Author Topic: Bipolar Power Supplies for OD pedals?  (Read 4595 times)

v00d00blues79

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Bipolar Power Supplies for OD pedals?
« on: January 18, 2012, 06:48:47 PM »
I've been looking at the Boneyard schematic and it got me thinking about bipolar power supplies for overdrive pedals.  I've been enamored with the clips I've heard of the Providence SOV-2 and I see that they are running that pedal with a bipolar +/-15v supply.  I was wondering, if the chip supports it, would this provide a bit more headroom on other overdrive pedals?  I know a typical single rail power supply running at higher voltages gives a bit more headroom, but I was wondering if a bipolar supply would allow for an even greater voltage swing before clipping?

I've not explored anything like this before and am a self proclaimed neophyte when it comes to solid state electronics, so if this question is worded incorrectly I apologize  :-[

Thanks,

Andy

raulduke

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Re: Bipolar Power Supplies for OD pedals?
« Reply #1 on: January 19, 2012, 03:46:58 AM »
Yes it would.

Single rail, +9V, pedals are designed to bias at half rail ie. a 9V pedal's signal is biased at 4.5V and can swing from 0V to 9V. Therefore there is theoretically 4.5V of headroom available from the op-amp on either polarity of the signal waveform before you hit the supply rail (and the signal clips). In practice it is usually less than 4.5V with most op-amps in 9V pedals.

Therfore with a +/- 15V bipolar supply you get 15V of headroom available; over 3x that of a normal pedal.

I seem to remember +15/-15V being a popular supply voltage for studio equipment. I might be wrong though.

stecykmi

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Re: Bipolar Power Supplies for OD pedals?
« Reply #2 on: January 19, 2012, 01:03:10 PM »
generating +/-15V is sort of a pain though. it's almost impossible to find good quality, bi-polar power supplies that are the right form factor for effects pedals. really the only way you can do it is to get an AC wall wart (like a ~30VAC) and rectify it yourself, which, although not complicated, does take up significant space in an enclosure.

raulduke

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Re: Bipolar Power Supplies for OD pedals?
« Reply #3 on: January 19, 2012, 01:38:46 PM »
generating +/-15V is sort of a pain though. it's almost impossible to find good quality, bi-polar power supplies that are the right form factor for effects pedals. really the only way you can do it is to get an AC wall wart (like a ~30VAC) and rectify it yourself, which, although not complicated, does take up significant space in an enclosure.

+1 to this.

API Lunchbox gear uses +/-15V so I thought I could build myself a kit without the lunchbox; I looked for ages and couldn't find a +/- 15V PSU for a reasonable cost.

Nice idea in theory though.

+18V is popular in pedals and gives you twice the headroom of 9V; most Catalinbread pedals are compatible with 18V for more headroom etc.

v00d00blues79

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Re: Bipolar Power Supplies for OD pedals?
« Reply #4 on: January 19, 2012, 01:42:15 PM »
I was thinking also about the voltage doubler in the Road Rage and how it cranks a ~9v DC supply up to around 17-18v DC and then also has the ability to get regulated voltage back down to whatever value regulator you decide to use.  I took this idea and drew up a schematic to see if it was viable.  I've attached how I think it would work, but I could be horribly wrong in my assumptions.

This is my first attempt to put an idea to paper, so be gentle.  :)

Thanks,

Andy


gtr2

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Re: Bipolar Power Supplies for OD pedals?
« Reply #5 on: January 20, 2012, 06:16:24 PM »
You can't take 18+ and turn it into -15 just by using a neg regulator.  If your coming off AC into a transformer and tie the a positive and neg regulator with the bridge rectifier you can, but not off a charge pump as shown.  I think I said that right..

Josh
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v00d00blues79

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Re: Bipolar Power Supplies for OD pedals?
« Reply #6 on: January 20, 2012, 06:33:28 PM »
Well crap.  Thought it seemed too easy.  Back to the drawing board.  I'd love to know how the providence guys do it.

Thanks,

Andy

v00d00blues79

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Re: Bipolar Power Supplies for OD pedals?
« Reply #7 on: January 20, 2012, 10:35:56 PM »
He's something I was able to find in the LT1054 datasheet.  It looks like exactly what I was trying to do before, but correctly.  I'm going to breadboard this one and see how it looks.

If anybody has any suggestions for this iteration I'd love to hear them!

Thanks!

Andy

Scruffie

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Re: Bipolar Power Supplies for OD pedals?
« Reply #8 on: January 21, 2012, 04:04:47 AM »
Both MAX1044 and LT1054 can be made to Split & Double.

I think what you've done looks rightish...

If it has clipping diodes there's not a lot of point in going so far, check out Merlins Glass Blower on DIY stompboxes for some high headroom boost from only 9V.
« Last Edit: January 21, 2012, 04:06:49 AM by Scruffie »
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