Home » Audio » Thermionic Emissions » Proud Papa Syndrome (Check out my new amp...)
Re: she's a beauty! [message #8790 is a reply to message #8789] Mon, 31 January 2005 05:49 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
This is a source of on-going astonishment for me, the microphonic 12B4. I have a small stash of them and have not had any more bad ones than any other sort of valve. Perhaps the sensitive 6SN7 crowd pushed this a little askew, but I have not found the 12B4 particularily microphonic.

Two 12BY7's per channel make the active-load/output buffer. 12GN7 is a direct plug-in and at 250% the gm, it won't be ong before I put them in.

Still need to get a few bits to put her together. cross your fingers.
regards,
Douglas

Re: she's a beauty! [message #8791 is a reply to message #8790] Mon, 31 January 2005 09:09 Go to previous messageGo to next message
TubeCraft is currently offline  TubeCraft
Messages: 30
Registered: May 2009
Baron
Well the gain is so low that ya' kinda have to shoot 'em with a BB gun to hear it, but it's there in most of the bulk packed ex-millitary stock 12B4s I have ;>)

I just use em anyway.

It's nothing like a microphonic 12AX7 when you accidentally knock over a Fender Princeton. :o()

Re: Proud Papa Syndrome (Check out my new amp...) [message #8794 is a reply to message #8770] Mon, 31 January 2005 16:31 Go to previous messageGo to next message
Thermionic is currently offline  Thermionic
Messages: 208
Registered: May 2009
Master

Wow! There's some very talented DIYers here at ART! Beautiful and very impressive work everyone. My hat's off to ya!

As I had promised Wayne, here's a pic of a current amp project. Nothing special at all, just a clone of a Dynaco ST-35 for a friend, with some different component values here and there, a better power supply with Fairchild Stealth hyperfast/soft recovery diodes and choke filtration, and a slightly changed circuit. I'm still using the 12DW7 driver, and the iron is all vintage Dynaco pulled from a scrapped ST-35 that my friend's buddy fished out of a dumpster!

He wanted it to have as warm, smooth, and romantic of a signature as possible, so all the resistors are carbon comps and the coupling caps are paper in oils.

It's not completed yet, but I threw some tubes in it and snapped a quick pic with my cheap, totally blurry camera. Sorry for the poor quality snapshot! I've had to shelve it back for several weeks now due to the avalanche of amp service jobs I've been getting.

The left hand control on the Dynaclone is the volume, while the right hand knob is a variable negative feedback control, with 0, 6, or 12dB of feedback. It also changes the voltage amplifier section's bias on the fly with the feedback, to increase the gain a bit in compensation as the feedback is increased. You may be able to see that a couple of transformer mounting screws are missing. There's a bracket inside with the choke and filament tranny on it that mounts on those screws, that's not in place yet.

The chrome acorn nuts on the iron are something I do on every amp I build, to me it looks classy and gives a well-finished look. The hammertone bronze and midnight black finishes were at my friend's request.

Pretty soon, I'll be building a DRD 300B, DRD 2A3, an EL34 PP with transformer phase inversion, and some various other stuff. All three amps will have choke loaded, battery biased 6C45 drivers, Plitron OPTs, and the DRDs will have motor run oil caps in the PSU. Can't wait!

Once again, mungo beautiful amps everybody, one and all! Congratulations!

Thermionic



Re: Proud Papa Syndrome (Check out my new amp...) [message #8802 is a reply to message #8794] Tue, 01 February 2005 00:20 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)
That's a really great looking amp! Thanks for the post!

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