How to decide what voltage is optimum for stomp box pedals

[smackoj]

Hello amigos; I have been building some vero board effects lately. My latest is an out-board version of the Sadowski 3 knob bass preamp. I am wondering what determines what voltage I should or could use to get best results? I read that some builders use 12 v or 15 v or some number close to these. Of course many builds use 9 vdc. But is it just a matter of taste what voltage to run the effect at? I realize that the components have to be able to handle higher voltage i.e. capacitors that can handle 12 or 15 volts. The main discussion I have read is that higher voltage gives more head room and sometimes better tone. Do any of you tech giants have an opinion or suggestion?

I also have acquired a few regulated 12 vdc power supplies but they are designed for loads that draw more current in the 3-8 amps range. Can I use these power supplies safely with a stomp box that only uses 50 miliamps

thanks gents

[BetterOffShred]

I know some effects like the famous Klon Centaur run charge pumps for more output, and/or headroom like you mentioned, but some effects require more or less voltage just for the chip to operate within accepted parameters.  Like the Robot from Death by Audio, requires around 3.5 volts for the HT8550 to operate correctly, and then the Echo Dream, runs best around 15 volts for the LFO chip to operate and not tick.  I have a variable voltage controller I built and I've run most of my pedals from 8-15 volts, most of them have no really noticeable changes.   I build a Ruby amp with a 386-3 which can handle like 20V or something, and yeah it's way louder with 15 Volts. 

I only order 25V or higher Electrolytics now for this reason!

As far as regulated DC power supplies, you're not guaranteed they are going to be well filtered, and I'd recommend building a little regulated power supply yourself with a 7812 or higher and some filter caps like the "huminator" design that's out there.  You could also run your 12V supply into a huminator style design to clean it up if it's noisy.   You can get a LM317 regulator kit with filtration for like $5 off ebay and build it into a nice little box for a regulated power supply that's pretty flexible with a digital readout.

I'm not by any means a pro on this, but as long as your components are rated for the voltage you'll be ok. 9V seems to be a vestige of available battery technology, and like I said most things work just fine at higher voltage.  When I built my Robot pedal I used some diodes from the power leg to get down to 3V to the HT8550, so if I run the pedal off anything other than 9V, that chip will be seeing more voltage and it either doesnt work at all, or sounds crappy.  In place of that you can run regulators to get a more flexible design for varied input voltage.  Just make sure you check out the chips and transistors data sheets before you go and fry a relatively expensive part! 

-Brett

[Joel]

I've kept my homebrew power supply at 9V.  Because it's the standard.  But most of the pedals I've built contain a voltage doubler so they're running at 18V.

[smackoj]

thanks for the replies. I guess if I could sum it up, "most" effects circuits can run on more than 9 v but the caps have to be rated high enough to handle higher voltage. I did not know that certain chips need like 3.5 v to operate at optimum. Are you referring to an op amp chip Brett?

I like the 'build your own power supply' idea and I'll have a look at those DIY pcbs out there.

thanks again,   

[BetterOffShred]

Most chips will have a voltage operating range listed in their data sheet.   I was referring to a couple specific chips I've used that require something well outside of the 9V range.   Buy caps rated for 25V or above, use quality 1/4Watt resistors and then just check the data sheet for whatever transistors and Integrated circuits are in whatever effect you're looking at. Most IC's have a fairly wide operating window of voltages to run in.   Some FET's will require drain biasing, which will require a different resistance as you increase voltage, so that's also something to be aware of.   

-Brett

[smackoj]

Thanks for the good info Brett.

[jojokeo]

Hi brother OJ,
It appears you've got the hang of soldering strip/veroboard! I love working with the stuff in the same way I can create various circuits using eyelet & turret boards. Not nearly as confining as standard etched & drilled circuit boards.
Way back in the day most all op-amps were ran using a bi-polar power supply. This was where you have +9 0 -9 volts. Your signal being an AC waveform travels up into the positive down through 0 into the negative side of the power rail and back up. The simple and net result is that it was the same as a pedal running at 18vdc today. Tone is subjective but not so much when describing headroom. On a typical OD or distortion pedal the extra voltage gives you more headroom as mentioned earlier since it can receive and output a larger waveform as a result. This is the simple non-technical answer. There's a lot of reading out there if you google it.
 
For your power supplies you always want more capacity / amperage available than whatever circuit is drawing from it. A circuit no matter what it is will only draw what it needs and won't be harmed if the supply has more available. It's the opposite that you must be aware of. Think of it in the same way as your amplifier's power section. If you use an underrated PT supply say having under 100mA but wanted to use a pair of EL34's you'd be in trouble. The tranny would run hot until it burned out. The tubes wouldn't perform near to their capability. Now if you used a PT that 1000mA (way overkill and heavy) it would work perfectly fine - but just be way too big and heavy to be practical for carrying to gigs or maybe fitting on your chassis? Also, know that when a power supply approaches it's design current draw limit, besides getting hot, it will begin to show signs of voltage drop or sag before breakdown and this is not usually a good thing like the same kind of sag in our amps.
 

the Robot from Death by Audio, requires around 3.5 volts for the HT8550 to operate correctly,

When I built my Robot pedal I used some diodes from the power leg to get down to 3V to the HT8550, so if I run the pedal off anything other than 9V, that chip will be seeing more voltage and it either doesnt work at all, or sounds crappy.

Consider using zener diodes...

[BetterOffShred]

Didn't have any in the right range.  But I made it work! Put a big muff pi tone stack on it, it's a fun pedal.
-Brett

[smackoj]

Brother JoJo. Very good to hear from you again! I always learn a bunch when you reply. I built two effects using Vero brd lately. A Sadowsky bass preamp that I put in a box, not on-brd. The other is, or was, a type of colored sound booster called, are you ready???, the Phat Phuk! The Sadowsky worked from the get-go but the PP or FF booster didn't pass signal and I didn't feel the urge to trouble shoot the pos. Me and vero brd don't seem to like each other much. Anyway, good to hear from you. Here is a new design Pink Jimmie came up with over at Freestompboxes. I listened to his demo recording on Youtoob and was floored by some of the 'cleaner' tones he was getting out of this LM386 Ruby modded amp. Check it out.

http://freestompboxes.org/viewtopic.php?f=28&t=28147

[BetterOffShred]

Pink Photon jimmy is the man!  I love his nasty octave effect too!   Yeah, the ruby amp is glorious in my opinion and I love what he's done to it there.   Thanks for the share!
-Brett

[smackoj]

Brett; yeah I really was amazed at the vintage type tones he was getting from that little amp, a strat and a 2x12 box. I am hoping he is going to do a run of pcbs for this one. He started working on it but I haven't heard whether they actually got built and tested? I told him I'm down for at least 2 when he gets 'em out the oven.

jack