advice or suggestions on a amp mod?

[ALBATROS1234]

i have a couple of silvetone r2r amp pulls that i want to use as guitar amps. the first one i just modified the input and added a bypass cap on one of the triodes. this sounds good and i will keep this as is. it is only using one 12ax7 the 6v6 and 6ax5 rectifier but the amps have a second socket which was used as a preamp on the r2r and is not in signal path in playback mode.for the second one i want to make something like a simplified marshall single ended. what i would like control wise is gain,tone and master volume. so far all i have done is add the preamp 12ax7 to the signal path and re-bias it to be similar to a marshall v1. it screams, but its really too much gain .i dont want to do a tmb stack. i was thinking of just one tone as stated above . i  have 2 possible ideas, one with a cathode follower into a tweed vol/tone then the second triode stage into the 6v6. next i was thinking perhaps paralleling the v2 into a tweed vol/tone into the 6v6 below are the schematics i am thinking of trying as well as how it is now with the overwheming gain.was wondering in your opinions which design would be better to reduce searing distortion which sounds good at low volume but is way too intense at louder volumes.also would it be advisable to add negative ffeedback,either set or adjustable(presence control) i am simplifying the schem to just signal path and omitting power supply as i am not changing any of that. thank you gentlmen.

[jjasilli]

The preamp stages are hi gain, with 220k plate resistors, etc.  You can reduce gain with 100k and K resistors to match.   And/or delete K bypass caps. 


And/or put voltage dividers between gain stages; or split plate resistors.


Maybe move the gain pot to before the 1st input stage.  That will tame input signal from the get go.


BTW, the power tube K bypass cap seems too small to make a tonal difference.


The 500k tone pot seems to also serve as the power tube grid leak R.  This is as odd combination of tone & vol.

[ALBATROS1234]

yeah that 4uf did seem small but i keep it for the time being because the amp started off a bit bass heavy and figured the smaller value bypass would be better for that as well as making a smaller impact on overall gain. so do you think i should try the cathode follower or parallel triode version ? thats my main head scratcher at the moment. without the first 12ax7 it sounded good but i wanted to go for a higher gain 5 watt se that sounds marshallish. the first triode is close to a marshall v1 except i didnt have a 2.7k so i used a 2.2k and instead of the .68 uf bypass i used a 1uf . on the second v1 triode marshall uses an 820ohm closest i have is 1k. marshall then goes to the v2a cathode follower into tonestack with a gain recovery v2b. i am gonna just skip the pi obviously and goto the 6v6. with the single tone maybe i dont need the cathode follower thats when i thought of trying the parallel triodes. maybe if i bias them near center at 1.5k or perhaps a 10k cold clipper in one like a jcm 800 but not sure how that works in parallel. also i know marshalls usually use negative feedback but i have never used negative feedback on anything yet.i guess i will just go to trial and error and see what happens. i was just wondering which direction would make most sense so i pulled over at the el34world gas station to ask the if i should take the high or low road. thanks for the response, ive only been dicking with tubes for a year and a half and even though i have read quite a bit and experimented alot i still have questions which cause hesitation.

[jjasilli]

IMHO if you want Marshal tone, copy a Marshal preamp.

[ALBATROS1234]

yeah, thats what im gonna try next, i tried paralleling the v2 triodes and its only marginally better. it sounds really good as long as i dont crank it because if i do it gets way ice picky and noisy, thats with biasing one at 1.5k and the other at 2.2k . gonna try cathode follower method. if i understand it right i will get no gain from that triode.

[sluckey]

Spend some more time on the drawing board. Your cathode follower will not work as shown.

[ALBATROS1234]

ok sluckey thanks