[sdiy] Panning with LM13700

[microtonalsynthesis at yahoo.com]

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> 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] Im Auftrag von Tom
>>>>> Wiltshire
>>>>> Gesendet: Sonntag, 1. Januar 2017 18:07
>>>>> An: 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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