anybody reduce the gain on ch3 on evh 5153 100 watt head?

D

donho

Member
love this beast, but would like to lower the gain on ch 3.
anybody know which resistor controls the gain on ch 3. like to open her up a bit with a bit less compression.
would like it more like ch 2.
r26 affects ch2, so i am thinking maybe r57 or r58 needs to be increased for ch 3.
any thoughts.
thanks
 

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R57 & R58 affect channels 1&2, and increasing their value would increase the gain, not lower it.
I would suggest paralleling another 220k resistor over R82, which is the plate resistor for the first gain stage of the red channel. This will give you an effective 110k at the plate of v1A and will reduce the compression and gain at that stage. Another non-invasive mod would be to try a 5751 in V6, V5,or V4. Try to find the spot that changes the tone the least.
 
fusedbrain":3cvowaef said:
R57 & R58 affect channels 1&2, and increasing their value would increase the gain, not lower it.
I would suggest paralleling another 220k resistor over R82, which is the plate resistor for the first gain stage of the red channel. This will give you an effective 110k at the plate of v1A and will reduce the compression and gain at that stage. Another non-invasive mod would be to try a 5751 in V6, V5,or V4. Try to find the spot that changes the tone the least.
Click to expand...

yes your correct. sorry too many schematics. lol
thanks
 
A couple more things you could try that are do-able from the top of the board would be to parallel a 1 meg over r29 to make 500k and / or a 1 meg over r63 to make approx. 450k. This will dump more signal to ground at these locations, and you can try it with jumpers from the top of the board to see how it sounds.
 
thanks. gonna try these.
i always thought lower values increased gain?
these only affect ch 3 correct? how about r82 only ch 3?
thanks again
 
Yes, all these tweaks I've suggested only affect ch 3.
R29 & R63 are connected at one end to ground, so in this case lowering the value will send more signal to ground and less to the next gain stage. Changing the values of R29 & R63 MAY affect the tone slightly, but it might get you where you want to go gain-wise. I would do R82 on V1 first because you're reducing compression there too and it might be all you need.

I've played around with the Stealth version to lower the gain and the R82 mod + a 5751 in V4 worked well. In the Stealth they also added another cathode bypass cap on the top of the board at R37 for even more gain on the Blue channel (the Stealth has just stupid amount of gain) that was easily removed from the top. I would try to do as much as possible from the top of the board because pulling the board out of the chassis looks like it would be a nightmare.

There are some guys that have used a 12au7 instead of a 5751, but I find that the 5751 keeps the tone the closest to a 12ax7.

I ended up putting the Stealth back to stock and selling it because I think the original version is the best overall amp, and I'm currently looking for another one. It's gonna get the R82 mod and I'm going to remove R4, R5 & R6 and replace them with pots for resonance controls like on the Stealth. Boom!! best of both worlds. The Stealth also has a .0047uf bright cap on the blue channel gain pot that is kind of interesting, and could easily be tested with jumpers.
 
paulyc":2efweutj said:
Reduce gain ?! Blasphemy ! Lol
Click to expand...
Yeah the Red channel on the original is a wee bit over the top, but reducing the compression helps a lot to open it up. There's will still be lots of room left on the gain pot for the OP if he needs it.

The blue channel on the original is killer :rock:
I really like the green channel on the original too.

Now the Stealth version.... that's just nuts. If your a gain junkie, that's your amp.
To me it sounded like a mushy, fizzy, gained out mess on both the Blue and Red channels. For me, for that type of sound, a Bogner Twin Jet stomped all over the Stealth, but YMMV.
 
I was just kidding being that we are guitar players and there never seems to be enough gain... at least for some of us.
 
well did the r82 mod. placed a 220k // with original.
tamed ch3 just rite. lessened the compression and reduced the gain just rite. sounds sweet.
give her a better try tomorrow but sounds like a winner so far.
thanks
 
On the original version 100 watt head, there is a 1000pf bright cap on the Red channel gain pot. Nothing on Blue or Green.
The 100S 6L6 version added a 4700pf bright cap on the Blue channel gain pot( it's under the board, so you cant see it if you pull the chassis). Red and Green gain stayed the same as original version.
The issue I had with the 4700pf on the Stealth Blue was that if you kept the gain low, the cap caused the sound to thin out, and if you turned the gain up to about 6-7, the tone thickened up nicely, but the gain and compression was too much.
I think a 4700pf on the Blue channel of the original version might be cool, but you'd have to try it and see what you think.
 
Yeah, lifting the 1000pf on the red channel would make the channel less bright, but I think the overall tone of the Red channel is pretty good the way it is. Remember, the effect of the bright cap is greatly reduced as the gain knob gets above 5-7.
Where are you running the gain on the red channel now that you did the R82 mod??
If you're at 6, I don't think you'll hear much of a difference.

The cap in question is C15 on the schem you posted. I would be careful if you do decide to lift it, and don't do anything that you can't easily put back. As stated in an earlier post, I would not want to have to pull the board to do any fixes. It's do-able, but it looks like it would be a real PITA.
 
I have 50w modded to stealth specs
I slapped a 12au7 in the red channel & it brought the gain down to a perfect spot. I may try one in the blue/green too
Much easier to check out than mods & worth a shot
 
thanks guys.
running my gain on ch3 at 9 oclock. gain on ch 2 around 1100 oclock/ noonish.
i am using active emg pups. probably adds a bit to the gain also.
i may try a lower tube too.

where would a guy put a cap for the bl ch? would a 1000pf be ok. i think that may be a good thing.
i do like the way ch3 cuts.
 
Yeah you could use any value you like, but I thought that the 4700pf on the Stealth sounded pretty good. 1000pf is a Marshall value as well, so it could be OK. B1 & B2 on a Bogner Ecstacy are 1000pf and 4700pf.
The cap would go from the middle lug of the gain pot to whichever outside lug is NOT connected to ground. According to the schematic, the outside lug that you would want to connect to should have a trace that goes to R25.

I mentioned in an earlier post that EVH Fender put the Stealth Blue channel bright cap on the underside of the board. This is probably because the middle lug of the gain pot connects to a relay, and not to a component with visible leads on the topside of the board. You could connect one end of your bright cap to the lead of R25 on the topside of the board, but I'm not sure you're going to be able to make the other connection on the middle leg of the gain pot from the top of the board. I don't have an amp in front of me right now, but looking at a couple of pics on the net, getting at that middle leg on the gain pot is going to be tough.
 
fusedbrain":1qu3w88v said:
Yeah you could use any value you like, but I thought that the 4700pf on the Stealth sounded pretty good. 1000pf is a Marshall value as well, so it could be OK. B1 & B2 on a Bogner Ecstacy are 1000pf and 4700pf.
The cap would go from the middle lug of the gain pot to whichever outside lug is NOT connected to ground. According to the schematic, the outside lug that you would want to connect to should have a trace that goes to R25.

I mentioned in an earlier post that EVH Fender put the Stealth Blue channel bright cap on the underside of the board. This is probably because the middle lug of the gain pot connects to a relay, and not to a component with visible leads on the topside of the board. You could connect one end of your bright cap to the lead of R25 on the topside of the board, but I'm not sure you're going to be able to make the other connection on the middle leg of the gain pot from the top of the board. I don't have an amp in front of me right now, but looking at a couple of pics on the net, getting at that middle leg on the gain pot is going to be tough.
Click to expand...
thanks again.
yah i was just thinking about it.
next time i open her up i will take a closer look. but thats great info!!! :rock:
 
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