[sdiy] Free SSM2044, SSM2056 chips for pickup and one question about single supply VCAs

[Tom Wiltshire]

I see a lot of +/-12V bipolar power supplies used in those schematics. All the SSM2056/SSM2044 stuff, and the surrounding op-amps, for example. The only part that seems to be single supply is the LM3094. Is that a version of the CA3094 OTA?


> On 5 Mar 2024, at 23:36, hannes.janetzek--- via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Hello - now that I have your attention I would like to bring up the sad topic of the numerous synthesizers covering in 80s home-organs that are daily thrown in the trash by their inheritors.
> Ok maybe this is a specific southern Germany problem where it appears every second home had a Hohner organ which outlived their role as status symbol by now.. In the US these model were sold as Wurlitzer Omni 3000-6500 - not sure if these are regularly in classified for pickup as well.
> 
> My interest in these devices is mainly in their MEG sound-generator for which I'm currently writing an interface library. As this starts to work out nicely I wanted to throw in the filter boards and was very surprised to see that all the VCAs and most of the mixing is powered with ground to 12V. 
> Has anyone an idea what could be the reasoning or advantage of this approach? (I'm very much a beginner on the analog electronics side)   
> The schematic is on page 35 and all boards I've seen use the BA6110 version:
> https://www.synthxl.com/wp-content/uploads/2020/08/Hohner-Symphonie-D98-Service-Manual.pdf <https://www.synthxl.com/wp-content/uploads/2020/08/Hohner-Symphonie-D98-Service-Manual.pdf>
> Page 24-29 for the sound-generator - if you are curious. 
> 
> Regards
> Hannes
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