[sdiy] Op-amp to boost VC signal with +5V/GND?

[Harry Bissell]

Many classic synths use CMOS (4000 series) and 12 or 15 volt supples, which would
require a gate voltage of between 6 to 7.5V minimum to trigger, possibly more if
a schmitt trigger gate was used.

5V is too low for a good gate imho. I think the 10V level would be best.

H^) harry


----- Original Message -----
From: Andre Majorel <aym-htnys at teaser.fr>
To: synth-diy at dropmix.xs4all.nl
Sent: Mon, 23 Aug 2010 10:11:28 -0400 (EDT)
Subject: Re: [sdiy] Op-amp to boost VC signal with +5V/GND?

On 2010-08-22 12:36 -0700, David G. Dixon wrote:

> My modular uses 5V gates throughout.  Gated modules are
> typically activated at about 2V.  5V gates are also convenient
> for interfacing with digital circuits.  Hence, why would one
> want or need 12V gates?

To modulate by more than 5 octaves without voltage gain.

Problem with attenuators that max out at unity gain is that the
resistance between the wiper and the end of the track never
quite reaches zero. In most cases, it seems to be 0.5 ~ 1.5 ohm,
which is not bad at all (1.8 cent/V for a 100 k pot). But I have
a pot here with 80 ohms at one end and 35 at the other.

Side note : on the MS-20, the attenuators on the CV inputs for
the VCOs and VCFs are log pots, even though the CV is
exponential. Is it better or worse than a linear control ? Well,
the usual setting is 1 for the VCO and 10 for the VCF so I don't
know.

What's really annoying is gate inputs that need more than a
couple volts to trigger. I wish there was a standard for that.

-- 
André Majorel http://www.teaser.fr/~amajorel/
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-- 
Harry Bissell & Nora Abdullah 4eva