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71A Direct Heat Triode Single End Class A Amplifier

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Hello,

The 7W is the output power of the outpout transformer of 71A SE. The output power of 71A single end class A is 0.8W.

I feel the sound of this low powered directly heated triode, 71A is so musical, smooth and a bit slow like listening to LP. This should be a kind of vintage sound of tube amplifier.

Thanks.
 
The vintage Cornell Dubilier Flat Pack 270MFD /420VDC capacitor was used on power filter.
 

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These are 15W output transformers made for 71A single end. Primary impedance is 4.8K ohms and secondary is 4 ohms and 8 ohms. The EI core is Z11 0.35 mm in size 76x26mm.
 

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Hello ming,

Thank you very much for selection of my amplifier and nice comments. The circuits of the original version and this new one are same. We upgraded the transformers of the new version and can be seen in the previous page. All the transformers were made in Hong Kong. Furthermore, we used German M-cap Supreme capacitors in the coupling stage between 6SL7 and 71A. Transparence and resolution can be improved. The CMC tube sockets keep good contact with foot pins and are very easy to use.

Cheers!

Tony.

ur original version is more pretty, however i need to keep away from children.
good job, i am happy for owning this amp.
0.8w output is more than i need :)
very nice sound with my 98db full range speaker.
 

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Intermezzo

Finally I got mine built. I wanted to stay very retro. RCA , engraved base UX-171A power tubes. No caps or resistors in the cct. just an input tranni (Hammond inter-stage Nickel core) and output tranni. Bias is provided by 4 X 9V batteries for 36V. Drives my Fostex FE206En speakers OK but with input impedance 400ohms I had to put a jFet backend on a single stage Tube (12AU7) amp.

I used an "80" rec. tube itself from the 1920s and the base is a wooden flower pot base from the 1940s. The top plate is timber and I fashioned it from 3ply. Most of the cct. hangs under the top plate with three trannies in the base. 240V is stepped down then backup by two power trannies, one in reverse. Then there is a filament tranni.
 

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