diytube.com

I built this last night, the board was pre-built, so really I just did
the mechanical stuff and wired it up. I followed Ed Brown's
post and tried a 6AV5GA, in Ultralinear mode. It's a standard
g*s*g board, with a 1K grid stopper to the tube socket, and the
cathode lead from the g*s*g's test points. The screens are connected
to the taps on the Edcor XSE15-8-5K output transformers.

It sounds really good, I'll crank it up later and see what it can do.
At about $ 3 per tube, they definitely give the 6B4G's a run for the
money.

This amp is a "convertible" and can quickly be changed to 6B4G's,
and with a socket and/or resistor change, to 6A3's or 300B's.

Bigger/More pix at http://tmamps.com

Good stuff! THe 6AV5GA also works well with 3K SE OPTs, and stays very clean sounding, at least in triode strapped mode (the Transcendar 3K 10Watters don't have UL taps).

If you want even more kick out of it, take an octal tube base and make a 6AX5 SS replacement, solder in 2 uF4007s, each with a 100 ohm, 5W WW resistor in series with the anode. I got fancy and also soldered in another UF4007, a red-orange LED< and a resistor in series, across the filament pins, in order to create an orange glow. I also added a plastic "tube envelope" but it is still open on top. At least it serves to keep the HV AC and DC out of the reach of inquisitive fingers...

This will deliver around 350-360V B+ and increase the output power and the "ka-whump factor" quite noticeably. I tried various values series resistrors, 200 ohms 5W got really hot, 100 ohms was just about right, and no resisto (zero ohms) really ran the tubes around 22W+ PD.

I still have two more G*S*G boards, so I Can try two more "mutants" sometime.

It looks like you have an endless supply of those XSE15-8-5Ks

/ed B

I made a diode plug for another amp, and put an Amphenol snap on
cap on it for safety. Not as snazzy as one that glows, but it worked.

Funny you should mention the big box of Edcor XSE15-8-5Ks !
I dug to the bottom and there are only two sets left. Actually,
one set got used twice. I stripped an amp and sold the chassis
to someone who didn't have the ability to drill/punch it himself
and I re-used the g*s*g board and transformers in new builds.

TomMcNally wrote:Funny you should mention the big box of Edcor XSE15-8-5Ks !

Aha! So you're the reason they have a 6 week backlog on all orders. They're busy winding transformers for your assembly line!