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First One - mosFET amplifier module

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Lazy Cat

Lazy Cat

Member
Joined 2007
dellama said:
I have a 10 kilo amp that I would like to fit with your VSSA. The PS rails are +/-70V, what do I need to change on your boards to use this PS? How stable is the VSSA? Have you measured its phase margin?
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Probably First One was on your mind, not VSSA. Well you would have to unwind some turns from transformer's secondary to get +/-63 V DC on smoothing capacitors as this is also max. recommended voltage for the First One module.

Closed loop phase margin is less than 1 deg at 100 kHz.
 
Lazy Cat

Lazy Cat

Member
Joined 2007
dellama said:
No, I think I remember reading still4given (Terry) say he was using +/-70V supply on a VSSA but I could be wrong. Maybe it was a slewmaster.
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As VSSA amplifier (all versions) author I can assure +/-45 V is an absolute maximum for PSU to deliver. Anyway VSSA's front-end could be adopted to higher voltages without any problem, but that is not genuine VSSA anymore. :yes:
 
Lazy Cat

Lazy Cat

Member
Joined 2007
glt said:
What kind of transistor isolators are people using?

Looking at eBay, you can find ready-cut ones from Hong Kong with thickness=.2mm
For thinner ones, 0.05mm they come in sheets from Bulgaria.
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To my opinion mica very thin (0,05-0,07 mm) isolators manually coated with silicon thermal paste is still the best electrical isolation for power transistors, very fast low-thermal resistance connection to the heatsink.

Best ones available at Buerklin, Farnell, Mouser, etc. ;)
 
G

glt

Member
Joined 2004
diyaudio.com/forums/showthread.php?s=&threadid=140669
Lazy Cat said:
To my opinion mica very thin (0,05-0,07 mm) isolators manually coated with silicon thermal paste is still the best electrical isolation for power transistors, very fast low-thermal resistance connection to the heatsink.

Best ones available at Buerklin, Farnell, Mouser, etc. ;)
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Thanks. The closest one I could find (Mouser) are for rectangular TO-3 0.07mm. One can cut to fit but the center holes in the mica insulator may not cover some of exposed metal of the power transistor. There would be an air gap of 0.07 mm though.
Would this be a problem?...Thanks.
 
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