[sdiy] THAT2180A

[Mattias Rickardsson]

Tom Wiltshire <tom at electricdruid.net> skrev:

>
> Separate question: Is there any analog way that *does* give a constant
> power panning curve? I remember seeing the “expo crossfade” example from
> the SSM2024 datasheet which uses a differential pair to split a linear
> control current between two linear VCAs (e.g. not applicable to the expo
> VCAs we’re discussing here) . If I remember correctly, when I tried it, it
> gives subtle “hole in the middle” effect as a panner, as the volume
> apparently drops as the signal reaches the centre. This experiment was a
> long while ago though, and I might be mis-remembering.
>

You mean two linear but opposing VCAs as left & right?

I've used that, just to be able to sum them and get a signal that's
unaffected by the panning. It's louder at the extremes, but bobody
complained yet. :-)

I don't think it's obvious what the best curve would be. With distant
loudspeakers in a free space - sure, equal power - but if you listen in
headphones and imagine a nearby sound source that moves around your face,
then the linear control described above is quite close to the reality while
an equal power panning is not.

What others have said about the VCAs is all true - you pick the
> cost/quality ratio you’re after and then the parts choice will make itself!
>

It's quite handy in THAT sense. And also quite frustrating, as there's
little room for making your own smart choices that trick the system. 8-)

/mr

>
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