[sdiy] drum accent circuit

[Theo]

Hi Dave,
Sorry for the mess, thinking outloud here.

IMO cause your talking HiHat in other words noise, distortion of the signal
by the VCA is not a issue.
So a single BF245 _without_ feedback resistor to the gate as a VCA would do.
Zero CV feed through guaranteed.
Having the FET followed by a opamp buffer is the common thing to do.
Bipolar power can be used with this.
The VCA can sit right after the BP filter (opamp 5a) the whole transistor
thing with open and closed HH trigger inputs would go away.
Everything then depends on the envelope you feed the VCA.

Even less components, if you ditch the whole transistor trigger/envelope
part like in the above.
Then opamp 5a can be the output buffer, the BF245 (your VCA) can sit right
after R8.

The HiHat is pretty high frequency no problems with "bass loss" cause of a
cap to block DC here.
So there is no real need to change everything to symmetrical power.

Also if you use the trigger part of the circuit, there "already is a
envelope" (one for open HH and one for closed HH).
For accent you only need to get the volume up.
If you don't like the accent circuit that is there, then a FET, bipolar or
4066 switch to change the amplification factor of a opamp (the output
buffer/mixer?) driven by the accent gate signal would do.

BTW you may want to add a switch to select between the "CY source" (IC1,2)
and the "noise source" (IC3,4) or both.
Instant timbre variation :)

Just some thoughts,
Theo



----- Original Message -----
From: Dave Magnuson <resfreq at hoohahrecords.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, July 29, 2004 5:13 AM
Subject: [sdiy] drum accent circuit


> Hi everyone,
>
> I'm cloning the DR-110 hi hat circuit, and I'd like to come up with a
> better way to generate accent.  The original thumps pretty loudly, and it
> has a single-supply output section.  I'd like something with better sound
> (no feedthrough), and a bipolar supply (to get rid of DC offset).
>
> I've used photoshop to cut down the schematics to only the hats, accent
> circuit and output section.  You can find them here (250K pdf file):
>
> http://www.hoohahrecords.com/resfreq/mods/dr110/dr110hh.pdf
>
> Now, what I'm thinking is this:
> Use a simple AD envelope generator (or fixed attack, variable decay) and a
> CA3080 based VCA.  I would bias the VCA so that it's always allowing
signal
> to pass at approx 50% volume, then the env generator could add accent up
to
> full volume.  Finally I'd use a TL071 or similar for driving the output.
>
> Is this a typical way of approaching this, or is there some easier method
> that I'm overlooking?
>
> thanks in advance,
> Dave
>
> Resonant Frequency:
> resfreq at hoohahrecords.com
> http://www.hoohahrecords.com/resfreq/index.html
>