[sdiy] SSM2164 panning curve

[Jerry Gray-Eskue]

<<If you simply have two VCAs connected together such that varying the
control voltage brings the gain on one up and the other one down, you have a
rudimentary panner, but the panner has a problem.  At dead center (both VCAs
equal), the loudness will be less than full right or full left. >>

I do not see this as a problem, to relocate sound without changing the
overall volume using panning you need headroom to "Move" the sound.

Take for instance you have the right and left channel outputting 10 watts of
power each you have a total of 20 watts, if you just reduce the volume in
one channel at the limit you are now outputting 0 + 10 watts, 1/2 the
volume. If on the other hand you decrease one side while increasing the
other at the limit you have 0 + 20 watts or the same power level. Panning is
usually done on a Log scale to give a perceived Liner motion of sound.

- Jerry



-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Derek Holzer
Sent: Thursday, July 23, 2009 8:21 AM
To: Tom Wiltshire
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] SSM2164 panning curve


Hi Tom,

sorry don't have an image right now, but let me try someone else's
explanation:

> Some words about panning and crossfading:  If you simply have two VCAs
connected together such that varying the control voltage brings the gain on
one up and the other one down, you have a rudimentary panner, but the panner
has a problem.  At dead center (both VCAs equal), the loudness will be less
than full right or full left.  You need some flattening of the response
curve to make this complete.  The Serge VCAs provide this equalized
left-center-right response curve, so panning sounds fairly natural.

From: http://www.serge-fans.com/wiz_vca_mix.htm

Does that explain my idea a bit better? At center position, all channels
should be at unity, and should never get louder than that.

D.

Tom Wiltshire wrote:
> Derek,
>
> I'm afraid I don't understand what you're trying to do. I need to see
> more diagrams for my visual head to get it. So long as you're clear
> about it, that doesn't matter.
>
> However, I have played with the SSM2164. 15V is too much for the control
> port. The datasheet gives the CV response as -33mV/dB.
> Hence you need 3.3V for fully off -100dB, and -0.66V for 20dB gain, with
> 0V giving you unity gain. I don't know of a way to set the SSM2164 up
> for attenuation only. You just make sure that you only have positive
> control signals. I don't think just a simple diode would work that well,
> since the diode won't conduct until the CV is significantly negative,
> which isn't what you want. You could modify the op-amps in the
> Electro-music schematic to precision half-wave rectifiers, which would
> give you a more accurate result.
>
> Regards,
> Tom
>
>
> On 23 Jul 2009, at 11:31, Derek Holzer wrote:
>
>> I've got a hopefully simple question about using the SSM2164 as a
>> joystick controlled quadraphonic spatializer/panner. I have been
>> looking at Marc Bareille's Quad VCA/CV-Mixer as a good model for this
>> project:
>>
>> http://m.bareille.free.fr/modular1/quadvca/quadvca.htm
>>
>> with some additions for the joystick control:
>>
>> http://electro-music.com/forum/viewtopic.php?t=24705
>>
>> My concern is this: when the joystick is it dead center the gain on
>> all channels should be unity. However, for this particular
>> gain/panning curve I don't want more than unity gain, only
>> attenuation. I am aware that this nulls the effects of half the range
>> of the joystick... however from what I have read this is the panning
>> curve used by the Serge and Buchla spatializers, and it makes sense
>> acoustically to me.
>>
>> So let's assume that set up the SSM2164 as in the datasheet, where 0V
>> is unity and minus voltage is attentuation. And I wire up my joysticks
>> as voltage dividers between +15 and -15 (or should it be +/-5V?). But
>> since I don't want any amplification, I use a diode to block the
>> positive voltage coming from the joysticks, making sure the diode is
>> rated not to break down anywhere near 15V (or 5V?). Am I on the right
>> track? Or is there a way to set up the SSM2164 itself so that it only
>> attenuates?
>>
>> Thx+best!
>> Derek
>> --
>> ::: derek holzer ::: http://blog.myspace.com/macumbista :::
>> http://www.vimeo.com/macumbista :::
>> ---Oblique Strategy # 52:
>> "Do nothing for as long as possible"
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>>
>
>
>

--
::: derek holzer ::: http://blog.myspace.com/macumbista :::
http://www.vimeo.com/macumbista :::
---Oblique Strategy # 107:
"Look at the order in which you do things"
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