx, they are 1uf ceramic caps stock

@ Third Age Amps, I can't wait to see the outcome.

Still can't believe how how many pages this topic spans :shock:

 

[2CDR]

its great to see this topic keep going.lots of great info and help to get an already fantastic sounding amp sounding even better.
Credit to the guys who have helped and provided the info.

 

[kramerxxx]

Depends on the tone you want. I always use film caps in the signal path, but I like a pretty even EQ spectrum. Ceramic is supposed to be a bit brighter or metallic. You can't go wrong with Orange Drops.

While you're at it, change the tantalum cathode bypass caps (little yellow arrow looking ones) to film as well. It definitely helps tighten up the tone.

2 questions:

What does increasing the value of the cap do for the tone? Higher value, Brighter?

Are the Tantalum Cathode bypass caps the ones on the tube sockets that were referred to earlier in the thread?

 

[kramerxxx]

I'm ordering 500k Audio Bourns pots from AmplifiedParts this morning for the Gain pot replacements and 250k for the Presence pots.

I have a 2006 3ch Dual Rec.
No one has brought this up but will it help Clean channel to do the Gain and Presence pots as well? If it were brighter, more sparkley I'd be happier with it.

Any other recommendations this morning before I place my order?

thanks to all that posted,.

Steve

 

[kramerxxx]

this is in my revG,not a reborn[i suspect its in every recto].your first post you have a gut shot with the one circled in yellow.c55?
what is it for?would removing it all together change the tone.

Should be C55, but I'm just going off the schematic.

I learned a while back that it actually doesn't remove high end at all. In fact, it's supposed to simulate better supply caps for high frequencies. Honestly, I can't hear one bit of difference with or without it. Much bigger differences to be had in changing the gain pot, removing cathode resistors (3ch models), and increasing the presence pot value.

If you had to choose, would you try 1m or 500k gain pots for a 3ch? I'm trying for a cross between a Mark series, (*for better leads), and Recitifier, for the tones of the amp. I can get close with an EQ in the loop and a TS8 out front, but prefer the general tone with the Loop/Master bypassed. If going with 1m Gain Pots, 250k Presence pots and a few small cap changes will get me there, I'm all in... I just need to figure out what to order, and where the components are for changing. thx

 

[kramerxxx]

OK, one last question.


I put linear pots in my guitars because I like the gradual increase in volume. Does that work the same for these Gain Pots? Or should I be ordering Audio taper? Does it matter? AmplifiedParts only have a single 1M linear Pot making me believe Audio is the way to go for this. What do you guys think?

 

[2CDR]

i found 250k[presence] to be much too bright for me in my revG.

 

[kramerxxx]

if the 250k was too bright, what did you go with?

Could you trade used a cap to filter some of the highs?

I'm looking for more mids//high mids

 

[Anonymous]

If you had to choose, would you try 1m or 500k gain pots for a 3ch? I'm trying for a cross between a Mark series, (*for better leads), and Recitifier, for the tones of the amp. I can get close with an EQ in the loop and a TS8 out front, but prefer the general tone with the Loop/Master bypassed. If going with 1m Gain Pots, 250k Presence pots and a few small cap changes will get me there, I'm all in... I just need to figure out what to order, and where the components are for changing. thx

What you're describing (Mark crossed with Rectifier) sounds pretty much exactly like a SLO to me.

If you want to stick with the Rectifier, I'd go for a 1M gain pot in channel 3 and 500k in channel 2. This will give you a bit of variety, and should work well with how the Rectifier is set up already. Either channel, but in particular channel 2, should be very nice for leads.

250k presence pot just extends the range of your presence control; no tone change. Only do this if you use the presence control on 10 and still find it too dark, and even then, only do it with channel 3.

Can you read schematics at all? If you can, buy two 10uF / 450V electrolytic caps and put them in parallel with the D and E power rail supply caps. You'll notice a bigger, bolder tone (this is the big difference between 2 and 3 channel models).

I put linear pots in my guitars because I like the gradual increase in volume. Does that work the same for these Gain Pots? Or should I be ordering Audio taper? Does it matter? AmplifiedParts only have a single 1M linear Pot making me believe Audio is the way to go for this. What do you guys think?

The point of audio taper is to hear a gradual increase in volume. Linear taper doesn't match our ears' curve for how loud we hear things, hence the logarithmic taper of audio pots is used. Not sure if maybe linear taper pots work better for your setup or why they would sound more gradual than audio, but the opposite is supposed to be true.

Anyway, I'd go for audio taper. That's what's used in most amps for gain.

 

[Third Age Amps]

2 questions:

What does increasing the value of the cap do for the tone? Higher value, Brighter?

Are the Tantalum Cathode bypass caps the ones on the tube sockets that were referred to earlier in the thread?

In most situations the larger the value of capacitor, the more of the EQ spectrum is passed. So a 500p will pass almost exclusively highs or treble and a .001u will allow some mids and high-mids to pass as well. Same goes for cathode bypass caps. A 1u cap will allow much more low end than a .47u cap. And reducing that value will make your amp sound less mushy, more chunky and present. It's not the same as turning down the bass pot, it's shifting the frequencies that are allowed into the signal path. I prefer using .47u Mallory 150M caps in the first two cathode positions to minimize the low end that is being introduced into the signal at that stage. Since the low end is introduced later it gives the effect of having a distorted tone in the mid and upper EQ spectrum, while the low end remains cleaner and tighter.

And yes, the Tantalum caps are the yellow ones in the middle of the sockets.

 

[2CDR]

Guys,can one of you please help a mesa brother out.
I need a pic of the gain pots{older 2 channel} and the caps that go on them.im not sure i soldered them back on the right arms of the pots.i have looked at some of the gut shots posted but there not clear and in some cases cant see the gain pots properly.
A quick run down,i changed the orange gain to a 500k{love the tone by the way}
changed the red to a 1M{very impressed} and removed c12. massive change in tone.
yesterday my curiosity got the better of me so i swapped out the 1M for another 500k.
well the whole amp sounds like poo again,almost as if nothing had been changed.i did nothing else other than above,but the whole tone it had is gone.need to turn both gains up over half to get a good sound again.
im wondering if i may have put the caps on the gain pots in the wrong place.i should have done a diagram ,i normally do but for this i did not.i plan to put the 1M pot back in on the red channel to see if the tone it had comes back.failing that i have no idea what i have done.

 

[Anonymous]

im wondering if i may have put the caps on the gain pots in the wrong place.i should have done a diagram ,i normally do but for this i did not.i plan to put the 1M pot back in on the red channel to see if the tone it had comes back.failing that i have no idea what i have done.

Sorry, don't have a gutshot, but just try putting the cap the other way. Should be jumped between the middle and an outer leg.

 

[Third Age Amps]

Looking at the pot in the chassis it should be on the center (2) and right (1) tabs. If you go center (2) and left (3), it acts as a treble bleed. Oddly enough the pots are numbered backwards, 3-2-1 looking at them from right to left mounted in the chassis.

 

[JCDenton6]

Cap goes on the same way for both pots.

 

[2CDR]

Thanks Guys,Much Appreciated

 

[rpurdue]

What can be done on a 3 channel dual just to increase the upper mids a little. I'm happy with the gain where it is. I'd just like to open it up a little i guess. Thanks in advance!