postive DC in place of negative DC?

[methodofcontrol]

using 4558's where the circuit calls for -9v on pin 4 and +9v on pin 8 and ground is 0v, is it possible to redesign the power supply so that pin 4 has 0v, "ground" has +9v and pin 8 has +18v?
my thinking is that there would still be an 18v difference between pin 4 and pin 8 and it would allow me to use a DC adapter for power instead of the AC one required to get that negative voltage.
and assuming the above theory is correct, would i simply transfer all original ground connections over to pin 4 where the voltage would now read 0v?

[JoeM]

This is a Boss SD-1 OD pedal. You can see how +/- 4.5 volts is derived from a single supply (9V battery or Adapter) using 2 33k resistors. (Needs AC coupling). What are you building?

[methodofcontrol]

i'm working on clone. it's a distortion pedal. original pedal has AC cable and internal transformer. i'd like clone to run off standard 9v boss style adapter. was thinking 9v into a voltage doubler, then i'd have a 9v rail and a separate 18v rail to play with.
perhaps i just need to know how to coax -9v out of a standard boss adapter or battery while still having the +9v. didn't think that was possible, hence my original plan of using +9v and +18v.

[defaced]

The stompbox guys use the MAX1044 for this all the time.

Check this schematic: http://musicpcb.com/wp-content/uploa...ted-121709.pdf
Source (Taylor is a cool cat with quality projects) http://musicpcb.com/pcbs/

[JoeM]

I've built quite a few op-amp boosters and buffers using a single supply. If you can find a copy, Walter Jung's book 'Op-amp cookbook' gives several good sample circuits using a single supply that you could adapt easily. Back when I started, the Max1044 wasnt around yet, so i dont have any experience with it, but that's another option.

[J M Fahey]

Agree.
It can be done, connecting pin 4 to ground, pin 8 to +9V (so far so good) *but* all points which had a DC path to ground (through a resistor) now will go to the 4.5V bias point and those which had an AC path to ground (through a capacitor) can still go to ground.
The single-supply circuit will be, say, 20 to 30% more complex than a split supply one because of it.
I have been making -9V out of +9V for ages, before those nice converters were invented,, using a cheap and plentiful NE555.

[kg]

i haven't touched a stomp box in years. is the boss wall wart 9vdc or 9vac?

[jmaf]

DC

[methodofcontrol]

great info! thanks for the tip on the max1044! i already have a 7660 chip i was going to use for my voltage doubler- looks like i can use that in place of the max1044 if needed. but now i'm thinking adding both circuits to my clone so i'll have +18v and -18v for more headroom and clarity.
any reason i shouldn't do this? might i be concerned about noise or excessive battery drainage?
and lastly...if i was adamant about having the 36v (instead of 18v) swing, would i be better off using 2x voltage doubling circuits to get 9v up to 36v? or one voltage doubling circuit and one max1044 charge pumping circuit to find negative voltage? using the max1044 option wouldn't require me to move existing connections as my ground point wouldn't move. but in terms of efficiency or noise, is one solution better than the other?

[J M Fahey]

Do this only if you really need it.
Battery consumption will quadruple in theory, in real time octuple or more, because of conversion inefficiency plus whatever power the converter chips will eat for their own life.
Short answer: don't get too carried away.

[Steve Conner]

i'll have +18v and -18v for more headroom and clarity.
any reason i shouldn't do this?

Well, what amp are you going to drive with it? If the first stage of the amp overdrives with 6v p-p of signal (as the usual 12AX7 first stage of a tube amp does) then having 32v p-p output capability from the pedal is not worth the bother.

The only thing that will change the sound is if reducing the rails causes an op-amp to clip before the pedal's actual clipping network does, when this wasn't the intended behaviour in the original design.

(Or something like the old Marshall preamp that overdrove the op-amps themselves without mercy, I can see this being sensitive to voltage.)

+/-9 (18 total) is nice, the usual op-amps like the TL071 get a bit cramped with only 9V total supply, although they work perfectly that way in millions of pedals.

[cjlectronics]

If you decide to use the ICL7660, use the MAX1044 instead. The internal RC oscillator on the 7660 runs at 10khz for a 5v signal. This 10kHz will be heard in your signal chain, I know because it happened to me. I switched over to the MAX1044 which has a higher RC oscillator frequency, (outside the audible range) and the high pitched whine was gone.

[methodofcontrol]

well i think i'll dismiss the voltage doubler idea for now. i'll also go ahead with the max1044 to avoid rewiring the circuit for positive voltage only. so i should have my separate +9v and -9v all off of a standard boss style DC supply. i'll keep you posted. thanks again for all the help!

[methodofcontrol]

so... i copied the top most schematic from this link:
New Page 1

i am most definitely NOT getting a negative voltage off of pin 5. 1 chip + 2 capacitors = what could possible go wrong?
i've got pin 1 and pin 8 hard wired to each other, (no switch) but according to the write up... that just changes the oscillating frequency to be above human spectrum, which i can't imagine why you WOULDN'T have that option engaged all of the time.
also, i copied this schematic: Voltage Doubler Circuit
and i'm having the same problem...i'm not finding my 18v rail anywhere!
i'm testing both of these circuits independent of each other and anything else. they are completely isolated w/ nothing but +9v and ground hooked up.
am i missing something simple?

[J M Fahey]

Maybe you are misreading the pinout.
As shown, those ICs are seen from above; pin 1 is top left, pin 4 bottom left, pin 5 bottom right, pin 8 top right.
Start by building the most basic datasheet example, just to check it works.
Worry later about whine and other smaller problems.
Good luck.
EDIT:
er ... you aren't using the 7660 with the 1044 pinout or viceversa, are you?