On Mon, 10 Dec 2012 08:44:40 -0600, Darrall Dougherty 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.