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-   -   recognize this old amp? (http://www.diyaudio.com/forums/tubes-valves/225160-recognize-old-amp.html)

trigger 7th December 2012 12:42 AM

recognize this old amp?
 
i purchased this old amp and was curious if anyone knew the make? any help would be much appreciated.

1958 Vintage Stereo Tube Power Amp Project 4 x EL84 Cool | eBay

Mickeystan 7th December 2012 01:01 AM

Hello trigger, I cannot tell you what brand the amp is or what it came out of. I can tell you the guys description of the tube types is wrong on at least two of the tubes. There is no 6AV6 or 6CA4. The 6CA4 is a nine pin rectifier and this amp has an 8 pin rectifier tube which is most likely a 5U4. Mickeystan

trigger 7th December 2012 01:18 AM

yeah figured it was a tall 5u4 and maybe a 12ax7 with a quad of 6bq5's, it looks similar to a magnavox or rca.. i am curious to find a schematic for it.

Eli Duttman 7th December 2012 01:36 AM

Trigger,

That almost certainly came from a console. When you have the unit in your hands, look for a power connector that fed a tuner/preamp.

I'm guessing the circuitry in that chassis is a "concertina" phase splitter for each channel into a pair of PP "finals". I agree with the 6BQ5/EL84 O/P tube assessment.

If my circuitry guess is correct, the "beast" could be made "self contained" by using a 12AX7 to form voltage amplifiers for the 2 channels and installing MOSFETs to take on the "concertina" phase splitter duties.

Joe Roberts 7th December 2012 01:47 AM

I can't say who made the amp but I'd bet ya $5 that those green Tropicaps are leaky.

wrenchone 7th December 2012 03:34 AM

Yeah, and ditch the cheapo wafer sockets.

trigger 7th December 2012 04:28 PM

Quote:

Originally Posted by Eli Duttman (Post 3274049)
Trigger,


If my circuitry guess is correct, the "beast" could be made "self contained" by using a 12AX7 to form voltage amplifiers for the 2 channels and installing MOSFETs to take on the "concertina" phase splitter duties.

thank you much for your well informative response.

this is my first dabble into a concertina, so please bare with me.

so without a double triode or mosfet to feed the concertina circuit there will be no gain?

i will research this for the next few days. is there a simple mosfet circuit that can easily be applied in general push pull amp applications?

20to20 7th December 2012 04:53 PM

Quote:

Originally Posted by trigger (Post 3274882)
thank you much for your well informative response.

this is my first dabble into a concertina, so please bare with me.

so without a double triode or mosfet to feed the concertina circuit there will be no gain?

i will research this for the next few days. is there a simple mosfet circuit that can easily be applied in general push pull amp applications?

The pre-amp section chassis had the actual VA driver and then that was cabled down to the splitter tube. By the looks of that amp, the best route would be to strip it for the iron and tubing and start a new build, chassis and all.

trigger 7th December 2012 05:17 PM

a complete rebuild would be fun and ideal yet i feel that would be a bit more than i can handle at the current time. being a long time running noob, i have no second eyes with electronics available, using the net as a learning tool only, Ive just never run into anyone interested in audio electronics. so far i have worked with several old pulled amps, made them plug and play, recapping... last winter i assembled a tda7294 feebay kit.

maybe i should give it a try. cabin fever is setting in and my home theater is a cheep china 4ch powered subwoofer,...lol

20to20 7th December 2012 05:37 PM

Quote:

Originally Posted by trigger (Post 3274944)
a complete rebuild would be fun and ideal yet i feel that would be a bit more than i can handle at the current time. being a long time running noob, i have no second eyes with electronics available, using the net as a learning tool only, Ive just never run into anyone interested in audio electronics. so far i have worked with several old pulled amps, made them plug and play, recapping... last winter i assembled a tda7294 feebay kit.

maybe i should give it a try. cabin fever is setting in and my home theater is a cheep china 4ch powered subwoofer,...lol

There is room on the corner to add a driver tube. But this one won't be as simple as adding some RCA jacks and a switch and a recap.


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