True PRECISION 8 User manual

TRUE
systems
PRECISION 8
8-CHANNEL PRECISION MICROPHONE PREAMPLIFIER with M/S decoding and Direct Inputs
OPERATION MANUAL
Version 1.2

2
SAFETY and OPERATING PRECAUTIONS PRECISION 8
WARNING:
ELECTRIC SHOCK HAZARD. Do not remove the top cover or
rear panel. Uninsulated dangerous voltage exists within the
product’s enclosure. Refer servicing to qualified personnel. Do
not defeat the earth ground connection in the AC power cable.
Tips for eliminating ground loops are discussed in the
“TROUBLESHOOTING” section of this manual.
VENTILATION:
This product is designed to operate in an ambient temperature
environment not to exceed 50°C (122°F). Please ensure that
this unit is mounted in such a way that vents are not blocked
and ambient temperature does not exceed 50°C.
MOISTURE:
Do not operate this unit in the presence of rain, liquids or
condensing moisture. Liquid entering the vents is likely to cause
failure or performance degradation as well as the possibility of
ELECTRIC SHOCK HAZARD. Failures due to moisture
entering the enclosure will not be covered under the warranty.
DEBRIS:
Do not allow any conductive objects or debris to enter through
vents. Conductive debris entering the vents is likely to cause
failure or performance degradation. Failures due to foreign
objects entering the enclosure will not be covered under the
warranty.
MOUNTING:
This unit should be mounted in such a way that vents are not
blocked. If this unit is rack mounted in a high-vibration
environment, it may be appropriate to provide additional side-
rails or rear support in addition to normal front panel mounting.
INTERFERENCE:
This unit is designed to reject external RFI and EMI. However,
in order to maintain excellent sonic purity, certain filter
components are not installed in the standard unit. If you have
an extreme RF interference environment, please contact TRUE.
Avoid mounting the unit in close proximity to devices that emit
strong magnetic fields.

3
CONTENTS
SAFETY and OPERATING PRECAUTIONS ........................................... 2
INTRODUCTION ..................................................................................... 4
FEATURES ............................................................................................. 4
UP-AND-RUNNING IN A HURRY ........................................................... 5
INSTALLATION ....................................................................................... 7
OPERATION ........................................................................................... 8
Connections - Location and Description ...................................... 8
Controls - Location and Description ............................................. 9
More About M/S Decoding ........................................................... 11
Optional Level Indicator Modes ................................................... 12
DESIGN APPROACH ............................................................................. 13
SPECIFICATIONS .................................................................................. 13
TROUBLESHOOTING ............................................................................ 14
WARRANTY ........................................................................................... 17

INTRODUCTION PRECISION 8
4
The PRECISION 8 is designed to provide the detailed, transparent sonic
performance necessary for the highest quality direct tracking and live sound
applications. It includes a unique combination of features which make it useful as
a complete input system for modular digital multitrack tape machines (MDM’s),
hard disk recorders (HDR’s) and digital audio workstations (DAW’s). Two
sonically accurate discrete FET Instrument Inputs (“DI’s”) are available for
recording or live sound applications in which realistic, “un-plugged” sound quality
is desired. The 5-segment peak-hold level metering with selectable peak
reference allows rapid optimization of program levels between the PRECISION 8
and devices to which it is interfaced. Dual output connections provide easy
interconnection as well as the ability to act as a mic splitter.
PRECISION 8 is ideal for location recording due to its compact, 1U rack size, 8-
channel format, useful level metering and easy interconnect. The integral M/S
decoder provides creative spatial image control and can be particularly useful in
attaining an exciting stereo image with minimum effort and microphone re-
positioning.
FEATURES
• Eight highly transparent solid state microphone preamps in a 1U rack
configuration
• Built-in M/S (Mid-Side) Decoding for creative spatial image control
• Active, high-impedance Instrument Inputs ( “DI’s” ) selectable on two
channels
• 5-segment level indicators with peak-hold feature and selectable peak
reference
• Dual output connections (TRS 1/4” and DB25) provide easy interface to
MDM’s, HDR’s, DAW’s, or consoles
• Integral power supply - no wall warts or separate modules and cabling.
• Very attractive cost / channel

