confusion regarding the TL072, TL082 and the 4580D

[mordechai]

If I understand correctly, the original chip in the Bluesbreaker was a TL072.  In the Analogman KOT, it seems that this has been replaced with the 4580D.  So in this type of circuit, I am guessing that the 4580D does what the TL072 does, but perhaps better in some ways (lower noise)?

Now, my question is this -- I've seen some posts where people have suggested that the TL082 is a suitable and sometimes better substitute for the TL072.  So are the TL082 and 4580D compatible op-amps?  In the KOT or Bluesbreaker-type circuit, what would be the benefit of one over the other as a replacement for the TL072?

[gritz]

*Caveat warning* I don't have any TL 082's to do back to back comparisons...

Manufacturers tend to quote the TL 072 as a lower noise TL082 and a glance at the spec sheets suggest that they are otherwise the same chip. Indeed, its possible that they're one and the same, having been graded for noise at wafer fabrication, or somesuch. The 4558D is different to both in that it's a bipolar (transistor) input as opposed to a fet input opamp and it needs a little input current to wake up it's input transistors. In most applications this isn't a big deal, but in applications where you need (google alert) low input bias current then the TL range wins. In real terms this means that if you're building something mathematical and you don't want your maths affected by having non-negligeable resistors hanging off everything (like if you're building a precision rectifier in a compressor) then you will want to avoid the 4558D. Otherwise the selection of components will be down to price, or reputation / mojo / B.S.

Opamps were originally created as "blameless" mathematical number crunchers for analogue computers, so don't be surprised if they all sound remarkably similar when put into a not - terribly - testing audio environment.

I would always suggest building the circuit, substituting the different opamps and asking a guitar playing friend (who can't see which opamp is being used) to lend an ear. the trick is in not letting him / her know that they're part of a test.

[amptramp]

I have the TI databook and the noise values are the same for the TL07X and TL08X devices at 18 nV/ root Hz, 4 µV for 10 Hz to 10 KHz and .01 pA/ root Hz.  What is different is the minimum open-loop gain of 25,000 for the 08X and 35,000 for the 07X at 25°C.  The 08X has a higher slew rate of 50 nsec vs. 100 nsec for the 07X for a 20 mV input with a 2K load and 100 pF.  Typical input bias current is lower for the 08X series at 30 pA vs. 65 pA.

There are so few differences that I wonder why TI brought out the separate TL08X numbers.  Noise is not one of the differences.  The TL06X series has lower supply current and higher noise and is sometimes used for LFO's where the current spike for an LFO is more important than noise.

[gritz]

Strange - the ancient datasheets (ST and Nat Semi) I have here in my dusty folder tell a different story:

Slew rate - broadly the same: TL072 = 16V/uS typical, TL082 = 13V/uS)

Equiv. input noise voltage (Rl=100R): TL072 = 15nV/Hz^.5, TL082 = 25nV/Hz^.5

So I guess that specifications really are subject to change without notice, the value of investments can go down as well as up, objects in the rear view...

Neither are particularly stellar in modern terms, but you'd probably have to be a fruit bat to be actually able to hear a difference.  

Edit: I notice that you refer to a 4580D in your original post and not a 4558D (apologies mordechai, I should wear my spectacles more oten). It's still a bipolar input opamp and from the rather scant datasheet I've just found on the web I'm not sure whether there's any kind of "special sauce" (real or imagined) in there.

[Jdansti]

Those three parts are fairly inexpensive. You could try all three and see if any sound better than the others.

[candidate]

I have seen TL082 recommended in LFO circuits due to the characteristics of their power draw.

As stated, TL072 is rumoured to have "better audio specs"

was the TL06X series the bargain chip?

[puretube]

I have seen TL082 recommended in LFO circuits due to the characteristics of their power draw.

As stated, TL072 is rumoured to have "better audio specs"

was the TL06X series the bargain chip?

6-series: low-powerconsumption type...

(yes, the 7-series used to be the selected lower-noise ones...)