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ayebee 29th November 2012 12:32 PM

Suggestions for dual PS

I have a DACT CT101 line-stage module (Data sheet for DACT's CT101 line stage / linear preamplifier module) that I'm planning to put to use. The power supply I have is a small wall-wart, that I believe could easily be bettered. DACT suggests using either batteries or their own CT102 power supply module (DACT audio power supplies). I don't want to mess with batteries, although they could possibly yield great results and the CT102 is too expensive for my taste.

The CT102 can output either +/-15V or +/-20V, max 200mA. The CT101 draws very little current, but I guess substantial overrating can be an asset...

Are there any (preferably) kit-based solutions that could be used as a replacement for the CT102?

Any help appreciated!


indianajo 29th November 2012 06:37 PM

You need 2.5 V headroom above your highest peak value signal for most op amps to work properly. Look at the output voltage swing tables versus power supply voltage. I'm using an op amp mixer to deliver either a 5 VAC radio or a 25 mv mag phono cartridge to a power amp, so I need +- 8v. I found an 18 VDC race car wall transformer, and with two 8 v 1n5344 diodes, two 22 ohm resistors, and the appropriate caps, made a +-7.8v supply. The connection of line to not-line ends of the two zener diodes is the signal ground, the rings of the RCA jacks. The wall transformer cost $1 at Salvation Army charity resale shop, the diodes were $1 each. (USA origin surplus).
Go to the charity resale shop and look through the bins and see how high voltage a wall transformer you can find. 24vac is common from yard lights and security camaras, for which you would need a diode bridge also. Printer-faxmachine-copier devices typically use a 30 Vdc 2.5 amp wall transformer. Typically $2 at the charity shops around here. A bit excessive current supply, but could be used to make +-14.5 IMHO. Watch for switcher PS versions of the 30v ones, these may make too much RF noise to be usable.
The cool thing about the build-it-yourself voltage regulator, you can include a series choke on the incoming DC and eliminate CB radio chatter and lamp dimmer howl if your op amps are in a steel box. I used twenty turns each on two toroid cores salvaged from a PCAT switcher power supply. My mixer used to emit beeping Dixie everytime that ******* CBer drove by until I abandoned the internal hum causing power transformer.

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