ROLAND GR 500 GS 500

Page 2

APR 20 1978 GR-aoo/Gs-aoo

C IRCU IT DESCRI PT ION

FV CONVERTER

Input at (a) is a square wave sent from the FUNDAMENTAL circuit. The
waveform at (d) is produced by delaying the signal. The output from Al increases
linearly according to the time constant of R1 and Cl. It is grounded when Sl is

closed by the signal of (d). The resulting waveform is (e).

SAMPLE and HOLD is activated by signal (g) at SOus before the (e) signal level
becomes ground level. (d) is delayed by 50us compared with (a). The result is a
direct current voltage of (f), which is a voltage that is proportional to T of

the input signal.
It is then fed to LOG amp to obtain a voltage that is proportional to l/T (frequency).

The voltage becomes ~15V when the input from guitar diminishes. At this time,
SAMBLE and HOLD is activated by the gate voltage (S3, S4).

SAMPLE AM HOLD

Because the frequency is somewhat unstable,the instant a string is picked, HOLD
is activated by closing S3 after the frequency becomes stable by means of 7us
delaying. The frequency for HOLD corresponds to the initial part of picking a
string. In order to follow vibrato or choking techniques, the voltage of
Fig.5-(g) that duplicates (h) is produced through R2 by closing S4 with Gate

signal.

If the guitar output frequency changes largely to cause an octave-equivalent
voltage variation due to the change of harmonic content while 83 is open, the
VOLT PROTECT circuit is activated to lock the primary voltage (the SAMPLE and
HOLD is turned off.)

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