Parasound HCA Amplifier Bias Settings?

absolve2525

Super Member
I used to have a chart that listed the different bias settings for the various models, but I can't find it. It was published by Parasound at some point. I need the settings for the 750a, 1000a, 2200ii. Thanks for anyone with this information!
 
For most Class A/B amps you are safe with 30 - 40mA, measured by dividing .030 / emitter resistor value to get the voltage to read across the emitter resistor. The only time this does not work is if the heatsink is exceptionally small (then use 25mA) or if the bias will not stabilize (then use 25mA.)
 
Thanks for the reply. I recall that the 2200ii bias settings were a little different from the other models. I'm not overly concerned, I just figured it would be nice to have the stock info available. Perhaps I can email Parasound. There was a cool You Tube video where a fellow showed the bias adjustment procedure, as well as the bias chart for the different HCA "A" models, but I can't find it anymore! I took a cell phone screen shot of that chart, but I'm not having luck finding it on my phones. It was over a year ago.
 
We did some experimentation with bias current levels vs distortion when I worked at Harman Electronics. We found that above 40mA the reduction in distortion was very small compared to the increase in current. The conclusion was that it made no sense to increase bias above 40mA.
 
Parasound is awesome about customer service.

Phil@parasound.com

For 750A...
Bias levels 10mV, allow amp to warm up for ½ hour, adjust TVR102 left CH & TVR202 right CH.

I haven't used those settings, if they're wrong...we should let Phil know about the mistake.
 
Hi i looked around and this was the latest trend on this matte, and so here goes, just to be claear to adjust the bias I have to apply the MM across the ammiter resistor. does it matter what side of the ER I put the positive - neg? So I blew a gfa 555 attempting this but I turned on the amp before I tried hooking up the MM and so I'm little reluctant to to this to my hca 2200 but I think it's because I should have had it off first, am I right? Thanks
 
Hi i looked around and this was the latest trend on this matte, and so here goes, just to be claear to adjust the bias I have to apply the MM across the ammiter resistor. does it matter what side of the ER I put the positive - neg? So I blew a gfa 555 attempting this but I turned on the amp before I tried hooking up the MM and so I'm little reluctant to to this to my hca 2200 but I think it's because I should have had it off first, am I right? Thanks

did we ever get an answer on this? In the middle of an HCA-1500a rebuild entire left channel was nearly roasted out in a lovely cascade event ...
 
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