Emu SSMs (was Re: [sdiy] A potential problem with a voice-assignable organ)

[George Hearn]

The ssm2040 is more 'configurable' than a lot of other filter IC's yes.  All
sorts of possibilities with it.  One chip could be a 4 stage phaser, or dual
2-pole SVF's, stereo eq as well as the usual LPFs, HPFs etc.  I've also
tried an Oberheim XPander style multimode VCF with the chip that works quite
well.  I guess the price of this extra flexibility is more external parts
etc.    
	With regard to the SSM2044 I remember seeing the internals of it
somewhere years ago along with a lot of other SSM chips.  I think the
SSM2044 was pushed as 'low cost' and that it was something to do with the
buffers in between each gm stage being changed/omitted (haze).  I could well
be wrong but my guess is that the requirement for a hi impedance, low offset
buffer between each gm stage in the SSM2040 made it quite a bit trickier to
produce from the fab's point of view and hence more costly at retail.  
	The change in (lack of) the buffers must also have something to do
with the fact the last filter stage has 10 times the transconductance
(Capacitor ~10 times smaller).  This was the subject of an earlier thread,
did we ever figure out why in the newer filter IC's this always seemed to be
the case?  George    

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Dan Snazelle
Sent: 08 June 2009 23:56
To: tom at electricdruid.net; ajhuovil at cc.hut.fi
Cc: sdiy
Subject: RE: Emu SSMs (was Re: [sdiy] A potential problem with a
voice-assignable organ)


i thought i had read that it was due both to VC resonance AND ease of use.

wasnt the ssm2040 a much more highly configurable filter (it could do more
than just low pass) and as such not as
plug and play

but i could be wrong

thanks





-------------------
----------------------------------------
> From: tom at electricdruid.net
> Subject: Re: Emu SSMs (was Re: [sdiy] A potential problem with a
voice-assignable organ)
> Date: Mon, 8 Jun 2009 21:45:50 +0100
> To: ajhuovil at cc.hut.fi
> CC: synth-diy at dropmix.xs4all.nl
>
>
> On 8 Jun 2009, at 21:32, Antti Huovilainen wrote:
>
>> Do you happen know the reason why SSM2044 was designed?
>> The folded Moog ladder is a clever design (and a way around the
>> Moog patent?), but IIRC, SSM already had SSM2040 at the time.
>
> I dunno!
>
> I'd like to have a guess though;
>
> 1) So they could add the missing resonance VCA
> 2) Cost. SSM2044 describes itself as "low cost".
> 3) The same reason that CEM went from the 3320 to the 3328, whatever
> that was.
>
> I'm willing to bet that I'm almost sure that it's certainly one of
> those!
>
> T.
>
>
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