MOTM

OK, time to show my ignorance.  I seem to recall this explained before but it didn't
stick.  What is so special about a VCO with through-zero FM?

Eric

--- davevosh@... wrote:
> In a message dated 00-11-16 22:46:23 EST, you write:
> 
> << Doug Kraul's MOTM vco with through-zero FM.
>   >>
> 
> 
> dave,
> a man after my own heart.....any idea on a timeline for this one?
> best,
> dave v.
> 
> 
> 


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To do "true" Chowning Frequency Modulation Synthesis (ala Yamaha DX-7) you
need a VCO where the FM can send the oscillator 'through zero.' In an analog
VCO this is tricky.

Someone please correct me if I'm wrong.

-----Original Message-----
From: alt-mode
To: motm@egroups.com
Sent: 11/17/2000 10:37 AM
Subject: [motm] Through-zero FM?

OK, time to show my ignorance.  I seem to recall this explained before
but it didn't
stick.  What is so special about a VCO with through-zero FM?

--- In motm@egroups.com, alt-mode <alt_mode@y...> wrote:
> OK, time to show my ignorance.  I seem to recall this explained 
before but it didn't
> stick.  What is so special about a VCO with through-zero FM?

You can get more dramatic FM timbres than one usually hears. Think DX-
7 type FM capabilities and timbres, but with analog oscillators 
instead of digital.

Moe

--- In motm@egroups.com, "Tkacs, Ken" <ken.tkacs@j...> wrote:
>  
> To do "true" Chowning Frequency Modulation Synthesis (ala Yamaha DX-
> 7) you need a VCO where the FM can send the oscillator 'through 
> zero.' In an analog VCO this is tricky.
> 
> Someone please correct me if I'm wrong.
> 

This is my understanding also. I believe sending the vco 'through 
zero' is another way of saying that the modulator can cause the 
waveform to reverse on itself, sort of like instantly flipping the 
phase.

Someone please correct me also if I'm wrong. Doug, you're on this 
list - do we have it right?

Moe

Can someone draw a graph of this (FM w/ through-zero) and FM w/o?  I don't
quite understand what's special.  I believe I understand FM, but maybe I
don't when it comes to near-0 voltages...

--PBr

> -----Original Message-----
> From:	Dave Bradley [SMTP:daveb@...]
> Sent:	Friday, November 17, 2000 7:54 AM
> To:	motm@egroups.com
> Subject:	[motm] Re: Through-zero FM?
> 
> --- In motm@egroups.com, "Tkacs, Ken" <ken.tkacs@j...> wrote:
> > To do "true" Chowning Frequency Modulation Synthesis (ala Yamaha DX-
> > 7) you need a VCO where the FM can send the oscillator 'through 
> > zero.' In an analog VCO this is tricky.
>  
> This is my understanding also. I believe sending the vco 'through 
> zero' is another way of saying that the modulator can cause the 
> waveform to reverse on itself, sort of like instantly flipping the 
> phase.
> 
> Someone please correct me also if I'm wrong. Doug, you're on this 
> list - do we have it right?
>

> To do "true" Chowning Frequency Modulation Synthesis (ala Yamaha DX-7) you
> need a VCO where the FM can send the oscillator 'through zero.' In an
analog
> VCO this is tricky.
>
> Someone please correct me if I'm wrong.

The DX-7 uses Phase Modulation (or so I'm plausibly told - I never
checked myself), which is even more tricky to implement in Analogue.
But rather easy in Digital.

Now yes, Thru Zero FM in Analogue is tricky enough, especially when
you want it free of artefacts during the zero crossing. (I have a
CEM3340-based
thru zero FM VCO on my homepage, but this does have such artefacts.)

Who is designing this VCO ?
What method is used ? Sign/Magnitude with reverible triangle core?
Or a BFO ? Or something entirely different ?

JH.

In a message dated 00-11-17 10:48:11 EST, you write:

<< What is so special about a VCO with through-zero FM? >>


phase reversal at the zero crossing enabling deeper fm with richer sidebands 
/ spectrum primarily.  it does sound better than "ordinary" linear fm but the 
improvement is incremental ( much less pronounced than the difference between 
"ordinary" linear fm and fm via exponential inputs is. ). notwithstanding, it 
is a desirable feature.  some very stable, useful designs have been published 
in "electronotes" over the years. hopefully, doug kraul will add some even 
more interesting improvements. 
best,
dave v.