Mini Mixer

Three Channel Audio Mixer Circuit

Description
Although the modular Portable Mixer design available on these web pages has become a hit for many amateurs, some correspondents required a much simpler device, mainly for mixing mono signals. This design should fulfil their needs, featuring three inputs with switchable high/low sensitivity and unusual level-control circuits, providing high overload margins and low-noise figures, proportional to gain-level settings. Low current consumption due to a simple, five-transistor circuitry, allows the Mini Mixer to be powered by a common 9V PP3 battery for many hours.

Circuit diagram:

Parts:



    • P1 = 5K
    • P2 = 5K
    • P3 = 5K
    • R1 = 180K
    • R2 = 2M2
    • R3 = 750R
    • R4 = 1K
    • R5 = 15K
    • R6 = 220R
    • R7 = 1.5K
    • R8 = 820R
    • R9 = 150R
    • R10 = 100K
    • R11 = 180K
    • R12 = 2.2M
    • R13 = 750R
    • R14 = 1K
    • R15 = 180K
    • R16 = 2M2
    • R17 = 750R
    • R18 = 1K
    • C1 = 1µF-63V
    • C2 = 100µF-25V
    • C3 = 220µF-25V
    • C4 = 100µF-25V
    • C5 = 220µF-25V
    • C6 = 1µF-63V
    • C7 = 100µF-25V
    • C8 = 1µF-63V
    • C9 = 100µF-25V
    • Q1 = BC550C
    • Q2 = BC547
    • Q3 = BC557
    • Q4 = BC550C
    • Q5 = BC550C
    • B1 = 9V PP3 Battery
    • J1,J2,J3 = 3mm Mono Jack sockets
    • SW1,2,3,4 = SPST Toggle or Slider Switches
Notes:



    • When SW1, SW2 or SW3 are open the input sensitivity is suited to high-output devices like CD players, tuners, tape recorders, iPods, miniDisc players, computer audio outputs etc.
    • When SW1, SW2 or SW3 are closed the input sensitivity is suited to low-output, low-impedance moving coil or electret microphones.
    • Sometimes, the 750 Ohm value for R3, R13 and R17 resistors could be not easy to find. In this case, two 1K5 resistors wired in parallel can be used to replace each item.
    • To make a stereo mixer, all the parts must be doubled excepting R6, C3, C5, SW4 and B1.
 
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No-Frills 6-Input Stereo Line Mixer
Updated 14th December 2010

(A companion article detailing a 6-output Line Distribution Amplifier can be found here:

I wanted a small (physically) mixer to accept line signals that was both simple and low-cost, for use as both an input expander for PC Soundcard input and also for general use in recording. Looking around the web reveals a whole host of designs, most of which are either over-blown, badly-designed or are just rubbish. My spec was simple and is as follows:
  • Flat frequency response 40-40,000Hz
  • Low Noise
  • Will run off a single polarity supply as low as 9 volts
  • Wide tolerance of input levels
  • Nominal Input Impedance ~1KΩ
  • Low cost
Normally this sort of thing is best realised with a few well-chosen low-noise op-amps, and this is the method chosen here. However, such an approach is somewhat boring, so I decided to give myself a little more practise at assembling SMD circuitry and implemented the design using SOIC op-amps. I realise that this puts off some who would otherwise be interested in building the project, so I’ve included the Eagle project, (see bottom of post for download) and it would be a simple matter to substitute the SMD op-amps with their ‘normal’ PDIP cousins if required, as there is plenty of room on the PCB. The circuit also lends itself to expansion (or contraction!) if required.
 

Eklentiler

  • Mini Mixer Uydudoktoru.zip
    1,3 MB · Görüntüleme: 69
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