Pass DIY Addict
Joined 2000
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Yep, as Radiodave indicated, by shorting that resistor leg to ground, it was trying to draw somewhere near 28v/0.1R or 280A of current out of your power supply! Instant toast. That little guy didn't stand a chance, it's only rated for 3w...
Good to hear that it seems the rest of your circuit survived! Does it still make nice music?
Good to hear that it seems the rest of your circuit survived! Does it still make nice music?
It's making very nice music. Prior to the R32 smoke-up incident, the amp was only hooked up to very inexpensive non-powered desktop speakers that I purchase at thrift store specifically for amp testing. I have since moved on to better speakers - small bookshelf speakers with a single wide-band driver that I can actually place on my workbench.
I'll be moving the amp to my listening room this weekend for a good long listening session.
Has anyone experimented with changing the distortion character. Nelson states in the Sony vfet part 2 article about adjusting the Cascode feedback resistors.
"There are numerous variations and lots of little tricks, and besides lowering the output impedance of the front end, it is convenient and effective for reducing and tweaking the specific distortion character of the circuit, as the positive and negative halves of the circuit can be adjusted independently."
My Dual Vfet version matches were not the best, so there is more 2nd harmonic. Maybe not a bad thing? Each channel is a little different when measuring the distortion so I was thinking about playing with the Cascode feedback values.
BDP
"There are numerous variations and lots of little tricks, and besides lowering the output impedance of the front end, it is convenient and effective for reducing and tweaking the specific distortion character of the circuit, as the positive and negative halves of the circuit can be adjusted independently."
My Dual Vfet version matches were not the best, so there is more 2nd harmonic. Maybe not a bad thing? Each channel is a little different when measuring the distortion so I was thinking about playing with the Cascode feedback values.
BDP
Yes, by changing the TL431 shunt regulator. Change R15 or R16 about 250 ohms per one volt change.
I have Teabags boards and that would be another option.
Making the adjustment at the outputs, where the mismatch occurs makes sense, but the Cascode feedback resistance would be easy to implement.
BDP
I’ve been listening to my amp, off and on, for about one half of a year. It’s now hooked up to a good pair of Klipsch Cornwalls (the very earliest “Cornwall II”) and it sounds clean and clear. I’m a very happy builder.
In my past, I have done a little professional audio work for a tiny $5B/yr company. I have also got an innate passion for good, clean audio. I’m of the opinion that the scarcity of the V-FET is most unfortunate, yet, that makes this project that much more special.
Mr Pass, thank you for sharing. Job well done, sir.
In my past, I have done a little professional audio work for a tiny $5B/yr company. I have also got an innate passion for good, clean audio. I’m of the opinion that the scarcity of the V-FET is most unfortunate, yet, that makes this project that much more special.
Mr Pass, thank you for sharing. Job well done, sir.
Hi Phil,
Try post #2766:
https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-277.html#post4991406
Cheers,
Dennis
Try post #2766:
https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-277.html#post4991406
Cheers,
Dennis
Here is a link to the Supplemental kit that was offered by diyaudio way back when. It doesn't give all the part numbers, but it's a start:
Pass VFET Power Amp Supplemental Kit – diyAudio Store
Pass VFET Power Amp Supplemental Kit – diyAudio Store
