The
Professional-Grade Performance of Three-Head Design
Independent-Suspension
heads
With their superior
performance and enhanced operating flexibility three-head machines are obviously
attractive. But there are several problems particular to the design of
three-head cassette decks. For example, it is no simple matter to fit there
heads into the cassette shell's openings. Fitting each head into a different
opening raises the problem of tape skewing between the heads which causes
azimuth error. Even slight azimuth error can result in audible high frequency
losses. Thus, decks that insert each head through its own opening often require
the user to re-adjust head azimuth before recording each side of each cassette.
However, placing the
record and playback heads through the same opening can cause improper contact
with the cassette's pressure pad, as well as interference between the two
heads. In this configuration, bias leakage and magnetic cross-feed can degrade
the monitored sound during recording when both heads are active. Sony with its
long experience in three-head recording,, has solved these problems with a
unique, new head configuration;
Independent
Suspension.
Unlike the vast
majority of three-head cassette decks, the Sony TC-K81 (and TC-K71), with
Independent Suspension, use physically distinct, individually-shielded record
and playback heads. Separate shielding reduces magnetic cross-feed and bias
leakage dramatically. While physically distinct from each other, both the
record and playback heads still fit into the cassette's center opening, in
fact, the two head gaps are intentionally brought close together - less than
3,1 milimeters apart. As a result, both gaps make proper contact with the
cassette's pressure pad. And the gaps are so close together that skewing error
is reduced to the vanishing point. There is no need for user-adjustable
azimuth.
Sony's
Independent-Suspension three-head design ensures that the frequency response
of these machines is not only extended, but also extremely stable. You can
expect good result on each cassette, from the beginning of the tape to the end,
on side A as well as side B. Of course the record and playback heads of these
decks boast Sony's Sendust and Ferrite head formulation (as described for the
TC-K44 and K61). The S & F design provides high permeability low specific
resistance. Un supressed maximum flux density and exceptionally long service
life.
Bias and Record
Calibration
The TC-K81
incorporates even more sophisticated adjustments for each tape formulation.
Bias and record calibrations permit the K81 to be handtailored to suit the
requirements of each tape. Built-in test-tone oscillators, the monitoring
capability of the three-head format and the deck's own Peak Program Meters
combine to make calibration quick, simple, and precise.
The bias calibration
procedure of the TC-K81 establishes flat frequency response by obtaining equal
output for a 400 Hz and an 8000 Hz test tone. These tones are recorded and
played back together, and displayed on the deck's meters. To make the
adjustment, you simply turn the Bias Cal Knob for equal readings on both
meters. Because switching to the calibration mode automatically increases meter
sensitivity, the adjustment is accurate to within 0,5 dB.
The result is flat
high-frequency response and low-distortion recording with any tape you use. In
addition, the K81 provides record level calibration with the 400 Hz tone. You
make adjustments with the left and right controls, setting the meters to the Rac
Cal reference marks. When set, Dolby noise reduction tracking in encode and
decode will be precise, resulting in accurate high-frequency sound during both
loud and soft passages.
Closed-Loop Dual
-Capstan drive
Conventional
cassette decks use a single drive capstan, engaging a single pinch rolle; to
drive the tape. While single-capstan drive often yields good performance,
dual-capstan drive - using two capstans and two pinch rollers - is a superior
system. The TC-K81 (and TC-K71) incorporate dual-capstan drive. Both capstans are
driven from the BSL motor by the same belt, in a closed-loop configuration. The
capstans are located on either side of the head assembly, for better control of
tape tension, and minimum modulation noise.
Combining this drive
system with a separate spooling motor, and two over-size anti-resonant
flywheels, the K81 (and K71) achieve
clear, unwavering sound, even during sustained notes.
Specifications
Drive Type: Belt
Servo Type: Frequency
Number of
Motors: Two
Motor Type: Capstan: BSL; Spooling: High-Torque
Number of
Heads: Three
Record/Play Head
Type : 2 x S&F
Erase Head Type
: 2-Gap Ferrite
Record Level
Calibration: 400 Hz osc.
Fast-Forward/Rewind
Time (C-60): 80 sec.
Wow and
Flutter: 0,04% (WRMS), 0,12% (DIN 45507)
Frequency Response
(±3 dB, Re: -20 dB)
Metallic Tape : 30 -
18,000 Hz
FeCr Tape : 30 -
18,000 Hz
EHF Tape : 30 -
17,000 Hz
SHF Tape : 30 -
15,000 Hz
Re: 0 dB Metalic
Tape : 30 -13,000 Hz
Signal-to-Noise
Ratio ( Dolby NR Off, Re: 3% THD, Peak, IHF-A Wtd.)
Metallic Tape : 60
dB
FeCr Tape : 60 dB
EHF Tape : 58 dB
SHF Tape : 54 dB
Improvement with
Dolby NR On : Up to 5 Db at 1 kHz,
10 Db at 5 kHz or above
Total Harmonic
Distortion (1 kHz, Re: 0 db Record level)
Metallic Tape : 0,8%
FeCr Tape : 0,8%
Crosstalk (1 kHz,
tracks): 60 dB
Separation (1 kHz,
channels): 35 dB
Erasure (400 Hz,
incl. Metallic Tape): 60 dB
Bias Frequency: 105 kHz
Meter Range: -40 dB, +8 dB
Line Input
Sensitivity/Impedance: 77,5 mV/50 k ohms
Mic Input
Sensitivity/Impedance: 0,25 mV/Low
Line Output
Level:
Fixed : 435 mV
Variable : 27,5 - 435 mV
Line Output Load
Impedance Nominal/Minimum: 50/10 k ohms
Headphone Output
Level: 4,9-77,5 mV
Nominal Headphone
Impedance: 8 ohms
Power
Requirements: AC 120/240 V 50/60 Hz
Power
Consumption: 26 W
Dimensions (W x H x
D): 430 x 130 x 290 mm (17" x
5-1/8" x 11-3/8")
Weight: 6,3 kg (13 lbs 14 oz)
