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 Forum index » DIY Hardware and Software
Bench power supplies
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Bogus Noise



Joined: Jun 03, 2009
Posts: 62
Location: Sheffield

PostPosted: Sun Jan 30, 2011 3:52 pm    Post subject: Bench power supplies Reply with quote  Mark this post and the followings unread

The time has come for me to pick up a bench power supply for working on circuits and building up modular boards. From a bit of research it seems I'm needing a variable linear power supply with +/- 15v, and somewhere in the region of 3a. Been scanning about on eBay over the weekend, wondering if this one should do the trick?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300514871499&ssPageName=STRK:MESINDXX:IT

Thinking 2a should be plenty. Haven't been able to find out for sure if it's switched or linear though. Any thoughts?
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rosch



Joined: Oct 03, 2009
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Location: germany

PostPosted: Sun Jan 30, 2011 5:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

this seems to be just for +15V, not bipolar
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Bogus Noise



Joined: Jun 03, 2009
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Location: Sheffield

PostPosted: Sun Jan 30, 2011 5:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah, is it?
I thought from looking at the sockets on the front that - GND + meant that it'd be giving a bipolar supply.
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Blue Hell
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PostPosted: Sun Jan 30, 2011 6:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

On bench supplies often - (minus) and GND are separate terminals, GND being connected to the case and to the safety ground when connected to mains with a three prong plug, the - and + being floating to that.

Edit : so you could ground + or - or none, as is best for the situation you want to use the supply in.

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Bogus Noise



Joined: Jun 03, 2009
Posts: 62
Location: Sheffield

PostPosted: Sun Jan 30, 2011 7:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmmm, ok then, thanks for the info!

How can I be sure I've found a bipolar power supply? Is there anything else I should be particularly keeping an eye out for? Was hoping to be able to get one for a bit cheaper than the £80+ I've been seeing in the usual online shops. Smile
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Blue Hell
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PostPosted: Mon Jan 31, 2011 10:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I think the word to look for would be "dual".

edit : like http://www.mpja.com/prodinfo.asp?number=9333+PS

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nerdware



Joined: Jul 11, 2009
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PostPosted: Mon Jan 31, 2011 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

I use a Maplin bench PSU. When you use all 3 power rails, it operates as a dual +- supply.
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Bogus Noise



Joined: Jun 03, 2009
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PostPosted: Tue Feb 01, 2011 3:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the tip and links Smile

Both a bit more than I was planning on spending, though expect something similar to the Maplins one could be found cheaper elsewhere.

Still a bit confused though! The Maplins one doesn't say anything like dual or bipolar, but can be used in that way. Checked the manual and it mentions you can connect the ground to positive or negative, or leave it floating, like the one from the eBay link I posted.
How can I tell the important difference between the Maplins one and the eBay one? It feels like I'm missing something to understanding how to choose the right power supply. Confused

The Maplins one also says switching, but I've been hearing that switching/linear doesn't really matter so much.
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nerdware



Joined: Jul 11, 2009
Posts: 91
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PostPosted: Tue Feb 01, 2011 6:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, the Maplin PSU is smart. However...

I just remembered, the Maplin PSU has limited voltage, so it's not so good if you want a +-15 or +-12 supply. It's great for testing more general, lower voltage circuits, but not so good for modules. It can also add a +5 rail to a +-15 or +-12 supply, but that's not what you asked for. Sorry. Embarassed

I forgot this because I now use an Oakley Compact PSU for module testing. I've spent more time in the last year messing about with non-bench PSUs. So I'd forgotten the details of this thing. In fact, I had to get both PSUs out just now and test them again to confirm this. I get 15v across the 2 Maplin rails and 30v across the 2 Oakley rails, so I'd say definitely get the Oakley, not the Maplin!

You can buy the CPSU ready made with a Yamaha PA-20 from Krisp1. That's how most of my recent tests have been done, with 2 or 3 modules in isolation from the rest of the synth. It was a literal test bed. Laughing

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Bogus Noise



Joined: Jun 03, 2009
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PostPosted: Tue Feb 01, 2011 6:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hehehe, cheers for digging them out and testing them!

