Finally the time has come to power the assembled amp up. What can I say? I´m really delighted by the clean tones. It´s not like later Blackface Fender sounds, but has a kind of wooden quality to it. I guess this comes mostly from the enclosure and the speakers. The overall sound is mostly bright and gets raspy once hit hard.
The guitar I used in the following sound samples is a ´81 Hamer Prototype, which is an all mahogany setneck guitar with a single coil shaped humbucker (OBL) at the neck.
This is a recording from the situation you see in the picture: Guitar straight into the amp, bright channel, no effects, U87Ai a meter away from the amp and also straight through a clean mic pre into the ADC. The sound is beautifully threedimensional and organic.
Then I added a bit of reverb and quite a bit of delay coming from my old Boss GT-6 to the amps sound.
The amp doesn´t stay clean very long. With the pickups in this guitar it begins to distort at around 3-4 on the volume knob´s scale. While a little overdrive creeping in when you hit the strings hard sound kind of charming to me, I´m not sure whether I really like the overdrive sound. The sizzling highs sit somewhere between 8-10kHz and don´t sound good to me. I used the “normal” channel for that and a SM57 microphone to make the following sample bearable:
Here are my settings on the amp:
I´m currently thinking about modifying the amp to stay more clean. 4 6L6CG should be able to be a lot louder without distorting. I have not yet tried to explore it further, but I guess the distortion doesn´t come from the power tubes at all, but one of the preamp or the phase inverter stage.
Any suggestions?
TAD Tweed Twin Build 
Did you manage to get the headroom you wanted? I’ve read that these twins should be clean all the way, at least with single coils. Maybe you set presence and bass too high?
Well, I didn’t try with real single coils yet, but I don’t think that this type of amp would be clean all the way to max volume. Maybe you are referring to the later twin reverb (black face oder silver face era)?
Your breakup shouldn’t be raspy. You may want to try a 470K resistor on the phase inverter grid. It will allow you to go more smoothly into overdrive. This is assuming the rest of your build is very clean.
You mean, I should swap the two 1M resistor for ones with about half the value? Could you please explain why?
The 1M is original according to Fender schematics.
Hello!
You’ll add the 470k resistor between the 1M resistor on the board and your phase invertor (V4/pin 7).
I can’t edit my response – I thought the 5E8 has 4 preamp tubes? In any case, you’ll add the 470K resistor to pin 7 of your PI (last 9 pin preamp tube), which is v3 in your schematic above. I have a couple extras laying around if you need them.
Best,
Frank