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

[Jorn218]

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.

It is. the only real problem is in rehearsal where I have to put the amp on standby to carry on a conversation. This just started right after I switched pots. Maybe a preamp tube is going south. Ill check that first.

 

[JCDenton6]

When I switched out all of my pots I used the same pots that were used in the 2 channel amps.
I haven't had a noise issue, same noise levels as before the mods.

It might just be preamp tubes as was stated earlier.
This is rather odd though, if it's not the tubes, can you obtain the same pots that mesa uses in the 3 channel heads? I'd give that a shot if you can't isolate the problem.

 

[Anonymous]

It is. the only real problem is in rehearsal where I have to put the amp on standby to carry on a conversation. This just started right after I switched pots. Maybe a preamp tube is going south. Ill check that first.

You get noise in all channels?

 

[Jorn218]

It is. the only real problem is in rehearsal where I have to put the amp on standby to carry on a conversation. This just started right after I switched pots. Maybe a preamp tube is going south. Ill check that first.

You get noise in all channels?

Im thinking I get some in all channels progressively more from green to red. Ill have to wait til tonight to check as the amp is at my rehearzal room. If he doesnt work tonight... Else ill find out tomorrow

 

[2CDR]

i removed c12 and added a 1m pot to the red and a 500k to the orange in my 98rev G dual, and i have to say........WOW
its a massive improvement in tone..and no boost pedal required.gain on red now sits somewhere between 9 and 10 oclock.
i should mention that the clean channel got better,i mean alot better.no idea how or why but its a really nice usable clean tone.
could it have something to do with the cap{green in my amp}that sits on the pot being removed? it broke while i was desoldering it.
what are those caps on the gain pots for anyway?
this amp i have used to belong to gear monkey and then vic from this board.i picked it up about three years ago now and have been very happy with it,but now im in love with it.
thank you to the guys who took time to show people how to do this mod and provide usefull info on these great amps. :mrgreen:

 

[JCDenton6]

@ 2CDR

Glad this worked for you, it's a great change that still makes me smile when I plug in.
The caps on the gain pots add extra brightness into the signal.

 

[2CDR]

i have a reborn as well,and honestly i dont think ill bother plugging back into it.my revG IS the mesa tone i have always had in my head now the mod has been done! :mrgreen:

i forgot to ask,what does/did C12 do to the tone before removal? and would there be even more tone improvements if i just did the jumps and not actually replacing some of the mentioned caps?

 

[JCDenton6]

C12 cut off some of the highs/high mids a bit to help prevent oscillations from occurring, but it's been verified that it can be removed with no harm to the amp, and adding some cut and tightness.
If you go ahead and change c55 to a .0047uf, remove and jump those (3) 47k resistors and and jump LDR 4 you will get the tone of a Rev D which is even tighter and more aggressive than you tone now.
IF you want to go all the way (Rev C) change your presence pots to 250k, brightening and tightening the amp further.

Those resistors and LDRs helped to form a better clean by reducing the gain in the preamp, but also took away from the high gain.
This might diminish the tone of your cleans a bit as the removal of said resistors and 1 LDR allow the full level of gain the circuit can provide to run through the preamp, but I saw you were using a 500k pot there so it might only have a slight impact.
I used a 1meg pot there and it's super loud so I have to really back off of the gain to keep it clean and cut back on volume.

 

[2CDR]

hmm interesting.
i really love the clean tone i have now.as i said before i cant explain how or why but the clean improved 100% after changing to the 500k pot and removing that cap from said pot?
the clean is fantastic with passives, actives there is still a touch of dirty in the clean but roll the guitars vol down a touch and its just as good.add a chorus pedal and it reminds me of a JC120.
i mite{for now} just do the jump mods and see how it goes.

 

[Shemham]

The more I read this thread, the more I get intrigued to try this on my Reborn head. Perhaps not on full scale, but rather switching the gain pots to 500k ohm for red and orange channels and removing the 100ohm resistors from the cathodes.

How much do you lose of the recto character if any? And how does it work for leads?

 

[Anonymous]

The more I read this thread, the more I get intrigued to try this on my Reborn head. Perhaps not on full scale, but rather switching the gain pots to 500k ohm for red and orange channels and removing the 100ohm resistors from the cathodes.

How much do you lose of the recto character if any? And how does it work for leads?

I'd bet that would sound great.

It works similarly to a boost, but a little better. There's stronger mids, it seems, and is noticeably tighter. I would say it sounds almost exactly the same, but when you play its character is a little different.

Leads are much improved IMO. Again, sound doesn't chance much, but it's easier to play.

 

[2CDR]

^^^^^^^^^^ THIS!!!!

 

[Shemham]

Thanks guys! That's the push I needed.

I'll mod the amp and post the results (perhaps with a clip or two) afterwards.

 

[Jorn218]

It is. the only real problem is in rehearsal where I have to put the amp on standby to carry on a conversation. This just started right after I switched pots. Maybe a preamp tube is going south. Ill check that first.

You get noise in all channels?

Sorry for not posting this earlier, but life gets in the way....

Wednesday night @ rehearsal...... noise got real bad. so much so that my drummer stopped playing and went over and started moving knobs around to try and help locate problem while I was playing.

The noise is directly connected to the Effects Loop pots. Messing with the send and return pots decreased or increased the white noise. I usually have nothing connected to the loop, but turn up the controls a bit for some added push. I am thinking now V4 is the culprit and is going south, hence all the white noise. I'll try using the NS2 in the loop tomorrow, but need to pick up some patch cables today. I have a bunch of 12ax7s that Ill bring and see if changing out V4 helps.

I am correct about V4 being for the effects loop correct? V5 is phase inverter?

 

[JCDenton6]

Yes, V4 is for the effects loop and V5 is the PI.

 

[Shemham]

Just jumped the 100 ohm resistors on all the cathodes on my Reborn Dual Recto. Frankly I wasn't expecting that much difference, but **** I'm actually really impressed!

I feel like there's more mid growl present. The sound is overall more organic. The attack became more urgent and the amp really feels more easier to play. Even the clean channel benefited in the same way.

Definately going to keep it this way. Now it's more like Reborn pre-500-head.

I'm still going to install the 500k gain pots later just for kicks.

 

[2CDR]

is C55 the one circled in the TheMagicEights pic in his original post?
any ideas what would happen to the tone[or the amp] if that was just removed and not replaced or just jumped?

 

[Anonymous]

is C55 the one circled in the TheMagicEights pic in his original post?
any ideas what would happen to the tone[or the amp] if that was just removed and not replaced or just jumped?

Do NOT jump the original cap! Removing without replacing is okay (assuming it's the same cap; I don't have a Reborn schematic), but jumping that WILL fry something.

 

[2CDR]

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.

 

[Anonymous]

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.