From: jk87377@cc.tut.fi (Kouhia Juhana)
Newsgroups: sfnet.harrastus.musiikki,sfnet.harrastus.elektroniikka
Subject: Re: Mixeri/summain
Date: 3 Jan 1993 15:10:42 +0200
Organization: Tampere University of Technology
Distribution: sfnet
NNTP-Posting-Host: cc.tut.fi

In article <KJA.93Jan1171755@stekt5.oulu.fi> kja@stekt.oulu.fi writes:
>In article <1huk4sINN71q@cc.tut.fi> jk87377@cc.tut.fi (Kouhia Juhana) writes:
>> Minulla muistaakseni on kytkentakaavio mixerista, joka

Loysin kaavion.
Ehka paras tapa olisi skannata kuva. Olikos jotain napparaa
ohjelmaa, jolla kytkentakaavioita voisi piirrella? (GNU-jotain?)

Toimintaperiaate on juuri kuten taalla arveltiin.
Tosin...


>Muutoin: kytkent{si ei ole summain, vaan keskiarvoistaja -kuten
>sanoit.  Alkuper{isen signaalin amplitudi putoaa siin{ N:nteen osaan.

Nyt en ymmarra taysin.
Jos kaikissa sisaantuloissa on sama signaali, niin
silloinhan pitaisi ulosmenon olla taysin sama.
Vai vaikuttaako tuo signaalien vaihto jotenkin erikoisesti?

Voisitko kertoa tarkemmin?
Missaanko jotain?

Alla on kytkentakaavioita.
Olen itse jakanut kaavion osiin, jne...
Kertokaa, jos jotain voi esittaa selvemmin; teen sitten muutoksia.


Juhana Kouhia


==============================================================================

Sampling audio mixer
--------------------
by Darren Yates, French's Forest, New South Wales
in magazine <?>.


This circuit uses a different approach to mixing audio signals.
Instead of taking the usual continuos sum of all the signals, it
samples each signal at approximately 40kHz in a sequential order. The
bonus of this is a better signal-to-noise ratio since only one of the
mixing resistors is switched on at any one time.

Because it is not a continuous sum, the volume of each sum can be set
with greater independence of the other two inputs. Each counter output
runs at about 40kHz.

When mixed, the signals feed a second-order low-pass filter with a 3dB
point of approximately 10kHz to filter out the sampling frequency. The
system can be expanded for up to ten inputs by moving the reset input
to the next unused ouput of the decade counter. The clock should run
at Nx40kHz where N is the number of channels to be mixed.

==============================================================================

Circuit: power
--------------

    + --o---(IC1)---o----o-- +9V
        |    |      |    |
        |    o-(R2)-o    |
       (C1)  |          (C2)
        |   (R1)         |
        |    |           |
      --o----o-----------o--

where

  --o--  is joint
    |

  R1 = 150
  R2 = 220
  C1 = 470y
  C2 = 100y
  IC1 = 7805

==============================================================================

Circuit: clock & sampler
------------------------

              o-------------------------- ck        ck en ----o
              |                               IC2             |
   o--        |          o--               0       1   2      |
   |  (IC1a)*-o-(C1)-o---o  (IC1b)*-o                         |
   o--               |   o--        |      |       |   |    --o-- ground
   |                (R1)            |      |       |   |
   |                 |              |      |       |   |
   o-----------------o--------------o      |   switchers for --o
                                           |   other channels  |
                                           |                 --o
                                           |                   |
                                           |                   |
                                  input --(IC3a)----(R2)-------o-- output
                                  from                             to
                                  a channel                        low-pass
                                                                   filter

where

  --o--  is joint
    |

  R1 = 3k3
  C1 = 1n
  IC1 = NAND gate 4011; '*' in figure means output
  IC2 = 4017
  IC3 = 4066

==============================================================================

Circuit: one channel
--------------------

                    o------o--------------o------------o-- +
                    |      |              |            |
                   (R2)    |              |            |   o----o
                    |     /              (R6)          |   v    |
  input ---o--(C1)--o---(T1)              |    o-------+--(R8)--o
           |        |     \*              |    |       |        |
           |        |      o--(C2)--(R5)--+----o--- -           |
          (R1)     (R3)    |              |          TL1 -------o-- output
           |        |     (R4)            o----o--- +                 to
           |        |      |              |    |       |            sampler
           |        |      |             (C3) (R7)     |
           |        |      |              |    |       |
         --o--------o------o--------------o----o-------o--


where

  --o--  is joint
    |

  --+--  is not joint
    |

  R1 = 1M
  R2 = 1M
  R3 = 1M
  R4 = 47k
  R5 = 10k
  R6 = 100k
  R7 = 100k
  R8 = 100k potentiometer; 'v' in figure means input to potentiometer
  C1 = 4y7
  C2 = 4y7
  C3 = 33y
  T1 = Transistor BC549; '*' in figure means output arrow
  TL1 = op.amp. TL074;
        '-' means negative at bottom of triangle;
        '+' means positive at bottom of triangle;
        in figure, wires in above and below are on sides of triangle;
        output at right is on the top of triangle

==============================================================================

Circuit: low-pass filter
------------------------

                             --o-- +
                               |          o----o
                               |          v    |
                              (R3)  o----(R5)--o
    input                      |    |          |
    from    --(R1)-o-(R2)-o----+----o-- -      |
    sampler        |      |    |         TL1 --o-(C4)-o-- output
                   |      |    o----o-- +             |
                  (C1)   (C2)  |    |                 |
                   |      |   (R4) (C3)              (R6)
                   |      |    |    |                 |
                 --o------o----o----o-----------------o--

where

  --o--  is joint
    |

  --+--  is not joint
    |

  R1 = 8k2
  R2 = 8k2
  R3 = 100k
  R4 = 100k
  R5 = 100k potentiometer; 'v' in figure means input to potentiometer
  R6 = 10k
  C1 = 1n
  C2 = 1n
  C3 = 33y
  C4 = 33y
  TL1 = op.amp. TL074;
        '-' means negative at bottom of triangle;
        '+' means positive at bottom of triangle;
        output of TL1 at right is on the top of triangle

==============================================================================