UP-AND-RUNNING IN A HURRY PRECISION 8
5
• Connect the AC power cord.
• Connect output signal cables between Precision 8 and your MDM, HDR,
DAW, mixer line inputs, etc. Use either individual cables with 1/4” TRS
(balanced) connectors or an 8-channel cable with DB25 connection. Wire 8-
channel cable per Figure 1 - or purchase optional interface cables from True
audio systems.
• Connect mic cables to MIC 1 through MIC 8 as needed.
• Turn on the AC power
• Set PEAK REFERENCE selector to +26.
• Set 48V and φ
φφ
φbuttons as appropriate on each channel.
• Depress the RESET button to clear Peak-Hold indicators.
• Adjust Gain controls for adequate signal level as indicated on the Precision 8
level indicators or on the level indicators of the device to which it is
connected.
TASCAM
wiring convention
If you’re using the DI’s for electric instrument input:
• Connect your instrument cables to Direct In 1 and Direct In 2 on the rear
panel. The Direct In jacks are located within the same connectors as MIC 7
and MIC 8. Simply plug your 1/4” phone plug into the center portion of the
desired connector. NOTE: DO NOT use TRS plugs for these inputs as the DI
will not function correctly.
• Set φ
φφ
φbuttons as appropriate.
• Adjust DI-1 or DI-2 Gain controls for adequate signal level as indicated on the
Precision 8 level indicators or on the level indicators of the device to which it
is connected.
If you’re using the M/S Decoder:
• Connect the cardioid or omni MID mic to MIC 1input.
113
1425
+-S+-S+-S+-S+-S+-S+-S+-S
87654321
Figure 1 - Output Connection Diagram

UP-AND-RUNNING IN A HURRY PRECISION 8
6
• Connect the figure 8 SIDE mic to MIC 2 input. Face the SIDE mic toward the
right side of the sound field (perpendicular to the axis of the MID mic). See
Figure 2.
• Depress the MID-SIDE ON button. “Left” signal is routed to Channel 1 output.
“Right” signal is routed to Channel 2 output.
• Ensure that the φ
φφ
φbuttons for Channels 1 and 2 are in the same position.
• Adjust the Channel 1 Gain control for adequate mono signal level.
• Adjust the Channel 2 Gain control to vary the image width as desired.
Figure 2
M/S microphone orientation
About the Level and Peak-Hold Indicators:
• SIG indicates that a signal is present on the channel. It illuminates when the
signal level exceeds -24dBu.
• +4 illuminates when the signal reaches normal operating level of +4 dBu.
• OL illuminates when the signal level exceeds +26 dBu, which is 5 dB below
the overload point for the Precision 8.
• The PEAK-HOLD indicators (PK,-3,-6) activate when the output signal level
exceeds the level set on the PEAK REFERENCE switch.
For example: With PEAK REFERENCE set to +26 the PK indicator
illuminates (and stays on) at +26dBu, the -3 indicator illuminates at +23 dBu
and the -6 indicator illuminates at +20 dBu.
NOTE: Only the OL light indicates impending preamp overload. The red PK
light simply indicates that the signal has exceeded the level selected on the
PEAK REFERENCE switch.
• Push the RESET button to reset the PEAK-HOLD indicators for all channels.
(It is normal for power-on transients and phantom power transients to activate
the PEAK-HOLD indicators. Simply depress RESET to clear the indicators.)
Mid
Side

