PM - 80R - Formula Sound
PM - 80R
PM-80R Introduction.
To celebrate 25 years since we manufactured the first PM-80 and in response to requests to
remanufacture it, Formula Sound has introduced a limited edition PM-80R production mixer.
The PM-80R incorporates all the loved features of the original PM-80 with the benefits which modern
components and manufacturing techniques can add to the original design. The PM-80R modules are
therefore not interchangeable with the original PM-80 modules.
The PM-80 was manufactured for over 13 years and in that time many mixers were modified and
features added for specific applications. We have captured the simplicity of the PM-80 making the
PM-80R as easy to use as the original, whilst also introducing some of these features.
The signal chain is as pure as the original PM-80 and will provide the same outstanding audio quality.
The PM-80R will appeal to all sectors of the industry due to the modular construction and versatility that
the universal input module offers. This product is unique and suitable for many types of application.
The use of custom aluminium extrusions and flexible computer grade ribbon cable, which is used for the
connection to the various modules, plus gold plated connectors for all internal signal connections make
this unit equally at home in a static or mobile environment.
Like the original mixer 4, 8, (19" rack mount) and 12 channel input chassis are available. Special sizes
could also be catered for.
General Description
The Input module has been designed to be universal and is internally configurable to accept all types of
input source.
Internal gold plated jumper links are used to configure the input module - these provide a simple and
reliable way of configuring the various options available.
Concealed switches for routing to a stereo Aux buss are also featured, with the option to select pre or
post fader.
The 3 band equaliser section has been designed to perform like the original PM-80 but we have also
provided for the possibility of special E.Q versions to be supplied (more cut than boost etc.)
The equaliser section may also be disabled if required.
Internal selection of input routing to a choice of 2 stereo mix busses is also possible, which adds to the
flexibility of the design. For example Microphone inputs could be sent to the output section via the mic
buss. Insert sockets have been provided so that any input routed via the mic buss could be connected
to external equipment, compressors, limiters, etc if required. Or the insert sockets could simply provide
an output of these sources.
The Output module contains the power supply which is internally switchable to operate from 220-240V
AC or 110-120V AC. All the mixing and output circuitry are also in this module.
The Main outputs are balanced. The mixer also has Zone, Booth, and Auxiliary outputs available in
mono or stereo. Record, Sub Bass, and Mono outputs are also provided.
A powerful stereo headphone amplifier designed to drive headphones of 32 ohms or greater is
Visual monitoring is provided by a stereo 24 segment led bargraph meter. The meter and phones are
connected to the same signal so what you see is what you hear.
External music mute has been added to help comply with modern fire regulations.
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Input Sources. The design of this module allows almost any input source to be
used. This is achieved by providing a balanced low impedance low noise
microphone pre-amplifier; a stereo RIAA equalised pre-amplifier (phono cartridge
input); a stereo balanced line level input stage and a stereo unbalanced line level
input stage.
Configuration - Internal jumper links fitted to pin headers select the input types
available. (Similar jumpers provide selection of other options.)
See later section on configuration Drg-1008.
Input Connectors - Rear panel mounted 2 - XLR input sockets, 2 - gold plated RCA
phono sockets, 1 - 1/4"- 3 pole jack socket (provides a connection to pick up the
microphone signal only, or connect external equipment into the microphone
Gain control allows the operator to compensate for variations in programme material
or signal level. (See later section on gain)
HF (High Frequency or Treble)
This control provides +10dB boost & -10dB cut @ 10KHz with a shelving response.
Mid (Middle Frequencies)
This control provides +10dB boost & -10dB @ 1KHz cut with a broad bell response.
LF (Low Frequency or Bass)
This control provides +10dB boost -10dB cut @ 100Hz with a bell response.
This response has been chosen so that sub sonic frequencies are not boosted by
this control.
All E.Q. controls have a centre detent at the (E.Q flat) centre position.
The E.Q. function may be disabled by the setting of internal jumpers. See later
section on configuration.
AUX - Aux send. A concealed push button with led illumination has been added.
When depressed the signal in this module is mixed with any other source selected.
The resulting mix is available at the Aux outputs on the master module. Internal
jumpers allow the source to be selected pre of post (before or after) the channel
Bal /Pan (Stereo balance & Pan)
With a stereo source selected this control provides adjustment to balance stereo
signals. With a microphone selected this control allows the source to be positioned
anywhere in the stereo image. A centre detent is provided at the control centre
MON (Monitor sometimes called Cue or PFL Pre Fade Listen)
Push button with red led illumination.
When depressed the signal in this module is connected to the Monitor mix buss. Any number of
channels may be selected simultaneously, the sum of which will be monitored in the master module by
the meter and headphone amplifier.
MASTER fader - A 60mm studio quality linear fader is fitted to fade up and down the volume of the
channel. For normal production operation the fader should be set at the top (No.9) and the gain control
adjusted for normal volume. The fader should be used to fade in the signal at the required time taking
the fader to the top. This lets you concentrate on the timing confident that the volume will be correct. If
you want to operate with some gain in hand (e.g. mic mixing) operate with the fader set at No.7.
