[sdiy] THAT2180A

[David G Dixon]

The THAT circuit looked really complicated for making an equal power panner.
I'd use a pair of linearized 2164 VCAs, and send them the sine and cosine of
a control voltage ramp.  These I'd generate by setting up a 0V to +5V ramp
and its inverse, and sending these through tri-2-sine converters, for which
one could use either the transistor pair-diff amp combo or a 13700.
Alternatively, one could fit the sine and cosine with line segments using
diode-resistor networks a la Horowitz and Hill Figure 4-94.

What am I missing here?  Why is this so hard?

 

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Tom
Wiltshire
Sent: Sunday, November 29, 2020 4:11 PM
To: drheqx
Cc: synth-diy mailing list
Subject: Re: [sdiy] THAT2180A

[CAUTION: Non-UBC Email]


> On 29 Nov 2020, at 04:54, drheqx <drheqx at gmail.com> wrote:
> 
> Thank you Tom. The DAC idea is really cool. It's true, performance will
dictate performance. I can get away with less noise performance here but the
linearity is important. Some of these pan circuits have a bump in the middle
or a dip. I'll have to work that part out. This is something where a
musician would certainly notice that bump. 

I did, and I'm no great musician.

On circuits with the bump the sound seems to get nearer as you pan it across
the spectrum, like the sound moves along a straight line from left to right
just in front of you, so the centre point is much closer than the far ends
of the line. On other circuits, you get the opposite effect, where the
centre dips and the signal seems to disappear into the distance, so it spins
from by your left ear, to miles in front of you, round to by your right ear.
Neither sounds "even". The ideal is something that gives a sound that seems
to rotate around you with you at the centre, not moving closer or further
away. The exact listening set-up obviously will affect how that illusion is
to be created, but the aim is pretty clear.



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