When I turn the Buffalo/Ivy stage on or off I get a very loud crack on my loudspeakers. I am driving a pair of Pluto active speakers directly from the SE IVY output using the volumite for volume control. I don't have this problem with other sources.

I am bit surprised since the IVY output has a relay, no? Maybe it's not doing it's job?

I'd be grateful for debugging suggestions. The units are stock units.

Peter

0.1uF works well for this. Something like this: http://search.digikey.co...Detail&name=P4610-ND

Yes, there's an easy to hear click coming from the relay. There's no turn on or off delay.

Edited by user Monday, August 17, 2009 1:17:40 PM(UTC)  | Reason: Not specified

Measured with a slow DMM, I get 1mv at running, but a spike of 10-15mv at turn off

I'll check that later.

Yes.

Partially - there's still a light pop.

I'll just try to AC couple the amp input. Easy done.

Dear Russ,

your intuition appears correct. I have 2.8V across one channel (top one when looking at the board). The thing is the music comes out fine (thank god for capacitor coupling...).

With 0V input I get 1.4 to ground on both of the balanced outputs for a total of 2.8. Those then are propagated to the SE output (which is the one I am using). The voltage on IC1 is fine: +/- 15 versus ground. The bypass caps on V- and V+ all have their corresponding voltage of 15V across them (I presume this suggests they are not busted). I have carefully checked all components and they are all correct according to their labels. However, I can measure some differences as I compare the corresponding places between the two channels (upper and lower board respectively) as well as I compare the differences between + and - paths in the upper channel. To wit. I have taken an Ohm meter and measured the resistors in situ (everything is turned off, but of course one would not ordinarily expect to see the nominal values in such a measurement). Here is what I get:

R2/3/4 all measure 187R while R1 measures 177R
R17/18/19/20 all measure 21R
R10/11/12 measure 1k8 while R9 measures 1k
R14/15/16 measure 1k8 while R13 measures 1k

So there clearly is some imbalance between the + and - branch of the upper channel.

What could be broken? I am totally mystified. I figure if IC1 is busted I shouldn't get perfectly fine music out of that channel...

Any suggestions on what to try?

Peter

The label says 187R. I do my measurement in situ. If this is my best bet for further analysis I will desolder it and measure it by itself.

Peter

I usually just do a visual inspection. It's possible that the opamp is damaged. If you want, you can send it to me and I will swap it out, or just send you a replacement part.