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Re: Quad Potentiometer - Does such a thing exist?

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On a sunny day (Mon, 29 May 2017 18:10:17 GMT) it happened Jan Panteltje
<pNa0nStpealmtje@yahoo.com> wrote in <ogho69$16do$1@gioia.aioe.org>:

>On a sunny day (29 May 2017 10:29:04 -0700) it happened Winfield Hill
><hill@rowland.harvard.edu> wrote in <oghlp001f08@drn.newsguy.com>:
>
>>Jan Panteltje wrote...
>>>
>>>On a sunny day (29 May 2017 08:42:54 -0700) it happened Winfield Hill
>>><hill@rowland.harvard.edu> wrote in <oghfhu012g4@drn.newsguy.com>:
>>>
>>>>oldschool@tubes.com wrote...
>>>>>
>>>>> My goal is to take a 4 channel (quad) sound system ...
>>>>
>>>> How about reading the value of a single pot, calculating
>>>> the desired gains and combinations, and use multiplying
>>>> DACs to effect the fractional sourcing for each output.
>>>> Hey, you'll only need 16 DACs to cover all combinations!
>>>>
>>>> Haha, that makes it clear why digitizing four channels
>>>> and computing new outputs in real time makes more sense.
>>>> Try an Arduino Zero running at 48MHz, easy programming.
>>>> Or step up to the Teensy 3.6, fast, 180 MHz.  Advantage:
>>>> extensive audio libraries written by Paul J. Stoffregen.
>>>> Plug Teensy into an adapter board to use Arduino shields.
>>>
>>> 16 DACs?
>>> 4 channels?
>>> 160 MHz?
>>>
>>> In the attic I think I may still have some of those Philips
>>> i2c controlled audio potmeters.. something like TDA7318
>>>http://www.google.nl/url?q=http://www.st.com/resource/en/datasheet/CD00000150.pdf&sa=U&ved=0ahUKEwiE4KXZx5XUAhVHa1AKHT9rDmgQFgg
>>>d
>>>MAE&usg=AFQjCNEcL7w0MpY1BLp4p4nmeLezQcOY9w
>>> then all you need is 2 (or 4) of these 
>>
>> Good. Dual is nice, but then aren't 8 required?  Direct and
>> combine, any part of four inputs to any part of four outputs.
>
>I dunno, each chip  has 4 left and 4 right inputs, 
>and 4 independent attenuators.
>It seems to me tha tsomewhere in the 'round' rotation all you need
>to do is switch inputs? (at 180 degrees?)

PS, actually that is interesting,
this is what I came up with:
 http://panteltje.com/pub/TDA7318_roundabout_IMG_6230.JPG

the restriction of the chips are that the 2 channels in each chip use the same switch position, both 'stereo' input switches are coupled.
The good thing is that we can set both left and right speaker attenuation from 0 -30 dB (leaving common main volume at 100% ).
By combining the 2 speaker output on the same chip we can get to 36 dB,

Now if you look at the right of the drawing you have 4 signal sources (quad audio) A, B, C, D.
at  the top right of the drawing we have speaker front (the one in front of us), it, at his moment in time, has as input source  A and B,
where A is not attenuated, and B maximum attenuated, so we basically hear source A in front of us.
Now we turn our rotary encoder clockwise, and decrease the gain G1 and increase the gain G2 (speaker attenuators remember),
so after turning the knob 45 degrees we have zero from source A and 100% from source B, now we hear B in front of us.
When we move the knob further to 45.001 degrees? we switch so the inputs B and C are selected, where B is set to 100% and C is zero,
nothing changes in the output.
Turning further we decrease B and increase C until at 90 degrees knob rotation we hear only C, and the source C is now in front of us.
And round and round we go...

Same procedure for the other speakers (outputs)
and you will notice that by some miracle the sequence of switch input always appear twice, so those will be in the same chip,

I have only drawn 2 output resistors, but to get to 36 db you need 4 resistors (one from each speaker (attenuator) output).
The limitation of only 36 dB range is a bit disappointing, if you need more then you will need to spend 4 x 2$ extra for 8 chips
and get 70 dB, there you are right.
But I doubt you can hear a 36 dB down positional error over 45 degrees ...
How much do we decrease / increase gain? Well sound goes a straight line from on speaker to an other, and halfway must be 50/50,
and half of half way should perhaps be half of 50 / 50, so maybe no need for sine lookup tables either but that requires deep mass
something I would do once I start coding... else try to avoid, but [sound attunates] square of distance or something?
Oh this get really complicated.

Hope this is a more precise answer to your question.

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Thread

Quad Potentiometer - Does such a thing exist? oldschool@tubes.com - 2017-05-29 03:51 -0400
  Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-29 09:23 +0000
  Re: Quad Potentiometer - Does such a thing exist? gray_wolf <g_wolf@nospam.com> - 2017-05-29 04:28 -0500
    Re: Quad Potentiometer - Does such a thing exist? tabbypurr@gmail.com - 2017-05-29 02:58 -0700
  Re: Quad Potentiometer - Does such a thing exist? "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-29 05:54 -0500
  Quad Potentiometer - Does such a thing exist? Anthony Stewart <tony.sunnysky@gmail.com> - 2017-05-29 07:38 -0700
  Re: Quad Potentiometer - Does such a thing exist? Winfield Hill <hill@rowland.harvard.edu> - 2017-05-29 08:42 -0700
    Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-29 16:55 +0000
      Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-29 17:18 +0000
        Re: Quad Potentiometer - Does such a thing exist? speff <spehro@gmail.com> - 2017-05-29 10:31 -0700
          Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-29 18:17 +0000
          Re: Quad Potentiometer - Does such a thing exist? krw@notreal.com - 2017-05-29 14:29 -0400
      Re: Quad Potentiometer - Does such a thing exist? Winfield Hill <hill@rowland.harvard.edu> - 2017-05-29 10:29 -0700
        Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-29 18:10 +0000
          Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-31 11:46 +0000
          Re: Quad Potentiometer - Does such a thing exist? Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-31 14:29 +0000
  Re: Quad Potentiometer - Does such a thing exist? Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2017-05-29 23:45 +0200

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