§ 3.8 - AC-coupled 8 Channel Stereo Mixer
Back to → Main Mixer Block PageBefore you attempt this build, please:
- Read through the numbered build procedure with the idea of performing the listed steps in order
- Examine the PCB layout
- Examine the schematic diagram
- Refer to each of the linked pages in the "See also" list
This will help ensure that you will have the best possible experience, resulting in a build that works the way you expect it to.
This Mixer Block build is an AC-coupled, unity-gain, line-level, eight-channel, stereo mixer.
To power this with the Power Block, use the +/- 12 regulated Power Block build.
Tip: Unity gain (zero gain) is important here. This is because if all eight inputs to one of the op-amp channels reach 1.23 volts, in phase, all at once, then at unity gain the mixer will produce a 9.84 volt output level. This would be highly unlikely, but it is always at least possible.
If the mixer were to be built with more gain, then the output voltage would get too close to the op-amp's power supply rails (typically +/- 12 VDC), and distortion would result.
If the mixer were to be built with more gain, then the output voltage would get too close to the op-amp's power supply rails (typically +/- 12 VDC), and distortion would result.
- C1—C2: .1 uF ceramic capacitor
-
C3—C4 optional: ceramic capacitors, only needed for op-amps that require compensation
TLO-72 and TLO-82 op-amps do not require compensation. - C5—C20: 2.2 uF ceramic or other non-polarized type capacitor (see frequency response calculator)
- C21—C22: 10 uF ceramic or other non-polarized type capacitor
- R1—R18: 10 k-ohms 1/8th watt resistors
- U1: TLO-72 low-noise op-amp, can substitute TLO-82, or similar. Observe polarity. An IC socket is strongly recommended.
- Install 3-pin jumper J1 — use .100 inch (2.54 mm) header pins; do not close
- Install 2-pin jumper J2 — use .100 inch (2.54 mm) header pins; do not close
- Install 2-pin jumper J3 — use .100 inch (2.54 mm) header pins; do not close
- Install 2-pin jumper J4 — use .100 inch (2.54 mm) header pins; do not close
- Connectors, quantity 4, optional: 5.08mm (.200 in) Spacing, 2-pin PCB Mount Screw Terminal Blocks
- M3 mounting hardware, 4 mount points
Tip: If you would like to DC-couple the outputs while retaining the AC input coupling, place jumper caps across J3 and J4.
| See also: | Recommended Tools Mounting to Wood Surfaces Mixer Block Parts Sources Wiring to Terminal Blocks |
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