my homebrew stereo tube hifi amp photos - Printable Version

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my homebrew stereo tube hifi amp photos - Texasrocker - 08-24-2009

I recently built a custom stereo tube hifi amp as a project. My wife added some photos of this custom amp at photobucket if anyone wishes to see them. Its a great sounding amp indeed!Still not completely finished, just working-out the final bugs. The old RCA chassis is a circa 1947 vintage auditorium PA chassis.Perhaps Doug H. can help verify the exact age? This amp yielded me some very expensive highly sought after Western Elec 618 B m.c. input transformers. The chassis had been stored for many yrs with lots of other vintage tube gear I recently acquired. It was in bad shape,some rust, most orig paint missing, ...nasty! It has a perforated metal roll-over wire tubecage not shown in the photos. I stripped all the orig parts & wiring, took the chassis apart, used a handgrinder with wire-wheel brush to take all the old rust / leftover paint off. I repainted it as close to orig colors as possible using automotive lacquers. All the knobs are orig.
I then started a complete rebuild as a home hifi stereo tube amp project. Two amps all in one chassis sharing one power supply. I mounted good used tube sockets in the already-punched chassis. I had to cut another hole for the second audio trans.
Built with all used spare parts:
Power trans: good tested used 450-0-450 off mid 50s large (4) 6L6 PA amp,
Matching early 60s Sherwood Labs handwound linear types audio-trans off a previously-hacked Sherwood mod S-5000.

Things I added in the new amp build was DC filament supply to the preamp tubes which allows for a totally hum-free amp design. I thought up the tube layout, and created my own schematic along the way, trial & error. I made some mistakes, found them, and kept moving on, using all parts here in my workshop backstock bins.

The design is simple. Both separate amps are cathode-biased, and tubes can vary , and sub easily. Ive tested the amps swapping in/out EL34s, 6550s, & 6L6s so far. My favorites are the sound quality of the 6550s overall, but all the tubes sound sweet in this amp! The preamp tubes lineup in each individual amp are 6C5, 6J5, w/ 6SL7 phase-inverter, driving either 2 EL34, or 6L6, or 6550s in p.p.Its been a fun project indeed! I have a very-slight distortion prob Im working out, but overall this amp ROCKS the house!

heres a photolink with slideshow if anyone would like to see my new all point-to-point handbuilt amp now in my collection. It was fun adding new-life & reason for future-use to the old RCA pa chassis indeed! ol Tx.

http://s576.photobucket.com/albums/ss202/Texasrocker1/?newest=1

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Re: my homebrew stereo tube hifi amp photos - kruc - 08-24-2009

Good looking amp there Tex. My hat's off to ya. My own 300B amp project is on the back burner while I'm rebuilding a couple of Philco 20s.
Dave

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