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Vintage threads from the first ten years

Budda Switchmaster Schematic

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12/10/1999 12:27 AM
Scott	Budda Switchmaster Schematic Anybody got one? I want to know how they safely switch speaker cabinets. Thanks.

12/12/1999 2:40 AM
Don Symes	Did I tell Scott right, or was I just being paranoid? Gee, Scott - I'm starting to feel like a real pinhead putting you through all this. Could someone please confirm or deny my assertion that using a properly rated A/B/Y box to switch an amp output between speakers is a serious hazard to the amp? I'm starting to hope I _was_ wrong.

12/13/1999 1:21 AM
Scott	wasn't doubting you...but Budda does it safely with their Switchmaster amps. i wanted to see how they did it.

12/13/1999 2:12 AM
Don Symes	I doubt me sometimes. Besides, I wanna know, too.

12/13/1999 10:21 AM
GFR	Custom Audio Electronics http://www.custom-audio.com has an "amp selector" that's supposed to switch different amp heads to a single cabinet " target="_blank">http://www.custom-audio.com/product/prd_media/ampsel1.jpg">

12/13/1999 10:51 AM
Scott	great idea GFR, but what about ONE head to TWO different cabinets?

12/13/1999 11:14 AM

I know a way to do it.

I designed and built one of these several years ago, using high-current DPDT relays, and a switched-in dummy load on the unloaded head (it also shorted the input of the unused amp, so there was no output signal, but loaded the output just to be safe). It worked real well, and never fried the two old Marshall heads I ran it with. If I can dig up the schematic, I'll post it as a DIY project on my webpage if anyone is interested. I still have the prototype sitting on top of one of my amps.

As I recall, the real trick was keeping the ground loops under control. Both amps need to be grounded through their AC cords, and I added a ground-lift switch to lift the shield going to the input of one of the amps. Transformer isolation would be better, but might color the tone.

It was also a pain to keep the speaker signals from crosstalking into the guitar signals inside the box, creating a nice squealing feedback signal. They must be well-shielded from each other.

Randall Aiken

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