[dcrane]

I think I used wrong values when calculating quiescent current.
opa627 should be 7ma, buf634 should be less than 8 when using 220 ohm - stacked 2 deep around 5ma each, plus 2 for the LED. This means I should be at 53ma. Do these numbers sound right? Switching to 8610s dropped the current 10ma. Which puts the chips in line with tangent notes about the 8610 coming in around 3.5ma

 

[joneeboi]

Have you tested the amp with a different source?

 

[dcrane]

Yes, briefly. And, it did not do it. I think I've found the problem or at least part of it. I hate to admit it but I put 2 of the caps in backwards -doh! The current draw is still the same but going down slowly along with the batteries. Does the current seem right for a class A pimeta? My thoughts are that it needed a certain amount of strain from the weaker source and sennheisers to cause the problem. I didn't try another portable device.

I was surprised how good the 8610s sounded because they were not so good in my ppa[JMT]. I ordered a couple of 8620s on adapters because the 8610s didn't quite fit right. They're the same price mounted from cimarron compared to digikey anyway.

 

[dcrane]

Something still doesn't seem right. I removed the class A components. The amp was still drawing a lot of power without any source. I unplugged the opamps and there was still a significant draw. Removing the buffers brought the current down to just under 5 ma which is for the LED. Should the buffers be drawing full power(based on R11 bandwidth setting) without any opamps or input?

 

[Pars]

Quote:

Originally Posted by dcrane /img/forum/go_quote.gif Something still doesn't seem right. I removed the class A components. The amp was still drawing a lot of power without any source. I unplugged the opamps and there was still a significant draw. Removing the buffers brought the current down to just under 5 ma which is for the LED. Should the buffers be drawing full power(based on R11 bandwidth setting) without any opamps or input?

Yes, that is their quiescent current draw (i.e., on, not doing anything) in the datasheet. Class A operation draws the same power whether it is playing or not. The closer you get to class A, the higher the quiescent current draw will be. And for BUF634s, higher BW will put then higher in current draw as well.