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Hi! I'm having problems with my Dual Mono Opus that i just can't fix, so i need your help. Everytime i turn the power on there is a 3 - 5 seconds of silence, then noise, scraping cracklig sound is starting to build up. It's increasing in volume and after about one minute it starts to decrease. Sometimes it's just the left, other times it the right or both channels. It's quite random. After another 10 minutes it's a lot better but not good. The noise is still there varying in volume and channel. Disconnecting the 4:1 MUX makes no difference. However, if i disconnect the Metronome leaving only the two Opus and IVYs powered it's dead silent. I have tried everything i can imagine. Stacking Opus->Metronome->Opus with no I2S cables exceeding one inch in length including MUX->Metronome, putting the modules beside each other, moving things around, making every cable as short as I can. Metronome 48KHz, Metronome 192KHz, shielded cables, different voltages. No matter what i do i get the same result. Should mention that it works and sounds good. Anyone please? Edited by user Tuesday, February 9, 2010 7:21:03 AM(UTC)
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What are your switch settings on Metronome and Opus modules?
A few pictures can often help in diagnosis. Try to show your power wiring relative to your I2S wiring, as that it the most common source of noise injection.
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Added pictures of Opus and Metronome. The only difference between the Opus on the picture and the other one, is the "mode" switch.
Thanks Brian!
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I had a similar problem in the past, but it is now gone. One thing I tried (which I'm not 100% sure was the thing that cured the problem) was installing a reset switch in the Metronome. If you read the datasheet carefully you will find that power cycling does not reset the chip, but that you need to pull a pin low (and then high, if I remember correctly) in order to reset the chip. Read the part about h/w reset.
I see you are using placid to power the analog side of OPUS. Excellent and worthwhile mod :-)
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glt wrote:I had a similar problem in the past, but it is now gone. One thing I tried (which I'm not 100% sure was the thing that cured the problem) was installing a reset switch in the Metronome. If you read the datasheet carefully you will find that power cycling does not reset the chip, but that you need to pull a pin low (and then high, if I remember correctly) in order to reset the chip. Read the part about h/w reset.
You're right. A couple of weeks ago i finished my Arduino program. At startup and whenever i changed the samplerate on the Metronome i did a reset. The reset pin was connected to the Arduino. Just did a couple of resets manually but it doesn't help. It does however change the pitch and the position of the noise randomly. A hidden feature maybe :) glt wrote:I see you are using placid to power the analog side of OPUS. Excellent and worthwhile mod :-) I hope i can enjoy this highend mod some day. Right now i have to turn up the volume to -35db to get rid of this terrible noise.
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The WM8741 has internal upsampling to 192K that is tied to the design of the filters. So with Metro at 192K, you need to turn off the internal upsampling (which you must already do with the Arduino, I believe). Ideally one would want to reclock a 44.1K signal to 44.1K with Metro, but you can't do this because the clock in Metro only supports 48K and multiples. And then let the DAC do the high rate upsampling. If you are using a WM8804 (the opus receiver), maybe you can omit the Metro. I had some email communications with a Wolfson engineer, and he indicated that the filters work their best if you let the DAC do the upsampling (although I can hear any differences with my speaker-based system) I read the papers on the WM8804 and it is different from other implementations in that after the PLL (clock recovery), it reclocks the data (through a buffer -they call it elastic buffer) with a new time-base derived from the 12MHz crystal, thus minimizing jitter. (thus this device begs to be tweaked with cleaner supplies, as it generates its own clock :-)) re: volume -35db? I typically listen at -20db straight from the DAC to (balanced) amp (Hypex ucd180). Sometimes with older CDs, before the loudness war, you can go to 0 db without breaking the walls. Edited by user Tuesday, February 9, 2010 2:20:36 PM(UTC)
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glt wrote:The WM8741 has internal upsampling to 192K that is tied to the design of the filters. So with Metro at 192K, you need to turn off the internal upsampling (which you must already do with the Arduino, I believe).
