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Roland Sustain Problem


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10/17/2000 7:28 AM
Ed Rembold
Roland Sustain Problem
I decided to build this for fun, after R.G.  
mentioned he had it posted at his site. But,  
No luck, it'll pass audio, but "no sustain"  
tried 4 different Led/Ldr's, 5088's and 5089's.  
I suspect some sort of schem. error, because  
if I remove the 10uf cap from between the 82k/220k  
at Q1, the output of the effect goes Way up, and  
it'll feedback on itself at about 400hz, regardless  
of input frequency, kinda cool, but I'm sure that's not what was intended. any thoughts? if anyone had  
any luck building this, I'd sure like to hear  
about it, R.G.??  
Thanks, Ed R.
 
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10/17/2000 4:11 PM
R.G.
I'll look at it with a more critical eye. It is a "donated" schematic, I haven't built one.
 
10/17/2000 5:31 PM
Ed Rembold

I should admit that it's possible that I have an error somewhere, as I think that Every time I've posted here ,whining about something not working, it has always been some mistake that I've made.  
on a side note- last night, before I went home,  
(with the 10uf lifted) I shut off my signal  
generator, and just waited to see how long  
the 400hz "feedback" would sustain, I finally  
went home, and when I got back this morning,  
it was still going- shades of Spinal Tap!,  
there is potential here!  
Ed R.
 
10/17/2000 10:52 PM
pete

Ed,  
 
You could also look at http://members.home.net/roma60/. His sustainer is supposingly based on the roland sustainer (it's under the guitar effects down the page)!  
 
Pete
 
10/18/2000 1:07 AM
Ed Rembold

Yeah Pete,  
saw that, nothing really different than R.G.'s.  
Might be me. if anyone builds , please post.  
Ed R.
 
10/18/2000 10:15 PM
Rob Strand

Ed, you might try driving the LED with a DC source just to make sure the gain control is A-OK. (This should stop the oscillation as well)  
 
It may be possible to solve your problem by adding a cap (10u-100uF) from the collector of the transistor that drives the LED to ground. The cap will need fine tuning to get the attack/decay times right.  
 
Regards  
Rob
 
10/19/2000 12:20 AM
Ed Rembold

good ideas, Rob.  
I'll mess with it tonight, (if time permits.)  
Thanks, Ed R.
 

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