CA3080 being made again?

[merlinb]

When using a LM13700 in place of a CA3080....what do we do with the other half? Treat it as you would a regular op amp?

A regular opamp has a lot of gain, as long as it's powered, so it could oscillate or latch up and suck power unless it's biased suitably.

An OTA is rather different in that its 'voltage gain' is not as great, and you also have access to the input diff' amp via the bias current input. If you feed it no bias current then it *should* switch off completely, and be quite incapable of doing anything unexpected. I would therefore be less worried about terminating it when not in use, and I haven't had problems leaving it unconnected. It wouldn't hurt to connect it like an opamp, of course.

[StephenGiles]

Great shame that the CA3094 was discontinued, EH designers used many clever tricks with this chip - Spacedrum for instance!

[alanp]

If they do the CEM vco/vcf/vca/bazillion other synth-on-a-chip series, for a decent price, I'd be all over that! (ISTR SSM also did a similar series, that's a lot of beer since I read it though.)

[Mustachio]

Just get over it and buy LM13700s like normal people. 

^^ This cracked me up merlin 

I agree, design around the lm13700 footprint maybe try to use the built in buffers if you want to use more of the chip or double your circuit to use both sides. Also theres a babyboard or vero you can use to retrofit a lm13700 into a socket for a ca3080. heck you could even just look at the pinouts and direct wire it in!

That being said when I first started building pedals I bought 2 nos rca 3080 can's and I think I paid somewhere around 15 bucks a piece haha If I only knew ! I also bought 10 fake ca3080s from china. You live you learn eh!

at 5 bucks a chip not really worth it to me, for some reason I thought I remember some one saying the lm13700 was a better OTA in some way. Cleaner ? I can' really remember maybe it was just the buffers it has over the lm13600.

I think there was a thread a while back about the ca3080 and some one mentioned the same company that is starting to make them again.

here's that baby board for drop in replacement.

[Scruffie]

Also, I have asked Rochester if they can re-make the CA3094E (Small Stone, etc.)

Now THAT would be good.

Then you just need to find someone to remake the SAD1024 & MN3005 and we're all a happy bunch of DIYers 
(Note - I was just joking before people jump in on it! Not happening  )

[jmasciswannabe]

Geez....I knew the lm13700 could be used in place of a ca3080, but for some reason thought it would be more complicated than that. Kicking myself as I wait on ca3080s (which are probably fake or off spec) from overseas.

[armdnrdy]

Then you just need to find someone to remake the SAD1024 & MN3005 and we're all a happy bunch of DIYers 
(Note - I was just joking before people jump in on it! Not happening  )

It's unfortunate that the mainstream effect companies veered toward digital and lower voltage analog effects.
If there was a demand in that market I'm sure that someone like Cool Audio would jump on board with the MN3005, 3010, etc.

[haveyouseenhim]

I just found these Harris chips a few minutes ago in a scavenge bin. After a bit of googleing I can't find a definitive answer if this is a 3080.

[armdnrdy]

I found this here if it's any help:

http://www.diystompboxes.com/smfforum/index.php?topic=44430.0;wap2


Third reply down:

http://www.diyaudio.com/forums/parts/200508-obsolete-parts.html

It looks so far like it's a Peavey factory number for a CA3080.

Edit: I'm about sure now....Peavey part #

http://music-electronics-forum.com/t9603/

[haveyouseenhim]

I found this here if it's any help:

http://www.diystompboxes.com/smfforum/index.php?topic=44430.0;wap2


Third reply down:

http://www.diyaudio.com/forums/parts/200508-obsolete-parts.html

It looks so far like it's a Peavey factory number for a CA3080.

Edit: I'm about sure now....Peavey part #

http://music-electronics-forum.com/t9603/

Ok thanks.  On the last reply it says:
-Pins 7 and 8 are shorted  and seem to be connected to a V+, (this seems to indicate a single OA)
-Pin 1 is connected to pin 6 which goes to pin 3 of a 4558.
-pin 2 and 3 are connected with a resistor (100 ohm) and pin 2 is not directly connected to pin 6
- nothing between 6 and 7 either.

I looked on the board and it has all of the symptoms listed above. I turned over the board and it has a peavey marking

I did read those links but I wasn't totally satisfied until I got off my ass and checked the traces on the board.

[armdnrdy]

I am 100 and 10 percent sure that it's a Peavey house number!

Page 16.....5th item down.

http://matthieu.benoit.free.fr/cross/competitive/Peavey_Transistor_Cross.pdf

[haveyouseenhim]

I am 100 and 10 percent sure that it's a Peavey house number!

Thanks so much for going out of you way to find that for me  

I kinda hate that I found these because I just paid $10 for some confirmed good 3080s from AU.

[armdnrdy]

No problem! I'm a bit bored today!

In fact.....I was so bored that I put together an etchable daughter board for the LM13700 to CA3080 conversion.

Tomorrow I'll build a sample to photograph and post all of the info.

This should ease some stress from the electronically impaired for it will plug right into an empty socket wired for a 3080.

[R.G.]

Notes on using LM13700 in place of CA3080:
- the LM13700, CA3280, and NE5517 are roughly equivalent to a pair of CA3094s in one 16 pin package, with the addition of diode precompensation for distortion.
- the OTA section is equivalent to the 3080 in action
- the Iabc pin on the LM13700, and I believe on the 3280 and 5517 sits at a DC voltage of two diode drops above V-, not one diode drop as in the 3080 and 3094.
- the sudden-death Iabc current for the 13700 is 2ma, where the sudden-death current for the 3080 and 3094 is 1ma

[StephenGiles]

Thank goodness I still have a few CA3094 left!

[R.G.]

I forgot to mention that at least one release of the Small Stone uses LM13700s.

Unless you're stuck with putting a chip into a pre-existing board, the LM13700 is an entirely satisfactory replacement for the 3080 and 3094 with the exception of pinout.

And you can do a lot with a spot of superglue and dead-bugging techniques.