Heritage Audio MCM-32 32-Channel Summing Mixer User Guide
- June 6, 2024
- Heritage Audio
Table of Contents
Heritage Audio MCM-32 32-Channel Summing Mixer
© 2017 All the documentation included in this manual is copyrighted by Heritage Audio S.L. All rights are reserved. No part of this manual may be reproduced, copied, translated or transmitted, in any form or by any means without the prior written permission of Heritage Audio S.L.
Heritage Audio S.L. reserves the right to make improvements to the products described in this manual at any time without notice. The information in this manual is intended to be accurate and reliable. However, Heritage Audio S.L. assumes no responsibility for its use; nor for any infringements of rights of third parties which may result for its use.
DESCRIPTION
The MCM-32 is a 32 x 8 channel summing mixer.
It employs a unique configuration, offering 32 input channels arranged into 8 (4 stereo) subgroups of 8 channels each. Unlike classic consoles employing a complicated switching matrix for subgroup assignment, the channels have a fixed-assignment in groups of eight. This arrangement not only makes the unit fit in a four-unit rack space, but greatly helps in making it affordable. Each channel features center detent Pan and Fader concentric controls plus balanced insert and mute switches.
The insert send points always have the signal present, so they can be
alternatively used as direct outputs for recording without additional patch
bays.
Each group has its own stereo fader and balanced insert point and all 4 stereo
subgroups are passively summed into the master bus. The gain is restored by
means of a 73 style class A, transformer coupled, mic preamplifier, featuring
a total of 4 transformers (2 in each channel).
The master section is also provided with its own balanced insert point.
All connections on the back are made by DSUB 25 connectors following the
Tascam* protocol, with the exception of the master bus connections, which are
by dedicated XLRs.
Comprising vintage quality sound with sophisticated routing options, the MCM32
is the perfect partner for hybrid setups, integrating analog gear with your
DAW.
Lots have been written on the pros and cons between active (current) and passive (voltage) summing topologies. Some may claim one is better that the other but truth is active summing is less susceptible to noise and voltage, passive summing has a nice, vintage sound associated with its gain makeup circuit.
The smart hybrid summing topology used in the MCM32, where the channels are current-summed ( active ) into their corresponding subgroups and the subgroups voltage summed ( passive ) into the master section, has proven to give massive headroom and lower noise without making any compromises to its vintage characteristic sound.
FRONT PANEL OVERVIEW
The front panel is laid out in 4 rows of 8 channels each, followed by their
related subgroup controls.
Right side of the unit comprises the master section controls.
Controls per channel are as follows:
- ON: When pressed, the related input is added to the subgroup bus. When depressed, it’s muted.
- INS: Turns the insert on. The insert send always have the signal present, whilst pressing the INS switch activates the insert return input.
- FADER: Attenuates the signal sent to the subgroup bus from unity to minus infinity. Fader all clockwise means unity gain, whilst 12 o’clock means an approximate 20 dB of attenuation. (Or -20dB of gain ).
- PAN: Places the signal within the stereo spectrum, left, center, right or any intermediate setting. The panoramic law follows a standard in which if a 0dB signal is hard panned, it is -3dB when center panned.
Controls per Stereo subgroup are as follows:
- ON: When pressed, the output of the subgroup is sent to the Master bus. When depressed, it is muted.
- INS: Turns the insert on. The insert send always have the signal present, whilst pressing the INS switch activates the insert return input.
- FADER: Attenuates the signal sent to the Master bus from unity to minus infinity. The control has a stepped feel for easy recall of settings. Fader all clockwise means unity gain, whilst 12 o’clock means an approximate 20 dB of attenuation. (or -20dB of gain ).
Right part of the unit is dedicated to the mixer’s Master section, as follows:
- VU Meters: Measuring the average level at the master outputs. They are calibrated so 0VU = +8dBu.
- Master Fader: Attenuates the Mix’s output from unity to minus infinity. The control has a stepped feel for easy recall of settings. Fader all clockwise means unity gain, whilst 12 o’clock means an approximate 20dB of attenuation.
- ON: When pressed, the output of the Master is sent to the Output connectors. When depressed, it is muted.
- INS: Turns the insert on. The insert send always have the signal present, whilst pressing the INS switch activates the insert return input.
