ITT - Index of

SAH190
MOS TONE GENERATOR
Table 1: The divider characteristics of a twelve
tone generator circuit according to Fig. 2.
Cycle duration Tn of Jitter Mean Relathe
output frequen- divider tive
cies f, to flO as a ratio fremultiple
of the cycle
quency
duration T g of the error
clock frequency
ppm*
T,-176T 176 +29
352T g 352 + 29
T.=209/210Tg n g 209.28730 +14
418:/419T. 1Tg 418.59460 +14
T,=248/249/250Tg 2Tg 248.89408 -1
497/498/499Tg 2T g 497.78816 -1
T'0 = 294/295/296/
297/298Tg 4Tg 295.98215 -17
590/591/592/
593/594Tg 4Tg 591.96430 -17
T,=186/187Tg 1Tg 186.46486 +25
372/373Tg 1Tg 372.92973 +25
T,=221/222/223Tg 2Tg 221.74200 +10
442/443/ 444T g 2T g 443.48400 + 10
T8=262/263/264/265Tg 3Tg 263.69319 -6
526/527/528/529Tg 3Tg 527.38638 -6
Tu=311i312/313/
314/315/316Tg
625/626/627/
628/629/630Tg
T,=1971198Tg
395/396Tg
T,,= 234/235/236T g
469/470/471Tg
5Tg 313.58109 -21
5T g 627.16220
1Tg 197.55102
1T g 395.10204
2T g 234.92554
2Tg 469.85107
-21
+17
+17
+2
+2
T,=278/279/280/281Tg 3Tg 279.37091 -14
557/558/559/560T g 3T g 558.74182 -14
T,,=330/331/332
333/334/335Tg 5T g 332.22486 - 29
663/664/665/
666/667Tg 4Tg 664.44973 -29
*1 ppm 1 part per million, that is 1 X 10 6
The Clo.ck Generator for the SAH190
A two-phase clock generator emitting two clock
pulses t1 and t2 which do not overlap, and
the amplitudes of which are - 20V is required
for driving the SAH190. The two clocks may
overlap at the most in the range from 0 to -3V,
and the duration of the negative flat tops of
the pulses must not fall below 0.2J.ts if reliable
operation of the SAH190 is to be ensued see
the oscillogram in Fig. 11.
'/\
" ,\ J
~ j \ J \ J 1\
Fig. ii-Oscillogram of the clock signals 11
and't2 in the circuit of Fig. 12. Vertical: 10V/
division. Horizontal: O.2J.tsldivision.
An LC oscillator with a pulse shaping stage
connected in series after it, as shown in Fig.
12 is proposed as the clock generator. The
oscillator consists of transistors T3 and T4 and
the frequency-determining tank circuit C1, L 1.
Frequency modulation for the vibrato effect is
generated by modifying the operating points
of the oscillator transistors. With a vibrato
voltage-of 15V peak-to-peak, vibrato of ± one
quarter tone can be obtained.
When designing the clock generator the coil
for convergence adjustment in colour television
sets proved useful as the oscillator coil. This
coil has a knob which can be used for chang_
ing the overall pitch. For this purpose the coil
is mounted in the control panel of the organ
and linked with the oscillator circuit via
screened cables with a maximum length of
approximately 25cm. If it is not necessary for
the oscillator frequency to be modified within
wide limits, any other coil with a lower inductance
variation can be used. When the highest
octave is to be c' to b' the fi rst type is to
be wound with 80 turns 0.3mm ",enamelled
copper wire, and the second coil with 72 turns
0.1 mm ",enamelled copper wire.
To adjust the pitch from the console, it is
possible for instance to connect a small variable
capacitor with a final capacitance of approximately
50pF in parallel with the capacitor
C1, located among the controls of the
organ and connected via screened cables with
a maximum length of 25cm to the oscillator
8-66