Recording two or more pedals in parallel - avoiding hum

[Guitarist]

Hi, I wondering the best way to record multiple distortion boxes at once. I'm not good enough or get too creative to overdub!
Would you ground the output on only one pedal and lift the other(s)? I rather not use iso-transformers. I can use batteries but also have a few tube based distortions which are powered from separate winding of a torrid transformer giving 12V AC.

Anyways, hoping to record some great tones for a possible debut...

[Leo_Gnardo]

So many ways to do this. One is, you can y-cord (or as many splits as you please) into your OD boxes, then mix the OD outputs with a simple line mixer, feed that into an amp or amp simulator, then onto a record track. Another way, Y-cord with one side going dry into your recorder, the other passed thru an OD box, amp or simulator, then into your recorder. Record your track, then take that dry track, send it into as many OD boxes as you want via mults (multiple Y-splits). This way you concoct your fuzzy soup after recording the track, and you can pay attention to the tones you get in the mix. Plus you already have one distorted track recorded as a reference, which you may or may not want to mix with the other sounds you develop.

If sending signal to more than one amp, sorry the best way IS via transformers, otherwise you're sure to generate ground loops with lots of hum & buzz you can do without. The good part is you don't need expensive transformers. I built a custom pedalboard 20 years ago with 5 parallel outputs to drive 5 amps. I built a quick easy buffer based on MXR MicroAmp, drove 5 cheap Mouser TL018 transformers with that, followed each transformer with a mute button, and had a very happy customer. Don't worry much about the theoretical loss of bandwidth with these transformers. The spec is given at the signal limit, and it's low end rolloff anyway which may turn out to be a blessing when driving OD & fuzz boxes. These are guitar signals, not hi fi, we don't need flat 20 Hz to 100 KHz response. Have fun! And put up some of your recordings here, or a link at least.

[Mick Bailey]

One thing to watch is that when you split your signal into parallel channels you reduce the impedance and can begin to lose some sparkle. Ideally any more than two FX ought to have a 1-in/n-out simple buffer/splitter.

The Stompbox Cookbook has a good circuit, as well as some surprising information about bandwidth and distortion with small transformers. The best way of finding out what you need is to set up your pedals and see first if you have any issues. A lot depends on whether your mains pedals are connected to mains earth, or whether the supply is double-insulated. My mains-operated tube pedals also use 12vAC via an unearthed wall-wart and there's no loop. There are a few ground-breaker plug-in boxes for the mains on the market that avoid the use of transformers but keep the earth (such as the Ebtech Hum X). Expensive, though.

[Guitarist]

Yes, I've made those ground breakers with diode/Ω/cap which takes a surprising amount of labour. I could modify an output from a pedal after the first transistor stage to feed another so the Hi-Z keeps up. My Audient interface has two inputs so thats covered. So far I'm getting excellent tones with a tube buffer or using an English Muff'n first and adding an amp sim. But I have some great modded pedals too ready to rock.
If I order from Mouser again, I'll buy a couple of those transformers. I have a dead mic here that I could pilfer its. The nice thing about running aside guys alike Eddie VH is that you can modify and build to suit, just as long as you don't lose creative momentum on another bunny trail...!
Thanks for the help gents.