Parallel Single Ended EL34 Amp Build

[dobrota]

I'm building similar mini tube EL34 SE amp with one 12AX7 in preamp and classic Fender tone stack between tube stages. It isn't almost possible to get more than crunch (using Strat with single coils) without another preamp stage because of Fender tone stack is heavy load and decreases anode signal about 8 - 10 times. So i'm thinking about to add one FET or MOSFET transistor before 12AX7. But maybe easier way is to use some distortion pedal.
I also tried only gain pot between 12AX7 stages and tone stack after preamp before EL34. It increases distortion, but it's still "old scholl" sound no modern hi gain.

[maxwedge]

Hi Scott

re: your last schematic - I see you have a 47k NFB resistor. Try upping that to say 100k (or even 220k) that will get a raw-er sound. Or try disconnecting it altogether.

Another simple thing you could try on that schematic is up that second plate resistor to 220k and drop the cathode resistor to 1k5.

Another 2CW

I had my schematic incorrect the whole time for the 6SL7.
The triodes were mixed up so the triode with the 150k plate was really #1.
So the 1st triode I left as is, 2nd triode I bumped the plate to 220 ohm and 1.5k cathode as suggested and increased the feedback resistor to 100k.

I had no feed back when I first built this and found when I added it that it improved the tonal rage of the amp. I think I made too may changes here at once to notice the difference from 47k to 100k.

IMO, it's sounding about as good as it's going to get with out adding another stage or dumping the tone stack but I think another stage is where I'll go because I still have a free socket in it and a fare stash of octal preamp tubes. Thats for later, I have to rest on this for a while!
It's still fairly clean at 1/2 and crunches really well and loud at 3/4 to full. That's without the raw. Adding the raw makes it grind pretty good.

I got a couple of questions:
I'm thinking I need to increase B+3 because of the lower plate voltage on V1B.
I'm wondering why the raw control, when turned down, had a big effect on the tone stack when I had it wired to the grid of V1B. One of the earlier schematics show it like that. I have it connected to the leg of the volume pot now and it doesn't tone stack when raw turned down.

Got a new correct schematic with all new voltages and values ect.

[tubeswell]

2nd triode I bumped the plate to 220 ohm and 1.5k cathode as suggested and increased the feedback resistor to 100k.

FWIW I said 220k - not 220R

[Groover]

Very interesting thread, and it bears on some of the experiences I am having with FMV tone stack loss.

maxwedge, I am curious as to why you chose to go with the 6SL7 for the preamp stages?

[maxwedge]

FWIW I said 220k - not 220R

Sorry I miss-typed, I'm sure you saw that the schematic was correct.
btw, I really appreciate your input. Your last suggestion really waked it up a bit.

I've since added a switch again between the raw pot and the volume pot because even when the raw is turned all the way down it really darkens up the tone of the amp.

[maxwedge]

Very interesting thread, and it bears on some of the experiences I am having with FMV tone stack loss.

maxwedge, I am curious as to why you chose to go with the 6SL7 for the preamp stages?

I picked the 6SL7 because I heard that they were really creamy/smooth sounding when overdriven and and had a better dynamic range that the 12AX7. Besides I already have 2 other single ended amps driven by 12AX7's, a champ rewired as a 5f2a and a 60 Gibsonette. Wanted to try something different.