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Old 19th April 2006, 11:54 PM   #1
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Red face Cheap but not too much !

If you have a minute or two that would be greatly appreciated !

I’m searching for a schematic of a amplifier that I can realize without being hungry for the rest of the year . I got around 450 US$ to make this project and I already got my chassis, so it’s 450 on tubes and components.

so here’s my restrictions:

- 2 Channel around 25 W Push-Pull (between 15W and 35W) per channel
- Max 3 tranny, 1 power tranny that power both channel and 2 output (Hammond would be perfect)
- A schematic that show not only the preamp section in Russian, but a complete circuit.
- With easy-to-find tube over eBay.. so no tube from 20`s

I think of 6V6 or 6L6GC would do the thing, but if you have suggestions... you know what to do . Thank you all for helping me!
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Old 20th April 2006, 11:41 PM   #2
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Hammond 1650H O/P trafos are approx. 80 USD each. A Hammond 372JX power trafo will do nicely and it costs approx. 95 USD. A Hammond 158S choke that costs approx. 18 USD rounds the "iron" set out.

Use a 5AR4 as the B+ rectifier. Follow with CLC filtration.

Self (cathode) biased and triode wired PP 7591As running in Class "AB1" should get you over the 15 WPC mark. A no NFB design is possible triode wired. Some sort of NFB will be required if you go UL to increase power O/P.

Study the various phase splitter topologies here. The Schmitt circuit with RK2 replaced with a constant current sink (CCS) will work well and does not require a B- supply. You will need a B- supply if you want to eliminate CG2 and (possibly) CG1. A 12AT7/ECC81 as the splitter would allow the amp to function without a preamp. Make RG1 and RG2 560 KOhms. couple the wiper of a 50 KOhm log taper pot to CG1.
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Old 21st April 2006, 01:05 AM   #3
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A pair of these and one of these with a quad of 6V6 will do you nicely
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Old 21st April 2006, 12:56 PM   #4
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Wow Edcore is for sure real cheat tranny, but does they sound good?
Geek, what about the shipping, if you have any experience with
them ?

For the power transfo is the Hammond 272 JX or the 372 JX will be enough for running both channel ?

By the way take for you input !
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Old 21st April 2006, 04:59 PM   #5
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You're welcome!

Quote:
Originally posted by guitvinny
Wow Edcore is for sure real cheat tranny, but does they sound good?
Yes.

With the amp I built that has only 3.5dB NFB, I'm getting 19Hz to 19.5KHz at the -3dB points and I've been listening to it for months now and they sound as good as any I've used so far.

Quote:
Geek, what about the shipping, if you have any experience with them ?
Yes again. They only charged me exact USPS rate. They also accept PayPal.

Tubelab has a great thread on a review of Edcor and he put them through a lot more abuse than I did.
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Old 22nd April 2006, 12:20 PM   #6
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Quote:
For the power transfo is the Hammond 272 JX or the 372 JX will be enough for running both channel ?
Yes, you would have enough current. Both the _72JX and the 5AR4 are rated for 250 mA. A 250 mA. B+ supply will be adequate feeding 4X 7591As and the driver circuitry.
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