[sdiy] Panning with LM13700

Tom Bugs admin at bugbrand.co.uk
Tue Jan 10 10:05:07 CET 2017


Yes, I agree -- THAT notes often need some detailed consideration - they 
use some absolutely bizarre resistor values.

I actually used the AN120 idea basis with V2164 VCAs - took quite a lot 
of multisim investigation first and then some physical prototyping 
afterwards.


On 09/01/2017 21:29, microtonalsynthesis at yahoo.com wrote:
> Like many app notes, the THAT AN120 is something of a DIY project in 
> itself.
>
> The control voltage inputs are reversed. U1 should use EC+ pin 2 and 
> U2 should use EC- pin 3.
>
> The breakpoint generator is very sensitive to offsets and the circuit 
> as given has unequal volumes for left and right sides. Adjustment of 
> all resistors going to -15V is needed. I estimate about 130.5K for the 
> 133K. Of course, if you adapt this circuit to 12V supplies then you 
> need to adjust some more.
>
> John
>
>
> On Sunday, January 1, 2017 6:24 PM, Richie Burnett 
> <rburnett at richieburnett.co.uk> wrote:
>
>
> You could always generate the two VCA control signals with the 
> appropriate pan law using a micro... Low cost pic with dual output PWM 
> perhaps? Pre-calculated values in lookup table on a low end micro, or 
> use  quadratic fit approximation if you're already using a dspic.
>
> -Richie,
>
> Sent from my Xperia SP on O2
>
> ---- Tom Wiltshire wrote ----
>
> >That's a fairly involved circuit, but I don't think I've ever seen an 
> analog panner with a switch to select different pan laws. Very impressive!
> >
> >I'll have a look over it and see if I couldn't use the gist of it in 
> a simpler way.
> >
> >On 1 Jan 2017, at 20:14, Tom Bugs <admin at bugbrand.co.uk 
> <mailto:admin at bugbrand.co.uk>> wrote:
> >
> >> Not LM13700 based, but the details within the THAT app note here 
> may be some use:: http://www.thatcorp.com/datashts/dn120.pdf (VCAs in 
> pan pot apps)
> >>
> >>
>
> >>>>> -----Ursprüngliche Nachricht-----
> >>>>> Von: Synth-diy [mailto:synth-diy-bounces at synth-diy.org 
> <mailto:synth-diy-bounces at synth-diy.org>] Im Auftrag von Tom
> >>>>> Wiltshire
> >>>>> Gesendet: Sonntag, 1. Januar 2017 18:07
> >>>>> An: Synth-diy at synth-diy.org <mailto:Synth-diy at synth-diy.org>
> >>>>> Betreff: [sdiy] Panning with LM13700
> >>>>>
> >>>>> Hi All,
> >>>>>
> >>>>> Happy New Year to everyone! Here's hoping you all have a great 
> year with
> >>>>> many (completed) synth projects.
> >>>>>
> >>>>> I've got  quick question - what's the best way to do equal power 
> panning (-
> >>>>> 3dB in the centre) with the LM13700? I'm assuming that such a 
> thing has
> >>>>> been done already, so it's seems silly to reinvent the wheel, 
> but I can't
> >>>>> find anything that isn't a simple linear crossfade (which is ok for
> >>>>> crossfading, but not so good for panning).
> >>>>>
> >>>>> Any tips/pointers appreciated.
> >>>>>
> >>>>> Thanks,
> >>>>> Tom
>
>
>
>
>
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