[sdiy] Yamaha CSY-2 solo synthesizer

Richard Atkinson rga24 at cantab.net
Wed Nov 10 12:21:24 CET 2010

You can summarise the differences as follows:

CSY-1 and SY-1 are the most similar. I believe they are contemporaneous. 
Both solo synthesizers exist in two forms, one with a single, large SM 
board containing all the NE modules, and a later version with SM1 and SM2 
boards, one containing VCO-III, VCF-LPF, VCF-HPF and EG-VCF, the other 
containing EG-VCA.

Incidentally the earlier version has a VCO-II module rather than a VCO-III 
module, this is documented in the SY-1 service manual. My CSY-1 service 
manual only mentions the earlier version; there is no mention of the later 
version, but these are known to exist because there are pictures of one at:


They both feature two effects called Attack Bend, one for Pitch and one for 
Tone. These are both decay envelopes which affect the VCO frequency and VCF 
frequencies respectively. On the CSY-1 organ both effects are preset, it's 
simply on or off. On the SY-1 synthesizer, Attack Bend Pitch is preset 
while Attack Bend Tone has controls for intensity and time.

It's interesting to note that the Attack Bend Tone envelope is in addition 
to the standard filter envelope, which is completely preset on the CSY-1 
and SY-1.

Additionally the SY-1 has a control for pulse width which the CSY-1 lacks.

SY-2 came later and exists only in a version with SM1 and SM2 boards. It 
may be that the change from a single SM board to SM1 and SM2 was prompted 
by the SY-2 design. SY-2 lacks Attack Bend Tone completely; instead the 
Tone Bend section allows you to vary three out of the five filter envelope 
parameters, namely Attack Time, Intensity (Attack Level) and Decay Time. 
The other two parameters are always preset, namely Initial Level and 
Release Time.

CSY-2 provides the same solo synthesizer controls as CSY-1 but with 
different internal construction, as outlined in my previous post. It 
evidently came last of all. Service manuals for the CSY-2 refer to the 
CSY-2 Series; it came in CSY-2 and CSY-2A versions where there are more 
Auto Bass Chord features in the CSY-2A. Some of the circuit boards in my 
CSY-2 have locations where missing components would go.


On Nov 9 2010, Doug Terrebonne wrote:

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