Inovonics 375 User manual

INSTRUCTION MANUAL
MODEL 375
TAPE RECORDING ELECTRONICS
August, 1975
0-
INOVONICS
1630 DELL AVE ., CAMPBELL, CALIF 95008
INCORPORATEO
(408) 374·8300

SECTION
1.0
2.0
3.0
4.0
TABLE OF CONTENTS
PAGE
GENERAL INFORMATION ........ . 2
INSTALLATION AND USE . . . . . . . . 7
OPERATIJN AND FUNCTIONAL DESCRIPTION
9
ALIGNMENT AND MAINTENANCE
· 17
PARTS LIST.
· 23
SCHEMATICS.
• 28

SECTION 1.0 GENERAL INFORMATION
The lnovonics 375 is a compact, up-to-date magnetic recording elec-
tronicspackage, completely self-contained with integral power supply.
Available in several versions, the
375 is equally well suited to new
installations, or to improve the performance and reliability of older
professional tape recorders.
The 375 is delivered with proper interconnect cabling for whatever
tape
transport is specified for use with it. When no specification
is made, the unit is supplied with cabling for Ampex 350/351 series
mqchines.
Among the features incorporated are:
Calibrated positions
on Record and Reproduce gain controls.
Provision for remote switching of all monitor and equalization
functions,
and solid-state switching to eliminate contact noise
problems.
3-speed equalization to
accommodate any combination of NAB and
IEC characteristics.
Harmonic and phase distortion nulling circuits.
Able to accommodate a wide variety of original-equipment and
replacement heads.
Optional
SYNC Reproduce Amplifier with independent equalization
and automatic SYNC-INPUT monitor transfer switching (-03 version
only).
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1.1 SPECIFICATIONS
NOTE: Performance of a magnetic recording system is limited in part
by the heads and tape employed. ihe Inovonics 375 is intended both
for upgrading older recorders in broadcast
and similar applications,
as well as for new studio installations. Hence two sets of specifi-
cations are given, each with respect to the heads, tape and standards
generally in use in each
installation situation. A third group con-
tains those specifications which are not application oriented.
1.1.1 Specifications derived using 3M 206 tape and a Taber full track
replacement
head assembly on an Ampex 351 t ,ansport.
Frequency
Response (in Hz)
15
; ps
+2dB 20
20k
7.5 ips
+2dB 20
15k
3.75 ips
+3dB
20
-
8k
Signal-to-Noise Ratio (in
dB, referred
to a "peak" record 1evel
6dB
above 200nW/m,
or approx. 3dB
below 3%
THO; 20Hz - 20kHz)
OVERALL
STANDBY
u'wtd. NAB wtd. u'wtd.
NAB wtd.
15 ips -67 -76 -76 -87
7.5 ips -69 -77 -76 -86
3.75 ips -66 -74 -72 -83
Erase/Bias Frequency
100kHz
Erasure
70dB erasure of 500Hz signal recorded 3dB below tape
saturation.
--
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Recorded
Distortion (at 15-mil wavelength bias
peak - typical)
LIN out LIN in
Operating
Level .45%
.02%
6dB above Op Level
2%
.015%
8dB above Op Level
3% .02%
10dB above Op Level
5.5%
2.2%
1.1.2 Specifications derived using 3M 250 tape, an Operatinq Level
of 320nW/m and Nortronics 9227 (erase), 9203 (record) and 9213 (repro-
duce)
heads -70-mil track width format, typical of multi-track appli-
cations.
Frequency
Response (in Hz)
30 ips
+2dB
60 - 22k
(SYNC reproduce
response essen-
15
ips +2dB
30 - 22k
tially identical
7.5 ips +2dB 20 ~ 16k
to normal overall)
Signal-to-Noise Ratio (in dB, referred to approx. 640nW/m or 3% THO;
20Hz - 20kHz)
OVERALL
SYNC STANDBY
u'wtd. wtd. u'wtd. wtd. u'wtd. wtd.
30 ips
-71 -78 -71 -80 -80 -87
15 ips -67 -77 -67 -77 -75 -86
7.5 ips -67 -76 -67 -77 -74 -85
Erase/Bias Frequency
250kHz
Erasure
lOdB erasure of 500Hz signal recorded 12dB above Operating
level, or approximately 3dB below tape saturation.
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Recorded Distortion (at IS-mil wavelenth bias peak - typical)
LIN out
LIN ,in
Operating Level
.5%
.15%
3dB above Op Level
1%
.3%
6dB·above Op Level
2.5%
.8%
1.1.3 Specifications Independent of Application
Equalization
3 speed with pushbutton
selection, automatic switching be-
tween INTER and LOW when transport provides closure. Accom-
modates NAB, lEe (or mixed) characteristics for 3.75 through
30 ips operation.
Amplifier Distortion
Record:
~.1% THO
<:.25% THO
Reproduce:
<:.1%
THO
~.5% THD
at Op Level
25dB above Op Level
at Op Level
at +24dBm Line Output (clipping level +25dBm)
Input '
Sensitivity:
Impedance:
-20 to +8dBm (-8 to , -f : 8dBm
input transformer)
10K bridging
with
-01 option
Outputs Line
Out~ut:
Headphones:
feeds 600 line, balanced
terminated
or not, at +4
Front panel jack
or
or
unbalanced,
+8dBm for Zero-VU.
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Panel Controls
RECORD GAIN (with pre-set CAL position)
REPRO LEVEL (with pre-set CAL position)
MONITOR: selects between INPUT, REPRO and SYNC (-03 versions)
SAFE/READY
RECORD
EQUALIZATION: manual selection of HIGH, INTER or LOW.
POWER
Power Requirement
105-130 VAC (230V available) SO/60Hz, .3A (plus transport)
Size
and Shipping Weight
x 19
11
3~1I X 10"
15 1 bs
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SECTION 2.0 INSTALLATION AND USE
2.1 Upon receipt of the equipment, inspect for shipping damage.
Should any be observed, notify the carrier immediately; if not,
proceed
as outlined below. It is suggested that the original ship-
ping carton
and materials be saved for possible future reshipment.
2.2
The 375 is packaged to mount in a standard 19-inch equipment
rack, requiring
3~-inches of panel space. When replacing original
electronics in an overbridge above the transport, it may be necess-
ary to
drill and tap an additional two holes to accommodate the 375
panel.
2.3
The signal, head and transport connectors are directly compati-
b'~ with Ampex 350, 351 and 354 equipment. Units ordered for use
with other transports- or for use in stereo pairs are supplied with
appropriate interconnect cabling.
2.4 Unless supplied otherwise to special order, units intended for
mono or stereo installations are delivered properly aligned for use
with 3M 206 tape at an operating level of 200nW/m, with Ampex 351-
type heads (1. 5mHy erase, 5-10mHy record ,and ·lHy reprod'lce) and
100kHz bias. Units for multi-track use normally operate with lower
inductance
heads (O.5mHy erase, 4-5mHy record, and 400mHy reproduce),
utilize 250kHz bias, and incorporate the optional SYNC reproduce amp-
lifier: Heads with inductances other than those suggested above can
be accommodated. Section 4.1.4.2 outlines the necessary changes.
2.5
As delivered, the 375 is calibrated to operate at a +4dBm signal
level. Should operation at +8dBm be necessary, clip the jumper shun-
tingthe 4.7K resistor near the line output connector and recalibrate
as described in paragraph 4.1.2.8.
2.6 The low source impedance of the 375 line output results in only
about
~dB level change from an unloaded to 600 ohm loaded condition.
._.
-7-

