Tiny combo - el95 with 12ax7 preamp - will this work?

[loudthud]

More voltage to the preamp also means more gain so as far as clean signal goes, you don't get much. Are you satisfied with the cleanliess of the signal when the volume control is turned down even though it's hard to set there? If there is too much distortion, that means there is too much gain in the first triode before you have a chance to turn it down with the volume control. That can be fixed by changing some resistor values and removing the cathode bypass cap. Or you could try a different tube. A 12AY7 or 12AT7 will plug into the same socket and give lower gain.

You can add another resistor across the volume control to reduce the gain. Try a 1Meg, 470K or 220K between the two end terminals of the Volume pot. This is an extension of the idea you tried above.

[mooreamps]

Don't be surprised if those voltages will tend to sag a little bit once that power tube starts to conduct...

-g

[j-stylez]

Allright, the resistor across the volume control did the trick, the controls of the amp are very workable now. It sounds great plugged into my 1x12 cab, and once I finish building the mini-combo I'll post some pictures and sound samples. Thanks for all the help again!
I'll try out the tubes you mentioned once i get a chance to buy them, it seems like a good experiment.

[KFTG]

Hello guys,

I'm building a tiny little practice amp combo with a 6" speaker.
I have an el95 tube for the poweramp, and 12ax7 for the preamp.
I want a single tone control, so I decided to try out the "Moonlight" tone control circuit. The poweramp is pretty much copied from a SE el95 i found someone doing a report on.

1.) If I want a single volume control, is it better to leave it where I have it placed right now (after the tone control), or is it better to put a master volume control, just before the power amp section?

2.) Also, if I want to play around with the value of the cathode bypass in the preamp, is it better to do that in the first or second stage or both? I read about the "fat" switch some people use, switching the preamp cathode bypass to another value...


Any other ideas are welcome, and please say if you spot any errors! help is appreciated!

[ATTACH=CONFIG]17604[/ATTACH]

Hi, on your input tube, don't you want a coupler cap from the plate to the tone circuits? This will block the dc and let the ac pass.

[J M Fahey]

It was added (as well as other missing parts) by post #13.

[ron vogel]

Thanks to you all, Ive got it working. Ive been playing around with the cathode bypass caps, but I just cant seem to tame the distortion. Theres too much gain!

Any ideas? I can see that while the tubes are warming up and the speaker is just starting to make a sound, theres a point in time when I really like the way it sounds, nice and clean, but by the time the tubes are warmed up completely its just too loud and too much distortion.

Could I try to increase the 100k plate resistors on the triodes to a higher value?

My cathode bypass cap values for now are: 10 uF first triode, 10uF second triode, 100uF powertube.
I have 56k grid resistors on both triodes.

Now how can I reduce the gain to get some clean sounds out of it at low volumes - and make to volume pot more usable (right now its too loud after maybe 10% of turn). Could I try a tonestack with some more loss? or nfb?

A lower voltage to the tubes will result in MORE distortion. It can be a matter of personal taste...but it will "brown" the sound using lower voltages to the preamp tubes. 12ax7's can handle up to 300ish volts. You will get more clean headroom running a higher voltage to them...it really won't effect the gain. I personally find 250-290 volts the sweet spot on my amps. YMMV due to circuit design and tube type/construction. I use old RCA's in my amps BTW.