DIY Electronics Question

[Paul Maddox]

Paul,

 I've attached a schematic (and I've CC'd you directly incase the
mail-list doesn't allow attachments).
I've worked on the assumption that originally INT_LPF1_CV was
connected to  LPF1_CV_OUT directly, similarly for LPF2.

This *should* do what you need, just make all the resistors the same
value (10K should be fine).

 What is happening is that we're using the way the opamp does it's
signal summing to create a a diode, basically signals that come into
R1 and R2 (or R4 and R5) don't see each other and don't "pass back".
it also sums the internal voltages with the external ones without
risking anything going bad due to misconnecting voltages.

 So your internal LPF CVs won't affect each other when you use your
external CVs, but the two internal CVs will be summed with the
external CV(s).

 I did this using two TL072s (dual opamp) but you could use a single
TL074 (quad opamp).

Paul



On 6 March 2013 21:38, punkdISCO <forums at punkdisco.co.uk> wrote:
> Hi PaulM
>
>> what happens to the internal LPF1 and LPF2 CVs when you plug the external
> inputs in?
>> do they cease to function or does adjusting them "add" to the external CVs
> ?
>
> If I plug both externals in, the joining mechanism is broken so the
> externals are now independent.  The external CV and internal CV both work
> together, I guess they are summed but not sure, but they defo both work..
>
> Btw, the way I joined them is just the standard way where the tip of socket
> 1 goes to the sleeve of socket 2 - when socket 2 receives a plug, the
> contact with its sleeve is broken.
>
> London
> www.punkdisco.co.uk
>
>
> _______________________________________________
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> music-bar at lists.music-bar.org
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