Noise with Computers, USB DACs, and Powerline Ethernet Kits

[Paul Birkeland]

For those who can hear their computer working away through their Crack or who are using a powerline ethernet kit and hear lots of clicking and static, a ground breaker installed in place of the buss wire between the chassis and the ground tab of the IEC power entry module will very likely solve this issue.  I recommend using a diode that's rated for at least 2A, and the voltage isn't particularly important.  Part number STTH2R06 looks to be a solid choice.  I do not recommend using a Schottky diode here. 

I've attached a photo of how this is retrofitted into a Crack. 

[denti alligator]

Would this work on any of the other kits? I have a S.E.X. that has this issue. I use an ifi USB filter that works, but it would be nice to bypass that.

[Deke609]

This is very cool.


@PB: can you explain how it works?


It doesn't make sense to me. Two ideal diodes paralleled with reversed polarities would do nothing, right?  All current/voltage would pass unimpeded in either direction. So I figure it must work ONLY BECAUSE real world diodes are non-ideal.


I've seen ground loop breakers that employ a diode bridge with a resistor and cap to greatly reduce ground loops - but you're using only the diode bridge. Does the tiny amount of resistance and capacitance of the diodes do the trick?  Or is something else at work here?


many thanks,


Derek

[Paul Birkeland]

Would this work on any of the other kits? I have a S.E.X. that has this issue. I use an ifi USB filter that works, but it would be nice to bypass that.

Give it a shot and let us know!

@PB: can you explain how it works?

It separates the safety ground by the voltage drop of one diode (in either direction).

All current/voltage would pass unimpeded in either direction. So I figure it must work ONLY BECAUSE real world diodes are non-ideal.

Yes, a perfect diode wouldn't allow this arrangement to work.

[Deke609]

Many thanks PB.

[Paul Birkeland]

A little more specifically, if you have a small AC voltage, say 100mV, the diodes present a pretty large impedance and this is what's broken.  If you have more than about 0.7V of anything AC or DC, then the diodes will start to short that out.

[Deke609]

I do not recommend using a Schottky diode here. 

@PB: why not a Schottky?


Many thanks, Derek

[cddc]

My Crack w/SB is dead silent, but marked in case come across some noisy tubes.

[Paul Birkeland]

@PB: why not a Schottky?

You want the forward voltage drop to be significantly higher than the magnitude of the noise you're dealing with.  The low forward voltage drop of a Schottky diode in this instance is a bit of a disadvantage.

[Deke609]

Ah, yes. That makes sense. Thanks.

[oguinn]

I’m thinking about giving this a shot. Is there any amp in the lineup where this would be unsafe or a bad idea? I assume not but don’t want to make a costly mistake.

[Paul Birkeland]

I don't see issues doing this with any of our products.  I do also plan to test whether a UF4007 can throw a 20A breaker and survive, as this could also be a suitable part to use.

[oguinn]

I picked up a dozen or so and will probably add them to every kit next time any of them are on the bench for one reason or another.

Any downsides to doing it besides the minimal effort and cost?

[Paul Birkeland]

In the event of a catastrophic failure, you may need to check and replace the diodes.

[oguinn]

Ok, I’ll just shoot for no catastrophic failures then