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RE: Opinions on 6P3S for Hi-Fi ?

I was quite happy to see this post - I really like the 6P3S . A while ago I purchased 36 of them and proceeded to current match them on my modified ST-70 . I swopped the 5AR4 in the ST-70 for a Russian 5C4M - this reduced Anode voltage to about 415V . I then adjusted bias to minimum and set balance adj. to the center position . I then use the ST-70 as a tube tester to current match the tubes , and then sort them into matched or closely matched quads .

The spread at 415V range ( within my 36 valves ) from 30 to 50 mA . One tube ran over 70 mA and two in the mid to high 50's . I gave the highest current quad to fellow South African valve aficionado , warning him that this was the hottest running quad and should be used at low anode voltages .

The hotter running remaining tubes ( 40-50 mA ) I run in Quad 2 monoblocks with the same 5C4M rectifier ( 5C3S also works ) , with bias resistors values increased from 180e to 250e ( 4x 1K 1 watt resistors in parallel ) .

The cooler running quads ( 30-40 mA ) I use in the Dynaco and bias to ~85% dissipation ( ~17W per tube ) using Rob Robinette's online bias calculator to find desirable bias setting .

Compared to a Quad of vintage CV1947's , and 3 sets of EL34's ( Mullard , JJ EL34L's and EH's ) they sound pretty good ; in the Quad 2's or ST-70 . I love 'em . :)

For the money , I reckon you can't go wrong .


" When in doubt, do the courageous thing. " - Jan Smuts



Edits: 05/25/17

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  • RE: Opinions on 6P3S for Hi-Fi ? - fredeb 11:40:28 05/25/17 (0)

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