BACK PANEL OVERVIEW
All the external connections are on the back panel, as follows:
- 5 pin XLR for the external HA-PSU02 power supply unit.
- XLRs for Mix Output L and R.
- XLRs for Monitor Output L and R
- XLRs (2) for Master Insert Send L and R
- XLRs (2) for Master Insert Return L and R
- DSUB 25 for Subgroup 1-8 Insert sends
- DSUB 25 for Subgroups 1-8 Insert Returns
- DSUB 25 (4) for Channel Input 1-8, 9-16, 17-24, 25-36
- DSUB 25 (4) for Insert sends 1-8, 9-16, 17-24, 25-36
- DSUB 25 (4) for Insert Returns 1-8, 9-16, 17-24, 25-36.
All XLRs are:
- Pin 1: GND
- Pin 2: Hot
- Pin 3: Cold
All DSUB 25 multi pin connectors are TASCAM protocol. This same protocol is also used by AVID* amongst many others, and is as follows:
The list of the DSUB connectors used and their corresponding channels are as follows:
CHANNEL INPUTS 1-8:
| TASCAM DSUB CHANNEL # | CHANNEL I/P 1-8 |
|---|---|
| 1 | INPUT #1 |
| 2 | INPUT #2 |
| 3 | INPUT #3 |
| 4 | INPUT #4 |
| 5 | INPUT #5 |
| 6 | INPUT #6 |
| 7 | INPUT #7 |
| 8 | INPUT #8 |
CHANNEL INPUTS 9-16:
| TASCAM DSUB CHANNEL # | CHANNEL I/P 9-16 |
|---|---|
| 1 | INPUT #9 |
| 2 | INPUT #10 |
| 3 | INPUT #11 |
| 4 | INPUT #12 |
| 5 | INPUT #13 |
| 6 | INPUT #14 |
| 7 | INPUT #15 |
| 8 | INPUT #16 |
CHANNEL INPUTS 17-24:
| TASCAM DSUB CHANNEL # | CHANNEL I/P 17-24 |
|---|---|
| 1 | INPUT #17 |
| 2 | INPUT #18 |
| 3 | INPUT #19 |
| 4 | INPUT #20 |
| 5 | INPUT #21 |
| 6 | INPUT #22 |
| 7 | INPUT #23 |
| 8 | INPUT #24 |
CHANNEL INPUTS 25-32:
| TASCAM DSUB CHANNEL # | CHANNEL I/P 25-32 |
|---|---|
| 1 | INPUT #25 |
| 2 | INPUT #26 |
| 3 | INPUT #27 |
| 4 | INPUT #28 |
| 5 | INPUT #29 |
| 6 | INPUT #30 |
| 7 | INPUT #31 |
| 8 | INPUT #32 |
INSERT SENDS 1-8:
| TASCAM DSUB CHANNEL # | INSERT SENDS 1-8 |
|---|---|
| 1 | INSERT SEND #1 |
| 2 | INSERT SEND #2 |
| 3 | INSERT SEND #3 |
| 4 | INSERT SEND #4 |
| 5 | INSERT SEND #5 |
| 6 | INSERT SEND #6 |
| 7 | INSERT SEND #7 |
| 8 | INSERT SEND #8 |
INSERT SENDS 9-16:
| TASCAM DSUB CHANNEL # | INSERT SENDS 9-16 |
|---|---|
| 1 | INSERT SEND #9 |
| 2 | INSERT SEND #10 |
| 3 | INSERT SEND #11 |
| 4 | INSERT SEND #12 |
| 5 | INSERT SEND #13 |
| 6 | INSERT SEND #14 |
| 7 | INSERT SEND #15 |
| 8 | INSERT SEND #16 |
INSERT SENDS 17-24:
| TASCAM DSUB CHANNEL # | INSERT SENDS 17-24 |
|---|---|
| 1 | INSERT SEND #17 |
| 2 | INSERT SEND #18 |
| 3 | INSERT SEND #19 |
| 4 | INSERT SEND #20 |
| 5 | INSERT SEND #21 |
| 6 | INSERT SEND #22 |
| 7 | INSERT SEND #23 |
| 8 | INSERT SEND #24 |
INSERT RETURNS 25-32:
| TASCAM DSUB CHANNEL # | INSERT RETURNS 25-32 |
|---|---|
| 1 | INSERT RETURN #25 |
| 2 | INSERT RETURN #26 |
| 3 | INSERT RETURN #27 |
| 4 | INSERT RETURN #28 |
| 5 | INSERT RETURN #29 |
| 6 | INSERT RETURN #30 |
| 7 | INSERT RETURN #31 |
| 8 | INSERT RETURN #32 |
SUBGROUP INSERT SENDS 1-8:
| TASCAM DSUB CHANNEL # | SUBGROUP INSERT SENDS 1-8 |
|---|---|
| 1 | SUBGROUP INSERT SEND #1 |
| 2 | SUBGROUP INSERT SEND #2 |
| 3 | SUBGROUP INSERT SEND #3 |
| 4 | SUBGROUP INSERT SEND #4 |