The 375 should, nevertheless, be connected to its intended load prior
to final calibration.
2.7 Even with the optional input isolation transformer option sup-
plied (-01 version
only), the 375 input impedance is 10K ohms or
greater. Should the equipment feeding the 375 require a terminating
load, a
600-ohm resistor should be placed in parallel with the 375
input.
2.8
No provision for meter indication of bias or erase current is
made, as the inherent stability of the circuitry is greater than that
of the heads and meter at bias frequencies.
2.9
When two Ot' more 375's are employed in dual or multi-track ap-
plications, the interconnecting cablinq supplied delivers AC power to
all units and to the transport, if it derives power from the elect-
ronics. The cabling also "slaves" all erase/bias amplifiers to a
single oscillator, thereby avoid-ing bias "beats" or the necessity of
synchronizing two or more oscillators.
-8-

SECTION 3.0 OPERATION AND FUNCTIONAL DESCRIPTION
3.1 OPERATION
3.1.1 The RECORD GAIN and REPRO LEVEL controls are provided with a
detented
CAL position at full CCW rotation. They are normally left
in these positions except for temporary correction for an improperly
recorded tape
or abnormal line level. Range is adequate to record
from a -20dBm line level (-8dBm with optional input transformer) and
to produce normal line output from a tape under-recorded by 10dB.
3.1.2 The MONITOR buttons determine whether the line amplifier will
derive
its si9~al from the incoming program (INPUT), the reproduce
head (REPRO), or in versions with -03 option, the record head (SYNC).
When any button is only slightly depressed to release all three to
their "out" position, the monitor selection is transferred to the
rear panel REMOTE connector. On versions with the -03 option, mon-
itor is automatically switched from SYNC to INPUT when entering the
record
mode.
3.1.3 The alternate-action SAFE/READY switch, when depressed, per-
mits the
375 to enter the record mode when the transport is in "record".
When this button is "out", the 375 will not enter the recoY'd mode,
thereby preventing accidental erasure of a tape or that track of a dual
or mult-track recording.
3.1.4
The RECORD button places the transport in the record mode. The
button will not illuminate, though, nor will ~he 375 go into "record"
unless the
SAFE/READY button is depressed. In dual or multi-track in-
stallations, depressing any RECORD button will place the transport in
the record
mode; only those 375
1 s in "ready" wi.l record,
however.
3.1.5 The EQUALIZATION buttons select record and reproduce equal-
lizationappropriate to the transport speed employed. Three independ-
ent
sets of equalizers are provided, although most transports are only
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