drez
Headphoneus Supremus
- Joined
- Sep 7, 2009
- Posts
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Hi Alex - Nice to see you back here! We may have had our battles, but I always respect your knowledge and input. Good info on the 575 - strange Digikey did not show a version with the Tri-state feature, or maybe I missed something. Or maybe it's not as important as Audiobyte says? That is the ability to disable the unused audio clock.
As you can see a few talented folks here are working some very interesting mods to the F-1. Maybe Uptone could do a Uber-F-1? That would be very interesting.
Nice! Your concurrence is appreciated. I can see the use of a toroidal in a small one unit case design - due to the EMI issues. But that can easily be a non-factor with an ext LPS box.
Researching yesterday I came across this comment:
http://www.stereo.net.au/forums/topic/55835-why-a-torroidal-instead-of-an-r-core-transformer-in-digital/
Also looked at shielding materials - came on this - looks like copper is pretty good.
http://www.ets-lindgren.com/pdf/emctd_1293_weibler.pdf
I was agonising over transformer selection for this power supply. I think the inductive coupling issue is real when it comes to rejecting line noise, and also possibly noise between secondary windings. The thing is though the transformer is not the only way to reduce line noise. You can also use a line filter, although I am not sure how these compare in terms of strengths, weaknesses, tradeoffs etc.
I was not able to find an appropriate R core for this build unfortunately. Not many with 5V secondaries. Especially in bigger transformers which have better voltage regulation. The secondary voltage seems to vary a lot over different load especially on the smaller units which might have been an issue with my power supply in that the voltage would have been a bit high at the load I would be using.
The shielding seems a good idea. I was looking at a shielded O core, or using mu-metal. For me the other thing is humming, which R cores are very low hum. The potted toroidals might be good also. I might still end up using the mu-metal as this PSU will sit right on top of my DAC digital circuits. Actually the EI core I bought for prototyping might be pretty bad for that as well as radiated EMF. I am keen to minimise vibrations as they seems to work their way back into the signal through microphonic components.