single ended el84 amps you've played/built/modded, etc

[wsaraceni]

so i just picked up a Dr Z mini Z. I want to build another el84 amp. I was thinking of going with a ef86 front end, but im not sure yet.

what have you built

[roberto]

I've modded Harley Benton GA5 and Epiphone Vale Junior, a pair of Cicognani Brutus ( http://www.youtube.com/watch?v=acoygg_zC-U http://www.youtube.com/watch?v=lO3uAIzRx_A ) plus some PSE amps for friends. I like the miniZ for its simplicity.

I don't like EF86 so much, I prefer just one 12ax7 in the preamp for EL84 SE, and maybe two if I have EL34 or 6L6 in the PA.

[wsaraceni]

so if i you wanted something that was single 12ax7 and single el84 that wasn't a mini z (as i have one already) what would you go for?

[roberto]

It depends on what you want to obtain, obviously.
You can use a Carmen Ghia preamp,
or a 1st stage Marshall (gain included) to a 100k 2k2 unbypassed stage,
or whatever you like.

With only one 12ax7 you have not to scoop too much mids between the two triodes.

[Gibsonman63]

I recently did a Mercury Magnetics upgrade to an Epiphone Valve Jr for a friend of a friend. It was a lot more than just a transformer upgrade and stupid expensive, but it was a great sounding little rock and roll amp.

[surfsup]

you can look at some reviews of this on their site:

http://ax84.com/p1.html

[roberto]

Yes, let's take this as an exaple:
http://ax84.com/static/p1/AX84_P1_101004.pdf

They use a 100R 1W in the supply to simulate the sag of a tube rectifier,
then 47µ on every stage. With a 100R in the power supply I'd use a 22µ on screens and preamp.

You have no grid stopper on first stage and a plexi-like gain pot configuration with resistance scaled 50% down, and an equalization just before the EL84 (for that tube maximum resistance grid to ground is 1M like the pot).

I'd prefer to use smaller values to ground EL84's grids (22n to 220k typical, but you'll notice that a 1M load will give you a bit more gain.

[surfsup]

They use a 100R 1W in the supply to simulate the sag of a tube rectifier,
then 47µ on every stage. With a 100R in the power supply I'd use a 22µ on screens and preamp.

Would you mind elaborating you reasons for the 22uF instead of 47uF?

[roberto]

I said 22µF but could be even less down to 8µF, simply because if I want a saggy power supply, I'd go for smaller caps too.