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 Handwired ST-70

35 WPC Push Pull Stereo

4x EL34s, 2x 12AU7, and 1x 12AX7

Based on DIYTUBE ST-70 Schematic

Completed on 10/31/08   

"This 2xKT66/channel amp is absolutely beautiful - both in the way it soundsand in the way it looks. Modern "audiophile" sonics but without omitting that great classic sound, and it has that great old-fashioned industrial look. Wide and deep soundstage, wonderful tone, and balanced from top to bottom. And Min was right about this amp being the quietest he's ever made - it is so quiet and free of background noise that the musical detail really comes through. I have purchased one-off amps from other people in the past, but Min is the only maker who delivers on time, stays in constant communication, and gets things done with no drama or issues. Thank you again, Min!!!   - KLM from NYC

Comments from KLM five months later -

The Mundorf caps and the "Genalex" tubes have broken in quite well. The thin sonic signature that I heard when the amp was just out of the box has changed, and it's gotten richer. Tight and detailed bass, fleshier midrange.  I'm using an EH 5U4G rectifier instead of my NOS 5AR4's; the former gives the amp a more relaxed sound; the latter was too forward.  Thank you again for such a great amp at such a great price and no delivery dramas.


Built on 17x10x3 Hammond grey steel chassis.



This is how it looks like if you don't use a PCB.


Power supply section, including the biasing circuit. 


I am using a star ground at three places on the chassis: 1) high current components like output tubes, center taps for irons, etc grounded at the -ve terminal of the first filter cap on the chassis, 2) 12AU7 preamp section grounded at the -ve terminal of the 2nd filter cap, and 3) 12AX7 preamp section grounded at the -ve terminal of the 3rd filter cap. Result? The quietest PP amp I've ever made.




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