[sdiy] Vactrols subbed for dual-gang pot

[cheater cheater]

Hi guys,
I understand how you get maximum and minimum resistance (the led being
on and off), but how do you get anything inbetween?
I understend you can use PWM to change the statistical average of the
diode's brightness, but doesn't the LDR respond to those changes
extremely quickly? Wouldn't it be then like a 'switched resistor'?
I might be missing something.

Cheers,
D.

On Sat, Jul 10, 2010 at 11:36, Tom Wiltshire <tom at electricdruid.net> wrote:
>
> On 9 Jul 2010, at 18:23, Dave Kendall wrote:
>
>> By hand-selecting LED/LDR pairs, I can match the off resistance of the home-rolled vactrols to within a few ohms, and limit the max resistance fairly easily, but between those points, I suspect the LDRs may "drift apart" due to different response curves to incoming CV. How would this affect the BPF circuit? Does it even matter?
>
> I agree with Paul - I don't think it matters either. You're talking about differences of linearity in components that are usually given 20% tolerances. Exact matching of responses and values will increase the cutoff slope and the Q, but I don't think that's exactly the point here. After all, if you wanted a precision instrument, you wouldn't be building it with vactrols, right? It'll sound funky as it is.
>
> Build it, don't stress about getting everything exactly matched, and call it "analogue character"!
>
> T.
>
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