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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS VCO - replacement for the lm394/MAT-02
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jmejia



Joined: Mar 12, 2009
Posts: 114
Location: portland

PostPosted: Sat Nov 21, 2009 11:47 am    Post subject: CGS VCO - replacement for the lm394/MAT-02 Reply with quote  Mark this post and the followings unread

So I'm having a tough time sourcing a part for these guys. Futurlec no longer seems to stock the lm394s.. I've read that that an ssm2210 wold work.

Is this my best bet?
http://www.newark.com/jsp/search/productdetail.jsp?SKU=19M1048&CMP=AFC-OP&CMP=AFC-OP

I was hoping for a cheaper part.. but if that's the best I can do it's the best I can do!
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TonnieWiegman



Joined: Jun 18, 2007
Posts: 6
Location: Kilder, the Netherlands

PostPosted: Sat Nov 21, 2009 12:17 pm    Post subject: CGS VCO - replacement for the lm394/MAT-02 Reply with quote  Mark this post and the followings unread

You can still order the LM394 at several places.
Last August I bought 20 pcs of the LM394 for $0.60 each at UTSOURCE: www.utsource.net.
You can have the parts shipped via the postoffice, costs $8.00.

Tonnie
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Rykhaard



Joined: Sep 02, 2007
Posts: 1290
Location: Canada

PostPosted: Sat Nov 21, 2009 2:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've used the SSM2210 for the last 4+ years for my VCOs, VCFs and VCAs where suitable. A couple of people on here within roughly the last couple of years, if I recall correctly, had reported the SSM2210 to being superior to the LM394 for ... some reason(s) which I've forgot.

I got email from Analog Devices a few weeks ago stating, that they have discontinued the SSM2210! Sad Now - I'm not 100% sure whether that is every single make of it, or not. I haven't checked as I still have a couple of spare ones in stock, as well as the remainder of my unfinished CGS VCOs, each having their 2210's installed already. So including my 4 uncompleted ones, as well as at least 2 extra chips, I'm good for at least 6 more VCOs on top of the 6 that I have now.

I will be keeping my eyes / ears open to suggestions for replacements though. Anybody? Weren't there a direct replacement from THAT?
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forbin



Joined: Jan 29, 2009
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Location: Fremantle, Australia

PostPosted: Sun Nov 22, 2009 7:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Bit sad about the SSM2210 being End-of-lifed! I have used the SSM2220 (the PNP matched pair) with quite a lot of success in the OTA style VCO's but have always used the LM394's for the sawtooth style. The THAT pairs do seem to have better spec's but are expensive! I am also pretty sure that they don't come in dual's only quad's. I am about to experiment with some THAT's for a MS50 VCO clone so I will let you know if it works!
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Rykhaard



Joined: Sep 02, 2007
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Location: Canada

PostPosted: Sun Nov 22, 2009 9:03 am    Post subject: Reply with quote  Mark this post and the followings unread

forbin wrote:
Bit sad about the SSM2210 being End-of-lifed! I have used the SSM2220 (the PNP matched pair) with quite a lot of success in the OTA style VCO's but have always used the LM394's for the sawtooth style. The THAT pairs do seem to have better spec's but are expensive! I am also pretty sure that they don't come in dual's only quad's. I am about to experiment with some THAT's for a MS50 VCO clone so I will let you know if it works!


Please do! In the future, I'll be needing something. If all comes to a pinch and I'm not able to find anything, I could always fall back on the fairly stable triangle VCOs that I have 2 of built, from Thomas Henry. Them with Ken Stone's (name forgotten) waveform mangler, do work extremely well. Smile

Still though - for tighter tolerances, I'll be keeping my ears / eyes open for mentioned replacements. Smile Appreciated.
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jmejia



Joined: Mar 12, 2009
Posts: 114
Location: portland

PostPosted: Sun Nov 22, 2009 1:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Can someone confirm that the part I linked above will work?
It's an SSM2210PZ

I'm just unsure what the 'PZ' means. . .
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e-grad



Joined: Sep 12, 2008
Posts: 142
Location: Berlin

PostPosted: Sun Nov 22, 2009 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

The suffix after the chips name gives some extra information as to the data sheet. Often this information is negligible for synth circuits if not it is usually stated in the documentation of any project.

For the SSM2210: The P stands for the package DIP and the temperature range -40° C to 85° C. No, information about the Z though.
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andrewF



Joined: Dec 29, 2006
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PostPosted: Sun Nov 22, 2009 5:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

it will be fine
the main points to think about are the ssm2210 part of the label and pdip or dip packaging, which it is.
The AD page for it is here.
you should find the meaning of PZ in the datasheet, probably something to do with temperature range or lead free....details Wink

As for the demise of supermatched pairs, i like to think that current manufacturing processes have evolved to a point where transistors specs are pretty close to each other (just speculation). So it won't be too tough to buy/test a dozen and find a matching pair that will be adequate for VCO duties. Get that authentic vintage sound (ie- drift) that many seem to seek, really old synths did not have supermatched trannies onboard.
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jmejia



Joined: Mar 12, 2009
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PostPosted: Tue Dec 01, 2009 3:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Has anyone tried hand matching BC547B or any other cheap transistors on the CGS VCO... or VCA for that matter? That would save me around $60 on my current parts order!
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andrewF



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PostPosted: Tue Dec 01, 2009 4:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

this thread might get you started.
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jmejia



Joined: Mar 12, 2009
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Location: portland

PostPosted: Tue Dec 01, 2009 4:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well i have an HFE section of my multimeter - so I think I can just use that to match... i'm more wondering if 2 of these transistors (assuming I get the HFE as close as possible) - will work on Ken's pcb as drop in replacements for the lm394 he calls for. . .
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andrewF



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PostPosted: Tue Dec 01, 2009 5:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

HFE varies pretty wildly, as Blue Hell wrote it may be considered as an initial test.
You could try Tillman's matching circuit
http://www.till.com/articles/QuadTrapVCO/vcocore.html
scroll down!
To change it for a NPN, just reverse the connections so the resistor is attached to C & B, then E is connected to ground.
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jmejia



Joined: Mar 12, 2009
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PostPosted: Tue Dec 01, 2009 5:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

oh ok - that's very helpful. Can his guideline be applied to other vco's and maybe even vcas?

