[sdiy] best ways of portable +/- supply

Harry Bissell harrybissell at wowway.com
Tue Jun 12 18:12:42 CEST 2012

(blonde mode on)

batteries ???


H^) harry

----- Original Message -----
From: dan snazelle <subjectivity at hotmail.com>
To: synthdiy diy <synth-diy at dropmix.xs4all.nl>
Sent: Tue, 12 Jun 2012 12:05:51 -0400 (EDT)
Subject: [sdiy] best ways of portable +/- supply

does anyone have opinions on the best way to get plus and minus rails into a portable synth/noisenaker/stompbox type project  WITHOUT using an on board transformer?

the options I know of are

1.AC to DC conversion (ac wallwart plugs in and is converted with regulators and caps to a DC dual supply.  Kind of bulky due to use of large caps.

2. Big DC wallwart....a 24 volts wallart would easily get plus and minus 10 volts once regulated. CHEAP and EASY. what are the downsides to this setup?

3. DC2DC converters (put in 5 volts get out +/- 15 or +/- 12volts//////) convenient BUT very expensive, bulky, they get very warm and can be destroyed with overvoltage quite easily.

4. CHARGE PUMP chips (max1044 etc)    cheap, easy...... VERY PRONE to destruction from over-voltage and static electricity. (though they are used in some pro boxes like the Moog Pedals so there must be ways
to make them less error prone)

Often I am hit with a LIGHTBULB kind of a moment "oh this would be such a great project....so few parts and I could put it in a tiny box!" and then i realize that I will have to provide 2 batteries or a charge pump. Suddenly the small box is a bigger box and the 
amount of parts has grown.

I have been messing around with the max1044/LT1045 charge pumps but overall I think they are a bit too delicate for road use....i have had a few MAX1044's die just from having a power supply 
hooked up to them which briefly spiked at a higher voltage than 10 volts 

(my Bench supply, when you turn it on, it seems to jump to a very high voltage for a split second....most chips seem fine with this but not the charge pumps (luckily I figured it  out quickly!)

Maybe there are ways of protecting these power conversion chips I dont know about. (i usually just put a zener in front of them to keep the incoming power in the proper range) 

ANY thoughts/advice appreciated


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