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#162623 - 07/17/03 04:03 PM Re: Single Volume pedal for two keyboards
kbrkr Offline
Senior Member

Registered: 11/19/02
Posts: 2866
Loc: Tampa, FL
Quote:
Originally posted by travlin'easy:
Guess I must have missed something along the pike. I've never seen a single potentiometer hooked to more than a single device. When two instruments are connected through the same input, the output inpedence of their respective transformers is halved because they become parallel, resistive devices. That's what pre-amps and mixers have separate channels, blocking diodes and lots of other directional components that prevent impedience changes and problems with polarity differences between various types of equipment. Personally, if they were my keyboards, I would go with either a 4-gang pot in the foot-volume control and dual controls physically hooked together.

Good Luck,

Gary


Gary, I see what your saying. Your thinking the outputs of the keyboards are being routed through the pedal and then from the pedal to the amp.

On the Tyros and the Triton, there is a stereo input specifically for pedals which as far as I know, do not intercept the input/output signal.

Al
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Al

Pa4x - LD Systems Maui 28 - Mackie Thumps

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#162624 - 07/17/03 04:23 PM Re: Single Volume pedal for two keyboards
travlin'easy Offline
Senior Member

Registered: 12/08/02
Posts: 15576
Loc: Forest Hill, MD USA
The master volume on most amps, keyboard or otherwise, is usually prior to the the output transformer used to drive the speakers, mainly in the primary circuit of the amp's final stages. The input volume controlled through the mixer is most often a small, 20K-ohm pot that dampens the signal, then passes it through the EQ circuit, through the Pan circuit, through a pair of blocking diodes, and finally through the main gain and outputted into the output transformer's primary coils. The secondary coils are what then sends the signal to the speakers--at least that the way my Peavey's, Crates and Polytone amps are wired. I'm not sure about some of the other brands, but I did run across a keyboard several years ago that had a positive ground, which was used in some systems in the early days of keyboards. You couldn't even connect this particular keyboard to an amp that had anything other than a floating ground without blowing a circuit breaker. I rigged a resistance mixer with blocking diodes for the guy and he was able to then plug into most PA's without encountering a problem. The only test to determine the safety of hooking a "Y" connector to a single foot-volume control would be to measure the electrical potential betewen both keyboards using either a voltmeter or an oscilloscope. He could get lucky and everything might be OK, but I would be very cautious about this one.

Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!

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#162625 - 07/17/03 05:32 PM Re: Single Volume pedal for two keyboards
kbrkr Offline
Senior Member

Registered: 11/19/02
Posts: 2866
Loc: Tampa, FL
Quote:
Originally posted by Dnj:
Al,

you might find your speacial cable here http://www.hosatech.com/

or you can have one made easily at Gig Cables http://www.gigcables.com/



This is exactly what I need:

YPP-308 STEREO ¼" PHONE (FEMALE) — TWO STEREO ¼" PHONE (MALES), 6 inches


Thank You, Thank You, Thank You!!!!!!
Regards,
Al
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Al

Pa4x - LD Systems Maui 28 - Mackie Thumps

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#162626 - 07/17/03 06:56 PM Re: Single Volume pedal for two keyboards
Uncle Dave Offline
Senior Member

Registered: 12/01/99
Posts: 12800
Loc: Penn Yan, NY
Hmmm,
I was talking a passive easy-in easy-out volume pedal, not a dedicated TRS type pedal that connects to a special jack. You can get a stereo volume pedal (Roland used to make one ... I think they still do)that has 2 ins and 2 outs. They are passive inputs and require no additional worry or connections. Use "Y" cords or sub mixers ... it won't matter. Just plug and play - couldn't be simpler.
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