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Old 23rd August 2007, 07:02 PM   #631
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Argh, now removing the - signal has no effect on the hum. If I go straight from the opus to the output jacks, no hum. If I have zapfilter to outputs but haven't connected the opus to the zap, no hum. There has to be some sort of ground loop between the two. I'm thinking of trying to remove R2 and R4 from the DAC boards.

Also, when I have both DAC boards connected to the spdif receiver, I get a very high pitched whine. If I remove one DAC or the other, the whine disappears.
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Old 23rd August 2007, 07:08 PM   #632
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How are you powering these?
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Old 23rd August 2007, 07:19 PM   #633
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Quote:
Originally posted by fierce_freak
I'm thinking of trying to remove R2 and R4 from the DAC boards.

Also, when I have both DAC boards connected to the spdif receiver, I get a very high pitched whine. If I remove one DAC or the other, the whine disappears.

Was any of this happening before?

One thing to keep in mind is that it would be better to wire each I2S signal direct from the receiver, do not daisy chain. Think of each wire as a transmission line.

If you remove R2 and R4 you might as well remove R1 and R3 as they all do the same thing. I don't think this will have any positive effect, and in fact will probably have a negative one.

Cheers!
Russ
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Old 23rd August 2007, 07:20 PM   #634
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Power for the Opus modules is coming from an LCPS with the toroids you guys offer. The zapfilter has it's own power supply board that is being powered by a different transformer. This is all in the same case getting power from one IEC inlet. Earth ground is connected to the chassis. Maybe I need to put together a ground loop breaker.

-edit- The high-pitched whine has been there since I put the zapfilter in. I'll rewire so each DAC gets its I2S directly from the receiver instead of daisy-chained. That'll be later, though...off to work now ;(
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Old 23rd August 2007, 07:25 PM   #635
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Quote:
Originally posted by fierce_freak
Power for the Opus modules is coming from an LCPS with the toroids you guys offer. The zapfilter has it's own power supply board that is being powered by a different transformer. This is all in the same case getting power from one IEC inlet. Earth ground is connected to the chassis. Maybe I need to put together a ground loop breaker.

-edit- The high-pitched whine has been there since I put the zapfilter in. I'll rewire so each DAC gets its I2S directly from the receiver instead of daisy-chained. That'll be later, though...off to work now ;(

Sory for the frustration, EMI/GND loop issues are never fun. Which reminds me, the humm could also be EMI, and not a loop.

Cheers!
Russ
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Old 23rd August 2007, 08:15 PM   #636
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It's certainly not your fault, but thanks. I also appreciate your patience in trying to help me.

When I first heard the hum, my first thought actually was EMI. I tried rotating and relocating the traffos and moving different components around with no effect. I'm not getting hum with only the zapfilter or only the Opus hooked up, so I'm guessing it's got to be a loop of some sort. My only thoughts on removing those resistors earlier was to remove any path to ground from the signal lines.

In my previous zap install, I hooked ground directly to AGND (AD1852 DAC). Judging from the schematic there's a measuring point between AGNDL and AGNDR. Would getting ground there change anything? It seems ground there would be the same as ground at the output.
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Old 23rd August 2007, 08:27 PM   #637
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Is your Zap filter GND connected to the chassis ground? If so, try lifting that connection.
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Old 23rd August 2007, 08:56 PM   #638
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[QUOTE]Originally posted by fierce_freak
[B]It's certainly not your fault, but thanks. I also appreciate your patience in trying to help me.




Is the ground connected to chassis on the zhaolu IEC plug?

allan
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Old 23rd August 2007, 09:03 PM   #639
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Ground from the IEC is connected to the chassis. I've lifted it, and it didn't change anything. I used to have a schematic for the zapfilter, but I can't seem to find it now...so I'm not sure if the zapfilter uses chassis for ground or not.
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Old 23rd August 2007, 09:22 PM   #640
awpagan is offline awpagan  Australia
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Quote:
Originally posted by fierce_freak
Ground from the IEC is connected to the chassis. I've lifted it, and it didn't change anything. I used to have a schematic for the zapfilter, but I can't seem to find it now...so I'm not sure if the zapfilter uses chassis for ground or not.

Mine (IEC Ground Lead) is not even there let alone connected, is something i intend to do.
schematic is on Lar's website.
I think some screw on the zhaolu are connected to chassis.
Will check again when i get back (sunday)

allan
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