Once again The Trident!

[Bjorn Julin]

>From: "Grant Richter" <grichter at execpc.com>
>To: Bjorn Julin <bnillson at hotmail.com>, synth-diy at node12b53.a2000.nl
>CC: jhaible at t-online.de, oldcrow at oldcrows.net
>Subject: Re: Once again The Trident!
>Date: Fri, 20 Oct 2000 10:14:56 -0500
>
>The EML 101 also used the exponential V-V followed by linear VCOs. >There
>were two V-V expo converters based on the uA726. One for the oscillators 
>and
>one for the filter.

Interesting, but one of my personal reason to use a V to V
convertr are in a system for many oscillators such as
a poly for example. Or a monster hughe mono with individula
voices.!

>The Moog oscillators that used a common expo converter for multiple
>oscillators, was that voltage or current?

I have no idea, maybe juergen, he mentioned that the moog
modulars used V to V's??

>You could also do the same trick with an expo current source. Drive >linear 
>CCOs from one expo converter using a resistor splitter and >offset one CCO 
>from the other by injecting additional current at pin >5 of a 3080.

Ahh, you ment PNP expo.

>What I did was add 56K/1K attenuators to each additional base input. >You 
>can now offset each one of them with a voltage, but they will >still track 
>the common emitter input at 1v/octave. This works good >for multi section 
>filters (like 8 parallel bandpass). I don't know if >tracking will be 
>accurate enough for multiple CCO cores.

I have done that with a oven controlled NPN expo, it tracks all OK.

>This would be the start of a harmonic generator though. Offset each 
> >current source by a multiple. Then each CCO would run at 1x, 2x, 3x >etc. 
>and "should" track a common 1v/oct input. HF compensation would >have to be 
>the De Franco type as each trannie is running on a >different slope of the 
>Rbe error curve.

I have tried that for just such a application, a harmo osc
and i was not pleased whit the amount of components needed
so i have walked the divider way, whit expos for amplitude
control instead, the problem is to get divider sections that
can divide  in a whay like a walsh osc. I think i will do it
in a GAL or PAL device, some how!!

Reg
BJ

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