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I finally got around to opening up the box and building a Buffalo II & Legato (v2.0.0) yesterday. Played music right out of the gate. About 4 songs into a listening session, the left side starts making a crackling sound, with and without music playing. Enough that the woofers move quite a bit. I double checked power supply and legato voltages and they seem to check out. I removed power from the Buffalo but kept power to the Legato and the crackling remains. I removed the Legato and re-soldered every thing again, and cleaned it really well. After putting everything back together the crackling is still there. What should I check next? Edited by user Thursday, August 18, 2011 10:17:49 AM(UTC)
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You could read http://www.twistedpearau...t.aspx?g=topics&f=46it's covering v.1 of the Legato but who knows, maybe it applies to version 2 as well. In short the problem was due to failing power resistors (too much power dissipation, i.e. too hot). They has been doubled in numbers in the version 2 hence the power dissipation has been halved - but who knows, it could be the problem. Are your power resistors more warm than "normal" ? Snip a picture - and post it here.
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I checked the resistance of the power resistors and they measure the same left side to right side. They do get very hot though.
Can they fail and still offer resistance?
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I've read the threads I can find concerning the Legato, but so far haven't found a resolution to this issue with the product. The crackling sound occurs with both the single ended and balanced output. It also sounds the same with or without music playing. I suppose I can order new resistors, but am not sure that the same issue wouldn't occur again. Are there any other suggestions or trouble shooting ideas? At this point it's not listenable. Thanks! Edited by user Friday, August 19, 2011 12:24:49 PM(UTC)
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"Can they fail and still offer resistance?"
That's what they did.
I replaced the resistors with equivalent values but another brand and didn't see the problem ever after.
It's worth a try, I mean, it's pretty easy.
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Wich power resistors are we talking about ?
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On Legato 1 it was R1-R4, R20-R21 and R23-R24
If I remember correctly the problem came from the 20 resistors.
I changed the whole lot once the Legato was out of the box (for only God knows which time)
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I'll try replacing all of the 150 and 680 ohm resistors. Need to order some now and there are a lot of choices.
What is the best resistor type to use? (metal film, carbon film, wire wound, etc.)
I believe these are 1/2W rated. Any advantage to use 1W or larger?
Thanks for the feedback.
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Metal film, and it's good to get 1W. Avoid wire wound. Edited by user Friday, August 19, 2011 1:32:35 PM(UTC)
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New resistors arrived. I replaced all of the 150 and 680 ohm resistors with 1W metal film type. Result: The crackling sound remains  Any other suggestions for solving this issue?
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About ready to bin this kit, as I am so far unable to diagnose and fix the crackling sound in one channel. However, as it is brand new I'd like to try and salvage it.
What other components could lead to a crackling sound which I should replace?
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Have you tried it on other equipments (amps, preamps)?
If not, I would do this first and if you don't have other equipment, bring it to a friend's house
Ciao!
Do
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Don't ditch it yet. Grab a picture of the rig and post it here. Sometimes pictures tell the story. Edited by user Tuesday, September 6, 2011 10:30:54 AM(UTC)
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It could also be ESD damaged to one or more of P channel FETs, this is rare, but it can happen. That is why ESD precautions should always be taken.
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