Yamaha RX-17 potentiometer Q's

[rob.ocelot]

Hey all,

It's my first post and my first bend.  

I'm almost finished this RX-17 bend, with 23 points taken from IC's 114 (XB811AO0) and 115 (XC258AO) and a 24th point as ground taken from the large metal heat sink.  Since most of these points were established safe/non-catastrophic bends I felt I didn't need to use any resistors or pots when testing them.  

Now that I've got the patchbbox finished I want to add a couple of pots to the box.  My tinkering with 100k and 10k pots gave some rather poor results -- I can't for the life of me get a usable range with any of the bends and that very small range is right at the end of the pot.  Wiring these pots like variable resistors doesn't seem to do much other than introduce a second quick transition at the other end of the pot (shorted to ground  -- remembering that the ground I'm using is also a patch point!).  I then tried 5k and 1k pots and both did pretty much the same thing though these seem to have slightly larger usable ranges.  All pots used were linear.

Where should I go next?  Should I start going to lower pot values like 500R or should I try modding these to behave like antilog pots so I can possibly get a less steep transition?

One thought occurs to me: the signals I'm bringing to the pot may be digital in nature (square wave) and the pot may just be attenuating the amplitude of the square wave until it drops below a threshold voltage where it no longer registers.  It would certainly explain the either/or behavior of the pot.  I don't have access to a scope at the moment (but I should have one next week).  

Of course, there's every possibility that the points I've brought to the patchbay may not really tolerate voltage changes all that much.  None of the bends I've done were of the pitchbend type that is probably more suited to a pot.

[Circuitbenders]

its because the data you ar trying to attenuate is digital and is therefore either on or off with no in between values, so in 99% of situations you won't be able to use analogue pots like that.

[rob.ocelot]

Thanks for the confirmation.

[Signal:Noise]

There are a couple of points on the rx17 that will add gradual distortions with pots...i think I used 10k linear. I'll see if i can find the pictures I took of the circuit board.

[Signal:Noise]

http://www.circuitbenders.co.uk/forum/index.php/topic,785.0.html

here's the topic