Martinsound Martech Modular Studio Series User manual

MSS-10
Modular Studio Series
Microphone Preamplier

2
5
1151 W. Valley Blvd. Alhambra, CA 91803-2493
800.582.3555 • Phone [phone] • Fax +1.626.284-3092
www.martinsound.com
Owner Manual
MSS-10
Natural Sound
Microphone Preamplier

0 9
© 2001 Martinsound, Inc. All rights reserved.
Under the copyright laws, this manual may not be copied, in whole or in part, without the
written consent of Martinsound.
Every effort has been made to ensure that the information in this manual is accurate.
Martinsound is not responsible for printing or clerical errors.
The Martech and Martinsound logos are Trademarks of Martinsound, Inc.
Other company and product names mentioned herein are trademarks of their respec-
tive companies. Mention of third-party products is for informational purposes only and
constitutes neither an endorsement nor a recommendation. Martinsound assumes no
responsibility with regard to the performance or use of these products.

Safety Warnings
Introduction
Microphone Preamplier
Line Driver
To Ground Or Not To Ground?
Rear Panel
Balanced Impedance Outputs
Getting The Most out Of Your MSS-10
Block Diagram
Operation
Setting Voltage • Changing the Fuse
Technical Specications
Design Team
A Short History
Table of Contents
1
3
4
5
6
7
8
9
12
13
14
17
18
19

1
The lightning ash with arrowhead symbol within an equilateral tri-
angle is intended to alert the user to the presence of uninsulated
“dangerous voltage” within the product’s enclosure that may be of
sufcient magnitude to constitute a risk of electric shock to persons.
Le symbole éclair avec point de  èche à l’intérieur d’un triangle équi-
latéral est utilisé pour alerter l’utilisateur de la présence à l’intérieur
du coffret de «voltage dangereux» non isolé d’ampleur suf sante
pour constituer un risque d’électrocution.
The exclamation point within an equilateral triangle is intended to
alert the user to the presence of important operating and maintenance
(servicing) instructions in the literature accompanying the appliance.
Le point d’exclamation à l’intérieur d’un triangle équilatéral est
employé pour alerter l’utilisateur de la présence d’instructions impor-
tantes pour le fonctionnement et l’entretien (service) dans le livret
d’instruction accompagnant l’appareil.
Copies of the UL and CE Certication Test Reports are on le at Martinsound, Inc.
Please contact Martinsound if you have any questions regarding these issues.
Safety Warnings
RISK OF ELECTRIC SHOCK
DO NOT OPEN
RISQUE DE CHOC ÉLECTRIQUE
NE PAS OUVRIR
CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK
DO NOT REMOVE COVER (OR BACK)
NO USER-SERVICEABLE PARTS INSIDE
REFER SERVICING TO QUALIFIED PERSONNEL
ATTENTION: POUR EVITER LES RISQUES DE CHOC ÉLECTRIQUE,
NE PAS ENLEVER LE COUVERCLE.
AUCUN ENTRETIEN DE PIÈCES INTÉRIEURES PAR L'USAGER.
CONFIER L'ENTRETIEN AU PERSONNEL QUALIFIE.
AVIS: POUR EVITER LES RISQUES D'INCENDIE OU D'ELECTROCUTION,
N'EXPOSEZ PAS CET ARTICLE A LA PLUIE OU A L'HUMIDITÉ.
CAUTION AVIS

