There is an Audio Mixer said 24 channel but they are 16 inlet and 16 Gain’s potensiometer. This is the Mixer.
The actual is, the manual book said that a mixer has 20 channels mean: 12 channels in mono mode and 4 channels in stereo mode. Stereo here mean 2 channels!
This time I’ll try to reveal it in schematic diagram, with my style.
SKEMA DIAGRAM MIXER INI
Saya coba saya terjemahkan tiap-tiap foto dan skema di dalamnya ya..
We can differentiate between mono and stereo input by looking for the marking at the channel number 12 and 13 ( XR20 ) and channel number 8 and 9 ( XR24 ).
LINE PAD, GAIN, LO CUT, PHANTOM
WHAT THE SCHEMATIC?
Here it is:
MIC PAD AND LINE SWITCH
A 48 VDC for Phantom power to connect the socket of XLR Microphone. The DC current signal was blocked with C38 and C49 but to pass the AC current.
After blockef by C38 and C49, the signal was selected by SW1A and SW1B to choose who the input using: LINE or MIC? As the schematic above, the LINE is also mono balance input too.
DOUBLE SWEEP OF GAIN POTENSIOMETER
The balanced signal was amplified with balance compound pair ( Q1 ,Q2 , Q3, Q4). And has a GAIN pot on between the Emittor. And that Output of the transistor was sent to OPAMP U1B at pin 5 and 6.
The output of the OPAMP now to be the unbalanced signal and processed to the next OPAMP U1A. There is a GAIN pot between the input of pin 2 and 3. The schema was look like an equalizer.
6 POT EQUALIZER
The Equalizer was in LINEAR MODE and PARAMETRIC MODE. The Linear Mode using HF Pot and LF Pot, then The Parametric mode using HM Pot ( Range and Gain ) and LM Pot ( Range and Gain ).
SCHEMATIC EQUALIZER
The Equalizer of this Mixer using OPAMP with type 2082
When SW3A pressed, the Equalizer active. VR2A as frequency adjust for HF 10kHz and VR7A as frequency adjust for LF 80HZ. The U3B and U3A work as 2 linear channel of Equalizer.
VR4A do as Gain control of High to Medium Frequency and VR3A do as range frequency adjuster ( 400 to 8000 Hz). This also do for VR6A and VR5A but the range was 80Hz to 2000Hz.
MUTE, FADER, PANPOT
If you pressed the MUTE button, it mean the bias current was occur at gate of Q5 and Q6 and they are OFF. The But if you depressed, there are no voltage for C58 while because the current was short to ground after R138 and making Q5 and Q6 was ON.
