[sdiy] EH frequency analyzer

[Scott Gravenhorst]

Tom Wiltshire <tom at electricdruid.net> wrote:
>
>On 8 Aug 2008, at 14:40, John Mahoney wrote:
>>
>> The Moogerfooger ring mod looks to be based on the LM13600. (Hey,  
>> isn't the 13600 all but extinct? I wonder what Moog is using now in  
>> these pedals. Maybe they've got a stockpile.)
>
>National Seminconductor still have the LM13700 listed. I never  
>understood exactly what the difference was supposed to be between  
>LM13600/LM13700 ( was 13700 a later upgrade?) but they seem to be  
>pretty much interchangeable.
>
>T.
>
>(http://www.national.com/mpf/LM/LM13700.html)

It's been mentioned here that in the LM13600, Iabc has an effect on the output
buffer, whereas the LM13700 has a buffer which is isolated from Iabc.  I just looked
at the datasheets for both and this is shown in the internal schematics of the parts.

Not sure _exactly_ what the effect of that is (thumping in a VCA?).  They are
interchangeable in many apps, but not all.  In a pinch, if one doesn't want the Iabc
output buffer effect of the LM13600, I think an external buffer can be used instead
of the IC buffer to emulate the LM13700.


-- ScottG
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