Handbook for Sound Engineers

Preamplifiers and Mixers 753

Figure 21-22. Block diagram of the Lectronics AM1612 mixer.

+15V

Mic in +

Mic in

Mic gnd

+

Mic preamp

Preamp gain 0 dB (line)

30 dB (mic)50 dB (mic)

Channel on

Speechfilter converterLog To a/D converter

From D/Aconverter

AudioVCA Variable low cuthigh cut/boost

Programmable input 1 Programmable input 2
Programmable input 3 Programmable input 4
Programmable input 5 Programmable input 6
Programmable input 7 Programmable input 8
Programmable input 9 Programmable input 10
Programmable input 11 Programmable input 12
Programmable input 13 Programmable input 14
Programmable input 15 Programmable input 16
Programmable input 17

Input #1 (of 16)

Programmable logic output 1 Programmable logic output 2

Programmable logic output 3 Programmable logic output 4

Programmable logic output 5 Programmable logic output 6

Programmable logic output 7 Programmable logic output 8

Programmable logic output 9 Programmable logic output 10

Programmable logic output 11 Programmable logic output 12

Programmable logic output 13 Programmable logic output 14

Programmable logic output 15 Programmable logic output 16

Programmable logic output 17 Programmable logic output 18

Programmable logic output 19

1 of 16

Processorcontrolled

variable resistor Mix Bus 1Mix Bus 2Mix Bus 3Mix Bus 4Mix Bus 5Mix Bus 6Mix Bus 7Mix Bus 8Mix Bus 9Mix Bus 10Mix Bus 11Mix Bus 12

controlledProcessor

variable resistor

From input 2From input 3

From input 4From input 5

From input 6From input 7

From input 8From input 9

From input 10From input 11

From input 12From input 13

From input 14From input 15

From input 16

controlledProcessor

switch array

Serial bus

Main in

Mix minus out (mini din jack)Expansion in

Auto mixlog in

Serial bus

Main out

Mix minus inExpansion out(mini din jack)

Auto mixlog out

Lecnet port(RS-232)

Nom in 1Nom in 2

Nom in 3Nom in 4

Nom in 5Nom in 6

Nom in 7Nom in 8

Serial bus converterA/D

68HC12uC

Audio exp in

Nom total 1Nom total 2

Nom total 3Nom total 4

Nom total 5Nom total 6

Nom total 7Nom total 8

Nom total 1Nom total 2

Nom total 3Nom total 4

Nom total 5Nom total 6

Nom total 7Nom total 8

converterD/A

Nom cut 1Nom cut 2

Nom cut 3Nom cut 4

Nom cut 5Nom cut 6

Nom cut 7Nom cut 8

converterD/A Audio exp out

10dB

10dB

10dB

10dB

10dB

10dB

10dB

10dB

line output 1Balanced

line output 2Balanced

line output 3Balanced

line output 4Balanced

line output 5Balanced

line output 6Balanced

line output 7Balanced

line output 8Balanced

mic/line output 9Balanced

mic/line output 10Balanced

mic/line output 11Balanced

mic/line output 12Balanced

Mic/lineswitch

Mic/lineswitch

Mic/lineswitch

Mic/lineswitch

10dB

10dB

10dB

10dB

Processorcontrolled

attenuators

Noise generator

Noise

source

Processorcontrolled

variable resistor