Re: [AH] Roland parts cross reference/compatibility chart?

From Florian Anwander
Sent Thu, Sep 6th 2018, 17:51

Hello Sam,


On 05.09.18 20:07 , Sam Mims wrote:
> Florian, do you take all your schematics with you when you go camping, 
> or do you simply have them all memorized? 
When I was a boy my mother locked me up in the attic until I could 
declaim all Roland Service manuals by heart.  ;-)))

> I'm not being snarky - I've always marveled at your ability to solve 
> circuit issues remotely, and now you're doing it while camping!  Hats 
> off, sir.
Rob Senso's site is also available via 3G mobile connections.
> Do you have a generalized explanation for when you can make such a 
> substitution (as for these pots controlling volume) and when the exact 
> value is critical?
Basically, there are two types of volume control: the potentiometeris 
used as a variable voltage divider circuit. Or: the potentiometer is a 
variable resistor in the feedback path of an opamp. For the voltage 
divider the only the relation between the upper and the lower resitor is 
important.
For the feedback version the absolute value would be relevant. But in 
the case of all Roland synths I know the voltage-divider version is used.

Florian