+/- 12V vs. +/- 15V power supplies.

OW · Joined: Nov 03, 2009 Posts: 122 Location: London

Is there much of a difference using +/- 12V as a pose to +/- 15V power supplies for modules?

I ask this because in the past I have previously used +/- 12V, however the current modules I am building require +/- 15V and I am unable to find a reasonably priced 15V AC/AC PSU in the UK. (If anyone could point me in the right direction of one, that would be great).

I use the MFOS wall wart power supply board to power my modules, and this time I am using 7915 and 7815 voltage regulators to power my 15V modules I am currently building. Would I be able to substitute in a 12V AC/AC power supply as I cannot seem to find a 15V AC/AC power supply?

Thanks!

decaying.sine · Joined: Aug 31, 2009 Posts: 92 Location: New Haven, CT, USA

The power-one and condor supplies can be trimmed to 12 or 15 VDC. You can find 3 amp ones on ebay for as low as $40 sometimes.

Some modules are fine with 12 or 15. Usually they will state this if it is the case. For example, some CGS and Ian Fritz designs run okay on both or run fine with small modifications.

prgdeltablues · Posted: Tue Jan 04, 2011 7:52 am Post subject:

Try Farnell -part number 1217073. It's a 15VAC output linear wall-wart. Only 500mA, but that should power a few modules. Euro mains plug, so you'd need a travel adaptor!

Or CPC (which is linked to Farnell) part no. PW00163 - looks like a UK plug

http://cpc.farnell.com/stontronics/ac-1550/plug-in-psu-15-vac-500ma/dp/PW00163

Peter

sonic · Joined: Dec 02, 2010 Posts: 106 Location: Victoria BC

Hello Friends,

My local surplus store has these Power One MAP110-4300 +3.3V/+5V/+-12V PSUs for $12.99 a pop. I'd really like +/-15V. Does anyone know if they are they likely to have parts to convert to +/-15V output?

Assuming this is possible I'll need to build it into an enclosure, switch, fuses, AC socket / cord etc too. I'd also really appreciate any advice or resources on how to do this.

Richard

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Clack · Posted: Fri Apr 15, 2011 4:11 pm Post subject:

HEy!

posting this for reference

http://www.musicfromouterspace.com/analogsynth/WALLWARTSUPPLY/WALLWARTSUPPLY.php

You can get away with a higher voltage AC wall wart

I am currently using the Rapid 24V AC wall wart to make +/-15v which is overkill but just like you I couldn't get one high enough.

the voltage stated is RMS so to get the peak voltage the regulator will get you do

24 x 1.414 (this is a magic number that converts it) = 33.94V

it will be a bit lower after filtering etc so each regulator will get probably 30v or so and they cut the voltage down to 15v. I checked the LM7915 datasheet and the LM7815 and they say that it can take 35v maximum so its safely within the limit.

it gets quite warm but not hot, I am powering a soundlab so I cant say more about how hot it gets at higher loads but it shouldn't be that bad below 500mA

Appliancide* · Posted: Fri Apr 15, 2011 4:37 pm Post subject:

sonic · Joined: Dec 02, 2010 Posts: 106 Location: Victoria BC

Ah it's switching. That's probably a no go then. Thanks for pointing that out, *Appliancide*.

Thanks Clack. Yes, I know of the MFOS Wall Wart supply. I have a stripboard layout from someone here. Uncle Krunkus perhaps? I plan to build one. I have some caps on order to do just that. No 15V AC wallwart yet though.

Let's face it though, wall-warts aren't the most aesthetically pleasing or elegant solution, are they? For a modular, I would far prefer to build my supply into the cabinet.

The Power One and Condor HAA15-* seem to be the goto supplies for synth builders here. I can't find one shippable to Canada at a reasonable price though. I could roll my own with transformer etc, but I'd take so long over it I'd have no time to work on anything else for a month.

Curses. Maybe I can't have my cake and eat it. Or can I?

vladosh · Posted: Sat Apr 16, 2011 7:44 am Post subject:

hi all ..
Just thought i'd ask .. since i had so many troubles with a PSU already ..
I found a PSU from an old printer giving -/+ 12 and ground .. now this PSU is working fine comparing to the one i used before .. but i've been told it's a switcher supply and reading the post .. just thought i'd ask .. do i risk something using a switcher supply ?
thanks a lot
greetings
vlad

blue hell · Posted: Sat Apr 16, 2011 8:02 am Post subject:

You dont really risk anything with a switching mode power supply, the switching may cause some audible artifacts, thats all. You may be able to filter that out, having a proper star grounding will help too to avoid such problems.

When using a computer supply ... those are able to deliver a lot of current ... which means that when you make a mistake with the wiring some stuff may go up in smoke ... you could use fuses for experimenting though.