Using one buffered pedal to drive multiple amps....

[Leo_Gnardo]

My circuit above in post #8 doesn't use any transformers. It's cheap, just a few op-amps and resistors.

I noticed that. Also noticed you're in the UK where it's rare to find amps that don't have a secure ground connection through their AC power plug. If that's the case you may be able to get away just fine with resistors isolating each output branch. Imagine what would happen to your op amps if one of your amps wasn't grounded but instead had 240VAC on its chassis, maybe not directly wired to the line hot side but through a "grounding" capacitor as we have in many pieces of gear in the US, say 0.047 uF 600V. Still going to deliver hum free operation? I don't think so. In the yet-to-be-civilized USA we have to contend with gear that isn't always safety grounded, in some cases a shock hazard via the "grounding" cap aka "death cap." This is why transformer isolated floating outputs are a useful feature. Sure, if you can get away without 'em, do so, no problem.

[Dave H]

I noticed that. Also noticed you're in the UK where it's rare to find amps that don't have a secure ground connection through their AC power plug. If that's the case you may be able to get away just fine with resistors isolating each output branch. Imagine what would happen to your op amps if one of your amps wasn't grounded but instead had 240VAC on its chassis

If I had an amp with 240V on the chassis the op-amps would be the last thing I'd be worried about

We've never had death caps over here, even my first guitar amp had a three prong cord so I've never had a problem with that circuit. I thought the death cap was history years ago in the USA and all electrical equipment now had three prong cords or IEC connectors. I know that wasn't the case 20 years ago in Texas. I found out the hard way by using a Fender combo as a seat while playing guitar. It shocked me right up the backside.

[Justin Thomas]

Death caps HAVE been history over here for a long time. But, our vintage amps are also history, and so there are still many out there looking to barbecue their next victim, because some Beavis doesn't want to affect the "vintage value" of his amp. "Vintage Value" be danged, I want my own vintage value more than any of my amps... I put 3-prongers on all of mine.

Justin

[Leo_Gnardo]

Death caps HAVE been history over here for a long time.

In spite of that, some manufacturers still install "death caps," many kits have them & builders go ahead & put 'em in because they don't know any better or think they must hew to the original design. And there are also many older amps that have been changed over to grounded cables but death caps left in, so when a ground lift adapter is employed or some well meaning nitwit rips the ground pin off the AC plug you're back in zap territory.

Although they may not be rated to stand off 120 or 240 VAC the Mouser transformers have worked wonders. For those who can afford Cadillac prices, same can be said for Dean Jensen's. I can tell you it was just wonderful to not get shocked on the job anymore.

[Chuck H]

Now you have heard of it: I used to get shocked all the time. From the first jam sessions in hi school up to the first day I encountered the Bradshaw output switcher in 1992. That was the day I thought to myself "why hasn't anybody done this before?" Expense, mostly, with a box full of Jensen nickel/iron. All amps safety grounded & no more shocks, what a relief!

Well, my thinking is on a smaller level where I'm in control of my own gear and know what to do. A stage full of half baked musicians and assistants could mean anything is happening. I imagine a lot of guys who've worked venues as you have could say the same.

And if we're going to be safe, let's also be sure to carry ground fault testers in our gig bags! I've played a lot of dives and I've observed a couple of things:

Bar owners like to save money.
Some fancy themselves handymen.
The ones that don't think they can handle electrical usually know someone that does think they can handle electrical.

At one club we played there were two AC plugs side by side. The bar owner pointed and said "You can use that plug, but not this one. It's on a different circuit and you'll get shocked."... Really.?. Okey dokey then.

[Chuck H]

I was just thinking... (Run! Save yourselves!)

If there's still time, and isolation transformers in an ABY pedal are part of the build why not include a phase switch for the A or B output.?. That way if you happen to be combining two amps with different output phase you can do it more easily and with just the one unit. Of course you probably know how the amps you're going to use work together, but why not include the feature in case it can help at some time with any other amps?

[olddawg]

Thanks for all of the responses and suggestions guys. I usually use a wireless because the mains in clubs are so whacko most of the time. I was primarily concerned whether a buffered pedal last in my chain would play nice with 2 amps. I think I will dry run it with a ground lift on one amp if necessary. If I have problems I will seek further isolation.

[Chuck H]

Thanks for all of the responses and suggestions guys. I usually use a wireless because the mains in clubs are so whacko most of the time. I was primarily concerned whether a buffered pedal last in my chain would play nice with 2 amps. I think I will dry run it with a ground lift on one amp if necessary. If I have problems I will seek further isolation.

Just because I took a beating on the matter of ground lifts... Ok, Maybe I like having you around too...

If you're going to fly with a ground lift adaptor then make sure you are the only one in control of your gear! I know you could manage it just fine. We sure don't want a forum without the dawg