P-3A DAC power supply details

audioengr · « **on:** 13 Apr 2003, 08:01 pm »

The following DIY project made significant improvements in dynamics and bass impact with the Perpetual Technologies P-3A DAC. The current capacity is also higher than the wall-wart. Here is the parts list:

1) Neutrik Panel receptacle - Allied 514-1265, Neutrik NC3FP-B-1 - $5.69
2) Schurter IEC inlet/switch 4302.2001 - Allied 509-3120 - $9.06
3) Hammond box - 1590J - Allied 806-1539 - $12.73
4) Hammond toroidal transformer - 182K9 - Allied 836-0816 - $41.10
5) Radio Shack MOV - 276-568B - 130V - $1.69

Total cost - $70.27

Pictures:
http://www.rdrop.com/users/nugent/P-3A_pwr_supply.html

KevinW · « **Reply #1 on:** 14 Apr 2003, 06:36 am »

Hey Steve,
So what color did you paint the box? Any special techniques for deciding this that you would like to share?

More seriously... how did you choose the transformer?

Lost81 · « **Reply #2 on:** 14 Apr 2003, 12:43 pm »

Nice Job, Steve!

I saw these boxes in Frys Electronics as well.
Their walls seem pretty thick though.
What did you use to cut through them?
They seem too thick for a Radio Shack nibbler to handle.

They don't seem hard anodized though, so drilling through them should not be too difficult

I have been wondering if I should invest in a rotary saw by Dremel/Craftsman. That would make cutting out IEC sockets/ 3/4" and 1" holes for XLR chassis-mount sockets easier.

I think my costs came to be about the same.
Of course, I had to add $26 for the engraving though.
(It adds no performance whatsoever, but sure looks nice.)

Cheers,
benny

JoshK · « **Reply #3 on:** 14 Apr 2003, 01:13 pm »

Thanks a lot Steve for the tip. Very good place to start in the DIY arena IMO is to start with power supplies. This one looks like a no brainer, especially when the monolithic offering is much more spendy that your diy project.

P.S. John, I think this one deserves a sticky!

audioengr · « **Reply #4 on:** 14 Apr 2003, 04:29 pm »

The transformer was chosen by the 9VAC output required and the >2500 ma current. The toroid is overkill, but will not get hot either and the magnetic field produced will be small. If you put one box on the other, you will get a tiny ticking hum, not really audible.

As for cutting the holes, these die-case boxes are extremely easy to work. I just use a coping saw with a thin metal-cutting blade. Cuts like butter in any desired shape. Drilling is also clean and burr-free, with little chips.

I used the XLR input on the DAC rather than the power plug because I wanted the option of connecting ground to the box as well. To disconnect the XLR connections, just remove the two SMT capacitors and jump over to the power connector. The XLR's also hold-on tighter than the power jack and they are cleaner to terminate. Notice that I twist all wires that have currents running in opposite directions. This lowers the inductance.