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AU-20000 vs. BA-3000

Orcinus

Orcinus

Active Member
I received my AU-20000 service manual today (finally! Took nearly a full month to get here!) and I noticed that the bias current is specified at 35 mA. Now, as we all know, the AU-20000 is a melding of the CA-3000 preamp with the BA-3000 power amp, of which I have the service manual for (downloaded it from the 'net). However, the bias current for the BA-3000 is specified as 20 mA. Does anyone know why this is? Will an incorrect bias current in my AU-20000 (i.e. set to 20 mA instead of 35 mA) cause any problems at all?

I'm really curious as to why these supposedly identical power amplifier sections have different bias currents... :scratch2:
 
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Thats a good question, the other one is how do you fit a CA-3000 and a BA-3000 into a AU-20000. I know the spec,s 170 wpc for the amp section are the same, but I am still confused. :headscrat Perhaps there are some reasons why the bias ratings are not the same. Lastly Orcinus, where can I find that BA-3000 service manual?
 
What makes you so sure that the amp section of the AU-2000 is the same as the BA-3000?

- Pete
 
totem said:
Thats a good question, the other one is how do you fit a CA-3000 and a BA-3000 into a AU-20000. I know the spec,s 170 wpc for the amp section are the same, but I am still confused. :headscrat Perhaps there are some reasons why the bias ratings are not the same. Lastly Orcinus, where can I find that BA-3000 service manual?
Click to expand...

the service manual can be downloaded here http://www.classicsansui.net/Schematics.htm


cant help you with why the different biasing but could it be because the ba 3000 can be bridged to mono?
 
LBPete said:
What makes you so sure that the amp section of the AU-2000 is the same as the BA-3000?

- Pete
Click to expand...

Because Sansui themselves have said so, it's well documented. Also, the schematics of the power amp section of the AU-20000 are pretty much identical to the BA-3000, except for the bridging circuitry (which just inverts the input of one channel, and you use the two positive connections for your speaker output)
 
radioactive said:
cant help you with why the different biasing but could it be because the ba 3000 can be bridged to mono?
Click to expand...


Hmm, there's a thought... but any amplifier with a common-ground output on the speakers can be bridged simply by inverting the input of one channel and then using both positive connections (skipping ground) for the speaker. (the AU-20000 does indeed have a common speaker ground)
 
I did a little homework since making that statement. The amp sections do indeed have a lot in common, right down to the component layout.

- Pete
 
Nudes

AU-20000

AU-20000.jpg


BA-3000

SANSUIBA-3000.jpg
 
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