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DC to DC Switching PSU (12Volts to +/- 18V & 48V)
Mic Preamp SC-1 with Cinemag input/output transformers

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SC-1mk2 and SC-1mk500 Mic Preamp Kits



SC-1mk2 Preamp Kit  SC-1mk500 Lunchbox Preamp Kit 
 Wednesday, March 26, 2008
Wednesday, March 26, 2008 6:31:57 AM (Central Standard Time, UTC-06:00) (  |  |  )
It's done :)  My switching DC-to-DC PSU.

I've been working on this design on and off since October 2007. Several prototypes later, and many $$$, I'm happy with it.  All output voltages are regulated and adjustable via multiturn trimmers, +18, -18 and it's a true +48V phantom power... all derived from a single 12Volt input.  Outputs are short circuit protected. Just a big spark, but keeps on ticking. Nothing gets blown. 


http://farm3.static.flickr.com/2322/2365867488_5f14133bbd.jpg

Powering my preamp and my I/O module (input and output trafo, pad, polarity) with Active DI, via 12V wall wart. No hashing sound, no RF leak, no noise. (Well, okay... when you're at 66-72dB gain... but could be caused by everything not in a metal enclosure.)


http://farm4.static.flickr.com/3068/2352224005_5dc492842c.jpg


Output on all 3 rails are typical like below:

http://farm3.static.flickr.com/2376/2365001131_8b2c1a26ac.jpg

Switching spikes on the DC output of about 0.06Vpeak-to-peak, and interval of 33.333Khz. I can set switching freq. to about 60Khz but the spikes get larger.

So I compromised for smaller spikes at a lower switching frequency... i.e. smaller spike/transients, less RFI energy emitted, less chance that it will interfere with sensitive mic pre circuitry.

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 Thursday, March 20, 2008
Thursday, March 20, 2008 3:54:00 PM (Central Standard Time, UTC-06:00) ( )
Yes!... got some time to do some electronics work today... away from the purchasing role.

Finally built and tested the final, final, FINAL prototype of the IO-module. And it's great.

Man, I love the sound of the Active DI going through the input transformer. Actually, love the sound of anything going through it.

Some pics:



Now, I haven't sent the PCB out for mass production yet, but I have (4) prototype PCBs left. I'm keeping (2) so that leaves (2) extra ones...

I know somebody out there is waiting for this patiently... you're getting these PCBs way in advance of the others.

I'd need to drill some square cutouts first on it... like this


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