[sdiy] Best AVAILABLE OTA for building new designs?

[Peter Pearson]

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> 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> 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
> <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
> *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 <https://www.alfarzpp.lv/eng/sc/AS3364.pdf>
> PDF Document · 494 KB <https://www.alfarzpp.lv/eng/sc/AS3364.pdf>
> <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> 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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