LM13600 amazing IC

[9Lives]

I have a few of these laying around and didn't realizea few things about it. I'm hoping some one with more knowledge about it can clear this up. I know it has 2 amps but I'm also seeing that it has 2 buffers as well. With these buffers do you need to set the impedance in and out your self with resistors? Or is is just straight in and out with no components? Also in order to take advantage of these do I just got from the circuit to the buffer input to the buff output to the op amp pin in and the go along the rest as normal?

[raulduke]

Hi 9Lives,

The LM13600 is a transconductance amplifier.

It was used in the MS20 filter, which you can see a 9V version schematic here (designed by tim escobedo):

http://www.diystompboxes.com/smfforum/index.php?topic=85279.0

From the look of the schematic the buffers are just hooked up without any external components to set impedance etc.

I'm sure someone else might be able to fill you in on more technical details.

I did a board layout for the 9V MS20 filter but never got around to getting it made. The MS20 filter is a classic.

[stecykmi]

OTA's are amazing, they're extremely powerful for analog signal processing mostly because you have so much control over the signal in several places in the on-chip circuit. They can be thought of like "regular" op amps, with extra pins for more control. You can use them in a manner identical to op amps, in fact.

The buffer is usually used as a simple envelope follower so you get a nice strong output signal (the darlington pair allows a lot of current to flow through). To use them, you usually only need to use 1 external component, a simple resistor.

I suggest looking at the datasheet for the part (or the LM13700 which is more common). Specifically check out simple circuits like the unity gain follower and notice how the output is configured.

i hope i answered your question...

[9Lives]

Thanks for the info. What kinds of things can I use this for as addons. I'm using half of one of these chips and the other half is WIDE open. It's for a compressor. My first idea was gave to me by a friend on here to add the tubescreamers gain stage as a grit control.or I would like to add a tonestack that won't drain my output. I can't find any info that actually gives me an example of an active tone stack schem. And leads?

[stecykmi]

Just keep in mind that you can use an OTA as a regular opamp if you want to. Therefore if you know of any op-amp-based designs for anything, you can likely use the other half of the 13600 in it's place.

one example of an EQ might be the tonemender at runoffgroove. if you're willing to experiment, you could probably sub the first op-amp buffer stage with the darlington pair contain in the 13600 package, then use the opamp stage for the post-eq gain stage. this would take some playing around with but it'd probably be pretty cool.

[9Lives]

you don't think that would be a lil over kill in a cp9? I would like to use that in a dist fo sho. What I really wanna do is use that half for the gainstage of the tube screamer and give it a lil somthin somthin. Although I can NOT get the layout right. I don't wanna kill it with gain tho. I had the stupidly wonderful tonstack by m hammer on the end but it sucked to much out put. The high roll off was actually pretty nice but this comp really doesn't have the lack of highs prob. The tonestack just really robbed it of swell and out put. You don't know of a good active 1 knob tone stack? Can't find one anywhere :/

[stecykmi]

I can't think of a single one. Maybe the diamond compressor with the tilt control, but i've never seen anything from diamond cloned or traced.

baxandall type tone stacks use 2 controls, a bass and a treble. that might work, but i can't think of any designs that use them offhand.

[cjkbug]

doesnt the bbpreamp use a baxandal tone
stack?

[raulduke]

Silly/Crazy idea;

Take the standard two knob active baxandall circuit (like the BB preamp etc.) and wire up a dual gang pot for the treble/bass controls. Reverse the wiring of the treble and bass pots (ie. hot to 3 on treble pot lugs and hot to 1 on bass pot lugs).

Then the pot at halfway = flat freq response.

Turn it Clockwise = Treble is increased + Bass is decreased.

Turn it Counter Clockwise = Bass is increased + Treble is decreased.

Probably a bit of an overkill but it would work as a powerfull, active, one knob tone control...

[jkokura]

Or crazier still, get one of those concentric pots from Smallbear - two controls in one pot! Then you can do both controls cut and boost but have them in one pot space instead of two.

Jacob

[raulduke]

Yep that would be damn cool 

[stecykmi]

Silly/Crazy idea;

Take the standard two knob active baxandall circuit (like the BB preamp etc.) and wire up a dual gang pot for the treble/bass controls. Reverse the wiring of the treble and bass pots (ie. hot to 3 on treble pot lugs and hot to 1 on bass pot lugs).

Then the pot at halfway = flat freq response.

Turn it Clockwise = Treble is increased + Bass is decreased.

Turn it Counter Clockwise = Bass is increased + Treble is decreased.

Probably a bit of an overkill but it would work as a powerfull, active, one knob tone control...

only trouble with this is baxandall circuits use log/audio taper, if you wire one backwards, it'll have crappy response.

you could fake it by creating an artificial taper by paralleling a resistor.

personally i would use two separate pots because that gives you more control and i think to get the taper correct of a single knob solution would take a lot of tweaking (and i'm lazy).

[raulduke]

Yep; I agree 100%. I would rather use 2 pots as well.

It would fit 9Lives 1 pot active control requirement though.

[cjkbug]

Or crazier still, get one of those concentric pots from Smallbear - two controls in one pot! Then you can do both controls cut and boost but have them in one pot space instead of two.

Jacob

i have trying to think of something to do with one of those!

[9Lives]

I love these ideas. I just want to have a wide range on the treb. To bad I fried the fkn board grrr. I accidentally hooked it to 15v andsome how my 16v caps couldn't hang. I've been replacing part after part and just can't fix it.. The pads are coming off. I think I know when to step back and just order a new damn board as bad as I hate it. This thing sounded so good and I used one of the pedalenclosures.com boxs.  Omg I loved this build... just ordered another one. Hope all goes smooth. Jacob. More debbuging to do... Anyway I'm gonna check out the baxandall circuit.