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schro20  
#1 Posted : Monday, August 17, 2009 8:24:25 AM(UTC)
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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
avr300  
#2 Posted : Monday, August 17, 2009 12:38:27 PM(UTC)
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Make sure that it's not coming from mains breaker. I had similar symptoms before I placed a couple of right-sized (can't remember the capacitance, but they are 600v) caps over the switch (breaking both live and ground).
Brian Donegan  
#3 Posted : Monday, August 17, 2009 12:53:44 PM(UTC)
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0.1uF works well for this. Something like this: http://search.digikey.co...Detail&name=P4610-ND
schro20  
#4 Posted : Monday, August 17, 2009 1:10:27 PM(UTC)
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That's worth a try. But before I do that, how do I verify that the relay is doing its thing? What is the delay supposed to be on it? Should I be able to hear it click if I listen carefully?

I am asking since I have used the same switch on other projects and haven't had this issue. Of course this circuit might be more sensitive to this issue. (The idea of bypassing the switch is probably a good idea in any case...)

Peter
avr300  
#5 Posted : Monday, August 17, 2009 1:13:13 PM(UTC)
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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

Russ White  
#6 Posted : Monday, August 17, 2009 4:33:41 PM(UTC)
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Check for any offset at the SE output.
avr300  
#7 Posted : Wednesday, August 19, 2009 10:57:40 AM(UTC)
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Measured with a slow DMM, I get 1mv at running, but a spike of 10-15mv at turn off Think
Russ White  
#8 Posted : Wednesday, August 19, 2009 3:16:44 PM(UTC)
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That almost sounds like there is some DC bias at the inputs of the next stage.
avr300  
#9 Posted : Wednesday, August 19, 2009 10:52:54 PM(UTC)
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I'll check that later.
Brian Donegan  
#10 Posted : Thursday, August 20, 2009 3:42:42 AM(UTC)
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avr300 wrote:
I'll check that later.


Are you experiencing the pop as well?
avr300  
#11 Posted : Thursday, August 20, 2009 6:37:06 AM(UTC)
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Yes.
Brian Donegan  
#12 Posted : Thursday, August 20, 2009 6:53:01 AM(UTC)
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avr300 wrote:
Yes.


But you said above that the problem went away with the addition of caps to your power switch?
avr300  
#13 Posted : Thursday, August 20, 2009 10:14:00 AM(UTC)
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Partially - there's still a light pop.

I'll just try to AC couple the amp input. Easy done.
james.evans@frost.com  
#14 Posted : Sunday, August 23, 2009 10:52:09 AM(UTC)
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I also get a pop/crack when switching buffalo/ivy on/off. Excuse my ignorance, but where should the 0.1uf caps go?

Also, slightly related question - I'm considering using this with a power amp that's dc coupled. Would I be best putting caps on the SE output of ivy?

Thanks

James
schro20  
#15 Posted : Sunday, September 13, 2009 9:08:48 PM(UTC)
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Russ White wrote:
Check for any offset at the SE output.


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
Russ White  
#16 Posted : Monday, September 14, 2009 4:44:35 PM(UTC)
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R1 should be 187R.

If it is not you will have a lot of offset.
schro20  
#17 Posted : Tuesday, September 15, 2009 6:36:42 AM(UTC)
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Russ White wrote:
R1 should be 187R.

If it is not you will have a lot of offset.


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
schro20  
#18 Posted : Wednesday, September 16, 2009 7:47:06 PM(UTC)
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Getting closer...

I desoldered R1 (what a pain...). In isolation it measures what it says on the label: 187. I then just kept looking around for where the problem might be. I discovered that I have a short somewhere between IN1.1 and GND. The thing is that there is only a very small range of board where this could happen. I examined everything with a very high magnification lens. I can't see any stray solder or some such. I carefully scraped between tracks for stuff that is too small to see. All to no avail. The one place I can't look is underneath IC1. After IC1 is baked on there, do you guys run tests that would reveal a short between pin 8 and 2?

I don't know what else to try now in terms of finding this short. Very frustrating!

peter
Brian Donegan  
#19 Posted : Thursday, September 17, 2009 5:38:26 AM(UTC)
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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.
schro20  
#20 Posted : Friday, October 2, 2009 8:46:09 AM(UTC)
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Brian Donegan wrote:
If you want, you can send it to me and I will swap it out, or just send you a replacement part.

Dear Brian,

I'll take you up on the offer of sending a replacement part. I took the IC off and found indeed a solder induced short between pin 7 and 8. Unfortunately the removal of the chip was destructive... :( Pads are still ok though.

Peter
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