2

3
Congratulations on the purchase of your MSS-10 Microphone Preamplier, one of the
nest sounding pieces of recording equipment ever developed. This remarkable tool will
enable you to make exceptional, natural sounding recordings like never before. Unlike
other units, the “watermark” left by your MSS-10 is pure sonic excellence. Its unique
lack of coloration or hype will reveal a naturalness that is startling, yet immediately
endearing. Your MSS-10 will quickly become one of the hardest working tools in your
audio toolkit. We’re sure that you will enjoy its use for many years to come.
At the heart of the MSS-10 are proprietary, high resolution, all discrete ampliers,
coupled with a custom, high-level, input transformer. These give the MSS-10 its unique
sonic neutrality and resolution, hence the natural sound and musicality. Every com-
ponent of the MSS-10 was evaluated and listened to, individually and collectively, to
assure the nest possible signal path. Coin silver with a stabilizing agent was chosen
for switch contacts because of its superior audio quality over gold. Different grounding
techniques were tried on the PC board layouts to nd the best sounding design. And
capacitors… we could write a book on them, which is why we eliminated them from
the audio path and use our own private label capacitors in other key areas. From all
this research and technology came the desire to build the world’s nest solid state
microphone preamplier. Our desire was not to pick the best shade of rose for a new pair
of tinted glasses, but to truly unveil the audio as never before.
The MSS-10 is comprised of dual signal paths in a single unit, allowing the user complete
exibility in getting audio from the microphone to the console or recorder input.
The primary signal path is a microphone preamplier using two stages of non-inverting
amplication from Mic Preamp In to Mic Preamp Out, providing wide bandwidth and
stability, while avoiding the sonic degradation of inverting ampliers. The microphone
preamplier features 20-65dB of gain switched in precise 5dB steps, and selection of a
20dB pad, polarity reversal, and 48V phantom power. The Mic Preamp Out provides the
user with the highest denition audio signal possible from the source microphone to the
outside world.
The secondary signal path is a line driver that can derive its source from either the
microphone preamplier or from the separate balanced Line In. The line driver features
a high quality level control with adjustment from ∞ to +10dB of gain for smooth level
riding, a Cal switch that shunts the level control for unity gain, a Mute switch, and a
buffered professional VU meter that follows the Line Out. Again no inverting ampliers
are used.
Let’s take a closer look at the layout of the MSS-10…
Introduction

4
Mic Gain
Switches the microphone preamplier
gain from 20dB to 65dB in precise 5dB
steps using excellent sounding, chemi-
cally stabilized, redundant silver switch
contacts of the highest quality.
This setting determines the output level
from the Mic Preamp Out XLR and the
level sent to the line driver when Line
is not selected.
48V
Applies 48 VDC of regulated power to
pin 2 and 3 of the Mic Preamp In XLR for
phantom powered microphones.
Ø
Reverses the connection between the
Mic Preamp In XLR and the input trans-
former. Polarity reversal is done at
this point because inverting ampliers
cannot begin to compare to excellent
sounding, chemically stabilized, redun-
dant silver switch contacts.
-20dB
Reduces the level to the rst amplier
using a voltage divider that terminates
the secondary of the input transformer.
There is no loss of audio quality when
using the pad, unlike a standard U pad
placed in front of an input transformer.
The custom MSS-10 input transformer
is designed to handle high signal levels.
Tip:
When setting the gain of the microphone preamplier, deselect the Line switch and
select the Cal switch. The VU meter will then read the actual level of the microphone
preamplier allowing optimization of the gain. Be sure to reset the Line and Cal switches
to their preferred setting afterwards.
Microphone Preamplier

5
Line Out
Adjusts the output level of the line
driver from ∞ to +10dB of gain, using
a high quality precision potentiometer.
Only the Line Out XLR level is affected
by the level control.
Line
Selects the Line In XLR as the line
driver source, providing an independent
line level path. An insert loop is formed
with Mic Preamp Out and Line In, using
Line to select the insert return. The line
driver is fed by the microphone pream-
plier when Line is not selected.
Cal
Shunts the level control, setting the
line driver at unity gain, providing indi-
cation on the VU of the line driver signal
level without the inuence of the level
control. The switch is out of the audio
path when Cal is selected.
Mute
Mutes the audio to the Line Out XLR.
The switch is out of the audio path
when Mute is not selected.
VU
Full size meter featuring professional
VU ballistics. Fully buffered, it reects
the Line Out XLR level, following any
type of load.
Tip:
The line driver may be used to provide VU monitoring of alternate sources when not
needed in conjunction with the microphone preamplier. Simply input a source into the
Line In, then select Line and Cal. Great for getting a true VU reading from the analog
return of a digital recorder, etc.
Line Driver

