LM13700 instead of CA3080

[AMK]

Being LM13700 more available\cheaper version than the CA3080 I wanted to replace it on the Moog LPF Build, her the schematic:



Mark(replay 9#) said in here:
https://www.diystompboxes.com/smfforum/index.php?topic=122003.0
"if a circuit is deliberately using a 3080 for its distortion characteristics, then subbing a 13600/700 or even a 3280 for it may not yield the same sonic result.  But if the purpose is getting a clean signal from the OTA, then a 13x00 shouldn't be an issue. It certainly hasn't impeded Electro-Harmonix."

Well, I guess it isn't my case? If understand correctly in this circuit the CA3080 act as an exponential voltage to current converter with a transistor based current source- so just to make sure, I don't need to have any mods(like this: https://effectslayouts.blogspot.com/2015/11/lm13700-to-ca3080-conversion-board.html)
and just use the half of the LM13700 as it is(swapping the pins)?

[merlinb]

In 99% of cases the two are interchangeable, the main difference is the voltage on the control pin of the 13700 is two diode drops instead of one. The moog is using current sources to feed the control pins, so I think you should be fine.

[ElectricDruid]

+1 agree.

I notice that there's a lot of 13700's already used in this schematic and I think the only reason they used a CA3080 was because they finished up needing an odd number of OTAs.

[AMK]

+1 agree.

I notice that there's a lot of 13700's already used in this schematic and I think the only reason they used a CA3080 was because they finished up needing an odd number of OTAs.

Thanks! It really seems like that...

[PRR]

I notice the Druid has a box of AS3080 at €4.38 ex. VAT, but he's on a break for some weeks.

What happened to Rochester's 3080? Not liking small orders?

[Kevin Mitchell]

I notice the Druid has a box of AS3080 at €4.38 ex. VAT, but he's on a break for some weeks.

What happened to Rochester's 3080? Not liking small orders?

I recall reading about how they have a stock of old wafers for these, so it's likely a make-to-order deal - for reasonable qty for the effort.
Speculating, of course.

FWIW; the AS3080 is very likely the same wafers as their 13700 or even their quad variant. It even has the diode bias pin. While I haven't checked myself I wouldn't be surprised if it also has the "two diode drops". The reasoning behind this guess is that if they have a quad OTA wafer and only 2 or three sections are functioning, then it's viable for a dual package. If only one, then single.

[ElectricDruid]

I notice the Druid has a box of AS3080 at €4.38 ex. VAT, but he's on a break for some weeks.

Only a week or so - back to work 10th March.

What happened to Rochester's 3080? Not liking small orders?

I haven't seen a decent quantity of genuine CA3080's for sale for several years. I thought they'd run out of wafers?..though I don't remember where I heard that.

FWIW; the AS3080 is very likely the same wafers as their 13700 or even their quad variant. It even has the diode bias pin. While I haven't checked myself I wouldn't be surprised if it also has the "two diode drops".

Interesting theory. I should really check.

I thought the bias pin was a nice touch because it uses an unused pin on the CA3080 pinout (there were two!), so it adds a feature but maintains backwards-compatability with the original chip.

[PRR]

I thot Rochester owned the MASK (or a workable copy).

The problem is that Rochester won't do a deal for less than $250 (in 2019). If you are refurbing aging bombers, that's less than the bar tab. In PedalWorld it may be an entire career. Some middlemen (middlepersons?) were buying dozens and selling onesies, but I didn't find anybody yesterday.

I would rate the 13700 different from 3080. Though literally one open-book copied the other, processes changed and some improvements begged to be included. OTOH there's probably no other chip as similar to a 3080 only much cruder and more sleeker.

[Kevin Mitchell]

While we're here;
Let us not forget that the first prototype of the preceding LM13600 comprised of two CA3080 ICs.


Interesting read;
Wayback article here