[sdiy] Best AVAILABLE OTA for building new designs?

[Tom Wiltshire]

I don't think it's a legal issue. Any patents that applied have expired by now, so there's nothing for lawyers to do. I think there are two problems:

1) Market size.
The CEM chips were used in a *lot* of synths, whereas the Yamaha chips were used only in very few.

2) Information
It's likely that Yamaha didn't provide full details of what they'd done in any patents they took out since copying their chips would have been pretty difficult for anyone smaller than they were back in the 1970's. The CEM technology is much better known.


> On 10 Aug 2024, at 01:57, Peter Pearson via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> I wish Alfa made clones of the Yamaha proprietary chips from the CS80 voice board.  Can anyone talk to them about that?  I can't imagine it's a legal issue if cloning CEM chips is fine, no?
> 
> On Fri, Aug 9, 2024 at 8:47 PM Chris McDowell via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
> Alfa is usually pretty responsive to direct inquiries. I've bought a whole bunch of their 2164s. 
> 
> At least a year-ish ago, AS3364 was $2.90 @ 100, $1.85 > 1000
> 
> Chris McDowell 
>> On Aug 9, 2024, at 11:31 AM, David G Dixon via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>> 
>> That sounds great.  My only issue is price -- The AS3364 seems to cost about $7 or more, depending on the source, and it does not seem to be possible to buy them directly from Alfa -- at least, I don't see any obvious way to do so from their website.
>>  
>> My latest project is going to require about 250 2164 ICs.  That's not a problem given what I'm paying for them.  Yes, in all but the filter application, the 2164s are all linearized, but I'm paying about 23 cents for TL074s and about 1 cent for 561 caps, so from a cost perspective, it just doesn't make much sense.  Linearizing 2164 does add an inch or so to the PCB real estate, but I'm sending the same voltage to a large number (48) of 2164s, so even though they are linearized, only one logarithmic amplifier is needed for all of those 2164s.  I do need to buffer those CVs locally, so there is a TL074 sitting next to the 2164, but I would need to do that with the 3364 as well (the datasheet is silent on the input impedance of the control pins (big negative issue for me), but I presume that it is measured in kilo-ohms, not tera-ohms).  And, I'm getting four linearized amplifiers from each 2164 this way as well, rather than the customary two.
>>  
>> I also (mostly now) use the 2164 as a four-quadrant (or variable-quadrant) multiplier, and it is not clear whether the 3364 is amenable to that application.
>>  
>> If I could get the AS3364 for less than $2 each, then I'd probably get more serious about using them.
>> 
>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org <mailto:synth-diy-bounces at synth-diy.org>] On Behalf Of mark verbos via Synth-diy
>> Sent: Friday, August 09, 2024 8:50 AM
>> To: Dan Snazelle
>> Cc: synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>
>> Subject: Re: [sdiy] Best AVAILABLE OTA for building new designs?
>> 
>> [CAUTION: Non-UBC Email]
>> Dan,
>> 
>> I’ve been using the AS2164 only when I need the exponential response. If I need linear VCAs I now use the AS3364, which is more or less a clone of the SSM2024. That’s the same pinout more or less as the SSM2164 but has linear response. So, it’s very easy to use, pretrimmed, quiet, CV referenced to ground, summing node signal ins, doesn’t require all of those 560p caps. That works out great when lots of VCAs are needed, Some people were really turned off by the 1% harmonic distortion, but I have yet to notice an distortion on a synth circuit. 
>> 
>> <preview.png>
>> AS3364
>> PDF Document · 494 KB
>>  <https://www.alfarzpp.lv/eng/sc/AS3364.pdf>AS3364 <https://www.alfarzpp.lv/eng/sc/AS3364.pdf>
>> PDF Document · 494 KB <https://www.alfarzpp.lv/eng/sc/AS3364.pdf>
>> 
>> Mark
>> 
>> 
>> 
>> 
>>> On Aug 8, 2024, at 8:08 PM, Dan Snazelle via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>>> 
>>> imagine someone asked you to make some new synth modules.
>>> then imagine that the last time you did so in any quantity above one---  it was 2017. 
>>> 
>>> 
>>> I am trying to get a handle on what the parts landscape is like now for cost-effective CV control. Back in 2017 the lm13700 was really the only available OTA . I was just starting to work with the ssm2164 at the time but never used it extensively.
>>> 
>>> In the interim I have built synth circuits but only in quantities of one where cost was no object and I was able to rely on my own extensive parts supply. 
>>> 
>>> 
>>> So my question is this-- if I am thinking about design for manufacturing—what do you think the best option is? 
>>> 
>>> Has anyone tried the quad ALFA OTA? Is it even readily available? Same for the new SSM2040​.  
>>> 
>>> OR would you just use the 2164 instead? 
>>> OR would you just try to make discrete OTAS out of say the  BCM856DS //BCM847BS
>>> 
>>> thanks for any and all opinions on this. 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
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