12AT7 push pull power tube

[krash]

My new Serena amp uses a 12AT7 in push-pull with a long-tail PI.

Here's a quick & dirty clip:

http://revelationamps.com/media/serena_quick_clips.mp3

Esprit -> amp -> Ceramic Silver Bell -> 2' of air -> miniature condenser -> minidisc

Just unstructured fooling around.

[dartanion]

Sounds sweet man!!!

Very cool indeed.

[Michael]

Schematic?

[jimipage]

NICE tone -- yes; schematic, please?

[krash]

y'all don't need no steenkin' schematic.

Here's a hint. AC30-style PI. 12AT7 push-pull into a 10W 8K:8 transformer, cathode-bias with 390 ohm res and 1000uF cap. 260V PT, SS rect, about 325V B+.

[Michael]

y'all don't need no steenkin' schematic.

Here's a hint. AC30-style PI. 12AT7 push-pull into a 10W 8K:8 transformer, cathode-bias with 390 ohm res and 1000uF cap. 260V PT, SS rect, about 325V B+.

That is damn-nice tone, and great chops on your part.

12AX7 preamp straight to the PI?

Michael

[krash]

Well the preamp is tweaky to some extent. Hey I'm tryin' to sell a product here so cut me some slack

There's a voicing switch in the amp that turns on a filter/voice stage that brightens up the voicing quite a bit, but that really complicates matters. So ignoring that for a minute, presuming it's "off";

then yes, it's basically a regular 1/2 12AX7 preamp stage not a lot different from the trem channel of an 18W, but you do have to put some extra attenuation between the plate-feed coupling cap and the vol/tone (about 1M or so) if you want ANY clean headroom.

I had to use a big cathode bypass cap (1000uF) in the output stage in order to knock out some kind of nasty sounding distortion that I figure is crossover distortion. 270 ohm cathode res. on the 12AT7 caused it to red-plate after about half an hour, but it sure sounded good before that

Now if you want any more detail than this, email me.