6
To Ground Or Not To Ground?
(There Is No Question!)
The MSS-10 must be properly earthed to preserve safety and proper operation!
Grounding has divided the professional audio community since transformers were aban-
doned as the preferred method of I/O interfacing. Should pin 1 of input and output
XLRs be connected to chassis (earth), analog ground (0 volts), or oated? Currently the
AES is discussing this hot issue and should announce a standard in the near future.
Martinsound is paying close attention to these talks in order to easily implement the
formalized AES standard(s) into current products.
Meanwhile, the Los Angeles Chapter of the AES discussed two grounding topics at a
workshop. As a result of the discussions, we are convinced as to how pin 1 should be
handled until AES standards are set forth.
The rst topic discussed a shield as an RF eld conductor or antenna, concluding that it
should not be introduced within the case of a piece of electronic equipment. Taking the
shield immediately to chassis at the connector allows the chassis to act as a Faraday
shield, protecting the electronics inside from interference.
The second topic discussed and demonstrated was the effect of a circulating current on
analog ground. A circulating current is introduced when pin 1 of a device’s various XLRs
are hooked up to different points of the ground circuit inside the device. Any current
owing through the resistance of the connecting ground trace causes minor voltage
uctuations. This causes hum when amplied by high gain ampliers. To demonstrate
the effect, a device called a “Hummer” was used to introduce a low level 60Hz current to
the shield of a cable attaching two pieces of audio equipment. When pin 1 of an XLR was
attached to audio ground, the 60Hz modulated the ground of that piece of equipment,
inducing hum in the audio signal. When pin 1 was attached to chassis, with only a single
reference between audio ground and chassis/earth, the only detectable noise was the
thermal noise of the electronics.
Both of these important topics are addressed by attaching pin 1 to the chassis at the
connector. The Modular Studio Series adheres to this approach of grounding. As a result,
pin 1 of all XLRs are connected directly to chassis through the XLR shells, with a single,
discrete connection between audio ground and chassis/earth. Therefore, RF elds and
circulating currents are not introduced into analog ground, but appear on the chassis
only, which is connected to earth through the AC cord.
Not doing so is both dangerous and unnecessary in properly built equipment. This may
y in the face of everything your mother taught you, but this philosophy of grounding
works extremely well. If you have further questions, please refer to the June, 1995 Jour-
nal of the AES for more information (SHIELDS AND GROUNDS: Safety, Power Mains,
Studio Cable and Equipment, Vol. 43, number 6).

7
Line In
Bridging Balanced In
10/10 kOhm • Pin 2+, Pin 3–
Nominal Input: +4dBu
Line Out
Single-ended Balanced Impedance Out
50/50 Ohm • Pin 2+, Pin 3–
Nominal Output: +4dBu
Mic Preamp In
Transformer Balanced In
2.5 kOhm • Pin 2+, Pin 3–
Nominal Input: 0 to –65dBu
Mic Preamp Out
Single-ended Balanced Impedance Out
50/50 Ohm • Pin 2+, Pin 3–
Nominal Output: +4dBu
Markings & Power Entry Module
Model # • Serial # • Manufacturing Date • Approvals • Warnings • Fuse values
Voltage Select Indicator • Voltage Select/Fuse Block • Power Switch
100-120VAC: 115V T500 mA 250V • 220-240VAC: 230V T250 mA 250V
Rear Panel

