First DIY amp schematic (I hope)

heekma

Well-Known Member
Here it is (I hope)!

Any and all comments and suggestions are most welcome. The main deviation I'm planning on right away is using smaller separate electrolytics under the chassis in place of the multi-section cans for filtering.

One other potential issue: Ryan was kind enough to post the specs of the Scott output xfrmrs-8,000ohm input, but this calls for 6,600 ohm input.

Am I gonna have to bust out the wallet and buy some outputs after all?

Thanks folks. I'm looking forward to any suggestions to improve on or simplify the design as well as any criticisms as well.

Best,
mojojojo
 
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Actually a pretty nice design from a quick glance. When scatch building I would opt for a all triode front end if it was me but still this will be fairly simple for you to get your feet wet and everything is laid out and labeled nicely with pin numbers. Takes all the calculations and trial and error out of the picture for you. I say build it as is from my initial look see.

Craig
 
Hey-hey!

Nice to hear from ya Ryan. I doubt you remember me as you've helped so many folks, but about 2 years ago I got a 299C and you were very kind, patient and answered my questions in detail so a newb like me could figure out which end of the amp was up ( I now know it's the end that lights up!).

After that I was ready to tackle a 296 when it came up for sale within driving distance.

And after that restoration I decided it was time to roll my own, so to speak.

The circuit is a re-print from an issue of Electronics World, don't know the year or issue number, but the article states the schematic is by Paul Jacobs and Praveen Jariwala from the tube division of Westinghouse. I get the feeling it was right around the time the 7591 was first introduced because there is a lot of references to the "7591 beam-power pentode recently introduced by Westinghouse Electric Corporation."

I came across the article, and with all the 5AR4s, 7591s and 6AN8s I've got lying around, plus the output xfrmrs from the 299C, the gears in my little brain started turning and smoke rolled out my ears.

If you're interested, I can e-mail a JPEG of the square-wave performance at various cps and watt output.

Thanks for the info on the 299Cs xfrmrs-great to know I won't have to break the bank for iron!

Gotta go, time to punch the clock and head for the hills. Have a good one!

-mojojojo
 
Craig,

Great to get your input, nice to know I won't be starting with a poor schematic right out the gate.

I've seen pictures of various voltage regulators-those glowing PURPLE tubes look fantastic. Even if they didn't perform a useful function they'd be great to put in just on the "pimp-factor" alone!

Take care, I'm off the clock and out the door!

Best,
mojojojo
 
When I very VERY first started looking for old tube amps, the first ones I found were a pair of Stromberg-Carlson PA amps that used a pair of 6CD6 outputs, and use an OD3 for voltage regulation. What a great introduction to tube glow!!! The amps used a lot of feedback to approximate flat FR, but still foregrounded the midrange. Ah that warm sound when I first fired them up with Ella Fitzgerald!

Great looking design, have a blast building it!
 
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