Hi Florian,
In your first post I thought you were suggesting that a PLL could give similar affects to a BBD, but from your second one I don't think you are saying that now (nice lucid description of a PLL by the way!). I also don't see that 'highspeed VCO' necessarily equates to 'expensive' (unless perhaps one wants it to track musically...) - a quick look at the 4046 CMOS PLL suggests it might be able to meet most of your requirements, and costs probably less than 1 euro. Indeed one of the circuits I came across last night configured the VCO in the 4046 to provide the 2 phase signal for clocking a BBD!

I also remain to be convinced about how 'sonically useful' either the PLL frequency output or 'offset CV' would be - a PLL's usefulness would probably depend a lot on how well it could track changes in the controlling VCO frequency, and this will depend to a larger extent on the loop filter, and also on the phase discriminator used. I have been thinking myself about how one could be used for closely tracking two VCO's for linear FM purposes, and I think similar considerations will probably make it impractical. I do concede however that there is a *huge* amount of scope for altering a PLL's characteristics by the way the filter and discriminator are implemented. It's likely that at some point in the future I will get hold of one of these chips, so maybe then I'll give some of these ideas a go!

Tim

[The views expressed above are entirely those of the writer and do not represent the views, policy or understanding of any other person or official body. Personal email. This email is personal. It is not authorised or sent on behalf of the sender's employer. This email is the personal responsibility of the sender.]

> -----Original Message-----
> From: Florian Anwander [mailto: Florian.Anwander@... ]
> Sent: 15 August 2002 18:01
> To: Doepfer_a100@yahoogroups.com
> Subject: Re: 1 Re: Request for Advice
>
>
> Hi Timothy
>
> > > So we are there where I always end up: I want a PLL-Module ;-)
> > I think I missed out on some understanding here - what do
> you want to do
> > with a PLL, and what features would it need (I'm intrigued!)
> A delay (whether BBD or real digital) is controlled by a
> clock, not by a
> CV. So for voltage control of the delaytime you need a
> vc-clock. This is
> nothing else than a VCO with square output, but in a quite
> high frequency
> range (usually between 20kHz to 160 kHz).
>
> It would be no problem to make the base frequency of a VCO
> that high, but
> then we have a very expensive Module (the Highspeed VCO)
> which can be used
> only for the delay. I would like it much more to use a
> standard VCO and
> feed the Pulse out into a module that can multiply the frequency. This
> module is the so called PLL in combination with an divider.
>
> Now what is a PLL
> A PLL compares the signals of two VCOs. If the edge of the
> one VCO comes
> later than the other, an offset voltage is derived from that time
> difference. The voltage is sent to the other VCO so that both
> VCOs run with
> the same frequency.
>
> === is audio
> --- is CV
>
> Controlling-VCO1=>==\
> PLL compares and creates offsetCV-->--+
> VCO2==+====>==/ |
> ^ | |
> | | |
> --------<-------------------------------------------+
> |
> +===============> Audio out
>
> This looks quite boring, since the Audio out will have the
> same frequency
> as the Controlling VCO, so what for The trick comes in with
> the divider:
>
> 1kHz
> Controlling-VCO1========>==\
> |
> 64kHz 1:64 PLL compares and creates offsetCV-->--+
> VCO2==+=>=Divider=>==/ |
> ^ | |
> | | |
> --------<------------------------------------------<------+
> |
> +===============> Audio out
> 64kHz
>
> Now we cheat the PLL. We let him compare the Signal of the
> Controlling VCO
> with a signal that is derived from the divider out; so the
> VCO2 will sound
> at a much higher frequency.
>
>
> This output signal can be used now for clocking the delays
> BBD or digital
> memory reading circuit. You may think of many nice games you
> can play with
> the offset CV - games you never could play with a VC-Delay.
>
> So: I want a PLL :-)
>
> Florian
> --
> Florian Anwander |ConSol* HP-Support
> Tel. +49.89.45841-133 |Consulting&Solutions Software GmbH
> Fax +49.89.45841-139 |Franziskanerstr. 38,
> D-81669 München
> email: florian.anwander@... | http://www.consol.de
>
> Yahoo! Groups Sponsor
> ADVERTISEMENT
>
>
>
> To unsubscribe from this group, send an email to:
> doepfer_a100-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
>

The Information contained in this E-Mail and any subsequent correspondence
is private and is intended solely for the intended recipient(s).
For those other than the recipient any disclosure, copying, distribution,
or any action taken or omitted to be taken in reliance on such information
is prohibited and may be unlawful.