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Just curious... Do you have your filter caps connected to the positive rail or to GND?
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Check your wire routing around the Legato. Do you have any pictures you can attach?
Also what power supply rails are you using? Which supply or you using?
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Filter caps - to ground. Placid supply. As mentioned, under test, no wires attached at all. edit: update. If I short the +-inputs to gnd, then it's quiet. So ok, it might be EMI pickup, but that's less than helpful, because I have to mount the BII on top again, and then the popping starts again. It's shown here with the IVYIII, all the wiring are the same in case Legato. All connectors are isolated, signal GND is floating. Edited by user Saturday, October 9, 2010 3:42:04 AM(UTC)
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Placid BP
Running on 15 volt. (also tried 12volt)
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Make sure your getting solid contact at the Legato inputs. Also make sure your placid BP is setup with at least 50-60ma headroom on the CCS.
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Ok - I might have found one here.
I'm burning 344mA in the positive leg of the Placid. And I measure a consumption of 320mA in the Legato. I'll change right away, and report back.
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G' - I even noticed, my negative supply was fluctuating. WTF was I thinking about when rigging the Placid ? Now I'm burning a solid 420mA in each leg (+-). Long live class-A. I wonder, how long my Placid will last. Ears to the tweeter, I now can hear similar faint hiss in each channel, so I might think, everything is ok now. I'll let it run through the evening, and I will report back. I guess, it was always a problem, I just hasn't noticed it before. And the fact is was only the one channel - could it be due to tolerances ? Streamerzone, what are your fuel consumption ? Edited by user Saturday, October 9, 2010 9:57:59 AM(UTC)
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That is why I actually recommend that people really think about using LCBPS here. This circuit really does not need the low impedance of PlacidBP anyway.
Easier to adjust, and less to go worry about. :)
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This one I REALLY worried about, because I just love the sonic signature of the Legato, and it would be a massive hit to give up this. Anyway, a big thanks to Russ. Edited by user Saturday, October 9, 2010 10:55:24 AM(UTC)
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No worries. If you find your pumping out more current then you are comfortable with, just crank the negative rail down a bit. Say 12V. You can leave the positive rail alone. Or decrease it slightly. Up to you.
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PS, I think you may find your paralleled FETs may sound a lot better now. ;)
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Don't pick on me, you... ;-) I have to make sure that this is steady state. If so (I really hope it) I'll parallel the fets again, and post my report on "the other" site. I'll lower to +-11V, then my heat sinks might be touchable again. edit, how about +11 -9 volt, as long the as the relay works ? Edited by user Saturday, October 9, 2010 11:12:18 AM(UTC)
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I'm sorry to say it, it's not gone  Back to scratch. Edited by user Saturday, October 9, 2010 11:36:08 AM(UTC)
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Do you have an LCBPS or other bipolar PS to use? If so give that a shot.
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Russ, does the paralleled FETs reduce the output impedance of the legato compared to a single fet?
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Maybe a little, but that is not the main benefit. :)
It basically makes the CFP even more effective. Reducing THD further.
To give you an idea. My simulation says -124db THD. I know thats not likely in real life. But I would say -117 -118db is certainly plausible.
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Yes, another PSU will be next. I don't have high expectations though. Remember, it's only one channel which is faulty.
I might need to buy another Legato to solve this.
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If the legato's where in stock I probably already had ordered a new one..... avr300, I've upgraded the cooling of the placid big time, with the IVY the stock cooling was maybe just ok, but with the legato I found the heatsinks far to hot for my taste. (80 - 85'c whitin 15 min and rising) I expect to see some smoke if one of the power devices fails due to overheating, giving the nature of the power supply. I wonder if Russ did some testing on that... :-) Emile Edited by user Sunday, October 10, 2010 1:25:14 AM(UTC)
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As expected, it not power supply related.
With LCBPS it's doing the same.
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