8610 on one channel?

[CingKrab]

Hi all:

I was curious how the 8610 would sound in my PPA, so I took one from the ground channel of my PIMETA and stuck it in as the opamp for the right channel. I have the 637 on the left and the 627 on ground. However, there's no sound coming from the right channel. I am pretty sure the 8610 works, as the PIMETA seems to work fine. I tried the same thing with the left channel, and the problem repeats itself on the left channel. However, when I put the 8610 on the ground channel, the PPA seems to work fine. Are there any issues with mixing 8610 and 637/627 in this manner?

 

[tangent]

There shouldn't be any problem with mixing op-amps like that.

Have you tried putting the op-amp back in the PIMETA to see if it still works?

What voltage is the PPA running from?

 

[CingKrab]

I've put it back in the PIMETA and I think it's okay; it wouldn't work without the ground opamp right? The 8610 is the ground channel opamp for the PPA right now, and it sounds good. Do you have any idea why putting in the right/left channel doesn't work? The supply voltage for the PPA is 24V (Elpac).

 

[morsel]

Perhaps you accidentally put it in upside down?

 

[CingKrab]

Does this look right? I had it in the same orientation when it was in L and R. Sorry for the poor quality; I only have a webcam, not a camera.

 

[morsel]

The BrownDog is oriented correctly, although the so8 on the BrownDog is not readable and thus the opamp orientation is not certain from your picture. You are showing it on the ground channel. Is it possible you put it in the other way when you had it in the left/right channels?

 

[CingKrab]

When viewed from the same orientation as in the picture, the markings on the chip are upside down. I am fairly certain that this is the way I placed the 8610 in the other two channels when I tried them. I searched for pictures of the PPA to make sure that the chip was in correctly.

 

[CingKrab]

OK, finals are finally over this week and I decided to retrace my steps (with pictures):

1) Listened to the PIMETA with the AD8610 in the ground channel. Works OK (both channels have sound).



2) Removed the AD8610 from PIMETA ground and inserted AD8610 in the PPA left channel. No sound in the left channel.



3) Removed the AD8610 from PPA left and inserted AD8610 in the PPA ground channel. Seems to work OK (sound in both channels).



4) Removed the AD8610 from PPA ground and inserted AD8610 in the PPA right channel. No sound in the right channel.



5) Removed the AD8610 from PPA right and inserted AD8610 in the PIMETA ground channel. Sounds the same as #1.



Here is a pic of the default configuration of the PPA (OPA637 in L/R, OPA627 in ground):



I realize that you can't see the markings on the AD8610, but I bought it mounted from Tangent, so I assume it's mounted correctly. Is there anything that I did wrong, or anything else I can try?

 

[CingKrab]

Bump... I measured the voltage from the + and - power supply pins today. With the OPA637, it's 11.27V on the + pin, and 11.30V on the - pin. With the AD8610, it's 11.33V on the + pin and 11.39V on the - pin. Is there anything else I can try to determine what's wrong?

 

[Glassman]

yup, check the voltage across R14 when ad8610 on ground ch and when on the left/right.. were these buffers assembled by you?

 

[CingKrab]

I measured the voltages across R14 in all the configurations I've tried, and the results are here:
http://www.geocities.com/cingkrab/R14voltages.htm
As for the buffers, actually it was you who built them, Glassman

 

[Glassman]

that looks just fine.. now try measuring voltage on those R14 referenced to input ground..

 

[CingKrab]

Hmm here they are:
http://www.geocities.com/cingkrab/R14voltagesground.htm
I'm pretty sure that's in volts, if I read my multimeter correctly.

 

[amb]

Quote:

Originally Posted by CingKrab Hmm here they are: http://www.geocities.com/cingkrab/R14voltagesground.htm I'm pretty sure that's in volts, if I read my multimeter correctly.

Whoa, you have a huge DC offset problem at the output of the AD8610! Carefully check to make sure that all pins of the chip is well soldered to the adapter, and that the adapter pins are making good contact with the socket when plugged in (use your multimeter in ohms mode to verify this with the amp powered off).

 

[CingKrab]

I checked the soldering and I think it looks OK. From each leg of the AD8610 to the corresponding pin of the BrownDog (top of the pin) is about 0.2 ohm, and makes a noise with the continuity meter. From the top of each pin on the surface of the BrownDog to each corresponding solder joint on the socket on the underside of the PPA board is also about 0.2 ohm, and also makes a noise with the continuity meter. Am I doing this right?