8
Many things were taken into consideration when designing the outputs of the MSS-10
to interface awlessly with other equipment, with no sonic compromise being the most
important. We were faced with three options; a transformer balanced output, an elec-
tronically balanced output, or go with a single-ended output.
The idea of a transformer was not a real contender. The size and weight for a truly stellar
sounding unit that could easily drive +24dB into 600Ω would have been unreasonable.
Also, the cost to develop a unit that satised us aurally was cost prohibitive. We also
realized that an output transformer would put off many people, no matter how good it
sounded. We felt that the only signicant advantage of a transformer was that it would
provide a true oating output.
Electronically balanced outputs are heavily used throughout the audio industry. When
evaluating the sonic characteristics of the many different balancing circuit designs we
found all to be seriously lacking. Whether as a result of delay imbalances between the
differential outputs, use of inverting ampliers, or ampliers operating on the verge of
instability, none sounded close to a piece of wire. After all the effort to achieve a truly
stellar sounding microphone preamplier it was unthinkable to destroy the sonic integ-
rity of the design at the nal output stage.
What advantage is gained using a balanced output? After careful examination, the key
benet we found is the identical impedance on both output legs. A transformerless bal-
anced input must see the same impedance on both input legs or its common mode rejec-
tion is seriously compromised. But, if a source presents a matched impedance to both
legs of a differential input full common mode is achieved, whether driven differentially
or single-ended.
The D2024 amplier developed for the MSS-10 has an extremely low source impedance.
When connecting a D2024 to pin 2 of an output XLR, a build-out resistor is used to iso-
late the amplier from external inuence giving a source impedance of 52Ω. To mirror
the source impedance of pin 2, a 52Ω resistor is used to connect audio ground to pin 3
of the output XLR. The lower output impedance properly terminates shielded pair audio
cable, while the balanced output impedance maximizes the common mode rejection of a
following device. And, because audio only appears on pin 2, output level and headroom
are never affected when connecting the MSS-10 to a balanced or unbalanced input.
We believe that this simple but elegant solution provides you with the best sound pos-
sible.
WARNING: The MSS-10 uses a very sophisticated design for limiting output current to
prevent damaging the unit in the event an output is ever shorted. Nevertheless, avoid
connecting the unit to cables or equipment that tie pin 2 to shield or ground.
Balanced Impedance Outputs

9
In this example the MSS-10 is placed in
the control room next to the engineer.
Mic Preamp In:
Connect to the microphone
Line Out:
Connect to the recorder
Line:
Deselect to switch the line driver input
to the microphone preamplier
Cal:
Select to use the VU to set Mic Gain
Mic Gain:
Rotate switch to select optimal gain
–20:
Select if lowest Mic Gain position pro-
vides too much gain, then set Mic Gain
Cal:
Deselect to use the Line Out control
Line Out:
Set and ride the line driver output level
Mute:
Select to mute the line driver output
This conguration gives the engineer the
ability to optimize gain, set and ride level,
mute the audio, and meter the level during
the record process. It works well for track-
ing and overdub sessions, or recordings
where a single microphone is recorded to
a track.
This method maintains the highest qual-
ity audio signal from the microphone to
the recorder.
The Minimalist Approach
Getting The Most Out Of Your MSS-10

10
In this example, the MSS-10 is placed in
the studio near the microphone or in the
control room next to the engineer, and
then connected to a console for mixing.
The Mic Preamp is selected to feed the
line driver, with the Mic Preamp Out con-
nected to a console. The Cal switch is
engaged to set the Mic Preamp Gain and
monitor the output with the VU meter.
Locating the MSS-10 near the microphone
keeps cable loss to a minimum for low
level microphone signals. This setup gives
the engineer the ability to set the best
gain and buffer the mic from a long cable
run. Final level is adjusted on a console
fader, permitting bussing and summing.
Locating the MSS-10 near the engineer
permits quick gain changes when required.
Also, the engineer can use the VU meter to
monitor the Mic Preamp Out level during
the recording process.
This method ensures the nest possible
signal integrity at the beginning of the
recording chain, where it matters the
most!
Mix to Taste!

11
In this example the MSS-10 is placed in
the control room next to the engineer.
The Mic Preamp Out is connected to an
external process chain, such as an equal-
izer and compressor. The process chain
output is connected to the balanced Line
In of the MSS-10. The Line In is selected
to the line driver and the Line Out is
connected to the recorder, with the Cal
switch disengaged. This setup gives the
engineer the ability to set the best gain,
process, ride the level, mute and unmute
the audio, and meter the output level
during the recording process. Again, this
works well for all tracking and overdub
situations where a single microphone is
recorded to a track.
This method maintains the shortest, fully
controlled audio path from the micro-
phone to the recorder while utilizing your
preferred outboard equipment.
Many other congurations are possible
so as to match the needs of the engineer
without compromising the audio quality.
We at MARTECH have sought to provide
a versatile tool that will reshape the way
you work as an engineer.
Tossing In The Kitchen Sink