Always operate with the gain set as low as possible to achieve the desired results.
(See the later section on gain)
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PM - 80R Master Module
The master module contains all the electronics
required for the various summing amplifiers, output
stages, VU meters, etc. The majority of
connections are on the rear of the unit.
The monitoring section is very easy to understand.
Visual monitoring is provided by the led bar graph
meter. Audio monitoring is via a powerful stereo
headphone amplifier designed to drive phones of
32 ohms or greater. Connection is via the 3 pole
jack socket labelled PHONES. The meter and
phones output are both connected to the same
signal so what you see is what you hear.
If any channel MON switched is depressed the
Monitor buss is connected to the phones amp and
meter. If no MON switch is depressed the main
output is monitored.
AUX MASTER - This master control adjusts the
output level of the signals derived from the Aux
sends on the input modules. The outputs are via 2
1/4" jack sockets. A mono signal may be obtained
by using the left output socket only.
BOOTH - This control adjusts the level of the booth
output which is a mix of the channels routed via
the music buss. The outputs are via 2 1/4" jack
sockets. A mono signal may be obtained by using
the left output socket only.
ZONE -The zone output is almost identical to the
main except that the output is unbalanced and not
available to the monitoring section The outputs are
via 2 1/4" jack sockets. A mono signal may be
obtained by using the left output socket .
MASTER - The fader sets the output level of the
main balanced output available via 3 pole XLR
connectors on the rear panel. A mono output is
also available via a 1/4" jack socket.
RECORD OUTPUTS 2 - gold plated phono sockets are provided for the connection of stereo recording
equipment. Record outputs are unaffected by the master fader.
SUB BASS OUTPUT - A mono output via a 1/4" jack is provided for driving a sub bass loudspeaker
system to enhance low frequency performance. The filter allows frequencies below 70Hz to pass
through. An internal jumper located on PC-396 allows higher bass output if required.
MUSIC MUTE - To help comply with fire regulations a music mute facility has been included. The fire
alarm panel needs to provide a fully floating pair of contacts to join the two pins on the control connector.
INSERTS MIC MIX - Insert sockets in the form of 3 pole 1/4" jacks are provided for the connection of
external signal processing equipment to any combination of channels routed via the Mic buss. Internal
jumpers allow the inserts to be disabled. Located on the rear panel the connections are:Tip = send (mixer output) Ring = return (mixer input) Body = common (ground)
Page 3
In an audio mixer different signal levels from various items of equipment need to be amplified or
attenuated to a common level so that they can be added or mixed together. These signal levels may
differ considerably depending on the equipment. The signal from a microphone for example may be
1000 times smaller than that from a CD player. For a mixer to be as flexible as possible and to accept
signals from a variety of equipment it is necessary for the first or early stage in the input circuit to be a
variable gain amplifier. The gain of this amplifier is set by the gain control.
The PM-80R universal input module has a combination of variable gain amplifiers to get the input signals
to the required operating level. 2 gain trim presets are fitted - 1 for each input. These are accessable
through holes on the rear of the module and are labelled accordingly. The stereo input gain trim is a
conventional single turn control. The Mic preset is a multi-turn trimmer. These trims should be adjusted
to set the maximum gain available for any input. The front panel gain control works in conjunction with
these presets. The system may be considered as coarse gain control on the rear presets and fine
adjustment on the front gain control.
When amplifier gain is introduced in a circuit noise is also introduced (this is a fact, you cannot have one
without the other). The PM-80R has been designed to keep this noise as low as possible by using the
latest technology. For the best performance set the gain control as low as possible to achieve the
desired output level. Gain introduced into the system and then held on the channel fader is a waste of
performance. Too much gain could result in overloading the first stage causing distortion and clipping.
The level can be checked by selecting MON and observing the output meter. Normal operating level is
with the meter just illuminating into the red section.
The installation of professional audio systems should be left to experienced engineers wherever
possible. The interconnection of audio systems can be fairly complex depending on the type and size of
system and obviously well outside the scope of this handbook. We have included a few basic points for
information for anyone who is new to audio systems.
Good wiring practice should be observed when connecting any audio equipment. Good quality
connectors and screened cable should be used for all audio connections.
Twin screened cable should be used for all balanced lines particularly microphone connections.
Always ensure cable clamps in connectors are fully tightened and gripping the outer sheath. Good strain
relief and mechanically sound connections will increase reliability at virtually no extra cost.
In our experience this is the most common problem encountered when connecting together different
items of audio equipment. It is the most common cause of hum (50Hz noise) on a system and is caused
by incorrect system grounding.
When several items of audio equipment are connected together with unbalanced connections (i.e. 2
connections, single screened cable, etc.) the signal common connection is the screen and this will be
connected to mains earth at some point. If several items of equipment have their signal common
connected to mains earth this will form a loop (hence ground loop). Current will flow in this loop and
appear in the form of hum (50Hz mains frequency) added to the audio signal. The problem is
aggravated if the equipment is located a distance apart as the loop is larger. It is possible to have
several ground loops within a system. The solution is to connect the system to mains ground only
once. This is usually done at the mixer. You will need to investigate the various items of equipment you
are using and isolate their signal common from mains earth. Many manufacturers fit a ground lift switch
for this purpose. On some equipment this is in the form of a removable link. Unfortunately with some
equipment you have to get inside to identify where the connection is and remove it.
