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This is my rendering of the Mini-Aleph based on MikeW's PCB. The
amp config is single-ended input, dual mono down to the power chord, biased to 1.5 amps. Its output is
estimated to be about 17 to 20 watts.
There is 72,000mF per rail; each channel has its own bank of
supply caps. I did not use air-core coils for filtering. Noise is low, however, not audible from the
listening position. I did not by-pass the filter caps yet. The transformers are EI type enclosed rated
at 12.6 CT, 8 amps each. There is very little hum coming from them and they do not get warm to the
touch. The rail voltage unloaded is 19v and 17v loaded.
The circuit itself does not use any exotic parts. The resistors
are Vishay-Dale and the caps are hi-temp bi-polars. Non-polarized caps are micas. The HexFets are
matched IRF9610 for the input stage and CCS and IRF48n for the output and CCS. The output Fets get
very hot to the touch. I can touch them for 1 second. The temp probe shows 60 degrees C for channel 2
and 72 degrees C after 15 minute on time. I need to look at this issue further. After a few hours of
playing music, the heat sinks heat evenly and are very warm but not painful to the touch.
The heat sinks are handmade. All pieces are milled aluminum.
There are no saw cuts! The chassis is 6061 ¼" aluminum and 3/8" plexi-glass for the back
panel.
Listening:
What can I say? It's a terrific little amp. Makes listening to
music fun.
Thank You!
Thanks Nelson Pass for your great generosity! I've been
following your designs since I found the Audio Review article on the 20w class A bi-polar design
from'77-'78. Thank God for You! Karen- thanks for the chassis advice. Apparently, an aluminum and
steel box design is not a problem in this amp. Thanks to everyone at Pass Labs!
Thanks to Lou Di Nenna for milling out the heat sink parts and
Paul Tashjian for fixing my cutting mistakes with your mill and for all the mechanical design ideas.
John Inlow for the DIY heat sink idea. Grey Rollins for putting
out your version of the Mini-Aleph. MikeW for the boards and the troubleshooting advice and everyone
at DIYAUDIO.COM!!!
Thanks,
Vince Di Nenna
vdi_nenna@hotmail.com |