LM13600 vs LM13700 Revisited

[ExpAnonColin]

I'm about to start breadboarding a Small Stone, dual OTA style, and was ordering some extra 13xxx's from mouser but noticed that the 600 was about half the price as the 700.  After some detective work (the search button and the datasheet-read maneuver) I found out that:

1) (most importantly) The input buffers of the 700 and 600 differ "in that the input bias currents (and hence their output DC levels) of the 700 are independant of iabc which may result in performance superior to that of the 600" and also may have caused the following problem (although I'm not sure-could this just be a difference in tolerance, warranting some slight trimpot tweaking?):

I also tried the LM13600, which hissed just as loud and added
CV "thump" to the noise level.

Posted concerning differences in noise in different OTAs.  And also, according to the LM datasheets, the buffer's input current range is .2-.4 for the 13600 and .5 to 2 uA for the 13700.

2) The Input offset voltages/changes in the 600 have a slightly higher maximum rating (according to NJM datasheets, although they are the same according to LM datasheets)

And somehow that warrants a 2x price increase for the 700s.

From Ed Rembold again from the same thread:

I know this is not going to be real interesting.... but
might help someone..

-Colin

[puretube]

check out other suppliers for priceing...
(I`ve seen it the other way `round in europe, very recently)  :wink:

[brett]

breadboarding

What style!!!  :wink:
Have fun...

[Paul Perry (Frostwave)]

In most circuits, there isn't a difference between the 13600 and 13700.
I don't think it would matter for the SmallStone.
Where I have found differences, is when supplying the bias current from a low impedance source, at the low current end of the range. And getting a whack of feedthrough bump.. I shouldn't have been doing that, anyway!

[StephenGiles]

I agree with Paul, you are really not going to hear any difference in sound, especially if a distorted signal is fed to the Smallstone input. These price differences are marketing differences only!
Stephen

[ExpAnonColin]

Interesting... well, I'll check other suppliers...  I just want this small stone to be as perfect as can be as I am very very picky about the phaser's sound and feel a bit guilty not using 3094s!  This is one occasion where I can't help but be mojo-concious.

-Colin

[ExpAnonColin]

...and after some googling and shopping, I found that Mouser's prices on them are really great, and that the LM's are normally about 1.50, and that the 13600s are usually the same or more.  So MOuser'sr $.42 apiece for the 13600s is a great deal, and so is the $.72 for 13700s.

-Colin

[DiyFreaque]

Wow, I didn't realize Mouser's prices were so low on the 13600/13700.

Wonder if JRC is going to resurrect the 3080?  That would be nice....

Cheers,
Scott

[ExpAnonColin]

While we're on the topic, I'll pay anyone here $6 shipped for 6 13700s, as I just did a mouser order and don't want to pay another 5 for shipping 6 chips... so if you can pop them in a letter and mail them via letter post, at about $1.20 probably, I'd appreciate it.  It may be a stretch but I have done like 3 mouser orders in the past two weeks because I keep forgetting to get stuff.

-Colin

[Brian Marshall]

hey colin

i was just sitting down tonight after buying a crap load of 13700's.  I got them about a month ago, and have a few plans for them.

I think a pretty versatile fitler could be made with them....

of course the obvious trems, phasers, ringmod.

but one thing i am noticing on the datasheet.  it seems to me that i feel as if im re-inventing the wheel.  basically the problems are that you have to make some choices about your circuit that you normally wouldnt if you did an opamp/opto circuit. (mind you im not talking about subjective things like sound)  Basically you have to deal with low input impedances, and/or reducing input volume, then reamplifying

It seems to me that ota's are kind of an electronic hack inside a chip so to speak.

That's not to say i wont use them.  i mean i have 50 of them.  I'd be willing to donate 5 of them to you since i know you are a guy that will report all of your findings to us.

[gez]

That's not to say i wont use them.  i mean i have 50 of them.  I'd be willing to donate 5 of them to you since i know you are a guy that will report all of your findings to us.

Colin, take Brian up on his offer, use them and learn to love them (a wonderful chip)...

[puretube]

Colin: do what GEZ sez, and don`t ignore what the app-notes have to offer!

[Paul Perry (Frostwave)]

The input impedance of the 13700 isn't all THAT low, when you consider the voltage divider that goes in front of it to get the signaldown to 100 or 200mV!
And something I have never seen done.. if you don't need the buffer at the output, then use the output buffer at the input :?: Replacing a CA3080 with a LM13700, you have a buffer left over.

[ExpAnonColin]

You guys don't have to twist my arm!  That's awesome, Brian, I'd love them and would be happy to pay you a bit if you want.  I've designed an all-right MS-20 based filter with one, and a so-so tremolo with one... they were bot perfect until the driangle wave came along, which on the tremolo wasn't smooth enough (and I can't stand shunting caps to ground on the output of the LFO as it makes it unstable) and on the filter the depth wasn't great enough.  You have a PM.

-Colin

[gez]

I've designed an all-right MS-20 based filter with one, and a so-so tremolo with one... they were bot perfect until the driangle wave came along, which on the tremolo wasn't smooth enough (and I can't stand shunting caps to ground on the output of the LFO as it makes it unstable) and on the filter the depth wasn't great enough.  

Experiment and be persistent...

[Paul Perry (Frostwave)]

Gez, you can make that triangle as flat as you want by overdriving half of a ... 13700!

[Brian Marshall]

You guys don't have to twist my arm!  That's awesome, Brian, I'd love them and would be happy to pay you a bit if you want.  I've designed an all-right MS-20 based filter with one, and a so-so tremolo with one... they were bot perfect until the driangle wave came along, which on the tremolo wasn't smooth enough (and I can't stand shunting caps to ground on the output of the LFO as it makes it unstable) and on the filter the depth wasn't great enough.  You have a PM.

-Colin

im thinking that the filter may need some work after looking at the datasheet.seems like it would have a pretty narrow range.

[ExpAnonColin]

I've designed an all-right MS-20 based filter with one, and a so-so tremolo with one... they were bot perfect until the driangle wave came along, which on the tremolo wasn't smooth enough (and I can't stand shunting caps to ground on the output of the LFO as it makes it unstable) and on the filter the depth wasn't great enough.  

Experiment and be persistent...

When something just doesn't work, normally I completely revamp one part of the circuit before I end up using 10 H11F3s... which in this case means the filter/ampliture modulator or the LFO.  The LFO has stayed

-Colin

[Hal]

omg i still have a lot to learn.

[Brian Marshall]

ok, so i came up with a pretty simple bandpass filter.... its not perfect as bandpass filters go...  

Im not sure the lower frequency is moving much...  and it is a total hack on my part.  maybe tomorrow ill try using the other half to even it out a bit.

ill try to draw something up soon