9vac power challenge

[Beo]

I now have three commercial pedals with fairly high current 9vac needs (0.5 - 1.0A) and different plug types (Whammy 2, Boomerang original and a Microverb I). Separate adapters run 20-30 bucks.

I've got DC power magic figured out, in terms of how much current draw my combination of pedals are pulling, and which ones are sensitive in terms of leaking LFO's across common grounds and needing isolated power.

But is there a good way of sharing 9vac for these heavy draw pedals? For instance the Weber WPDLXFMR-2 can have a 9vac out... could these feed three 0.5-1.0A draws? Or is the only real solution to have separate adapters?

[slacker]

The pedals will all rectify the AC to get whatever DC voltages they want internally, these will either be positive and negative DC supplies or higher voltages or both, they will probably do this in different ways so you can't necessarily power them all from the same AC supply.
If you can find the schematic or trace out the power sections someone here can probably tell you if it would work.
If you're thinking of building a power supply using the Webser transformer you could just make the box a bit bigger and add an extra dual secondary 9 Volt transformer to get two more 9 Volt AC outputs.

[Rob Strand]

There's a good chance you will get hum powering from the same AC supply as current pulses charging the filter caps can flow through the ground.

[spyrusthevirus]

Do the pedals need AC or DC fed to their power plugs? It sounds weird as a design choice to ask for 9V AC, rather than DC, since the DC power adapters are more commonly available and an AC2DC stage would add extra part numbers and costs. If they have tubes that would make more sense (and matches the rather large current draw you are reporting).
If they ask for "9VAC", it doesn't matter what they do with it internally, as long as you can provide the current they ask for- any 9VAC is the same to them.

If you do need AC, you can build an "AC box" of sorts-it would take your mains voltage and output 9VAC on various adapters for you to use.
It's very simple really, but you need to be extra careful since mains voltage is involved. They only thing you have to figure out is the current each pedal needs from the transformer, and get one 220(or 110 depending on were you are)VAC->9VAC for each, rated for said current. Then, you connect every primary winding in parallel to the mains voltage, through fuses and switches, and that's it pretty much. Getting 1 transformer for every pedal will make sure there is no interferences and hum from one another. Smaller transformers are a bit easier to source as well.
The transformers can even be on separate enclosures, to make the whole thing more versalite. they tend to be heavy, and carrying 3 of them when you need only one may get uncomfortable in practice.

[PRR]

Don't connect multiple AC loads to one AC power source.

There are several ways the internal AC-DC converters can be wired. The DC side is also linked though the audio Ground. Different AC schemes connected together at their output grounds WILL blow-up.

Get three 9VAC transformers.

[Beo]

Thanks everyone... three separate wall warts it is, until I build my own 9vac multi-transformer supply.

[Beo]

So I'm thinking of putting together my own power supply with enough AC and DC outputs I need, in a form factor that works with my homemade pedal board. I've been wanting to do this for a while now using the Weber WPDLXFMR-1 transformer. I've been using the Smallbear Smallwart 200 which I built a few years ago, so I'm okay working with mains.

So the Weber transformer gives eight 11vac 300ma secondaries and one 9vac 2A secondary. I'd like to add two or three more 9vac 1A outputs, maybe using dedicated single transformers. Does anyone know of a good 9vac transformer out there that is good to 1 or 2 amps?

[Jdansti]

Something to watch out for, Beo: I took a plain Jane 120VAC:16VAC transformer and placed a couple of 9VDC and 12VDC regulator circuits on the secondary. Everything was fine until I tried powering a stompbox with one of the regulated DC outputs AND powering a small amp with the 16VAC secondary simultaneously. The wiring from the 16VAC to the amp got very hot. My memory is that the amp wouldn't work. I believe that the ground from the regulated DC was creating a short for the AC since the stompbox ground was connected to the amp through the signal cables.

This may or may not be an issue for your design, but I thought I'd let you know what I ran into. It might not be a bad idea to sketch it and have the resident gurus take a look.

EDIT: Maybe I did what PRR warned against:

Don't connect multiple AC loads to one AC power source.

There are several ways the internal AC-DC converters can be wired. The DC side is also linked though the audio Ground. Different AC schemes connected together at their output grounds WILL blow-up.

Get three 9VAC transformers.

[PRR]

> Maybe I did what PRR warned against

I think you were a little cleverer. But yes, don't do that unless you know and understand how the several rectifiers will come-together again at the common audio ground.

> The wiring from the 16VAC to the amp got very hot.

Unless you used very fine wire, hot wires are for-sure a sign of excess load, and in this case probably a dead-short (through the various rectifier diodes).

For real fun, use small-gauge wire clip-leads to hook up power to the radio in your jeep. Then have a +12V battery clip come loose and find a good ground. Do it at night. The wire lights up exactly like an incandescent lamp, but burns-up instantly, leaving a small cloud of PVC smoke. Since then I obsessively crimp and bundle my car-radio wiring so it can't come loose.

[Jdansti]

^Yow!