Transfer Console Input-Gain-Filter-Output
Elliptic Equalizer for Mastering with 12dB/Octave Slopes
Insert Switcher, Passive, Fully-Balanced, Two Insert with
Class-A II Line Driver and Headphone Amplifier
MS Matrix Schematics and
Line Driver-Receiver and Other
Alternative Applications for the MS Matrix Board
Using the Precision MS Matrix
Encoder to Drive "A Mid Side Speaker Array For A Big
Ambient Sweet Spot"
Visit The Pro Audio Design
MS Matrix is Offered as A Bare Circuit Board, PC Board
with THAT ICs, or Assembled and Tested Shown Above.
This is the
new "MS-II" Matrix based on the original MS design
published in the Pro Audio Design Forum and used by
mastering facilities world-wide. The MS-II offers a number
of new features including Mid/Side Gain Offset, Variable
Width control, a Tilt Equalizer in Side and multiple
The Precision MS-II Matrix uses THAT1240 and 1246 line
receivers with resistor matching of 0.005% to perform high
accuracy mid-side sum and difference functions.
Encode/decode crosstalk performance is typically >55 dB
across the full audio band.
The Precision MS-II Matrix provides simultaneous
encode/decode capability. THAT1246 line receivers and
THAT1646 OutSmarts® line drivers provide fully-balanced
I/O for the encoder and decoder inputs and outputs.
The MS-II has a number of new features to make MS easier.
For those wanting a quick look, the schematics are
Insert Gain Offset.
M/S processing can often create level challenges for both
outboard gear and internal to the MS matrix itself. Side
levels are often significantly lower than Mid. With
highly-correlated elements Mid often has "mono build-up"
producing level increases of 3 to 6 dB.
The MTC-MS-II addresses MS level challenges by applying
switchable Insert Gain Offset between Mid and Side. The
Encoder can operate with 0, 6 and 12 dB offset between Mid
and Side. When gain offset is applied in the Encoder, the
Decode gain is compensated to maintain the original M/S
Mid Gain Offset: Reduces Mid Encode Gain by -6 dB. Mid
Decode Gain is automatically increased by +6 dB to
compensate. Mid encode headroom is increased by 6 dB.
Side Gain Offset: Increases Side Encode Gain by +6 dB.
Side Decode Gain is decreased by -6 dB. Side gain offset
allows outboard gear to be driven hotter.
By using Mid and Side Gain offset together, an offset up
to 12 dB is available.
and Decode Bypass.
The MTC-MS-II's Encoder can be bypassed to forward Left
and Right into the Insert. The Decoder can be also be
bypassed to forward Mid/Side to the final Left and Right
Outputs or jumper-configured to forward the Decode inputs
directly to the output.
By using Encode and Decode bypass together the Insert can
be switched from Mid/Side to Left/Right processing.
Mid and Side have individual Insert bypass relays. Need to
compress only Mid? Bypass the Side Insert completely.
Processing both Mid and Side? Bypass one at a time to hear
each processes' contribution. On-board relay logic is
available to bypass Mid and Side Inserts simultaneously
for instant A/B comparisons.
On-board Width Control.
The MTC-MS-II has on-board Width control ranging from 0 to
200% by varying Side Level from -∞ to +6 dB relative to an
anchored unity gain Mid level. Control is smooth and
predictable with a "feel" similar to the Width Controller
using the LR±S method. A potentiometer or stepped
make-before-break rotary switch can be used. The Width
Control is relay-bypassed.
On-board Tilt Equalizer
Provides Frequency-Dependent Width.
tilt equalizer can be inserted into the Side channel
to provide frequency-dependent Width. The range at 10 kHz is
+/-3dB. As 10 kHz is boosted, 100 Hz is decreased by an
identical amount with a "pivot" frequency of about 1.2 kHz.
A 0 to 6 dB range in frequency-dependent Width is available
from the 100 Hz to 10 kHz with either positive or negative
slope. Width can increase with frequency or decrease with
frequency. The Tilt Equalizer follows the overall Width
control and is relay-bypassed.
Individual Mid and Side
The Mid and Side channels have individual relay mutes to
audition the processing of each insert. The Mid and Side
channel mutes are placed in the return path rather than the
Insert Send to eliminate "compressor recovery" artifacts
from muting sends. When Mid is muted, Side is presented to
the Left and Right outputs in their actual perspective
similar to an "in place" Solo function. (Side is a "mono"
single-channel signal. When presented "in place" the
positive polarity is heard in Left and the negative in
Right. This is how we hear it in the stereo image when
recombined with Mid.)
Improved Encoder and
Mid Side encoding is well-known for Mid "build-up" on
The MTC-MS-II eliminates Mid build-up and the resulting
headroom reduction with Mid Gain offset. Internal encode
headroom in Mid is increased by 6 dB.
Though not fully-appreciated Mid Side decoding has
additional gain build-up during Left and Right
reconstruction. When M+S is added to M-S to produce "L" the
actual result is 2L. The MTC-II avoids L and R buildup by
using the THAT1240 and 1246 line receivers to provide
summation without gain.
By switching the THAT1240 in a unique way its gain can be
varied from -6, to 0 and to +6 dB. This provides the
opportunity to provide switchable gain offset with high
precision without the requirement for additional stages that
would add differential phase delay to one process path but
not the other. High frequency crosstalk performance is
To learn more about the MS-II Precision MS Matrix visit the
Pro Audio Design Forum.
The Precision MS Matrix is sold as either a bare PC board, a
"kit" including THAT1240, THAT1246, THAT1646 ICs and an
OPA2134, or an assembled and fully-tested module.
A Mouser Electronics Project Manager bill-of-materials is available
for DIY builds of the Precision MS Matrix.
Bare PC Board
Bare PC Board Including THAT ICs for MS Matrix
(6 each THAT1240, 1246, 4 1646,
Assembled and Tested MS Matrix PC Board Including All
Questions, ready to buy?