You must not disconnect the mains earth wire from the mains plug of any
equipment. This is fitted for safety reasons and must be connected to
ensure that the case is earthed.
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PM-80R Specifications
Frequency Response
E.Q. set flat
20Hz - 20 kHz +/-0.5dB
Maximum output level
Main, Zone, Booth, Aux.
Record output.
Main output active balanced.
For unbalanced operation strap pins 1&3 to ground and use pin 2 hot.
This will result in no loss of output level or performance
Any output @ max level
< 0.01% typically <0.005%
Noise measured 20Hz-20 kHz
Stereo inputs e.q. flat gain set to max
RIAA stage ref. 5mV 1kHz Input shorted
Microphone input (ref 150R)
EIN < -98dB
-80dBV "A" weighted
EIN < -124dBU
(Master Fader @ unity -6dB)
Stereo inputs rear trim @ max
Microphone input max
+/- 12dB
+ 68dB
Maximum input level
Stereo input (Balanced)
Stereo input unbalanced
Stereo input (RIAA)
-8dBV 400mV
+4 dBU
Input Impedances
Stereo input balanced (XLR)
Stereo input unbalanced (Phono)
Riaa (Phono)
Microphone input
> 20k ohms
> 15 k ohms
> 47k ohms
> 2k ohms active balanced
3 band e.q. per channel
+10dB -10 dB @ HF 10 kHz
Mid 1kHz,
LF 100Hz
Internal channel jumpers allow the e.q. stage to be disabled if required.
Other E.Q options available.
(Exc. Knobs & connectors):
8 Channel
4 Channel
12 Channel
Height 267mm (10.5"-6RU)
Depth 110mm (4.33")
Width 483mm ( 19" )
Width 330mm ( 13" )
Width 635mm ( 25" )
Installation Cut-out
Height 267mm Width:- 4 channel 280mm. 8 channel 433mm. 12 channel 585mm
Page 5
Removing and Refitting Modules.
A removable cover on the rear of the mixer provides access to the ribbon cable which connects to all the
modules. This cover is secured by 2 screws. Although modules can be removed and replaced from the
mixer front when necessary, removing the rear connector cover makes disconnecting modules easier
particularly if more than one module is being removed.
To remove an input module from the chassis first disconnect all connections from the module and ensure
that the power cord is disconnected. Input modules are secured by 2 screws, removing the screws will
release the module. Carefully ease the module out of the chassis and disconnect the ribbon cable
The output module is secured by 4 screws and connected by 3 connectors to the ribbon cable assembly.
We recommend that the rear connector cover is removed to facilitate disconnection of the ribbon cable if
this module is removed.
The master module is normally factory fitted to the right hand end of the chassis although the design of
the ribbon cable allows modules to be fitted into the chassis in any position. We would recommend that if
any blank modules are fitted, that one be fitted between the master module and channel modules. We
would also recommend that input modules configured for Microphone or phono cartridge are not fitted
adjacent to the master module. This avoids any stray hum pick up from the mains transformer. The
output module is the width of 3 input modules and uses 2 of the connectors for its operation.
Ensure that the connectors are fully mated before refitting the rear cover.
The modules have a clearance of approx. 0.25mm. This is deliberate to allow the modules to be easily
removed and refitted to the chassis. Use a strip of thin card (postcard) to set the spacing between the
modules when reassembling. Do not push all the modules tightly together as this will make them difficult to remove and leave an unsightly space. Remember 0.25mm is only 1/100". This is the normal
spacing clearance but in an 8 channel chassis, if you push the modules tightly together the resulting
space will be 2.5mm which is 1/10" and looks unsightly.
Formula Sound reserve the right to alter specifications at any time without notice.
All Formula Sound products are designed and manufactured in our own factory which enables us to
maintain strict quality at every stage of manufacture. This attention to detail has helped to win us 14
industry awards to date and has earned us a worldwide reputation for the high quality and reliability of
our products.
Formula Sound Ltd.
Unit 23, Stadium Business Centre
North End Road,
Tel +44 (0)208 900 0947
Fax +44(0)208 903 8657
E-mail [email protected]
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TELEPHONE +44 (0)208-900-0947
+44 (0)208-903-8657
email [email protected]
We declare that the products listed conform to the following directives and standards
89/336/EEC amended by 92/31/EEC and 93/68/EEC
BS EN 50082-1
BS EN 50081-1
PM 80R
The CE mark was first applied in 1995
B. J. Penaligon
General Manager
The attention of the specifier, purchaser, installer, or user is drawn to the fact that good wiring practice must
be observed when connecting the above equipment. Good quality connectors and screened cables must be
used for all audio connections. Twin screened cables should be used for all balanced lines.
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