Tape Speed Deviation; Wow And Flutter; Frequency Response; Total Harmonic Distortion Factor - Akai 1700 Service Manual

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IIOW TO NIICNSURE
DESIGNATED VALUES OF SPECIFICATIONS
TAI'I] SPDtrD
DEVIATION :
\{OW AND
FLUTTER :
Reco.d the l,000cps. sine curve of
the tap€ speed at rating sp€eds with
a standa.d sound recorder (AMPEX
351A, for instance) which is little af-
fccted by lhe tape sPecd deviation
tlrroughout the whole i€ngth of the
tape. Put th;s standard taPe on th€
tapc recorder unde. test for playing
back, and nreasure its outPut bY a
couDte., then codvert thc value into
rating power frequeDcy to cvaluate
the tape speed dcviatior.
Fo. a rough measurement, the taPe
spe€d deviation can also be measured
with a testing tape for speed by astop
Playback thc 3,000cps sianda.d tape
that guarante€s wo\d and flutter with-
h 0.07 p€r cent, aid read the effect;ve
valuc otr wow mere.
Since the sedsibility of wow and flut-
tcr frequency bclow 2cps and above
5 cps. d.ops, the frequency over 5cps.
i s p u t t o 3 d b / O C T c i r c u i t , a n d t h €
frequency bclow 2.ps. is put to 6db/
OCT circuit for adjustment This ad-
justed value is called auditory com-
Connccr to thc input tcdninal of the
rcco.dcr, .ccord a sine curve swecp
f.equency at 100 cps -10
db. from
Audio frequency Oscillator.
Adjusl toDe volume to flat, playback
the tape by .onnectidg VTVM tosp€-
aL€r out put then read the frequency
response to adjusl a maximum devia'
}.RLqUI]NCY
RESPONSE:
(OVI]RALL
I'REqUENCY
RESPONSE)
TOTAL HARMONIC
DISTORTION
FACTOR:
Provide the input terminal ol the
, e c o r d . r w i t h 1 . 0 0 0 . p s . ' : n F , u r v F
signals and .ecord these signals on a
recording tape at the zero level on the
recorder's VU mete.
Then playback the siSnals under the
no.mal recording condit;on to meas-
u.c the distortion factor by an oscil
lator.
Remove the recording tapc
from the recorder, then read the noisc
lcvelon the oscjllator to 8ct the requ;r-
€d dhtortion factor by the following
formula:
d 0 : d - d l d 2
d 0 . . r e q u i r e d
d...overall distortion factor
d l . . . n o i s e l € v e l
d 2 . . . d i s t o . t i o n f a c t o r o f t h e o s c i l l a -
to. uscd
SICNAL TO
NOISE:
Playback the sine curve, 250 cPS. tape
rccorded on a standard recorder on
th€ reco.der to measur€ the voltag€
Removc the taPe, then measure the
noisc level under the same condition
Calculate the ratio between the two
i n d € c i b e l .
OUTPUT:
I'layback on the recorder thc 1,000 cps.
sine curvc tape which was record€d
at the zero VU level on a standard
recorder. T€rDinatc the test recorder
with €ight ohms.
Square the voltag€ rcading, then di
vide the figure by eight ohms to get
thc r.m.s. Powcr output.
CROSS TALK:
Record 1,000 cps. signal at +3VU
on
the third tack, then playback this
signal through a l,000cps. Band Pass
Filter.
Compare the output of tracks I and 3
in decibels.
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