INSTALLATION PRECISION 8
7
Unpacking/Repacking
We recommend that you keep the shipping carton and foam supports in the
event that the unit must be shipped at some time in the future. DO NOT package
the unit in “packing peanuts” or similar material as it will settle during shipping
and damage will likely occur.
Mounting
The PRECISION 8 is designed for conventional rack mounting, or stand-alone
mounting by use of the adhesive rubber feet supplied. Avoid locating the unit
next to equipment that emits strong electromagnetic fields. Avoid locating the
unit where moisture or debris can enter the ventilation slots. If the unit is to be
permanently mounted in a high-vibration environment, you may wish to provide
additional side or rear support to prevent possible distortion of the mounting
ears.
Ventilation
We recommend that you provide adequate ventilation so that the air temperature
surrounding the unit does not exceed 55°C (122°F). If multiple units are to be
mounted in a poorly ventilated rack or a sealed travel case, a 1 3/4” blank space
should be located after every two units (two units mounted together, blank
space, two more units, etc.).
A Word About Cables.....
Most users of the PRECISION 8 have invested much time and money in their
selection of microphones and preamplifiers. We recommend that you give some
consideration to the microphone and output cables you select, as well.
• Use high-quality, low capacitance cable. Manufacturers such as Canare,
Mogami (and others) make high performance cable of this type.
• Use cables with high-quality connectors (Neutrik, Switchcraft, etc.).
• Replace damaged connectors.

OPERATION PRECISION 8
8
Connections - Location and Description
AC Power Connection
• 120V, 60 Hz AC power only. (consult factory for other options)
• Always maintain an earth ground connection - DO NOT use isolators.
• Use delayed 0.5A fuses. NEVER use a replacement fuse of higher value.
1 Signal Ground Lift. Signal ground is isolated from earth ground in the LIFT
position. This switch will normally be in the grounded (down) position. See
“TROUBLESHOOTING” section for usage tips.
2 Balanced Output connections. Two styles of output connection are
provided: a DB25 eight-channel connector (see Figure 1) and individual
TRS 1/4" connectors (tip is +, ring is -, sleeve is shield). Both outputs may
be used simultaneously to connect to Line Inputs on mixing consoles,
recorders, etc. If both outputs are used, care should be taken to avoid
system ground loops. See “TROUBLESHOOTING” section for tips on
avoiding hum caused by grounding problems.
3 Dual-Purpose Input Connectors. Insert XLR microphone connector for
normal operation (pin 2 is +, pin 3 is -, pin 1 is shield). Insert 1/4" phone
plug for use as Direct Input for instruments. NOTE: Use only tip-sleeve
(unbalanced) phone plug for DI connection. DO NOT insert 1/4" tip-ring-
sleeve (TRS) plug here as DI will not operate properly.
4 Mid-Side microphone inputs. When using Channels 1 and 2 in the M/S
mode, the Mid mic (normally a cardioid) is connected to MIC 1 input. The
FIRE RISK
Replace with same type fuse only
M
I
Di
r
BALANCED OUT
1
2
3
4
5
6
7
8
120VAC, 60 Hz, 44 W
LIFT
WARNING- SHOCK HAZARD. Do not
open. Service should be performed by
qualified personnel. Do not expose to
rain or moisture. Do not defeat AC
ground connection.
1-8
(4-40)
S/N
A product of Sunrise Engineering
Tucson, Arizona
1 2
MIC 1MIC 2MIC 3MIC 4MIC 5MIC 6
MIC 7MIC 8
Direct In
Direct In MS
PIN 2 +
PIN 3 -
3 4

