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Joined: 5/22/2012(UTC) Posts: 21  Location: Guantanamo Bay
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I finished the BIII that I have been working on and all seemed fine with it. I sent it to its new owner and have an issue that I have no clue about. When he has it plugged in to either of his amps, YBM built Beta22 and M3, the volume stops getting louder at about the 3 o'clock position and starts to get softer. Along with this as he turns the attenuator(Goldpoint) there is static between each step. This is happening on both amps and only with the BIII attached. His other dac works fine. Does anyone have any ideas as to what could cause this?
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probably needs to AC couple.
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Joined: 5/22/2012(UTC) Posts: 21 Location: Guantanamo Bay
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Thanks Russ.
Can you explain why this would make a difference? Or at least point me in the direction of an explanation.
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Rank: Administration
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The schematic should shed the light. :)
If the load shunts DC current away from the cct it will start to behave badly.
Also - you need to be sure the load is fairly high impedance. > 10K is ideal.
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Rank: Member
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Joined: 5/22/2012(UTC) Posts: 21 Location: Guantanamo Bay
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Okay, is the load the value of the attenuator of the amp being fed? If so that should be good as I believe that it is 50K.
I'm feeling pretty dumb right now to be honest. I've looked at the schematic dozens of times and I know I'm missing something. I know that the Legato 3.1 does not have AC coupling caps in the circuit when used balanced. I thought that was the point of this version.
So I guess my next question is what cap sizes are recommended and where do i need to put them?
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Well they are not *always* required, so we made them optional.
4.7-10uf should do nicely for that load.
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Rank: Member
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Joined: 5/22/2012(UTC) Posts: 21 Location: Guantanamo Bay
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I just looked at the Legato 2 schematic. I take it that c5-c8 are the coupling caps in that circuit. If I add them inline between the Legato and the output plug I should be good, right?
There are a couple of other issues going on as well. When first turned on it loses lock intermittently until the power supplies warm up. I set the dac input voltage to 4.8v and about 490mA to allow for the 4-input board and the power indicator led. If I turned the voltage up it would click, pop and drop lock constantly. Is this something that changing the dip switch settings can fix?
Also, when compare to the other dac being used it takes volume knob turn to match the volume. The other dac is an Emotiva XDA-1. I looked at the specs and it says that the output voltage is 1vrms nominal and 9vrms peak. It is being run with the volume control on it all the way up. I think the difference is the output voltage between the units but thought I would ask anyway.
Again, thanks or all the help.
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