[AH] CV current droops (was Regelwerk)

From earache
Sent Tue, Dec 1st 1998, 14:32

    I had this same problem with my Pulse +. I had to have 
a tech build a buffering circuit inside it because otherwise I found
it unusable with my 2600 and A100 - tuning would sag the more destinations
I patched it to.  A blemish on an otherwise fine instrument.

>Date: Tue, 1 Dec 1998 14:26:01 +0100 
>From: Haible Juergen <redacted@example.com>
>Subject: AW: Re: [AH] Regelwerk
>> > I've just taken delivery of a Doepfer Regelwerk, and it is a great
> >> controller. 8 CV & gate outs!
> >> The one thing that bothers me is that if you connect more than one synth
>> > a CV-out, the voltage drops and the synths cannot be tuned.
>> > Does anyone else have this problem?
>> > 
>> Anyone who did this would have this problem ;-)
>You only have this problem when the outputs are either
>cheap, badly designed, or simply not intended for
>precise V/Oct CV's. (I don't know the circuit of the Regelwerk,
>so this is not meant as an offense. I'm trying to give a few
>helpful hints *in case* that there is a problem with voltage
>droop - for this unit, or for similar output stages. Wheather there is such 
>a problem with the Regelwerk or not I don't know.)
>> Any synth's CV input is a current drain; the higher the current drain,
>> the more the voltage seen at each synth's CV in will sag.
>> To solve this you can build a simple circuit based around an Op-Amp

>As someone said before, such a buffer should probably have been built into 
>the box in the first place.

>It's not a question of "designing around physics", as someone posted. It's
>part of the price you pay when you buy low budged gear. You don't see things
>like this from the outside, nor does it usually appear in the specs. But it
>can make a difference.