Beginner to build an Aleph30 needs some help - Page 3 - diyAudio
 Beginner to build an Aleph30 needs some help
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 20th January 2014, 07:09 PM #21 diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain R12 - yes but value of R12 is transposing further exactly voltage resulted across R23-R26 so - do not alter their value unless you know what you're doing tip - even if you can't grasp what's going on - just print all original Aleph schematics and study them one of them will suit your needs , then follow it blindly __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
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Join Date: Oct 2010
Quote:
 Originally Posted by cowneko For the heatsinks, here the big babies
You are building a 6- device Aleph with 32V rails.

Your heatsinks are not all that big...

But they will work.

Quote:
 Originally Posted by Zen Mod one of them will suit your needs , then follow it blindly
Probably Aleph 5 or 2.

Last edited by 6L6; 20th January 2014 at 07:32 PM.

 20th January 2014, 07:16 PM #23 diyAudio Member     Join Date: Sep 2003 Location: Upstate NY The sense resistor value fits into the equation, but we usually play with the smaller cheaper ones. The gain is set by the ratios of R20 to R12 and R23-26 net to R35, 37, 39 net parallel. With the sense resistors equal to half the parallel source resistors and R20= R12 we get ~50% AC gain, IIRC. Yeah, those heat sinks are sissy sinks for the build you planned. They probably will be awful hot at 180W. Cut back to 4 pairs. Looks like store cases packaging. The 3 pair 30V rail amp needs the 5U case. Last edited by BobEllis; 20th January 2014 at 07:19 PM.
 20th January 2014, 07:27 PM #24 diyAudio Member   Join Date: Apr 2013 Location: Valenciennes Maybe the pictures doesn't do those heatsinks justice, but they are 5U heatsinks (300mmx210mmx40mm) given for 0.2C°/W I just find them huge cause I never came across heatsinks those big
 20th January 2014, 07:29 PM #25 diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain 4U is good up to 100W diss per side , confirmed in real life ( though , not in Bombay ) 5U is for not much more ..... say 125W max __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 20th January 2014, 07:30 PM #26 diyAudio Moderator     Join Date: Oct 2010 Location: Denver, Colorado You might need a fan. No worries, moving a little air makes a big difference. __________________ Illustrated Build Guides - Pass F4 - Pass B1 - Pass F5 - Pearl 2 - O2 HPA - Hagerman Bugle 2 - Pass Aleph J - Me at BA '13 -Pass F5Turbo - BA-3 Amp - BA-3 Preamp - F6 AmpCampAmp
 20th January 2014, 08:35 PM #27 diyAudio Member   Join Date: Apr 2013 Location: Valenciennes Well, I have to think of something for the cooling then..... maybe a 120mm bequiet computer fan (15db at 12V) be quiet! Silent PSU & Cooling for your PC Witch will be placed on the top plate of the amp in blowing mode (outside air pumped inside the chassis with a little 30VA 2x15v (for the Speaker protections) and 1x9v (for the fan) Transformateurs torique - Transformateur torique 30VA 2x15V + 1x09v plus a little regulator psu to feed the fan with DC voltage Alimentation linéaires - AMC - kit Alimentation régulée 1.5/30VDC 3A LM1085 I will make a BOM for the amp, I hope you'll be able to tell me if there's something odd with it
 20th January 2014, 08:57 PM #28 diyAudio Member     Join Date: Sep 2003 Location: Upstate NY Save yourself a transformer and the fan controller - use the same transformer for protection circuit and fan. Set it up ct, use a bridge for +/- and a single 1n4007 followed by a small cap for the fan supply. You can make very simple fan speed control with a pot and a mosfet. You can add an extra cap across the resistor to help starting if slow speed operation becomes a problem. All fits on a small piece of perfboard. Layout not critical. Papa posted a circuit for this many years ago, I will try to redraw it when I get home, but will try to describe it; 1N4007 and 100 uf (value not critical) cap create a ~9V supply from a 15VAC winding and ground. 10K pot connects across the 9V and ground. Can be single turn, 10 turn or 25 turn if you really like turning things. To +9V connect the fan + To fan - connect the drain of an n channel mosfet. General purpose anything like IRF610, IRF510, etc. (to name what's in my parts bin) Source of mosfet to ground. Wiper of pot to gate of mosfet. 1-10 uf from mosfet gate to V+ if needed to help startup. The voltage at the mosfet gate controls current, which is controlled by the voltage divider created by the pot. The cap from V+ to gate creates a spike on turn on that will give the fan plenty of juice to start and then drop down to a lower running speed.
 20th January 2014, 09:22 PM #29 diyAudio Member   Join Date: Apr 2013 Location: Valenciennes Thanks a lot BobEllis, I think I will learn a lot with this project and everybody advises (even if some of them are still little obscure form me right now) I'm eagerly waiting for your drawing, but I will try to understand the concept from your description.
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Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
oomph
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