OPERATION PRECISION 8
9
Side mic (figure 8) is connected to MIC 2 input. See Figure 2 for mic
positioning.
Controls - Location and Description
1 Phase reverse selector. Output signal polarity is reversed when the φ
φφ
φ
button is depressed.
2 Phantom power selector. Phantom power (+48V) is activated when the
48V button is depressed.
3 Overload warning indicator. OL illuminates (and holds) at +26 dBu which
is 5 dB below actual overload. Depress RESET 10 to clear OL.
4 Peak-Hold indicators. These are provided to help optimize level setting
when the PRECISION 8 is remotely located from the device to which it is
connected. The PK indicator activates (and holds) at the level selected on
the PEAK REFERENCE selector 9 . The -3 indicator activates at peak
level minus 3 dB. The -6 indicator activates at peak level minus 6 dB.
Generally, the PEAK REFERENCE selector is set for the maximum level
you want to present to your mixing console, recorder, etc. Depress
RESET 10 to clear PK.
NOTE: Only the OL light indicates impending preamp overload. The red
PK light simply indicates that the signal has exceeded the level selected
on the PEAK REFERENCE switch.
5 Signal Present indicator. The SIG indicator activates at approximately -24
dBu.
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TRUE
systems
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SIG
+4
-6
-3
48V
Ø
OL
3
PK
SIG
+4
-6
-3
48V
OL PK
SIG
+4
-6
-3
48V
OL PK
ON
MID SID
E
1
2
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5
6
8
7
ØØ

OPERATION PRECISION 8
10
6 Operating level indicator. The +4 indicator activates when the output level
reaches +4 dBu normal operating level. When the PEAK REFERENCE
selector 9 is set to the -10 dBV position, the operating level indicator
activates at -10 dBV output level.
7 Mid-Side mode selector. When the ON button is depressed, Channel 1
output becomes “Left” and Channel 2 output becomes “Right”. The
Channel 1 gain control adjusts the mono signal level applied to both the
Left and Right outputs. The Channel 2 gain control adjusts the stereo
image width.
8 Gain control. This control adjusts the preamp gain over the range of 16 dB
to 64 dB.
9 PEAK REFERENCE selector. This sets the level at which the Peak-Hold
indicators 4 activate. It also changes the operating level indication 6
to -10 dBV operation when the -10 dBV position is selected.
10 Peak-Hold reset. RESET clears the peak-hold indicators on all channels.
NOTE: It is normal for the Peak-Hold indicators to activate when phantom
power is applied, when AC power is applied, or when a new setting is
made on the PEAK REFERENCE selector - simply depress RESET to
clear the indicators.
11 Direct inputs DI-1 and DI-2 are controlled by gain controls for channels 7
and 8, respectively. The gain range for the direct inputs is from -4 dB to
+44 dB.
12 AC power switch. This is the main power switch for the unit. The green
power LED indicates that the unit is on.
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+26
+22
RESET
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PEAK
REFERENCE
PRECISION
8
SIG
+4
-6
48V
OL PK
SIG
+4
-6
-3
48V
OL PK
DI 1 DI 2
+24
+20
+18
-10
dBV
ØØ
-3
9
10
11
12

OPERATION PRECISION 8
11
More About M/S Decoding:
M/S (Mid-Side) decoding is a particularly creative feature of the Precision 8.
While the M/S microphone technique has been around for many years, the
opportunity to use it is frequently limited by the need for specialty microphones
and/or decoders.
What is M/S?
It is a stereo microphone placement technique which uses a center, forward-
facing omni or cardioid mic (Mid) and a side-facing figure 8 mic (Side). The
signals from these two mics are passed through matrix circuitry which combines
them in particular phase and level relationships to produce a stereo L and R
output.
Mid
Side
What good is M/S versus the typical XY microphone placement?
Originally, M/S was used because it provided a stereo signal with good mono
compatibility. While this is not very interesting for contemporary stereo CD’s, it is
still valuable for broadcast and film sound production. But there is another
significant benefit: varying the gain of the Side mic in relation to the Mid mic
causes a variation in the stereo image - from none, to extreme separation. It is
not necessary to change the angle or position of the microphones in order to
change the stereo image. This feature can really speed up the time-consuming
process of finding a “sweet spot” that provides both good tonal quality and good
imaging.
What are the best applications for M/S?
M/S does an excellent job of capturing the natural sonic perspective of acoustical
ensembles.
• Orchestral and choral recording: use an M/S pair for the central array
(channels 1 and 2). Use the remaining channels for side fill, solos, or for
highlighting individual instruments or voices.
• Drum kits: use an M/S pair for drum overhead micing.

