Yamaha CA-400 asymmetrical power rails? - diyAudio
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Old 24th August 2010, 08:17 PM   #1
Artie is offline Artie  United States
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Location: Jax, FL
Default Yamaha CA-400 asymmetrical power rails?

I've never seen this before, and was wondering why they might do this? The positive rail is fairly conventional, feeding both the positive output and driver. But the negative rail provides a different voltage for the driver than the output trans. Can anyone tell me why they might do this? Just seems odd.

Here's a simplified drawing of the relevant PS circuit, and then the full schematic if anyone wants to see it.

Thanks all;

Edit: Whats especially odd, is that it requires a special transformer, (not cheap), that provides an extra "tap".

And here's a link to the full schematic if you want to see it: Yamaha CA-400 (It's fairly large.)
Attached Images
File Type: png CA-400-segment.png (7.6 KB, 178 views)

Last edited by Artie; 24th August 2010 at 08:19 PM.
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Old 29th August 2010, 04:03 PM   #2
Artie is offline Artie  United States
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Location: Jax, FL
No one?

I know it's a somewhat obtuse question, but it intrigues me. Yamaha had to use a unique transformer to obtain the oddball negative voltage. It just seems like an odd thing to do on a low-line amp. They don't do it on any others. (That I've seen.)
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Old 4th April 2011, 01:17 PM   #3
pezza89 is offline pezza89  Australia
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does anyone know the value of the zenar diode on the output board? i need a replacement but not sure of its value! thanks!
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