Author: Kaz Kylheku Date: To: Darrall Dougherty CC: ada-mp1 Subject: RE: Wow: quite a difference from replacing the EQ section op-amp!
On Mon, 10 Dec 2012 08:44:40 -0600, Darrall Dougherty
<darralld@???> wrote: > Why did they put the 4559's in if they were already putting 5532's
> in some locations anyhow?
It was probably to save costs. Putting 5532's in some
locations is cheaper than putting them in all locations.
An interesting question is why does the NE5532/4 appear in the
particular places in the MP-1 that it does?
Why does the schematic call for a TL071 at the output of the
chorus section, but a NE5534 is installed?
Or, why is the MIDI board U11 a NE5532? That's hardly even used!
It's the rear-jack balanced line input whose impedance is too low
for guitar, which people ended up bypassing with a rear jack mod
which even ADA themselves started doing.
Some of the other places I can understand; it has decent driving
ability, down to 600 ohms, so from that perspective it's not a bad
choice to use for output buffers.
4559's are still found in low-end gear today. I was
surprised to see them in the preamp section of a Tascam
USB 122L interface, which makes me wonder whether they also
used child labor. I recently gutted a 1993 vintage
rackmount crossover unit from DOD to build my own project.
The original circuit board is loaded with 4559's.
They are found in 1980's Peavey stuff like the Bandit.
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