[sdiy] JRC4558D, LM13600/13700 Questions

[harrybissell]

er... I'll take question part two for $100  ;^P

The LM13600 has the darlington buffer variably biased by the Gm (control)
input...
the transistors themselves are different from the LM13600 as well. This makes
the
LM13600 work better at low bias currents, with the flaw that fast moving Gm
inputs
(can you say fast attack?) may cause a DC bleedthrough (thump) into the audio
channel.

The 13700 has a fixed bias and does not thump, but doesn't work as well as the
13600
for low Gm inputs.

You need not use either buffer... it could be replaced with a JFET transistor
which would work
well at low or high currents... (just takes more parts)

H^) harry

extra credit...

Check out the spice models for each and check out the transistor parameters in
the buffer... they
are NOT the same...

Steven Downhill wrote:

> Hi all,
>
> I've recently acquired 4 JRC4558D ICs from an old AIWA tape deck and was
> wondering if these were useful for any synth diy projects that may be
> lurking on the net.
> I know that a number of effects peddles from the late 70's and early 80's
> used them, although for what reason I've no idea (I can't find a
> datasheet/schematics anywhere for them).
> Are they similar to the more modern NJM4558's ?.
>
> Also, there has been a number of mentions of adding a couple of components
> (FET transistor etc) to the input? stages of an LM13700 so that it behaves
> more like the LM13600 (if not the same).
> However not being very electronically minded at all, I've no idea how to go
> about this (I can read schematics so can build things without a problem,
> although I have no idea why the circuits operate as they do).
> Can anybody explain how to do this simply and preferably with a small
> diagram of what to connect to what.
>
> Thank you for your patience and time.
>
> Regards
>
> Steven
>
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