TL072 vs. 4560?

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I have a little problem in Fender´s Bassman 400. There is everywhere used tl072 except one opamp, which is 4560. Unfortunately I am not able to find any 4560 where i live.
Is there any good reason why would one use 4560 instead of the rest of 072?
I know 072 is jfet and 4560 is bjt, but from the schematic it is not clear to me why the jfet is not used.

I suppose I can replace the 4560 with 4580, which should be even better, right?
 

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i know it´s just signal detection, but why is there used another type of opamp? I don´t think any of the inputs gets too near to rail (I once heard jfet opamps don´t like it), so I just don´t know.
In fender bassman 200, the 4560 is used more, also in the signal path, even though the 200´s circuit is nearly the same as 400´s, except it has just one parametric eq.
 
Hi,
is the odd man only only monitoring a voltage and driving a LED indicator?

Why go for quality, speed, accuracy here?
Why change from 072 and add complications of inventory?

Why has the rest of the circuit got so many redundant half chips? or are they used in another channel?
 
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