Schematic for single ended 71A stereo amp

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lego4040

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Schematic for single ended 71A stereo amp
« on: 19 Mar 2018, 03:23 am »
So I'm trying to set some builds so I can fill up my bench and I'd like to try a 71A. As simple as it can get is preferable, since I strongly believe in the K.I.S.S. When I google a SE 71A schematic 2A3/45 comes up a lot, I am no electrical engineer but I do have tube amp builds under my belt . I'll read and study a build for 6 months sometimes before I build so I know whats ahead of me and to get to know the circuit. Thank you and much appreciated

FullRangeMan

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Re: Schematic for single ended 71A stereo amp
« Reply #1 on: 19 Mar 2018, 03:42 am »
The schematics I copy from internet were incomplete or purposely wrong.

doggie

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Re: Schematic for single ended 71A stereo amp
« Reply #2 on: 21 Dec 2019, 01:20 pm »
The 71A is my favorite tube with the 45 following just behind. Needs some very efficient speakers though. I made this as a headphone amp years ago. No schematic. Scratch built with a lot of experimentation. I used WE 417a tubes on the input.

I sold it and wish that I could buy it back.



FullRangeMan

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Re: Schematic for single ended 71A stereo amp
« Reply #3 on: 21 Dec 2019, 09:54 pm »
Great amp, congratulations.
How is the 417A sound?
The OPTs are Tango?

doggie

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Re: Schematic for single ended 71A stereo amp
« Reply #4 on: 22 Dec 2019, 12:45 am »
Yes. Tangos.

I really liked the combination of the 417a and the globe 371A tubes. I had a pair of Lundahl interstage transformers underneath. I tried them as ITs but ended up wiring them to choke load the drivers. I played with DC and AC filaments also. AC sounded the best to me but had hum. I ended up using DC filaments with small chokes in the filtration.

I thought that it sounded great but moved on to try other things for my headphone listening. Wish I still had it.

FullRangeMan

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Re: Schematic for single ended 71A stereo amp
« Reply #5 on: 22 Dec 2019, 12:53 am »
Maybe the hum came from the 417 small space between filament and cathode, so DC are recommended, but sino amps usually use a hum pot for lower costs and fewer parts.