OPERATION PRECISION 8
12
• Vocal and instrumental ensembles: use M/S to give realistic perspective to
backup vocals or instrumental groups.
• Individual instruments or vocals: try M/S on acoustic guitar and in situations
where you wish to capture room ambience.
• Broadcast/film sound: use M/S to capture audience noise or background
ambience. M/S can also be used in TV and film work to match the sonic
image width to the visual image width.
Optional Level Indicator Modes
The Peak-Hold level indicators can operate in two modes. As supplied, only the
OL and PK indicators will hold (after they are activated) until RESET is
depressed. An optional mode is available which causes the -3 and -6 indicators
to also hold until RESET is depressed. This mode can be helpful in live sound
and recording applications where the PRECISION 8 is remotely located from the
device(s) to which it is connected. Jumpers inside the unit select this optional
mode. If you wish to configure the unit for this mode, proceed as follows:
WARNING - ELECTRIC SHOCK HAZARD. Dangerous voltage exists inside the
enclosure of this product. Refer servicing to qualified personnel. NEVER open
the product enclosure while the AC power cord is attached.
• Disconnect AC power cord.
• Remove the twelve screws securing the top cover to the enclosure. Remove
the cover.
• Locate the eight upright printed circuit boards along the front panel.
• Select level indicator mode by setting jumpers (J2) as shown below.
J2 J2
Normal Mode Optional Mode
(OL, PK remain on) (OL, PK, -3, -6 remain on)
• Replace cover and secure with twelve screws. Make sure no tools, loose
hardware, debris, etc. remain in the unit prior to attaching the cover.

DESIGN APPROACH PRECISION 8
13
PRECISION 8 uses a high-voltage composite architecture with discrete matched
transistors plus premium integrated circuits. It offers very low noise and distortion
as well as high headroom. The totally balanced dual servo design eliminates
nearly all capacitors in the audio path and is DC-coupled at the output. Many
components are military grade and are hand-matched for optimum performance.
Critical devices have been selected on the basis of extensive listening tests as
well as engineering tests. All this results in a very detailed and transparent sound
quality that challenges even the most esoteric (and expensive) mic pre’s.
The discrete FET Direct Inputs are also of a high voltage design and offer very
high input impedance. This produces excellent detail, articulation and
smoothness from electric instruments.
SPECIFICATIONS typical performance at 25°C ambient
Gain (microphone): +16 to +64 dB
Gain (direct input): -4 to +44 dB
Frequency Response (gain=40dB): 1.5Hz to 500kHz (+0/-3 dB)
Maximum Output Level: +31 dBu
Maximum Input Level: +15 dBu
Input Impedance (microphone): 5.5 Kohms
Input Impedance (direct input): 2 Mohms
Noise (Rs=0 Ohms): -132 dB e.i.n. (20Hz to 30kHz)
Slew Rate: 40 V/us
CMRR (CMV= +10 dBu): 80 dB
Crosstalk: -130 dB
THD (+26 dBu, 100 kOhm): .0008% (20Hz to 30kHz)
Power Consumption 44 watts

TROUBLESHOOTING PRECISION 8
14
No signal output. Main power switch
is on, but green power LED is off.
• Check AC power source and
cord.
• Check fuse (pull fuse drawer
under power cord inlet)
No signal output. Main power switch
is on and green power LED is on.
• Check status of phantom
power.
• Check continuity of mic and
electric instrument cables.
• Check continuity of output
cables.
Output signal is distorted. Outputs
are connected for balanced
operation.
• Make sure gain is adjusted so
that the OL indicator does not
activate during the audio
program.
• Make sure the high output
capability of this unit is not
overloading the device or
monitoring system to which it
is connected - set PEAK
REFERENCE selector to
match capability of device or
monitoring system, then
adjust gain according to
indications on the Peak-Hold
LEDs.
• Check continuity of output
cable.
• Make sure outputs are not
connected to a load
impedance of less than 600
ohms.
Output signal is distorted. Outputs
are connected for unbalanced
operation.
• Make sure the minus (-)
output signal pins are
connected to the shield - not
left unconnected.
• Check troubleshooting tips for
balanced operation (above).

