One transistor VCA

[houshu at dsp.cl.nec.co.jp]

Hello Marjan,

The curve of resistance of saturated transistor is shown in Japanese.

http://www.asahi-net.or.jp/~wz4k-tnk/kairo/vcf1.html
http://www.asahi-net.or.jp/~wz4k-tnk/kairo/trvol.jpg

Solid lines are for normal transistors. Dashed lines are for reversed.
Unfortunately, Ib range used in the 1 tr VCA is much smaller than that
in the figure.

Hope this helps.

> Date:    Sun, 14 Jan 2001 12:23:04 JST
> From:    ">>>marjan<<<" <urekar.m at EUnet.yu>
> 
> Hi all,
> 
> Take a look at this familiar quick schem of 1 transistor VCA,
> known from Korg MS10/20/Polysix, this time in Rolands similar
> version (from JX-3P). It's not yet linked from my page.
> 
> http://solair.eunet.yu/~urekar.m/1t_vca_roland.pdf
> 
> Now, this little VCA got me thinking, what response it is?
> I thought it's expo, but JH got me thinking, assuming it's
> lin or some cross between lin and expo. I'm not shure at all.
> I used it on breadboard when I planed MS20 clone but never
> test it in that way.
> 
> Anyone with idea? I ask this because I've had an idea to sub
> all audio VCAs in JX-3P (see the scematic) with SSM2164 quad
> VCAs but those are expo, so I'm not sure if it would work
> in there. I guess if I'm not in luck, I'll use LM13700 VCAs
> which are still better than original ones IMHO.
> 
> Cheers,
> 
> marjan

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 Osamu HOSHUYAMA                    NEC Corporation  Kawasaki JAPAN
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