TL072 vs. 4560?

kubeek · 13th July 2006, 10:29 AM

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?

Ryssen · 13th July 2006, 11:07 AM

They are both as bad..

They are both dual Ic´s on the schema 4560
is not in the signalpath its only used as signal detection.I think.
I belive 4580 should work as well in that place.

kubeek · 13th July 2006, 10:31 PM

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.

Ryssen · 13th July 2006, 10:47 PM

Aren´t the 4560/80 cheaper and that´s why they use them?

john curl · 14th July 2006, 12:41 AM

I doubt it. Warning!

anatech · 14th July 2006, 12:49 AM

Hi kubeek,
Here is the datasheet for the NJM4560 . It's actually not bad if you consider the NJM4559 and NJM4558. The NJM4560 is a low noise, dual op amp. It slews around 4V / uS. Bipolar input as Ryssen noted. NJM4665 or NE5532AP should work well in that location.

-Chris

AndrewT · 14th July 2006, 12:50 PM

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?

anatech · 14th July 2006, 01:20 PM

Hi Andrew,
It may have something to do with output current. 4558 might be fine there.

-Chris

kubeek · 14th July 2006, 08:42 PM

Andrew, the other halves are used in the rest of the circuit, but I too don´t understand why potentialy noisy ("switching") rectifiers are on the same chip as the signal part.

13th July 2006, 11:07 AM	#2
Ryssen diyAudio Member Join Date: Dec 2003 Location: Sweden--> Here	They are both as bad.. They are both dual Ic´s on the schema 4560 is not in the signalpath its only used as signal detection.I think. I belive 4580 should work as well in that place. __________________ Regards Åke

13th July 2006, 10:47 PM	#4
Ryssen diyAudio Member Join Date: Dec 2003 Location: Sweden--> Here	Aren´t the 4560/80 cheaper and that´s why they use them? __________________ Regards Åke

14th July 2006, 12:50 PM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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? __________________ regards Andrew T.

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13th July 2006, 10:31 PM	#3
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	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.

14th July 2006, 12:41 AM	#5
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	I doubt it. Warning!

14th July 2006, 12:49 AM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi kubeek, Here is the datasheet for the NJM4560 . It's actually not bad if you consider the NJM4559 and NJM4558. The NJM4560 is a low noise, dual op amp. It slews around 4V / uS. Bipolar input as Ryssen noted. NJM4665 or NE5532AP should work well in that location. -Chris

14th July 2006, 01:20 PM	#8
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Andrew, It may have something to do with output current. 4558 might be fine there. -Chris

14th July 2006, 08:42 PM	#9
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	Andrew, the other halves are used in the rest of the circuit, but I too don´t understand why potentialy noisy ("switching") rectifiers are on the same chip as the signal part.

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