Help Identifying a Tube Amp

[gdmoore28]

The short backstory: My old WWII electrician friend recently passed away. He was the only other person in our small southern town who was a fellow audio enthusiast. Before he died, he sold me all of his NOS Altec and University speaker components. Last week, I finally received his two tube amps and a Dynaco PAT IV preamp. One of the amps is a Dynakit Mk IV. The other is a mystery, and I suspect that he either built it from scratch or based it on another existing design. My old friend was quite picky about his gear, and kept it all in his home inside closed cabinets, so all of this gear looks like it just came from the box. It's that nice. I know nothing about tube amps - ZERO. But even at this advanced age I still know how to read, so I've been doing a lot.

Since acquiring this gear I've bought another nice Dynakit Mk IV to make a stereo pair, but I'm unsure what I have or what to do with the other amp. Can anybody give me some idea from the pictures? Specifically, if I decide to sell it, I need to know how to list it.

GeeDeeEmm

 

[seanrr]

That looks like a mono block with EL84 tubes unless it has speaker terminals for two speakers - then, it would be a SEP El 84 amp, and you can use it as is with a preamp. Can you show a picture of the speaker binding posts?

 

[gadget73]

Whats the small tube in there?

Looks very homebrew, but using a good transformer and the build quality seems to be pretty good.


Could be this one

http://diyaudioprojects.com/Schemat...-6V6-6AQ5-Dynaco-A-410-Tube-Amp-Schematic.png

 

[mhardy6647]

DIY push-pull EL84 mono power amp with a good output transformer.
What's the small-signal tube? Probably something like a 12AU7, 12AT7 or 6EM7 (twin triode).
Very old solid state rectifiers in the power supply.
Electrolytics (at the least) should be replaced 'for best results'.

 

[battradio]

http://www.the-planet.org/gkaufman/pdf/transformer.pdf most likely figure 3

 

[gdmoore28]

You guys are just fantastic. The wealth of knowledge here just blows my feeble, easily impressed mind. Thanks to all for the responses. Attached is the requested image of the amp binding posts. The bottom cable, of course, was attached to the speaker.

GeeDeeEmm

 

[mhardy6647]

http://www.the-planet.org/gkaufman/pdf/transformer.pdf most likely figure 3

Maybe a variant thereof -- the amp in question's got solid state rectifiers... could be virtually the same otherwise, though.

 

[Zibi]

Same (?) chassis with cage for sale:
https://www.etsy.com/uk/listing/192739432/new-unused-radio-amplifier-chassis-or

 

[Hi-FiGuy]

It looks like it could be half of an ST-35, is the small tube 7247?

 

[gdmoore28]

That chassis looks almost identical.

The small tube reads: "7025 USA" The larger tubes are EL84.

Thanks, guys.

GeeDeeEmm

 

[gadget73]

7025 is a 12ax7. Very possible its that circuit from the Dynaco manual then.