INSIDE PEAVEY UNITY 2002

PEAVEY UNITY 2002 is an audio mixer made by Peavey in the 80-s which it has input variants: 12, 16 and 24 channels.

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PREAMP SECTION

Result of edit image of preamp schematic diagram of PEAVEY UNITY look like below:

The mic preamp uses an XLR socket and there is a DC current from the 48VDC supply or we call it Phantom Power.

The line preamp is connect to a balance input or stereo battery.

This input signal goes to the base of the preamp transistors Q10 and Q13, respectively.

The pair of transistor inside preamp circuit is commonly call this with “complementary darlington amplifier” to produce a large current GAIN so its enter the U1A OPAMP circuit for amplification.

VR100 is a gain potentiometer which in principle is that it passes AC current from the signal at both Q11 and Q12 emitter pins.

The output of these transistor preamp circuit goes to the inverting and non-inverting pins in the OPAMP to then becoming one output on pin number 1 of the OPAMP.

TONE CONTROL SECTION

Here is the schematic diagram of tone control section of UNITY2022 of PEAVEY:

Tone control circuit consists of 3 potentiometers for control, its named LOW, MID and last is HI.

Inside the circuit, its uses only 1 OPAMP therefore its to amplify the audio signal from the tone circuits.

The supply voltage for the OPAMP is 16 VDC symmetrically. After amplified the signal by OPAMP, it will enter the FADER potential for controlling the LEVEL OUT signal.

FADER MON EFF BUS

After tone control circuit, the signal enter to OPAMP and distributed to MONITOR OUT, EFFECT OUT, and there is a BALANCE OUTPUT potentiometer.

The circuits uses only 1 OPAMP to amplify level signal from output of the FADER then to distributed to another Potentiometer of EFECT, MONITOR.

After that, its available a PAN potentiometer inside the circuit to make balancing output.

Inside PEAVEY UNITY 2002 has a level signal indicator. Its working by picking up level signal from input of FADER potentiometer and its processed by Q14 transistor until drive LED CR104.

MASTER

The master circuit only uses 1 OPAMP, namely the number U20A for channel L and U20B for channel R.

The output of this master OPAMP will then be split into the next 3 circuits: the main output, headphones and tape out.

NOTE

All above in master section are using simetrical supply 15 VDC.