[sdiy] Yamaha CSY-2 solo synthesizer

Doug Terrebonne dougt55 at yahoo.com
Tue Nov 9 23:42:38 CET 2010


Very interesting. I have a SY-1 and SY-2 and always assumed the versions they 
stuffed into their organs were identical...

Doug



----- Original Message ----
> From: Richard Atkinson <rga24 at cantab.net>
> To: synth diy <synth-diy at dropmix.xs4all.nl>
> Sent: Tue, November 9, 2010 7:16:51 AM
> Subject: [sdiy] Yamaha CSY-2 solo synthesizer
> 
> This email may be of particular interest to anyone who has studied the first 
>and second generations of Yamaha synthesizer, namely the SY-1 / SY-2 / GX-1 
>synthesizers with epoxy potted NE series modules in the first generation and the 
>CS series of synthesizers with IG series chips in the second generation.
> 
> It turns out there is an intermediate generation of Yamaha synthesizer between 
>these two generations. I found this when looking inside my newly acquired Yamaha 
>CSY-2 organ yesterday. This is a later version of the CSY-1 organ, which has 
>been featured in a few web pages and Matrixsynth articles and which contains the 
>same epoxy potted NE series modules as the GX-1.
> 
> I took the lid off my Yamaha CSY-2 yesterday with a friends's help. The insides 
>of my CSY-2 were rather dirty, having played host to a number of spiders and 
>other objects over the years. There was evidence of damp damage on the base of 
>the machine; it has clearly been kept on a damp surface at some point for quite 
>a while.
> 
> It turns out the CSY-2 is very, very different internally from the CSY-1.
> Whereas the CSY-1 is a fully discrete design with many circuit boards, some
> of them held vertically in a rack frame, the CSY-2 has the first signs of
> integration.
> 
> In particular, the auto bass chord circuit board (ABC CSY-2) has two large
> YM chips on it and there is another board with another large YM chip. The
> function of the auto bass chord system on this organ is quite different
> from the CSY-1, and this would seem to explain why. There is no rack of
> vertically mounted boards; there are much fewer boards and these are all
> mounted horizontally.
> 
> Of particular interest is the solo synthesizer section mounted on the
> underside of the top panel of the organ. Like my CSY-1, the solo
> synthesizer boards in my CSY-2 are very clean, much cleaner than the rest
> of the instrument. This no doubt has to do with being mounted upside down,
> gravity being in its favour.
> 
> The CSY-2 does not however contain either of the versions of the CSY-1 /
> SY-1 solo synthesizer circuits. It's a completely different, much more
> integrated version of the solo synthesizer. The boards are not named SM1,
> SM2, SK, SP1 and SP2 as in the SY-2. Instead they are named VCO, VCF, VCA,
> FEG, AEG, SK and SP.
> 
> VCO is the only board that contains any of the old NE series modules. It has 
>the VCO-III module as seen in later versions of the CSY-1, SY-1 and all SY-2s.
> 
> The VCF board has four ICs on it, all by Rohm. Two BA626s and two BA627s. I
> have been unable so far to identify what these are but what is most
> peculiar about this is that the organ features neither the older NE module
> based filters, nor the IG chip based filters of the CS synthesizers and the
> later Electone organs, but a generation in between. This is the only
> example of this generation of Yamaha synthesizer filter I have ever seen,
> and as far as I'm aware it's completely undocumented on the internet.
> 
> VCA, FEG and AEG contain standard parts, CA3080 OTAs in metal can packaging
> and so on. The VCA board is self explanatory, the FEG board is for the
> filter envelope and the AEG board is for the amplifier envelope. No NE
> modules here, in particular no VCF-EG or VCA-EG modules. This is the only
> example of these Yamaha envelope generators I have seen, again completely
> undocumented on the internet as far as I know.
> 
> The remaining boards, SK and SP, seem to be the same as in the older
> machines. They are for the gate and trigger pulse recovery and for the
> presets.
> 
> Sound-wise, it behaves much like a cross between the two generations. The 
>oscillator definitely has the same timbral qualities as an SY-2, but the filters 
>are much, much cleaner. I wouldn't go so far as to say they sound like CS series 
>IG chip filters, but they are certainly more well behaved than the highly 
>distorting diode bridge filters in the NE series epoxy filled modules.
> 
> Richard
> 
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