Noise with Computers, USB DACs, and Powerline Ethernet Kits

[grufti]

No, using them in the power supply would not have been good, not for those diodes and not for the rest of the amp.

[Deke609]

@PB - I recognize that this mod was only intended to deal with the bigger (noisier) problem of junk on the power lines (for those that have this problem) and not meant to be a fix-all for all types of noise.  But I'm wondering whether this would prevent rfi/emi induced currents picked up by shielding from draining to earth ground?


I was thinking a tiny cap in parallel might provide a workaround a la Broskie and others for high frequency noise, but this wouldn't provide a path for lower frequency noise to drain (e.g., currents induced by a PT or power supply chokes).


Any thoughts?


I like the idea of the protection this simple mod provides. But I don't have discernible noise on my mains - although I do believe my sound take a sight hit when my son is watching tv.  At the same time, I don't want to do anything that compromises all the other "protection" I've built in with extra shielding and drains to ground.


many thanks, Derek

[Paul Birkeland]

You could certainly put a 0.1uF ceramic cap across the diodes. 

[Deke609]

Thanks PB. My concern, perhaps (likely) based on misunderstanding, is that this would work well for higher frequency noise -- e.g, 10kHz+ -- but less well for 60/120Hz transformer noise caught by shielding to which a 0.1uF cap would present an effective resistance in the 1000's of Ohms. Does this matter? Or does even such low frequency noise signal, having nowhere else to go, pass directly to earth ground even if provided only a highly resistive (reactive) path to earth ground?


many thanks again, Derek

[Paul Birkeland]

The cap would indeed create a short circuit for high frequency noise from the chassis to the earth ground.  Of course, you don't want to create too good of a short, otherwise the noise we are attempting to block will be passed by the cap, and thus defeat the purpose of the diodes in the first place. 

[Deke609]

It just occurred to me that there is relatively easy solution for dealing with lots of shielding that needs wiring to ground: install your two-diode mod, but isolate the shielding from chassis ground and wire the shield drains directly to the earth ground lug of the iec inlet. 

[Paul Birkeland]

You can do that or move the diodes to between the audio ground and the chassis ground.

[Deke609]

That's an even better idea! Thanks PB.

[Deluk]

I've just put in the diode mod and have to say the results were not much short of a revelation. Full volume from the PC and full volume on my MkI crack and it's so silent I think I'm missing something! All of those tiny twitters and buzzes are gone. As a test, I played this at about half volume (HD600) and the silence at the end really enhanced the performance. If Steven Wilson is an unknown name to you please listen. If you're not emotionally drained at the end I'm sort of sorry for you.


Thanks, PB. This should be added to the original build IMO. Just a few pence for such a good result. It's also a good incentive for me to get the Speedball fitted

[Tom-s]

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.

PB, what's the result of this experiment? As i have some leftover uf4007's from my original Crack build and am planning on reusing them..

[Paul Birkeland]

The peak current rating of the UF4007 is sufficient that this seems less concerning than it once did.  I wouldn't be concerned about using them in this application.

[watonwak]

Would a pair of 1N5402 diodes be suitable? They were the only ones I managed to find locally

[Paul Birkeland]

They could be a little bit on the large side physically, but electrically they will work OK.

[watonwak]

You were not wrong! a bit of a tight fit but now it is totally silent with nothing playing, even with the volume turned up full and positioned next to my router

[takkos]

Worked like a charm  Thanks PB