9v VS +12v/-12v

[OctaveB]

Hey people V V

First post there, happy to join this forum I've been checking loads 

I have done some DIY stuff but mainly in the Eurorack format, and I am thinking of making some pedals because I have some gear that isn't modular and I would like to do a bit of modular into stompboxes. Like a few inputs and outputs to make it semi modular. As I started in the Eurorack world I have worked with +12v/-12v.

It is pretty convenient for opamps and one thing I have noticed from looking at gear schematics is that they are running at pretty high voltages very often.

So here is my question, how does max voltage can be involved in the sound. Does it make headroom shorter when you have a virtual ground on a 9v battery against the +30v of an old JFET compressor ?

I would maybe like to make a pedalboard with +12v/-12v who knows..

Cheerz

Lucas

[ElectricDruid]

Certainly if you're used to using Eurorack and +/-12V supplies, then 0-9V is going to seem like reduced headroom. In practice, the signal out of most guitars is far less than 9V anyway (probably 1Vpp is more typical, but it does vary *hugely* depending on pickups etc etc), so it's not actually as bad as it sounds. That said, more headroom is always better so if you fancy building a Eurorack-standard pedal rack, you wouldn't be the first person to think it's a good idea, because fundamentally, it *is* a good idea! In fact, there was a discussion about this on another thread recently.

So...yeah, you could make a Eurorack-powered pedalboard, and it definitely is convenient for op-amps. Saves a lot of single-supply messing about, for sure. And you would have more headroom (24V) than even the 18V pedals on the market. Whether that gives you a better SNR is going to be down to good design at some point, but you at least start from a good position!!

[Ripthorn]

The only real concern is pedals where the op amp is properly clipping. Those will not sound/ feel/ work the same. Still, that can be dealt with by modifying the op amp gain values.

[MikeA]

And... welcome!

[Mark Hammer]

Many circuits CAN work with a +/-12V supply.  But the question is whether they will work "better".

For instance, drive circuits that stick a diode pair on the output of an op-amp often rely on headroom limitations of a 9V-powered op-amp to "pre-clip" the signal, before clipping it again with the diode pair.  Raising the headroom by nearly tripling the supply voltage (from 9V to 24V) can make that "pre-clipping" disappear.  From a high-fidelity perspective, that's great, but it may simply take away from how the circuit is intended to behave.

Then there are various modulation circuits that may be calibrated in anticipation of a 9V supply.  That doesn't mean they can't be made to work with a +/-12V supply, but it now becomes your responsibility to figure out what changes to make to facilitate that.  If you're up to the task, more power to ya. But you may be inviting more trouble and burden than you want.  Just sayin'.

All of that said, you came to the right place to ask such questions. 

[OctaveB]

Thanks for those very interesting replies. I will give it a try as I have my lab designed for +12v/-12v. In the end, I can get happy results trying to convert some 9v designs to 24v.

Experimentation and oscilloscope are the way to go, and smoke detector maybe. 

[Mark Hammer]

I'll just add that it is no great hardship to use an LM78L09 regulator to drop a +12V common-bus supply-voltage down to +9V for a specific circuit.

[iainpunk]

welcome to the forum

dont forget that there are circuits out there that really don't like going over the normal 9v, or atleast have a voltage cap way below the 24v you have. most CMOS can't handle such voltages. before using a chip, read the datasheet

cheers