I'm thinking about an acoustic amp (combo style but with the amp in it's own space above the speaker) with tone controls to drive a 16 litre bass reflex cab with a Celestion TF0818 (94dB) plus tweeter.
I've tested my guitar with Fishman preamp through a +20dB preamp and ST-35 into a similar sensitivity speaker and feel tha overall gain is ok.
I thought of using a PP EL84 circuit with a Baxandall tone control preamp at the front (both using 6SL7) The tone circuit has around 30dB of gain at tone flat. I figure 6SL7 will be slightly less gain and I could always lose the cathode bypass caps to lower it further if necessary. The tone circuits came from here. http://www.angelfire.com/electronic/fun ... one-A.html.
Would use a solid state PSU
So it is really an audio amp
Questions are to do with joining the two together and where to put the volume control. I've looked at a couple of versions of the Ampeg Portaflex circuits which use 6SL7 but they put the tone controls like the diagram below in one version with the volume after that and one version with the volume after the first gain stage and the tones between the second stage and the phase splitter. They also have a 120k input resistor with a 2-5M resistor to ground at the input.
Should I input via the usual 68k grid resistor and 1M to ground and lose the 0.047 cap?
Also thought of running the 6SL7 heaters from DC as the tranny has a 12.6v winding. Also possibly sub 6V6
Any comments on the circuits / project welcome.