3080 vs 13600/13700?

[digi2t]

Hey folks,

Just wondering if the 13600 or 13700 can be used as a replacement for the slowly disappearing 3080? I don't need the buffers, but does the rest of these chips offer the same performance? I've seen it used as a replacement for the 3080 in the odd project, but does it need any particular changes in surrounding parts to offer the same performance, or is it PnP?

[bean]

I've done several projects subbing the LM13700 and it's always worked out great. Never really worried too much about performance since I've gotten the results I've wanted. Plus, you can sometimes utilize those buffers outside your phaser/envelope filter/whatever if you need it. On the FFX Accufunkture, we took a Mutron Micro V, converted it to LM13700 and I used one of the buffers on the input of the circuit. It saved a few parts and lowered the cost just a bit.

Don't remember off the top of my head but maybe the CA3080 has higher voltage tolerances? Or more suited for split-rail power? I'm sure someone knows better than me.

[amz-fx]

Don Sauer, one of the two guys responsible for the LM13600/13700 development, wrote this about the chips:

So the development spec for the LM13600 was that it needed a schematic to train someone
in IC layout. It needed to have 16 pins. And we were going to layout the 3080 anyway.
The schematic part was easy. Just used the 3080 exactly.

regards, Jack

[bean]

Don Sauer, one of the two guys responsible for the LM13600/13700 development, wrote this about the chips:

So the development spec for the LM13600 was that it needed a schematic to train someone
in IC layout. It needed to have 16 pins. And we were going to layout the 3080 anyway.
The schematic part was easy. Just used the 3080 exactly.

regards, Jack

The one thing I don't like about the 13700 is the actual pin layout. It's fine for double sided boards but it can be a real PITA when routing for single sided ones. Of course, I have no idea what would make it simpler.

[Kevin Mitchell]

does it need any particular changes in surrounding parts to offer the same performance?

Nope. You're clear for landing.

I've seen these used interchangeably in many builds - in particular I've seen them used in compressors and the FSH. In the FSH the buffers had been utilized in the circuit to omit the external buffers on the 3080 boards - such as the tonepad project. Pretty nifty.

[aion]

Has anyone done any direct A/B comparisons between the LM13700 and a CA3080 in something like the Ross circuit?

I know Fuzzdog's Ross/Dyna compressor has space for either the 13700 or 3080 using overlapping IC footprints, so I feel like that one may be a good candidate.

https://shop.pedalparts.co.uk/Super_Skwisher_Ross_Dynacomp_Boutique_Compressor/p847124_12489286.aspx

[Kevin Mitchell]

Has anyone done any direct A/B comparisons between the LM13700 and a CA3080 in something like the Ross circuit?

I have with the engineer's thumb. As far as I could tell it worked just as well. People say the LM13700 is superior in performance but I haven't come across a situation where it was debatable. Not for my applications at least.

[R.G.]

The LM13600/13700 uses a different current mirror on the input, and I suspect that it also uses it internally, at least on some of the later revisions - it's an old chip design. The consequences of the internal current mirrors don't make it outside the chip much, if any.

The Iabc input uses a current mirror that requires a voltage of two times a silicon diode drop, not a single silicon diode drop as in the 3080. So you'll find that the 13x00s will work in most circuits, but the actual voltage at the Iabc input will be higher.

This only matters where you're trying to drive the input with a voltage through a resistor.. The current will be slightly lower than you intended. There are situations where this matters, but I suspect not all that many. The only reason I dug through this is that I ran into the issue in some unpublished designs.

Swap away! Should work, and has worked for me.

[digi2t]

OK. Thanks guys. Phil and I are working on a project with a bunch of 3080's in it, so we would like to get away from it for cost and ease of sourcing. Just wanted to be sure that we weren't missing out on some detail that would throw a wrench into the works. Gracias!

[Mark Hammer]

The 3080 is less tolerant of higher input levels than its various successors are, generally starting to distort with input levels exceeding 100mv.  That's why 3080-based circuits attenuate the signal before the OTA and then attempt to restore level afterwards.

