assymetric to symetrical power supply question

[snk]

Hello,
I have an Ibanez Renometer pedal which I love a lot (it's an inductor eq from the 70s with a very special sound).
It is powered using 2x 9V batteries, fuelling the circuit with a symmetrical +/-9V power.
I would like to get rid of batteries, and I am wondering which would be the best way to do so.

- Should I make a 9V to bipolar +/-9V daughterboard (using a chargepump)? I've used these kinds of solutions in the past, with success, but it gave me headaches and i start thinking it might not be so reliable (From a recent thread, I learnt it can be quite noisy and unpredictable)...
- I know that with batteries, we can wire the + of the first battery and the - of the second one to create a bipolar power supply, but using adapters it would mean using two adapters, two plugs... which is not very elegant.
- Given that I have 9V, 12V, 15V, 18V power supplies, is there any easy solution to feed "unpiloar" 9 to 18V current, and get +/-9V at the output?

I feel i'm missing something obvious, but i can't figure out how to feed the Renometer (and I wouldn't want to mess it)
Thank you!

[snk]

Oops, once again, I forgot elements of context 



https://mirosol.kapsi.fi/2013/08/ibanez-no-95-renometer/

This requires two 9V batteries, as it runs with +9V and -9V, using gorund as vref. Measured current consumption settles round 5mA, so those two batteries should last a long time. Couldn't believe my ears how loud this thing is. The sliders are basically five simplified cry baby wahs that are wired for cut and a boost. Oh. Once again, Dirk has a perfect schematic published on his site. His unit seems to run on JRC4558 and it has an dc jack. Neither of which are present in my unit.

Schematic here : http://www.dirk-hendrik.com/techstuff.html
http://www.dirk-hendrik.com/temp/ibanez_renometer.pdf

https://www.tonehome.de/ibanez/first-series/no-95-renometer/

[PRR]

Check this carefully!

[Rob Strand]

Check this carefully!

It was very tempting to put up something like that but I really think snk should get a DC/DC converter working.

For the single supply it's a probably better to leave R10, R11 to ground and add a coupling cap between the switch and R12.  Then add a somewhat larger resistor from R12 via that resistor to Vcc/2.   Then there's the need to add dethump resistors on the input and output.  That was my thought process before thinking the DC/DC converter doesn't/shouldn't change much.

The values of R10 and R11 are very low.  Crazy low to the point where the values might not be correct on the schematic.
[It's crazy low but for a reason:  you want the divider output impedance to be low compared to 1k5.  A way around that
would be to add a equalizing resistance to the unattenuated arm and reduce R12.]

[snk]

Thank you for the suggestion, PRR & Rob.
If possible, I would like to avoid to modify the circuit itself (as the pedal works great the way it is and I'm a bit reluctant to take the risk to mess it up). Making a daughterboard on vero to put instead of the batteries is fine, drilling a hole in the enclosure to put a power socket is obviously fine too.

[ElectricDruid]

I feel i'm missing something obvious

The middle knob?!? 

[snk]

 

[duck_arse]

not to derail or anything, but -

if you had one of these .....



.... you would have a Ren(o)meter and a Stimp(y)meter.

carry on, kids.

[antonis]

Making a daughterboard on vero to put instead of the batteries is fine, drilling a hole in the enclosure to put a power socket is obviously fine too.

You DO know how to make a +/- 9V bipolar supply of 2 X 9V single supplies, don't you..??
(so far as they don't share the same ground..)

[snk]

You DO know how to make a +/- 9V bipolar supply of 2 X 9V single supplies, don't you..??(so far as they don't share the same ground..)

Like that?

[antonis]

True, Correct & Verified..

So , if you have handy 2 X +9V supplies, go for it...!!!

[snk]

Yes, that is something to consider indeed. This means drilling 2 holes for 2 power sockets, but that also means no additional circuit, no mods. 

[PRR]

This means drilling 2 holes for 2 power sockets

Or an adaptor from two 9V plugs to the JK3 socket on the pedal. (Or is that a phantom? I don't see it in the pictures.)

[Rob Strand]

True, Correct & Verified..

So , if you have handy 2 X +9V supplies, go for it...!!!

Another perfectly valid solution is a voltage doubler,  it's the second type on this page under "2). Full Wave Voltage Doubler",
https://www.electricalvolt.com/voltage-doubler/

For a dual supply take 0V at the center of the caps.  The input is an AC power source.


That trick is used in many pedals (and other devices for that matter).

You can get a bit if thump on power up.  To stop that use a resistor in series with the AC, you will get a bit of voltage drop.

It's possible to add regulators if you want but don't overlook regulation
of the input supply and drop out of the regulators.

[Chillums]

Or if you don't mind using an AC source (with an isolated socket) you could whip up one of these.  I think MFOS also carries the PCB's last time I checked.

https://musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/wallwart_added_load_rs_schem.pdf

[R.G.]

DC to isolated DC converter module, accepts 9V in, puts out isolated plus and minus 9Vdc at up to 56ma, costs $4.56 in ones at Mouser.

https://www.mouser.com/datasheet/2/670/pdm1_s-1311551.pdf

[snk]

Thank you all for all the suggestions!

[mzy12]

Like that?

Can't you achieve that with using a regulator to isolate a second +9v (ish) and run it like that?

[antonis]

Can't you achieve that with using a regulator to isolate a second +9v (ish) and run it like that?

Any schematic available..??

[R.G.]

Can't you achieve that with using a regulator to isolate a second +9v (ish) and run it like that?

As antonis is coyly pointing out, probably not. The issue is not the voltages, it's where the ground wire connects. If you meant what I think you meant, no, a simple regulator won't do it because any regulator has to somehow make its purportedly -9v(ish) output be below ground on the original +9V and ground, and its most positive voltage be connected to the original 9V supply's ground. Something gets shorted out.