TROUBLESHOOTING PRECISION 8
15
Hum can be heard in the audio
program.
• Set ground lift switch to LIFT.
• Check continuity of output
cables (particularly shields).
• Disconnect shields on one
end of output cables. Set
ground lift to the grounded
position.
• If both outputs (TRS, DB25)
are in use, try disconnecting
shields on DB25 only, or TRS
only.
Channel 1 signal can be heard in
Channel 2 output - and vice versa.
• Check status of Mid-Side ON
selector. It should be “out” for
separate-channel mode and
“in” for M/S mode.
Channel 2 seems to have no output
when used with Channel 1 as a
stereo pair
• Check status of Mid-Side ON
selector. It should be “out” for
separate-channel mode and
“in” for M/S mode.
• Make sure the φ
φ φ
φ selectors for
both Channels 1 and 2 are in
the same position.
In M/S mode the stereo channels
are reversed (Channel 1 is Right
and Channel 2 is Left)
• Make sure the front of the bi-
directional “side” mic is aimed
90 degrees to the right of the
axis of the “mid” mic.
In M/S mode the stereo channel
phasing is incorrect
• Make sure the φ
φ φ
φ selectors for
both Channels 1 and 2 are in
the same position.
Electric instrument connected to a
Direct Input does not produce a
signal or signal is distorted.
• Check continuity of electric
instrument cables.
• Check the batteries or AC
power source of any “foot
pedal” effects processors
connected to the Direct Input.
• Make sure that the instrument
cables have standard tip-
sleeve 1/4” phone plugs. - DO
NOT use TRS plugs.

TROUBLESHOOTING PRECISION 8
16
RF interference can be heard in the
audio program
• Make sure that mic cables are
of good quality (Mogami,
Canare, etc.) and that the
shield is properly connected.
Avoid excessive length.
• Make sure that earth ground
connection is maintained via
the AC power cord - DO NOT
use an isolator.
• Contact TRUE for optional
extended RF filter modifi-
cations.

WARRANTY PRECISION 8
17
TRUE systems warrants that the PRECISION 8 will be free from defects in
material and workmanship, when properly installed and used according to
instructions in the Operation Manual, for a period of one year from the date of
purchase.
Components proven to be defective will be repaired or replaced at the option of
TRUE systems, providing that the buyer gives prompt notice and satisfactory
proof of defect or failure. Buyer must obtain a Return Authorization (RA) number
prior to returning a product and must prepay freight charges to return the product
to TRUE systems. TRUE systems may require proof of the purchase date in the
form of a dated copy of the original retail invoice. Repaired products will be
returned to the owner freight prepaid within the Continental United States.
Outside Continental United States, products will be returned freight collect.
TRUE systems reserves the right to inspect product submitted for warranty
repair. This warranty will not apply if, in the opinion of TRUE systems, the
product has been abused, misused, misapplied, or has been damaged by an
accident. This warranty will not apply if the product is damaged due to
unauthorized repairs or modifications. This warranty will not apply to cosmetic
damage incurred due to normal handling and use.
TRUE systems EXPRESSLY DISCLAIMS ALL IMPLIED WARRANTIES, INCLUDING, BUT
NOT LIMITED TO, WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE.
IN NO EVENT SHALL TRUE systems BE HELD RESPONSIBLE FOR INCIDENTAL OR
CONSEQUENTIAL DAMAGES OR LOSSES RESULTING FROM THE USE OF THIS
PRODUCT.
TRUE systems is a product line of Sunrise Engineering and Design, Inc.
8175 E. Slate Ridge Drive
Tucson Arizona 85715
520-721-2735 (voice)
520-722-4057 (fax)
[e-mail]