Bottom line: 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.

[PRR]

Small Bear works with Rochester to source known-good '3080s, now new-made. I suspect availability will be good for years. They may be available new after we use-up all the 13700 and reject-13700 ever made.

Yes, that is single-source in the USA. (Two selling offices; but getting to be the same batch and SB is more set-up for small orders, Rochester likes big orders.)

[R.G.]

The 3080 is less tolerant of higher input levels than its various successors are, generally starting to distort with input levels exceeding 100mv.  That's why 3080-based circuits attenuate the signal before the OTA and then attempt to restore level afterwards.

Bottom line: 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.

Good catch, Mark. Yes, the 13x00 was set up to be more tolerant of big inputs, especially using the new input diode connection pin.

[Mark Hammer]

Small Bear works with Rochester to source known-good '3080s, now new-made. I suspect availability will be good for years. They may be available new after we use-up all the 13700 and reject-13700 ever made.

Yes, that is single-source in the USA. (Two selling offices; but getting to be the same batch and SB is more set-up for small orders, Rochester likes big orders.)

After my friend, and former forum member Peter Snow passed away a decade back, I set about the task of helping his wife sell off his sizeable collection of guitar, synth, e-percussion and general electronic gear, bit by bit.  There were a lot of desirable chips left in the parts bins, and Steve Daniels very graciously agreed to buy most of them, at what were very generous prices on his part.  I seem to recall there were at least 50 or more NOS 3080s in there.  That's not enough to provide "availability for years" but is representative of what Steve goes through to assure the parts we want.

[bluebunny]

Yes, that is single-source in the USA.

FYI, in case Phil (or anyone else over here) wants to get a hold of these, Thonk in Brighton stocks them.

[digi2t]

Thanks gents. All great info for sure. Quite frankly, the project we're working on requires nine 3080's, so besides proper operation, we're just trying to keep the project cost reasonable as well. Since the 13700 is half the cost, and offers double the OTA's, we thought "two birds one stone".

Of course, "reasonable" is relative as well.   

[bean]

Thanks gents. All great info for sure. Quite frankly, the project we're working on requires nine 3080's, so besides proper operation, we're just trying to keep the project cost reasonable as well. Since the 13700 is half the cost, and offers double the OTA's, we thought "two birds one stone".

Of course, "reasonable" is relative as well.   

Well nine 3080s is 4.5 13700s so I guess you gotta figure out whether or not it's worth sawing one IC in half for every build ☺️

[digi2t]

Fair nuf. Since it's half the price, I suppose we can turn a half blind eye.

[StephenGiles]

Thanks gents. All great info for sure. Quite frankly, the project we're working on requires nine 3080's, so besides proper operation, we're just trying to keep the project cost reasonable as well. Since the 13700 is half the cost, and offers double the OTA's, we thought "two birds one stone".

Of course, "reasonable" is relative as well.   

I've never understood why folks will pay totally extortionate prices for beer (which I do not drink) and yet whinge about paying a couple of pounds/US$ more for an IC???

[digi2t]

Thanks gents. All great info for sure. Quite frankly, the project we're working on requires nine 3080's, so besides proper operation, we're just trying to keep the project cost reasonable as well. Since the 13700 is half the cost, and offers double the OTA's, we thought "two birds one stone".

Of course, "reasonable" is relative as well.   

I've never understood why folks will pay totally extortionate prices for beer (which I do not drink) and yet whinge about paying a couple of pounds/US$ more for an IC???

I don't drink beer either (yeck!), but I figure the money saved could go towards a nice Bordeau. Or better yet, a Grey Goose martini. Cheers!

[PMowdes]

Yes, that is single-source in the USA.

FYI, in case Phil (or anyone else over here) wants to get a hold of these, Thonk in Brighton stocks them.

Thanks,

I've reworked the design for lm13700, it seems to make sense in a bunch of levels especially cost

Where in the UK are you Marc??