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RevMen
diyAudio Member

Join Date: Feb 2011
Location: Austin, TX
As always, thanks for the fast response, Salas.

It seems like this one should work. Do you think so?
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 20th February 2012, 09:09 PM #602 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece No, see rightmost column, it gets to 2C/W under forced convection, i.e fan blower. You need 2C/W on natural convection.
 20th February 2012, 10:41 PM #603 RevMen   diyAudio Member     Join Date: Feb 2011 Location: Austin, TX Understood, but the 2 C/W is for a downward facing orientation (flat side on the top). If I set it on its end, convection will be more efficient. Still, though, I don't know how much more efficient, so it's probably best not to guess. I reckon I don't understand how to determine how much heatsink is needed. I was thinking in terms of the 11W dissipation at dT=60 for natural convection, which I suppose would mean ~6.4 W at dT=35 (60C-25C). And I suppose that allows us to dissipate 21 mA at 300V, or have I got that wrong? How much spare current would we expect in this circuit? Would it be higher or lower than 20 mA?
 20th February 2012, 10:53 PM #604 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece When you got over 40C in a valve circuit box such a sink can rise up to 75C. 300Vx0.02A= 6W and a 2C/W will get you to 55C in a hotter day which is much more agreeable. When having 55C on a sink its not difficult to have 100C plus on the silicon junction to have a picture. Don't skimp on sink area, this is constant current giving it no cooling off cycle %. 20mA spare is the recommended compromise. If you give it 30mA the reg's spec gets better and so it goes. Measure 60C max on your sink for max spare after half an hour in real box is a safe rule of thumb.
 2nd April 2012, 08:31 PM #605 RevMen   diyAudio Member     Join Date: Feb 2011 Location: Austin, TX How should turntable chassis ground tie into the circuit?
 2nd April 2012, 09:09 PM #606 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece To a chassis post while the chassis will be at ground potential with one wire from PSU 0V.
 4th April 2012, 04:09 PM #607 RevMen   diyAudio Member     Join Date: Feb 2011 Location: Austin, TX OK, thanks. That makes sense. Does it make sense to tie PSU 0V to the chassis at the location of the chassis post? Or does that matter?
 4th April 2012, 04:16 PM #608 Salas   diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece It usually doesn't matter.
 8th April 2012, 12:18 PM #609 woodturner-fran   diyAudio Member   Join Date: Jan 2006 Location: Ireland Has anyone tried the RIAA caps that Felipe organised for us? I'll admit that I'm very reluctant to open mine up - its sounding fantastic! Would be interested to hear people's opinions vs the Russian caps... Fran
 8th April 2012, 12:34 PM #610 merlin el mago diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe I still not tried, did you tried?

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