New project: Something British This Way Comes

[mirage_indigo]

I am finishing up the Donut Princess with cab fabrication happening this week for the head. Then I'll be building a Sorado head + Fearful 15/6 cab.

---then---

What I want is something more like a hot AC30 pentode channel + verb/loop + EL84 power section. I'm starting to put together a plan for something vox/matchey/hiwatty based loosely on the following:
Clubman style preamp topology 12ax7 into tonetack into ef86. Split into effects loop + reverb driver
LTPI with reverb wet into the non-inverting input (ala chieftain).
Probably an el84 quartet, but I could be talked into a pair of el34s. Cathode Biased.

Surely somebody has already built this, but I couldn't seem to find a close analog.

I'm looking for a sound with that high chimey but kinda grainy/throatey distortion that you get in a vox. This will be the other "big" amp to pair with a JM/wonderland build.

[ChopSauce]

12AX7 into EF86?

[Roe]

the ac30/4 w. ef 86s is unbeatable, except for the 82R cathode resistor which is best replaced with a 50R. adding a loop is easy enough. not sure you need a seperate reverb though. and an 12ax7 is hardly necessary, the ef86 offers plenty gain and the verb and loop wont work too well with a phase inverter and power amp that distorts

[ChopSauce]

... and an 12ax7 is hardly necessary, the ef86 offers plenty gain...

This is something of my experience with and without a triode in front of an EF86 that it pushes the signal somewhat too far/soon/hard into distorsion.

Nevertheless, I saw (afterwards) on the Clubman schematic that the 12AX7 "drives" the tonestack and that it doesn't seem to offer much gain, having no bypass cathode cap - as far as my poor studying of the subject allows me to catch things - which might be a good reason for this.

Do you plan to use a Vox-style tonestack, rather?

[Colossal]

the ac30/4 w. ef 86s is unbeatable, except for the 82R cathode resistor which is best replaced with a 50R.

Hi Roe,

I have an EF86 channel only AC30/4 build in my queue. What are your thoughts behind the hotter 50R bias, versus the AC30/4's 82R bias? Better tone? I think I calculated 11.8W of dissipation with 82R, assuming my guesses on the voltages were correct.

[chief mushroom cloud]

look at Selmer Zodiac circuits

[mirage_indigo]

Wow the Selmer Zodiac 50 has a really odd reverb mixer. It looks like it folds the reverb back into the input signal which is then coupled back out the other direction through the 560pF coupling cap. The PA B+ is also fed from the far side of the choke Dynaco style. That's a really interesting circuit, thanks for the pointer.

I think part of my problem might be that I don't want to believe a single EF86 can really sound that good. Surely it must be more complicated! Maybe it's just not and I should just build a single channel HC30 and be done.

[Roe]

the ac30/4 w. ef 86s is unbeatable, except for the 82R cathode resistor which is best replaced with a 50R.

Hi Roe,

I have an EF86 channel only AC30/4 build in my queue. What are your thoughts behind the hotter 50R bias, versus the AC30/4's 82R bias? Better tone? I think I calculated 11.8W of dissipation with 82R, assuming my guesses on the voltages were correct.

Yes it sounds better to me. Its not subtle

[Colossal]

the ac30/4 w. ef 86s is unbeatable, except for the 82R cathode resistor which is best replaced with a 50R.

Hi Roe,

I have an EF86 channel only AC30/4 build in my queue. What are your thoughts behind the hotter 50R bias, versus the AC30/4's 82R bias? Better tone? I think I calculated 11.8W of dissipation with 82R, assuming my guesses on the voltages were correct.

Yes it sounds better to me. Its not subtle

Great to know! Thanks! 50R it is then. That's interesting because it seems when Vox changed PT's from the Haddon 285-0-285 to 280-0-280 on the AC30/6, that's when they changed from 80-82R down to 50R.

[Roe]

Hi Roe,

I have an EF86 channel only AC30/4 build in my queue. What are your thoughts behind the hotter 50R bias, versus the AC30/4's 82R bias? Better tone? I think I calculated 11.8W of dissipation with 82R, assuming my guesses on the voltages were correct.

Yes it sounds better to me. Its not subtle

Great to know! Thanks! 50R it is then. That's interesting because it seems when Vox changed PT's from the Haddon 285-0-285 to 280-0-280 on the AC30/6, that's when they changed from 80-82R down to 50R.

yes the 50R runs the tubes hard, so you must be careful with the plate and screen voltages