Increasing gain at Mixer Circuit?

Marshall Amp Discussion

Moderators: pompeiisneaks, Colossal

Post Reply
fusionbear
Posts: 478
Joined: Thu Nov 01, 2007 4:42 am
Location: Southern California

Increasing gain at Mixer Circuit?

Post by fusionbear »

Just curious if any of you have played with increasing the 470k to ground on the mixer circuit and the effects of doing so....

It seems like an easy way to increase gain. As you increase the value of the 470k resistor to say to 560k, or even 680k, will it cause blocking distortion in V2?

Thanks!
Learning to learn...
User avatar
xtian
Posts: 6990
Joined: Mon Apr 19, 2010 8:15 pm
Location: NorCal
Contact:

Re: Increasing gain at Mixer Circuit?

Post by xtian »

Have you run out of amps to experiment on, Carl?!?
I build and repair tube amps. http://amps.monkeymatic.com
Roe
Posts: 1643
Joined: Thu May 31, 2007 2:10 pm

Re: Increasing gain at Mixer Circuit?

Post by Roe »

it's dead easy but you will need to adjust the cap to keep roughly the same mid response (though it will change some). Before you do any modding, just turn the normal channel volume to 7, this will increase the gain notisably
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
Stevem
Posts: 4551
Joined: Fri Jan 24, 2014 3:01 pm
Location: 1/3rd the way out one of the arms of the Milkyway.

D

Post by Stevem »

From Euro tubes order yourself up a 12ax7 that tests out at a strong 1ma to the design spec for a 12ax7 of 1.2ma and you will not have to change out parts to have more gain , you then will also have a great tube to hear the effects of such with the cathode follower driving the tone stack!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
fusionbear
Posts: 478
Joined: Thu Nov 01, 2007 4:42 am
Location: Southern California

Re: Increasing gain at Mixer Circuit?

Post by fusionbear »

Thanks guys. I should have noted that I was referring to the 2203 circuit.... Doh! That would have given better context.... I ended up just using a 560k to ground at the mixer. I have a 1uf attenuated with a 1.2k across a 5.6k in the second stage. The first stage is stock. I have a 1uf across the 820 of V2a. PI couplers are .047. Rest is stock. This is a beastly 2203 build that someone commissioned from me. Using 7025 Chinese on V1, 12AX7B on V2, 12AX7E on V3. JJ EL34's (not EL34L's)

http://imgur.com/a/ZccY7
Learning to learn...
fusionbear
Posts: 478
Joined: Thu Nov 01, 2007 4:42 am
Location: Southern California

Re: Increasing gain at Mixer Circuit?

Post by fusionbear »

Learning to learn...
Roe
Posts: 1643
Joined: Thu May 31, 2007 2:10 pm

Re: Increasing gain at Mixer Circuit?

Post by Roe »

an old trick with the four input amps is to turn up the volume of the channel you are not using to 7. This will give more gain, since the voltage divider of the channel mixer circuit changes from 470k/470k to ca. 470k/1M
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
Travis_HY
Posts: 63
Joined: Thu Aug 13, 2009 3:18 am

Re: Increasing gain at Mixer Circuit?

Post by Travis_HY »

I've used a 1meg to ground and a 330k/500pf and that is a cool sound. I don't remember ever having problems with stability.

If you do have problems, just add a 10pf from the output of the mixer network to ground. That usually stabilizes anything after the volume pots. Or you can omit the 500pf for a different flavor.
"Genius manifests itself. You got a hammer. You either build a Cathedral or you build a shithouse." - Carl Schroeder
User avatar
jelle
Posts: 2372
Joined: Sat Feb 04, 2006 7:55 pm
Location: New Jersey

Re: Increasing gain at Mixer Circuit?

Post by jelle »

Roe wrote:an old trick with the four input amps is to turn up the volume of the channel you are not using to 7. This will give more gain, since the voltage divider of the channel mixer circuit changes from 470k/470k to ca. 470k/1M
heh, I do that too, never heard of others doing that. :D
Post Reply