[sdiy] Panning with LM13700

Richie Burnett rburnett at richieburnett.co.uk
Mon Jan 2 00:16:41 CET 2017

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.


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)
>> On 01/01/2017 19:55, Tom Wiltshire wrote:
>>> Yeah, I've seen that Thomas Henry one. The same idea appears in the SSM2045 datasheet. But this design is -6dB centre, constant level, not constant power. I was looking for something that does a smooth pan of a mono input. The -6dB pan sounds like it starts in your left ear, then shoots off somewhere in front of you, and then zooms back into your right ear. I find it quite distracting, and it seems to narrow the stereo field for me.
>>> On 1 Jan 2017, at 17:26, Matthias Herrmann <matthias.herrmann at fonik.de> wrote:
>>>> i recently used a simplified version of this one:
>>>> http://electro-music.com/forum/viewtopic.php?t=54633
>>>> i have seen something similiar before (tom gamble, IIRC).
>>>> cheers,
>>>> matthias
>>>>> -----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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