Ideally one would want to reclock a 44.1K signal to 44.1K with Metro, but you can't do this because the clock in Metro only supports 48K and multiples. And then let the DAC do the high rate upsampling.
If you are using a WM8804 (the opus receiver), maybe you can omit the Metro. I had some email communications with a Wolfson engineer, and he indicated that the filters work their best if you let the DAC do the upsampling (although I can hear any differences with my speaker-based system)
I read the papers on the WM8804 and it is different from other implementations in that after the PLL (clock recovery), it reclocks the data (through a buffer -they call it elastic buffer) with a new time-base derived from the 12MHz crystal, thus minimizing jitter. (thus this device begs to be tweaked with cleaner supplies, as it generates its own clock :-))
re: volume
-35db? I typically listen at -20db straight from the DAC to (balanced) amp (Hypex ucd180). Sometimes with older CDs, before the loudness war, you can go to 0 db without breaking the walls. I needed more inputs so i have the 4:1 S/PDIF MUX. Noise aside, i really don't want to omit the Metronome as a think it is an upgrade soundwise. I have borrowed a friends Metronome and 4:1 MUX. So i will swap them this weekend to see if it makes any difference.
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Brian Donegan wrote:What are your switch settings on Metronome and Opus modules?
A few pictures can often help in diagnosis. Try to show your power wiring relative to your I2S wiring, as that it the most common source of noise injection. Hello Brian, I have tested with another Metronome and it did not make any difference. However, if i leave out one of the Opus/IVY, running the other in a normal stereo setup, the problem is gone. Still think the noise levels are a higher than i expected. So I am simply giving up the dual mono. Still, it would be nice to get a comment on the pictures, if there is something i have missed or can do better.
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Here are my comments:
1) I do not see power wire for VD of your modules in the pictures. This is the wiring I most wanted to see, as its proximity to the I2S lines is 99% of the time the cause of the noise you are hearing. Your layout looks generally good, however, and your I2S lines are nice and short. Just be sure your VD line enter the terminal blocks at 90° angles to the direction of the I2S lines, and are not run close to the boards.
2) Do not daisy chain your grounds like that. They should all be home runs (power supply ground terminal to board ground terminal). This could very well be related to your noise.
3) The VA mod on the two Opus boards, while fine if done correctly, is not something we can support as it is easy to mess up. It would be best getting them working in the default configuration first, then modding the VA supply. Basically, keep it simple, then make it more complex in steps.
You said you are having fewer issues with stereo then mono. Does it matter which board you use in the stereo configuration? Wondering of one of the boards has issues.
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Another suggestion: try using twisted pairs (e.g. cat 5 cables) for the I2S connections. Perhaps (just guessing) having double the amount of unshielded wires would cause problems
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Brian Donegan wrote:Here are my comments:
1) I do not see power wire for VD of your modules in the pictures. This is the wiring I most wanted to see, as its proximity to the I2S lines is 99% of the time the cause of the noise you are hearing. Your layout looks generally good, however, and your I2S lines are nice and short. Just be sure your VD line enter the terminal blocks at 90° angles to the direction of the I2S lines, and are not run close to the boards.
2) Do not daisy chain your grounds like that. They should all be home runs (power supply ground terminal to board ground terminal). This could very well be related to your noise.
3) The VA mod on the two Opus boards, while fine if done correctly, is not something we can support as it is easy to mess up. It would be best getting them working in the default configuration first, then modding the VA supply. Basically, keep it simple, then make it more complex in steps.
You said you are having fewer issues with stereo then mono. Does it matter which board you use in the stereo configuration? Wondering of one of the boards has issues.
I'll keep it simple starting with only a single (VA restored) Opus without IVY. I have only tested one Opus in Stereo mode so i will also hook up the other one to see that there are no differences between them. Thanks!
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glt wrote:Another suggestion: try using twisted pairs (e.g. cat 5 cables) for the I2S connections. Perhaps (just guessing) having double the amount of unshielded wires would cause problems I will use cat 5 cables twisting them individually with a ground cable as you did. Thank you!
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