DIY Deluxe Big Muff: Most efficient way to get +/-5v from 9v?

Started by aion, December 20, 2015, 09:49:04 PM

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aion

I repaired a Deluxe Big Muff a few years ago (first version / EH 3053 circuit) and remembered it while I was putting together an op-amp Big Muff circuit recently. It's a pretty cool pedal - a Big Muff with a Soul Preacher compressor in parallel, and a blend knob to control the mix. Hasn't really been cloned to my knowledge, though the schematic is readily available:
https://sites.google.com/site/electroconducive/EHXDeluxeBigMuff.pdf?attredirects=0

The curious thing about this lil guy is that it runs on a bipolar +/-5V supply.

That is suspiciously close to your standard 9V/2 floating ground circuit in pretty much any other IC-based drive pedal out there. But, while I am sure it's possible, I don't really want to go through the trouble of converting it to 9V with a floating ground. Primarily this is because I don't know enough to add the coupling caps where they need to go - but also, presumably they chose to go bipolar for a reason, since it adds a bunch of parts compared to your standard 9-volt operation - better noise performance and the like.

I am wondering what the best option would be to get that supply. I'm calculating that for eight 4558's at +/-5V, I would need around 16 mA of power. (5.7mA max current draw at +/-15v according to the datasheet, so a figure third of that for +/-5V operation) To be on the safe side we'll say 20mA since there are a couple of transistors in there as well.

The options:

1) Regulate 9V down to 5V using a 78L05, then use a TC1044 or LT1054 voltage inverter to get -5V. Advantage: Only one regulator needed.

2) Invert the 9V first and then use a regulator on each side of the supply. Advantage: perfect 5V on both sides; also each regulator only needs to dissipate half the power compared with option 1.

3) Suck it up and just convert it to floating ground already - this is a Big Muff for crying out loud. Advantage: much easier to build once it was properly converted. But I'd need some pointers on how to approach this.

Any advice on the best option to take? Anything I am missing? Do the power requirements rule out any of the above?

R.G.

Go for door #2, which is pretty sure to work.

#1 is more noise prone.

#3 is prone to not getting enough to really make ±5V, as you're starting from less than 10 in the beginning.

Perhaps even better: use #2 and mess about with #3 and see if it works if you don't like #2.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

stringsthings

I'd be really interested if you clone this.  The Big Muff side is not hard to do, but I've tried cloning a soul preacher with
little success.   There's a few schematics on the net, but I couldn't get any of them to work on the breadboard.

digi2t

I agree with R.G. on door #2. It's the same scheme used in the Rand-o-matic, 9v bipolar, then two 5v regulators.
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aion

Fantastic, thank you! I'll go that route then and we'll see how it turns out.

PRR

> eight 4558's at +/-5V, I would need around 16 mA of power. (5.7mA max current draw at +/-15v according to the datasheet, so a figure third of that for +/-5V operation)

2) Opamp current does NOT go down, much(*), at lower voltage.

1) '4558 is a dual opamp, 5.7mA is for *both* units in a package. 4 packs, 14mA to 23mA.

About another 3mA (1mA-10mA) in an LED.

(*)  http://www.ti.com/lit/ds/symlink/rc4558.pdf
Fig 1 shows supply current at +/-4.5V about 80% of current at +/-15V. So 4.5mA per pack, 18mA for four packs.
(You got a right-enough answer, because the error of 2 is opposite to the error of 1/3.)
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I don't see any darn reason this could not run on +/-9V (or +9V/-8V). Then your problem is reduced to an "inverting power converter", which is a fairly standard thing.
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