"For this VCO I would recommend matching the base to emitter voltage, VBE with a zero collector to base voltage and a collector current of 32 μA. "

And again - after I've matched a pair of transistors - can I just drop them onto Ken's pcb w/out any crazy maneuvers or extra parts?
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andrewF



Joined: Dec 29, 2006
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PostPosted: Tue Dec 01, 2009 5:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have read matching is best achieved over a range of operating conditions, which is why Patchell's cct tests for two different currents. The 32uA is particular for Tillman's cct, tho for some sections, it is not so different to the CGS.
It doesn't have to be exactly 32uA for every cct.
To get really keen you could test with a few different resistor sizes, say 220k, 560k and 1M. then choose the transistors that match closest for all three currents.

yes, once matched just drop them into the CGS VCO, I doubt any mods should be needed.....tho we'll have to wait n see

Good on ya for trying this! Very Happy
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slacker



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PostPosted: Wed Dec 02, 2009 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

jmejia wrote:
Has anyone tried hand matching BC547B or any other cheap transistors on the CGS VCO... or VCA for that matter?


I've built the Yusynth VCA, which is a similar design to Ken's, using transistors just matched with my multimeter's HFE tester and that works fine.

I've got the core of the VCO on breadboard at the minute with a couple of roughly matched transistors in place of the LM394. I haven't tried calibrating it properly yet though so I don't know what the performance is like. Be interested to hear how your experiments turn out.
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jmejia



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PostPosted: Wed Dec 02, 2009 12:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice.. what would be the potential drawback of using unmatched transistors in a VCA?
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slacker



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PostPosted: Wed Dec 02, 2009 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think if the transistors are very different it may be hard or even impossible to stop the CV bleeding into the audio signal, I could be wrong though.

I took some quick measurements from the VCO and at the minute mine is doing about 0.92 volts/octave I tested this over 5 octaves and it seems consistent. If I can get it properly tuned over the same sort of range I'll be more than happy.
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jmejia



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PostPosted: Wed Dec 02, 2009 1:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

awesome! let us know the results!
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slacker



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PostPosted: Tue Dec 22, 2009 12:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Finally managed to get some time to play with the VCO some more and built it up on stripboard using a pair of 2N5089s matched for gain using the HFE tester on my meter.
After a bit of tweaking I've got in tuned to 1V/octave to within a couple of Hz over 5 octaves. After that it starts going sharp plus I'm starting to hit the limits of my test equipment.
I don't know how that compares to using an LM394 or whatever but it's good enough for me Smile
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emdot_ambient



Joined: Nov 22, 2009
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PostPosted: Tue Dec 22, 2009 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

A 5 octave range seems to be pretty good for analog oscillators. Sounds like it worked fine.
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jmejia



Joined: Mar 12, 2009
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PostPosted: Tue Dec 22, 2009 12:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

awesome! thanks for letting us know your results! sounds like it works great!

<edit> just to clarify was this the yusynth vco or ken's vco? (eitherway I'm assuming results will be similar between the two!
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slacker



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PostPosted: Tue Dec 22, 2009 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

It's just the core of Ken's VCO with a few minor changes, basically the same as Richard Brewster's stripped down version.
I'd guess the results would be similar with other VCOs but YMMV.
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gddfp



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PostPosted: Fri Dec 25, 2009 10:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

jmejia wrote:
Has anyone tried hand matching BC547B or any other cheap transistors on the CGS VCO... or VCA for that matter? That would save me around $60 on my current parts order!


Yes, I did (for the VCA's)... matching on VBe.
I found it an easy and painless process - a bit boring, though - but had to come to the conclusion that's it's almost not worth the hassle. Out of the hundreds of modern & cheap transistors I tested, there were only a few which were "off the scale"... (like in: 2 or 3 out of 100). Most of them or so close to eachother that I guess it won't make any difference in practical use.
The good thing is that I now have three bags of really-very-close transistors... it wouldn't hurt to use those here and there, I reckon.
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mark_olson



Joined: Oct 26, 2006
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PostPosted: Thu Jan 07, 2010 3:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've been trying to puzzle my way toward a solution to the scarcity and/or cost of transistor pairs too.

Does anyone have experience with the THAT340P14-U?

It looks right to me but I am not sure what to do with the pins I don't need. They need to be tied to something, don't they? But what?

Although they're not cheap, Mouser has them and I'll be ordering other stuff from them anyway so that has the effect of bringing the cost down since I won't be paying shipping to another vendor.

But if somebody can tell me that the THAT340P14-U won't work the quest will continue.

Mark
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andrewF



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PostPosted: Sat Jan 09, 2010 5:03 am    Post subject: Reply with quote  Mark this post and the followings unread

I think it will work very well.
The substrate pins should be grounded. The PNP pins could probably be cut off/ignored.
Tho if it were me i would probably find a use for the PNP pair, too good to waste. Something like an onboard VCA, this one uses a pnp matched pair :
http://urekarm.tripod.com/synth/serge_vca.pdf
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