Reformatted tables below for ASCII
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
(from 10 Hz voltage
MOTM-850) clock (semitones)
(volts)
(from interval with no previous measurement
MOTM-850) (seconds) clock reading (semitones)
(volts) (volts)
(from interval with no previous measurement
MOTM-850) (seconds) clock reading (semitones)
(volts) (volts)
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
> -----Original Message-----Voltage stage with (volts) from input
> From: John Loffink [mailto:jloffink@...]
> Sent: Sunday, June 27, 2004 6:48 PM
> To: cgs_synth@yahoogroups.com
> Subject: [cgs_synth] ASR drift
>
> The question of ASR drift has come up before and I finally had my system
> in
> a state where I could measure this. I 'm calling it drift rather than
> droop
> since the voltage drifts upwards rather than downwards. As a first test I
> measured the output voltage of each stage of a dual ASR module. I
> believed
> I had matched the 1% output stage resistors to better than 0.1%, but the
> reading on OUT3 would seem to indicate otherwise. (This information is in
> table format and may display strangely if you receive in ASCII only.) The
> input clock was about 10 Hertz so there was no opportunity to drift and
> the
> output voltages were fairly constant. Measurements were taken using an
> Extech MM-560 multimeter with 5-6 digit resolution.
>
> Input ASR Voltage Difference Difference
(from 10 Hz voltage
MOTM-850) clock (semitones)
(volts)
> 2.68899 OUT1 2.69811 0.00912 10.94%Voltage time Voltage from from prior
> OUT2 2.69754 0.00855 10.26%
> OUT3 2.58515 -0.10384 -124.61%
> OUT1B 2.71238 0.02339 28.07%
> OUT2B 2.71382 0.02483 29.80%
> OUT3B 2.70626 0.01727 20.72%
>
> Next I measured the output drift of OUT1 by disconnecting the clock
> signal.
>
> Input ASR OUT1 ASR OUT1 Difference Difference
(from interval with no previous measurement
MOTM-850) (seconds) clock reading (semitones)
(volts) (volts)
> 2.68899 0 2.698 0.00901 10.81%Voltage time Voltage from from prior
> 20 2.698 0 0.00%
> 40 2.700 0.002 2.40%
> 60 2.710 0.01 12.00%
> 80 2.719 0.009 10.80%
> 100 2.729 0.01 12.00%
> 120 2.738 0.009 10.80%
>
> Finally I compared this to a MOTM-101 Sample & Hold. You can consider the
> first time interval reading as the offset error.
>
> Input MOTM OUT MOTM OUT Difference Difference
(from interval with no previous measurement
MOTM-850) (seconds) clock reading (semitones)
(volts) (volts)
> 2.68899 0 2.6673 -0.02169 -26.03%
> 20 2.6671 -0.0002 -0.24%
> 40 2.6588 -0.0083 -9.96%
> 60 2.6468 -0.012 -14.40%
> 80 2.6347 -0.0121 -14.52%
> 100 2.6226 -0.0121 -14.52%
> 120 2.6106 -0.012 -14.40%
>
> The numbers measured indicate that the output offset error of a CGS ASR is
> about the same as a MOTM-101, while the drift is slightly better. My
> circuit boards used the CA3140 for the S&H buffer amps, no sockets, and
> high
> quality poly caps, Mouser part number 1429-2473. I also believe that I
> used
> the lowest offset voltage version of the TL074. The drift seen is minor
> for
> notes at a moderate tempo, but would be significant if you want to hold
> them
> for significant lengths of time. Overall, other than the anomaly of the
> OUT3 voltage, the circuit met or exceeded my expectations, as drift is a
> common problem in sample and hold designs.
>
> John Loffink
> The Microtonal Synthesis Web Site
> http://www.microtonal-synthesis.com
> The Wavemakers Synthesizer Web Site
> http://www.wavemakers-synth.com
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> See the following URLS for the CGS Modular Synth home page:
> Main: http://www.cgs.synth.net/
> Secondary: http://otherunicorn.0catch.com/synth/
> Yahoo! Groups Links
>
>
>
>