You don't use a multimeter. Use the amp meter on your 12v power supply to monitor current draw. Use your scope to check for symmetrical clipping.
You can't measure the bias without the amp being powered up.
You can't measure the bias without the amp being powered up.
Ok thank you perry. With my amp meter hooked up I have .63 amps at idle. Where I had it set to by ear with my phone hooked up to take out distortion I had an increase of .07 amps per channel and it has .77 amps at idle. One of the pots is almost all the way up though and the other is 3/4 the way up.
My phone probably doesn’t send a good signal so I probably have to crank up the bias pot? I’d rather not set it this way and use my meter to set it. How much of an increase should I see? The current never takes off and just slowly increases on my meter, it never goes over 1 amp with the bias pots cranked fully clockwise.
My phone probably doesn’t send a good signal so I probably have to crank up the bias pot? I’d rather not set it this way and use my meter to set it. How much of an increase should I see? The current never takes off and just slowly increases on my meter, it never goes over 1 amp with the bias pots cranked fully clockwise.
Phones will produce a perfectly clean signal.
You set the bias with no input. You would double-check with signal, after the bias is set while watching current draw.
1 amp would be well below what I'd expect but it's well above what you need for the minimum idle current.
Do you have a scope? You can't rely on 'by ear' to determine if the amp is clipping normally.
This is how you'd adjust the bias when doing so by current draw.
http://www.bcae1.com/temp/ausettingbias.swf
You set the bias with no input. You would double-check with signal, after the bias is set while watching current draw.
1 amp would be well below what I'd expect but it's well above what you need for the minimum idle current.
Do you have a scope? You can't rely on 'by ear' to determine if the amp is clipping normally.
This is how you'd adjust the bias when doing so by current draw.
http://www.bcae1.com/temp/ausettingbias.swf
I set it with my meter on amps and it is right by where I had it set to get rid of the distortion. It is at .78 amps at idle. Also I referenced some photos I took of when I first cracked the amp open and where I have them now is just a slight increase from before.
I checked it with my oscilloscope and both channels clip at +-33v.
I’ve been playing music with my iPhone and a 5” speaker hooked up for the last few hours and it gets warm but I can hold my fingers on the mosfet clamps. I was also playing a test tone for the first half hour and it never got hot, just warm. So I think it’s good to go and time to check it in my truck.
Thank u very much for your help Perry, I really apreciate it.
I checked it with my oscilloscope and both channels clip at +-33v.
I’ve been playing music with my iPhone and a 5” speaker hooked up for the last few hours and it gets warm but I can hold my fingers on the mosfet clamps. I was also playing a test tone for the first half hour and it never got hot, just warm. So I think it’s good to go and time to check it in my truck.
Thank u very much for your help Perry, I really apreciate it.