Difference in the sound between different power amps in if it is not over driven.

[Alan0354]

I just build the JCM800 2204 front end into my Bassman. My question is how much the difference in sound compare to the real 2204 IF I am not driving the power amp into distortion. I know the power amp make a difference in sound when drive very hard. But how about the sound when I only have the amp up to 4 or 5 before the power amp clips?

[big_teee]

Is your 2204 front end the cascade version, where you are using both V1 stages at the same time?
I''ve built a couple of them, one with EL34s, and one with 6L6s.
The biggest tone factor IMO is the size of bypass Caps, and the Caps used between the PI, and power tubes.
I always try to split the difference between the marshall and bassman tone.
Both the 6L6 version and the EL34 version sound similar.
I just recently took out the 500v PT, from the EL34 version, and put one in that is about 405-415v, and that made more difference in tone than I thought it would.
Also another thing, does your bassman circuit, have the CF, or the later version without the CF?
GL,
T

[Alan0354]

Is your 2204 front end the cascade version, where you are using both V1 stages at the same time?
I''ve built a couple of them, one with EL34s, and one with 6L6s.
The biggest tone factor IMO is the size of bypass Caps, and the Caps used between the PI, and power tubes.
I always try to split the difference between the marshall and bassman tone.
Both the 6L6 version and the EL34 version sound similar.
I just recently took out the 500v PT, from the EL34 version, and put one in that is about 405-415v, and that made more difference in tone than I thought it would.
Also another thing, does your bassman circuit, have the CF, or the later version without the CF?
GL,
T

Thanks for you time.

This is the version I build. I ONLY build the front end. I build the CF stage in also. In fact it is identical all the way to the Master Volume.
http://schems.com/manu/marshall/jcm8...l_50w_2204.pdf

I am running 6V6 with 400 B+ and OT is Bandmaster/Vibrolux made by Classic Tone. The power amp circuit is just standard design with NFB.

[Alan0354]

The front end sounds ok in my amp, very low gain, I can't exactly call it a cascade gain or high gain. It barely distort enough for blues type playing. When I use a clean booster,then I can get enough OD. So far, it sounds ok, not like some people that raving about the 2204. So my first instinct is question the rest of my amp.

The reason I build the front end is because I don't want to spend the money buying the whole amp and just want to check out the characteristics by faking it with the existing platform I have.

[big_teee]

That is the later JCM800 cascade version, and the the one I use.
If the jacks are wired correctly, when plugged into the high side you are cascading the V1a & V1B together, for greater gain.
The earlier JMP master volume version, didn't use the cascade frontend.
I use that circuit, but have it modded quite a bit, to add some bypass caps, and have some different component values I like better.
I will try to mark up a current layout of it.
My version has a little more gain.
T

[Alan0354]

That is the later JCM800 cascade version, and the the one I use.
If the jacks are wired correctly, when plugged into the high side you are cascading the V1a & V1B together, for greater gain.
The earlier JTM master volume version, didn't use the cascade frontend.
I use that circuit, but have it modded quite a bit, to add some bypass caps, and have some different component values I like better.
I will try to mark up a current layout of it.
My version has a little more gain.
T

I would love to see you circuit. Thanks.

I did not put two jacks, I just wire up as cascade stages. But I follow the exact value. I did experiment and I like either using a 1uF bypass cap on the cathode of V1b( parallel with the 10K) or using 2.49K instead to increase the gain some.

[Alan0354]

Is your 2204 front end the cascade version, where you are using both V1 stages at the same time?
I''ve built a couple of them, one with EL34s, and one with 6L6s.
The biggest tone factor IMO is the size of bypass Caps, and the Caps used between the PI, and power tubes.
I always try to split the difference between the marshall and bassman tone.
Both the 6L6 version and the EL34 version sound similar.
I just recently took out the 500v PT, from the EL34 version, and put one in that is about 405-415v, and that made more difference in tone than I thought it would.
Also another thing, does your bassman circuit, have the CF, or the later version without the CF?
GL,
T

1) What do you mean about bypass cap? Is it the filter caps?

2) What specific OT you change that is 410V?