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Motorized pot for Master Volume?


 
10/28/1999 1:50 AM
Steve A.
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Motorized pot for Master Volume?
    While designing the relay boards for the... humble amp project I am working on, it occurred to me that it would be really cool to use a footpedal to control a motorized master volume pot. Looking in Mouser I see that they do have 100kA motorized pots for about $10 each. Does anybody sell 1M versions of these pots? Possibly with two sections for a post-PI MV? In any case if anyone has tried this idea any suggestions or tips would be appreciated!  
 
Thanks!  
 
Steve Ahola
 
10/28/1999 3:40 AM
Trace
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Steve;  
 
Have a look at the Soldano/Caswell preamp. It's all motorized as far as the pots go. As I recall you could step on a midi pedal and the pots would change instantly to whatever was preset. I aslo understand it took ALOT of work to get it some what quite! (ha, ha)  
 
Trace
 
 
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10/28/1999 4:54 AM
SpeedRacer
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Soldano uses what I believe are called stepper motors on that pots. You send a control voltage and the pot turns to *that* setting.. (as opposed to an analog signal just rotating the thing)  
 
as far as motorized pots though, Neil Young has you all by about 15+? years... ;-) he had a thingy called "the whizzer" built which twiddles the knobs on his tweed Deluxe for him from a footpedal I believe.  
 
 
10/28/1999 2:05 PM
Don Symes
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I believe DigiKey has motorized slider pots, possibly stereo.  
 
You're gonna need some kind of servo circuit, too. Your motor control needs to know where the pot is so it can know which way, and how far to move.  
 
How would you feel about an 8-channel WIRELESS motorized knob twiddler? Check out an RC hobbyist site for radio/servo sets - possibly used - to get the difficult stuff already done (cheap, too). Your challenge becomes a re-package job rather than some from-scratch nightmare.
 
10/28/1999 6:47 PM
Steve A.
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Don:  
 
    Speaking of wireless I do have a Sony stereo receiver that uses a motorized volume pot which is controlled by the IR remote... I guess the remote just sends one signal to turn it clockwise and another signal to turn it ccw, which would simplify things a bit (since it doesn't have to monitor the exact setting of the pot).  
 
    Speaking of motorized knob twiddlers, it just occurred to me that Honeywell makes a Modutrol motor (for opening dampers, etc.) and I've seen them wired up to a "wheatstone bridge" style circuit in which the damper shaft moves in unison with the trim pot... But those Modutrol motors are

HUGE

like a 6"x6"x6" cube plus the linkage...  
 
    Does anybody make an automated mixing board that uses motorized rotary pots? Perhaps we could borrow the circuitry out of something like that... Maybe it is out of the ballpark for home-brewers, but it seems like the companies selling amps for $5k+ could add in something like that to give the buyer something more for their money! (I still like the idea of a control pedal with the volume control following the setting of the pedal...)  
 
Steve Ahola
 
10/28/1999 7:57 PM
Don Symes
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I kind of doubt you'll find rotary 'flying fader' controls unless you're way up in the studio market. Still, they may have a couple of junked channels you could play with at your favorite local studio.  
 
Your stereo's motorpot only knows you want 'more' or 'less' volume and - like you said - could give a rat's ___ about where it is now. Now, if you find that sort of control acceptable, and want to go with a pedal that actuates a toe-switch and a heel-switch to set direction and how long to operate... you know what to do. You just lose the positional feedback of a full servo-control pedal.  
 
You'd wind up with something like that third 'pedal' on a digitech floor thing. Busted stereo junk ought to be DIRT cheap, too (hint hint, nudge nudge).
 
10/29/1999 3:00 AM
Steve A.
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New topic: 300-in-One Tube Guitar Amp Project Lab?
Don:  
 
    Since that idea sort of fizzled out I thought I'd bring up another one I've been mulling over. Rather than have us hack up an old Fender amp to experiment with in learning about guitar amps, maybe one of the distributors here could put together an experimenter's kit (just like the "300-in-One Electronics Project Lab" that they sell at Radio Shack). A nice chassis with plenty of holes, a decent set of trannies, a bagful of components, and most important, a project book that would show how the classic amp designs would be wired up on the included all-purpose eyelet board.  
 
    I think many of us have already taken this route in one form or another, but by packaging the materials together in a kit, there should be a decent discount compared to the items purchased separately. These kits could be also be sold for classes on guitar amps at the local night school or junior college; if a class ordered a dozen kits there could be an additional discount (and still plenty of money to be made by the distributor... hint, hint!) If a project turned out particularly well, the student could order a cabinet to mount it in (which would be even more money for the distributor). Sounds like a win-win situation to me, and if sales didn't match expectations the distributor could just put the items back into his regular inventory... and I don't think that he would have any problem selling the project books he had printed up.  
 
    Here's a drawing of a bassman eyelet board stuffed with components for my latest project, just to illustrate what I'm talking about. With drawings like this to follow, lots of people could get their feet wet building their own amps and experimenting with different designs. All without having to hack up still another SF/BF Fender amp...  
 
http://www.techaccessinc.com/blueguitar/l3988009.gif  
 
Steve Ahola
 
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