The voltage issue had been mentioned on the circuitbenders.co.uk forum, so am after a 30v one to get +/-15v. But need to be sure that whichever I go for can act as a bipolar/dual supply. Good to have the voltage side of it clearer in my mind though!

The Oakley one doesn't quite do what I'm after, as I want something adjustable, and be more suitable for putting on a bench. Wink


I will at some point be building power supplies, and already have a board waiting to be drilled and populated, but want the versatility of a bench supply. Also don't think I should be building power supplies until I know a little bit more about them!
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adambee7



Joined: Apr 04, 2009
Posts: 420
Location: united kingdom

PostPosted: Tue Feb 01, 2011 8:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://www.rapidonline.com/Electrical-Power/Power-Supplies/Bench-PSUs/Triple-output-30V-linear-bench-PSUs/81535

Very Happy Very Happy
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nerdware



Joined: Jul 11, 2009
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PostPosted: Wed Feb 02, 2011 1:58 am    Post subject: Reply with quote  Mark this post and the followings unread

I bought my CPSU built, so all I had to do was pay for it, but I agree that a variable supply is more versatile and better suited to a lab bench. adambee7's recommendation looks good.
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prgdeltablues



Joined: Sep 25, 2006
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PostPosted: Wed Feb 02, 2011 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

It's probably just me being ignorant, but why would some-one need so much current capacity in a bench supply for synth diy? To test modules I'm building, I just use one of Ray Wilson's wall-wart based dual power supplies using LM317L/337L, built into a little ABS box. Only 100ma capacity, but that's enough for the job. Cost less than £10.

Peter
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nerdware



Joined: Jul 11, 2009
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PostPosted: Wed Feb 02, 2011 7:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Of course, you wouldn't a PA-20 for a bench PSU. I only use that because that's what I have. Laughing I bought my CPSU at a time when the PCBs for the Low Noise PSU weren't in stock, so I wanted to use it with a PA-20.

For bench use only, you should ask for a CPSU built for use with a lower current transformer. You won't even need a centre-tapped unit for that, as efficiency won't be an issue.

However, a proper bench dual PSU will be much better suited. I'll probably get a decent one someday, most likely when my CPSU gets installed in a cabinet and used to power parts of my synth. Until then, I'm happy with my bench setup. The only thing missing is an actual bench...

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adambee7



Joined: Apr 04, 2009
Posts: 420
Location: united kingdom

PostPosted: Wed Feb 02, 2011 11:30 am    Post subject: Reply with quote  Mark this post and the followings unread

prgdeltablues wrote:
It's probably just me being ignorant, but why would some-one need so much current capacity in a bench supply for synth diy? To test modules I'm building, I just use one of Ray Wilson's wall-wart based dual power supplies using LM317L/337L, built into a little ABS box. Only 100ma capacity, but that's enough for the job. Cost less than £10.

Peter


I use a proper supply with 3A because i do other audio stuff aswell and repair work. its handy i can tell you. but if your just building modules, ray's PSU boards are pretty easy and reliable. Add two pots and its adjustable from the front. Very Happy Very Happy
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jurekprzezdziecki



Joined: Mar 22, 2016
Posts: 11
Location: warsaw

PostPosted: Fri Apr 01, 2016 4:22 am    Post subject: Reply with quote  Mark this post and the followings unread

did you ever needed more then one output for building, testing, repair work?
i just consider single output vs double outputs bench power supply.

your advice would help

thanks j
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AlanP



Joined: Mar 11, 2014
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PostPosted: Fri Apr 01, 2016 11:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Most synthesizer circuits out there use a dual supply -- +15V and -15V for 5U stuff, +12 and -12V for Eurorack.

Old Moog stuff used +12V and -6V.
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jurekprzezdziecki



Joined: Mar 22, 2016
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Location: warsaw

PostPosted: Fri Apr 01, 2016 12:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
Most synthesizer circuits out there use a dual supply -- +15V and -15V for 5U stuff, +12 and -12V for Eurorack.

Old Moog stuff used +12V and -6V.

As an output I mean one single channel of a certain voltage / current source.
For example TTI PL303 power supply. Sorry for not being precise.
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