[sdiy] New long term project

[Mark Rivera]

so theoretically, your reproduction might be the mean of all originals

On Mon, Aug 10, 2009 at 10:15 PM, cheater cheater<cheater00 at gmail.com> wrote:
> The Synthacon is from the 70s. The differences between parts from the
> same batch back then were bigger than differences between models of
> parts nowadays. In other news, if it works, it works.
>
> That's all I have to say regarding subs. :^)
>
> On Tue, Aug 11, 2009 at 2:53 AM, David
> Ingebretsen<dingebre at 3dphysics.net> wrote:
>> For purely nostalgic reasons (short history below if you are interested) I
>> want to build a Steiner-Parker Synthasystem/Synthacon clone. Nyle gave me
>> schematics to his modules in 74, but (long story) they are gone. I found
>> some Synthacon schematics which nearly fit the bill but I have some
>> questions.
>>
>> While I can read a schematic, and I took upper level EE classes as an
>> undergrad and some more in grad school, I am -not- pretending to be an
>> analog guru.
>>
>> In the schematics, the matched NPN pair (2N5172, I still have a boatload of
>> them and the PNP's Nyle used from when I was building an SP in 74, but alas,
>> no FET's) is a pair of discreet transistors which were bent over and a
>> thermistor stretched across the both of them.
>>
>>        1a.     Can this pair be replaced by an SSM chip? What
>> characteristics would be important when trying to see if I can substitute
>> the SSM chip?
>>
>>        1b.     Is it your experience that making this substitution will
>> somehow change the character of the oscillation? I hated matching transistor
>> pairs back then, and don't think I'll like it any better now but will do it
>> if it will preserve some audio quality.
>>
>>        2.      Next, as I lamented, I don't have the old 2N5163 FET. I have
>> found some cross references, but am unsure again which parameters I need to
>> compare to match them. Can I just trust the cross reference charts and
>> blindly substitute the one recommended?
>>
>> For what it's worth, this is not for profit, or sale. I just want to say I
>> finished what I started as a 17 year old so many years ago.
>>
>> Thanks
>> David
>>
>>
>> ***********************************
>> Historical note:
>> Nyle was my neighbor and I don't know how, but I got his name as I was
>> becoming interested in synthesizers. I called him and he invited me over. I
>> left with a fistful of schematics and was totally inspired. Over the course
>> of the next 9 months or so, he gave me more help, demonstrations, and even a
>> summer job soldering PCB's in his shop. I only ever got a VCO and keyboard
>> working. Life happened, I was gone for a couple of years and my brother
>> threw it all out, schematics and all. All I have left are a handful of pots,
>> and some transistors.
>>
>> So, with my mid-life crisis in full gear, I am now at a point where I want
>> to finish the thing that really got me started. I want to build a true
>> Steiner-Parker synthesizer voice. VCO, VCA, VCF, EG at the least.
>>
>> I don't know what I'll do with it other than look at it and feel happy :)
>>
>> ************************************
>>
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>
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