I used TL074BCP. It has the lowest input offset voltage, 3 mV typical. It
would be better to get op amps optimized for low voltage offset, but I don't
know if these come in quad packages. I seem to be getting more error from
the resistor dividers anyway.
Only the parts around the S&H capacitor will make a difference in drift.
This means only the 4052 switch and the buffer op amp where I used the
CA3140. So there should not be any problem with sockets for the chips you
mentioned.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
would be better to get op amps optimized for low voltage offset, but I don't
know if these come in quad packages. I seem to be getting more error from
the resistor dividers anyway.
Only the parts around the S&H capacitor will make a difference in drift.
This means only the 4052 switch and the buffer op amp where I used the
CA3140. So there should not be any problem with sockets for the chips you
mentioned.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
> -----Original Message-----
> From: Richard Brewster [mailto:pugix@...]
> Sent: Monday, June 28, 2004 6:13 PM
> To: cgs_synth@yahoogroups.com
> Subject: Re: [cgs_synth] ASR drift
>
> Nice report, John! Thanks. I am just about to build my two ASR's. I
> am following your advice and using CA3140's and soldering these in, as
> well as the 4052 chips. Do you see any problem with using sockets for
> the TL071, TL074, and CD4024? It seems to me these are less critical,
> and I do like the option to change chips easily.
>
> What made of chips did you use? I didn't know there were many choices
> available for TL074.
>
> I am using:
>
> Texas Instruments: TL071ACP, TL074CN, CD4024BE, CD4052BE
> Intersil CA3140AE (DIP, could not find metal can anywhere)
>
> -Richard Brewster
>
> John Loffink wrote:
>
> >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.
> >
> >
> >
> ...
>
>
>
>
> 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
>
>
>
>