MOTM

Hi
Im a knew MOTM user, just received my first 4 modules and the soldering iron 
is still hot. The quality is just as great as expected from what I ve heard from 
this list and the MOTM website and I cant wait to get everything up and 
running. 

One of my modules is the 410 tripple filter which includes some 4558 op-
amps in the design.The 4558 is more or less a twin 741 which is not the best 
audio opamp. It says in the manual that these were there in the original Korg 
design and thats why these quite old opamps are used.  I dont now the 
original Korg 3100 sound and there is nothing wrong with vintage design but 
has anyone tried to use never "better" opamps. TL072 should replace with no 
problems I assume.

For now I think I ll put in some good quality IC sockets for easy replacement 
then I can test different opamps later.

Greetings from Denmark

Gregory

>
> One of my modules is the 410 tripple filter which includes some 4558 op-
> amps in the design.The 4558 is more or less a twin 741 which is not the best
> audio opamp. It says in the manual that these were there in the original Korg
> design and thats why these quite old opamps are used.  I dont now the
> original Korg 3100 sound and there is nothing wrong with vintage design but
> has anyone tried to use never "better" opamps. TL072 should replace with no
> problems I assume.


Certainly the TL072 is "better" but the 4558 has a distinct sound to them which 
is why they are used.

In fact, if you look at all the world's "audio stuff" built from 1985 to 1995, 
the 4558 was king!

Paul S>

> Certainly the TL072 is "better" but the 4558 has a distinct sound to them
> which
> is why they are used.

Has anyone managed to quantify this distinct sound? I don't doubt that it
exists; I'm just curious whether it's some sort of frequency-response
characteristic or non-linearity or something else that can be described
quantitatively.
 
> In fact, if you look at all the world's "audio stuff" built from 1985 to
> 1995,
> the 4558 was king!

Looks like it goes back further than that. The Mu-Tron Bi-Phase I bought
recently is full of 4558s.

--Adam
(keeping fingers crossed for the Schreiber clan)

a) Sorry, I meant to say "1975-1995".

b) the 4558 and also the low noise (but power sucking 5532) have a very
distinctive 'peaky in the midrange' sound. They don't have a "big bottom
end" and the overall sound is sort of 'grainy'.

c) Look at the 'mythical' Ibenex Tube Screamer pedal for folks who even
like *certain date codes* of 4558s :)

Paul S.

>b) the 4558 and also the low noise (but power sucking 5532) have a very
>distinctive 'peaky in the midrange' sound. They don't have a "big bottom
>end" and the overall sound is sort of 'grainy'.

Isn't the 4558 one of the op-amps that doesn't phase reverse and/or
latch-up? That should make a difference when you start punishing it.

-- 

Terry Bowman, KA4HJH
"The Mac Doctor"