12
+48V
Input
XFMR
48V
Ø
Gain:
14dB
1:5 Ratio
Line
Line Out
Level
Cal Mute
3
1
3
1
2
2
Gain:
21dB
Gain:
5 ~ 30dB
5dB Steps
Loss:
0 ~ 20dB
5dB Steps
Gain:
Unity
Mic Preamp In
3
1
2
Line In
Mic Preamp Out
-20dB
Gain
PadD2024
D2024
D2024
D2024
+
–Gain:
10dB
Optional
1:1 ratio
Standard
3
1
2
Line Out
3
521
12
07
10
3
20
Block Diagram
MSS-10: Modular Studio Series Microphone Preamplier Block Diagram 2 9/13/96

13
Inputs are balanced. Outputs are single ended balanced impedance. XLR connectors are
wired to AES standards: pin 2 +, pin 3 –, pin 1 chassis. XLR connectors are solder type
allowing pin conguration to be changed by a qualied technician if necessary.
Place the unit in the studio by the microphone or the control room by the engineer. Set
Gain to 20 and select Mute. Plug a mic cable into Mic Preamp In. Select 48V for a phan-
tom power microphone. If 5dB gain changes are adequate plug a line cable into Mic
Preamp Out, otherwise plug into Line Out. Select CAL and deselect Mute. Select -20dB
if the signal is too high on the VU meter. Adjust Gain for an average level of -5 to 0 VU. If
Line Out is being used, deselect CAL and adjust Line Out level as necessary.
ATTENTION: In designing this unit for sonic excellence, we found that all hum, RF, and
static protection circuitry seriously diminished sound quality. Therefore, extreme care
was taken in the mechanical construction and grounding of this unit to prevent problems,
but under adverse conditions unexpected results may occur.
Operation
Les puissances sont en balance et les puissances de sorties sont, unique à l’extrémité
impédance en balance. Tous les connecteurs XLR ont branche che 2 haute, che 3 bas,
che 1 écran (Pin 2 +, Pin 3 –, Pin 1 shield) adaptant à les criteria d’AES. Les connecteurs
XLR sont la soudure en type, en tenant compte la conguration de la che, être en char-
ger intérieurement si nécessaire par les techniciens qualiés.
La pièce pourrait situé près du microphone en le cadre d’enregistrement, au situé près
de l’engénieur dans la régie. Changez le bouton Gain à 20dB et appuyez le bouton Mute
“ON”. Se branchez le câble du microphone dans le Mic Preamp In. Si utilisant un micro-
phone avant besoin de la puissance fantôme (Phantom Power) appuyez sur le bouton
48V “ON”. Se branchez un câble ligne dans le Mic Pre Out si gros gain changements
de 5dB sont sufsant, autrement se branchez le câble ligne dans Line Out. Appuyez le
bouton Cal “ON” et réglez le bouton Gain si bien que le compteur VU indique un niveau
moyen entre –5 et 0. Appuyez le bouton –20dB “ON”, si le niveau est trop haute avec le
gain a réglé a 20dB, ensuite ajustez le bouton Gain. Si vu vu avec branché dans la Line
Out, puis après ajustant le gros gain, fermez le bouton Cal et ajuster le bouton Line Out
au niveau de sortie précis.
ATTENTION: En dessinant cette pièce, pour sonique excellence, nous avons trouvé que
tout renement, RF, et circuitry statique protection ont diminué la qualité du son grave-
ment. Donc, le plus grand soin eut pris dans la construction mécanique et en mettant en
prise de terre pour enn d’empêcher des problème, mais sous les conditions contraires,
les conséquences imprévues peut-être arriveraient.
Attention: XLR connectors are wired according to AES standards • Pin 2 +
Attention: Les connecteurs XLR ont branché selon que les criteria d’AES • Fiche 2 +

14
Pry out the Voltage Select/Fuse Block
To change the fuse and/or voltage:
Turn the power switch off and disconnect
the AC cord
Pry open the Power Entry Module with a
small screwdriver
Position the Fuse Block with
the metal clip on the left
Remove the metal clip from
the Fuse Block
Selecting Voltage • Changing The Fuse
CAUTION: ALWAYS USE AN APPROPRIATELY
RATED FUSE FOR THE VOLTAGE SELECTED
PRENEZ PRUDENCE: UTILISEZ UN FUSIBLE CORRECTEMENT
CLASSÉ POUR LE VOLTAGE SÉLECTIONNÉ TOUJOURS