| 5 | SUBGROUP INSERT SEND #5 |
| 6 | SUBGROUP INSERT SEND #6 |
| 7 | SUBGROUP INSERT SEND #7 |
| 8 | SUBGROUP INSERT SEND #8 |
SUBGROUP INSERT RETURNS 1-8:
| TASCAM DSUB CHANNEL # | SUBGROUP INSERT RETURNS 1-8 |
|---|---|
| 1 | SUBGROUP INSERT RETURN #1 |
| 2 | SUBGROUP INSERT RETURN #2 |
| 3 | SUBGROUP INSERT RETURN #3 |
| 4 | SUBGROUP INSERT RETURN #4 |
| 5 | SUBGROUP INSERT RETURN #5 |
| 6 | SUBGROUP INSERT RETURN #6 |
| 7 | SUBGROUP INSERT RETURN #7 |
| 8 | SUBGROUP INSERT RETURN #8 |
It is worth noting that, in order to avoid ground loops, the Dsub ground connections are lifted on the MCM32 side, leaving the ground paths of your DSUB snakes only acting as shields and preventing any current returns.
SIGNAL FLOW AND BLOCK DIAGRAM (Dsubs omitted for clarity)
GAIN STRUCTURE
The gain structure in the MCM32 is quite simple and intuitive. At the same
time, no compromises have been made on the “secondary” inputs and outputs,
like the inserts sends and returns. Therefore all connections are balanced and
all outputs are nominal +4dBu and able to drive 600 ohms.
The gain structure is that all faders up, any input to any output is unity
gain.
+4dBu at one channel input, fader all the way up, subgroup fader all the way
up, gives +4dBu at the channel and subgroup insert send points, and at the
main send and output as well.
+4dBu at the channel or subgroup insert returns will give +4dBu at the main
send and output as well.
+4dBu at the main insert return will give +4dBu at the main output.
MCM 32 POWER SUPPLY
The MCM range of summing mixers features a hybrid power supply concept, in a
very similar way to the On Slot Technology (OST) employed in Heritage´s
successful 500 series enclosures range.
An external switching power supply enters the unit by means of a 5 pin XLR
connector, where it is further filtered using a PI configuration, using a big
common mode choke.
Further, linear regulation stages are used. Different regulation is used for
channels and buses, and output stages.
TECHNICAL SPECIFICATIONS
- Channel Input Impedance: Greater than 20 Kohm.
- Maximum channel input level: Greater than +26dBu
- Maximum insert return input level: Greater than +26dBu
- Maximum insert send level: Greater than +27dBu, able to drive 600 ohm.
- Maximum output level: Greater than +26dBu into 600ohm.
- Frequency response: ±0.5dB 20Hz to 20kHz
- THD + N: Not more than 0.07% from 50 Hz to 10 kHz at +20dBu output (22 Hz to 22 Khz bandwidth) into 600Ω.
- Noise, all faders up, all subgroups in, measured at the main output, 22Hz to 22Khz: Better than -80dBu
Heritage Audio S.L
C/ Alfonso Gómez, 38, 3C
28037 Madrid
Madrid – Spain
For technical questions not included here: tech@heritageaudio.com
For general info: info@heritageaudio.com
Skype: heritageaudio
Tel: +34 917 266 189
www.heritageaudio.com
TASCAM and AVID are trademarks of their respective owners and Heritage Audio is in no way affiliated with them.
References
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