[sdiy] Difficult 2164 behaviour between different sections.

Neil Johnson neil.johnson71 at gmail.com
Mon Jul 15 21:14:01 CEST 2019


The 2164 is quite temperature sensitive - there is a reason the data sheet
mentions a warm up time as part of the device spec.

It is also why temp.co schemes work quite well, and also why it is the
cardinal rule that any compensation gain cell is on the same silicon as the
cell it is compensating. The same goes for the Irwin linearised VCA.

It is worth bearing in mind that any control voltage more than a couple of
volts is going to have a noticeable heating effect on the silicon and that
will affect the gain coefficient of the surrounding cells.

Neil

On Mon, 15 Jul 2019, 19:39 Erik Dower, <electronicpresskit at gmail.com> wrote:

> I was thinking that might be the way to go. On my circuit, there is a very
> small amount of fm happening when the gain cell is attenuating, but a very
> distinct jump in frequency once it starts amplifying.
>
> epk
>
> > On Jul 15, 2019, at 4:57 PM, Tom Bugs <admin at bugbrand.co.uk> wrote:
> >
> > I didn't exactly - I rejigged things so that different sections were
> used for the critical parts.
> >
> > Best, Tom
> >
> > On 14/07/2019 21:05, Erik Dower wrote:
> >> Hi Tom,
> >>
> >> Did you ever resolve this issue? Unfortunately I find myself in a
> similar situation.
> >>
> >> Thanks,
> >>
> >> epk
> >>
> >>> On May 30, 2018, at 10:29 PM, Tom Bugs <admin at bugbrand.co.uk> wrote:
> >>>
> >>> Thanks all.
> >>>
> >>> Beefing up the 0V is something I tried on another point of the
> circuit, but I don't think I tried it on the 0V pin itself - good point!
> >>>
> >>> I will try Rbias some more for sure.
> >>>
> >>> And agree with many of the points from David - it has been an eye
> opener & I will have a few more deep sessions with it.
> >>>
> >>> I'll report back..
> >>>
> >>> Cheers - Tom
> >>>
> >>>
> >>> On 30/05/2018 19:41, David G Dixon wrote:
> >>>> That's an excellent idea.  I was thinking something similar, because
> if
> >>>> there is any external impedance at that pin, then those control
> inputs are
> >>>> going to interact because of those internal 5k impedances.  That's
> probably
> >>>> the issue -- your ground isn't really ground.
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On
> >>>>> Behalf Of Oakley Sound
> >>>>> Sent: Wednesday, May 30, 2018 9:11 AM
> >>>>> To: Synth DIY
> >>>>> Subject: Re: [sdiy] Difficult 2164 behaviour between
> >>>>> different sections.
> >>>>>
> >>>>> It could well be internal to the 2164 but have you tried
> >>>>> lowering the the resistance to the 0V pin? Temporarily cludge
> >>>>> a ruddy big wire from the PSU's 0V directly to pin 8, in
> >>>>> parallel with what you've already got on the board, and see
> >>>>> what happens.
> >>>>>
> >>>>> Tony
> >>>>>
> >>>>> www.oakleysound.com
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