[sdiy] Panning (again)

Tom Bugs admin at bugbrand.co.uk
Tue Dec 22 22:50:58 CET 2020

Today Alfa said their AS3365 was available along with a new datasheet: 
Interesting & potentially very useful configuration of building blocks - 
VCAs aplenty - I have just been reading about the VCA3 RMS generation 
methods - not quite sure how Graham Hinton's notes apply to it yet!
There's some good detail (not quite as exemplary as the SSI ones ;0)

Another interesting chip to add to the pile!

On 22/12/2020 17:03, Neil Johnson wrote:
> Someone a while back posted a link to a post by Graham Hinton on
> MuffWiggler with some relevant information:
> https://www.muffwiggler.com/forum/viewtopic.php?p=1674967#p1674967
> I'll copy the pertinent text here for those who don't frequent MW:
> ---
> The proper professional stereo pan law was defined by the BBC way back
> in the 1930s from empirical research and is neither -3dB in the centre
> (so called equal power) nor -6dB (linear crossfade). Mixer designers
> have heated arguments about whether it is actually -4dB or -4.5dB in
> the centre, but more important is the shape of the curve towards the
> extreme attenuation side.
> Stereo panning is an illusion based on a loudness balance whereas the
> brain decides the panoramic position of a sound from the delay between
> arriving at the ears. That is why panning on headphones goes over the
> top of your head rather than around the front--the differential delay
> of panpots is always zero. To get a law that feels right when turning
> the knob and doesn't rush across the middle you need the BBC law. The
> balance is very delicate and a 0.5dB error can produce a 25% position
> shift. I know this because I designed the Solid State Logic
> Programmable (read VC) Panpots for the BBC in the 80s. I also designed
> their Programmable Surround Joysticks for a Lucasfilm console and the
> laws for that are equally non-obvious.
> It is easy to replicate the BBC's method, all you have to do is
> balance a left and right channel volume and measure the level
> difference for apparent position. It is easy to do and check, but
> people keep repeating the same misinformation without thinking.
> ---
> Neil
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