Any real difference between the SSM2044 and NJM-2069

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zaphod betamax
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Any real difference between the SSM2044 and NJM-2069

Post by zaphod betamax » Sun Aug 24, 2014 4:15 pm

Any real difference between the SSM2044 and NJM-2069

TEChygeek question:
The NJM2069 is supposed to be the clone of the SSM2044.
Anyone who has heard both, or knows both, is there any
sonic difference between the two filters in vintage gear?
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/mr
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Post by /mr » Sun Aug 31, 2014 10:06 am

After a quick googling I read that
"Unlike the SSM2044 which is a ladder filter, the NJM2069 is most certainly a quad OTA VCF."
Source: http://www.sdiy.info/w/NJM2069

Is there any datasheet for the NJM 2069 around?
I thing I've only seen this pinout/structure picture:

Image

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The Real MC
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Post by The Real MC » Sun Aug 31, 2014 5:04 pm

The SSM2044 is not a ladder filter. The SSM2044 and NJM2069 are both quad OTA 24dB/oct VCF with a fixed LPF configuration. The NJM2069 includes a 12dB/oct tap, two channel mixer with iABC control currents for voltage controlled mixing, and VCA with log and linear CV inputs.

I've never seen a datasheet for the NJM2069. At the time Korg was owned by Yamaha and that IC would had been forged in Yamaha's fabrication labs. Maybe Yamaha has the datasheet...
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Post by /mr » Mon Sep 01, 2014 3:25 am

The Real MC wrote:The SSM2044 is not a ladder filter. The SSM2044 and NJM2069 are both quad OTA 24dB/oct VCF with a fixed LPF configuration.
Is SSM2044 an OTA filter? I've only heard it described as some kind of "folded ladder" design that circumvents the Moog ladder patent.

The double capacitor pins also suggest ladder more than OTA, but I've never seen any clone or more detailed schematic than the datasheet shows, I think. So I don't know much. :-)

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Post by ndkent » Mon Sep 01, 2014 4:58 am

Not the expert. The SSM2044 was meant to be a pretty basic straight forward sort of moog-like low pass IC (= small and hopefully matched over a bunch of voices) that didn't violate existing Moog patents. Sort of Helvetica vs Univers if you are into fonts

Looks to me the NJM2069 is Korg's later low pass filter IC - going poly they needed an IC chip and for whatever reason did their own and they weren't demanding it to do more afaik than the 2044. Clearly not a drop in replacement I'd suspect they didn't want to count on SSM to keep manufacturing the 44. Korg had previously been using the 2044

As for DIY, I'm sort of against people messing with old synth chips in new designs, not that I haven't caved in and bought something with one to get a vintage synth using chips sound.

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Post by The Real MC » Mon Sep 01, 2014 9:02 pm

The SSM2044 uses a differential output OTA (Wilson current mirrors), those are the gm cells in the datasheet. Because the moog ladder filter patent explicitly specifies using the emitter resistance in the transistor pairs as the control element for the frequency cutoff and it predated OTAs, the 2044 doesn't infringe on the patent. Architecture-wise it looks like a ladder filter, but circuit-wise it isn't. Read US patent 4,404,529 for the real dirt on the SSM2044.

Asian companies put an emphasis on domestic suppliers. Yamaha has their own IC labs to make their own ICs. Korg and Roland eventually dropped CEM and SSM for their own designs.
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Post by zaphod betamax » Tue Sep 02, 2014 10:57 am

Thanks for the info.
The clone info I got came from wikipedia

http://en.wikipedia.org/wiki/CEM_and_SS ... nthesizers

i guess this is not the case.

and now i know they are not pin for pin.

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Post by Don T » Thu Sep 04, 2014 11:51 pm

I'm surprised no one has pointed out the major difference between SSM2044 and NJM2069:

NJM2069 has a VCA in addition to the filter, the SSM2044 does not.

NJM2069 has linear and expo inputs on the filter, as well as the VCA. SSM2044 does not.

NJM2069 Has voltage controlled resonance, SSM2044 does not.

I think they both sound great, but not the same. If using an NJM2069 for a project, be VERY careful on how much resonance you allow, it can very easily be a tweeter-cooker!

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Post by The Real MC » Fri Sep 05, 2014 8:32 am

Don T wrote:I'm surprised no one has pointed out the major difference between SSM2044 and NJM2069:

NJM2069 has a VCA in addition to the filter, the SSM2044 does not.
I did point that out, see above.
NJM2069 has linear and expo inputs on the filter, as well as the VCA. SSM2044 does not.
Missed that one. SSM2044 has only expo input.
NJM2069 Has voltage controlled resonance, SSM2044 does not.
True of the 2040, but the 2044 does have VC'd resonance. Check the datasheet.

Another interesting feature: the SSM2044 has differential inputs.

Never heard a bad sounding 2044-equipped synth. Have a DSS-1 waiting to be restored, looking forward to hearing those 2069s.
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Post by Don T » Fri Sep 05, 2014 8:55 pm

The Real MC wrote:
Don T wrote:I'm surprised no one has pointed out the major difference between SSM2044 and NJM2069:

NJM2069 has a VCA in addition to the filter, the SSM2044 does not.
I did point that out, see above.
Oops.
The Real MC wrote:
Don T wrote:NJM2069 has linear and expo inputs on the filter, as well as the VCA. SSM2044 does not.
Missed that one. SSM2044 has only expo input.
That's what I meant, maybe I didn't type it correctly.
The Real MC wrote:
Don T wrote:NJM2069 Has voltage controlled resonance, SSM2044 does not.
True of the 2040, but the 2044 does have VC'd resonance. Check the datasheet.
Yeah, right after I hit "Submit", I realized the reverse audio taper pot on the datasheet was a voltage divider instead of being in the feedback loop. I almost went back to edit it, but I figured someone would catch it! 8_) That said, I don't remember any synth built with a 2044 that actually used a reverse audio taper pot for the resonance control.
The Real MC wrote:Another interesting feature: the SSM2044 has differential inputs.

Never heard a bad sounding 2044-equipped synth. Have a DSS-1 waiting to be restored, looking forward to hearing those 2069s.
I think you'll like it. To me, it's similar to an SSM2044's "tone" combined with the resonance behavior of the early MS-20 VCF, hence the "be careful of the tweeters" warning! :). Many people who have done the "Moog Slayer" (I hate that name for it) mod on their Poly-800 have learned this the hard way! :sadbanana:

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Post by zaphod betamax » Wed Nov 25, 2015 10:54 am

I still like the tone of the NJM2069 in my DW-6000 synth.
Thanks for all the info.

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Post by jhulk » Fri Nov 27, 2015 12:02 pm

i have rev4 dss1 upgrade boards still

waiting on rev5 which is a new 32bit micro board for the korg dsm1 which has 16 of the njm chips the new upgrade will also bring back resonance as in the dsm1 it was tied to ground

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