Ideas for Buffered Amp Switcher...

[hairyandy]

Hey all,

I've been thinking about this and I thought I'd post and get any interested feedback.  I'm planning a pedalboard that I have to make this week and at the output it needs to take the mono signal and split it to 4 separate outputs.  Each of the 4 outputs will have it's own switch as they need to be able to be switched on and off independently---2 outputs will go to 1 or 2 guitar amps, one for an acoustic DI and one for a bass amp.  That part is pretty easy as I don't need to have outputs switch off as others turn on.

What I was thinking of doing is making an AMZ Super Buffer with 4 outs as is discussed in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=44654.0.  I think though that I will need to incorporate the transformer isolation from R.G's Hum-Free Splitter on the outputs because they'll be sent to different sources (ie:  amps & DIs) with potentially different grounds.  Am I correct here do you think?  Also, is there an easier way to do this, or more to the point, has someone already done this here on the forum?  I've done some searching but I haven't found exactly what I need yet.  I'm not married to the Super Buffer but I have built it before and I like how it sounds.  I'll probably be doing this on vero or perf so if anyone has any layouts that they think might help I'd be much obliged, particularly for R.G.'s Hum-Free Splitter.  If there isn't anything already done I'll probably be doing my own layout in Bancika's program which I will gladly post when it's complete.

The reasoning behind this is that I have to remake all of my looms for my Bradshaw rig for the guy that I tech for because our stage layout is changing on our next tour.  While I'm at it I figured I'd build a back-up pedalboard for his rig that we can also use for fly dates that will approximate the routing/switching of his Bradshaw.

Thanks for any replies,

[hairyandy]

Any ideas?  Comments?  Bueller?

[Satch12879]

Absolutely without question go with isolation transformers on ALL of the outputs.  I was working a gig last night and to my surprise the cat that I tech for had just recently started splitting his signal to two amps via the outs of his Boss DD-3.  Just as I expected, the ground loop and buzz coming out of one of them was just hideous.  However, they play real loud and rarely stop to catch their breath so it wasn't noticeable to anyone except me and the sound guy - another friend of mine.

That being said, I've personally had the same problem experimenting at home - splitting a signal to two amps from a Boss Digital Delay and a simple box with an isolation transformer totally did the trick.  I don't think I'd EVER bi-amp without using them.

Also, if you're going to be interfacing into a Bradshaw rig - which is seriously heavy duty - don't skimp on the transformers.  Order of quality - and invariably price: Triad Magnetics, Hammond, Lundahl, Jensen.

And Jack's design is quite excellent; however I'd substitute a really swanky opamp for the TL071, like a Burr-Brown OPA2134/4134.  Or you can do a two stage device with a JFET input opamp as the buffer coupled to a NE5532 on the output for max drive.

Just something to think about...

Good luck and let us know how it goes!