Is the TL072 less noisy in a tubescreamer/SD-1 circuit?

[Silvio55]

Since I'm doing some mods to my SD-1 clone, which has a 4558, and remembered reading that TL072 may be less hissy in this circuit I wanted to ask if this is true. I have some TL072 laying around but dont have chip sockets. What do you say? It's really less noisy or just the same?

[PRR]

Depends on the circuit. At medium impedance '4558 is not bad. At high impedance it becomes a snake, TL07x is better. (Yes, I avoided the SD-1 part of the question.)

[Silvio55]

Depends on the circuit. At medium impedance '4558 is not bad. At high impedance it becomes a snake, TL07x is better. (Yes, I avoided the SD-1 part of the question.)

SD-1 is basically a tubescreamer. My electronics knowledge is very limited, don't know how to calculate the impedance of the op amp in this circuit.

[antonis]

SD-1 is basically a tubescreamer. My electronics knowledge is very limited, don't know how to calculate the impedance of the op amp in this circuit.

It just is the value of non-inverting input bias resistor..

For SD-1, you don't have to worry about it 'cause there is a transistor voltage follower (buffer) in front of the op-amp..

[ElectricDruid]

In terms of datasheet figures, TL072 is a lower noise op-amp than the 4558. Whether that's a big enough difference to hear in a specific circuit is an open question. PRR gave a good suggestion for when it might be, and Antonis pointed out that doesn't really apply here.

While it might be worthwhile pulling a chip out of a socket and trying a different one just to see, I'm not sure I'd bother desoldering an 8-pin DIP in order to put a different one in just on spec.

[KarenColumbo]

Try stacking them Fun and probably better SNR

[Silvio55]

Yeah, having a buffer in front I suspected it runs with a low impedance so theoretically it wouldn't mind. I wanted to put a socket on the board but didn't have any so I think it's not worth trying desoldering the chip just to try.

[amz-fx]

Since I'm doing some mods to my SD-1 clone, which has a 4558, and remembered reading that TL072 may be less hissy in this circuit I wanted to ask if this is true. I have some TL072 laying around but dont have chip sockets. What do you say? It's really less noisy or just the same?

Modern production 4558 chips are going to do better than the specifications would lead you to believe, and the TL072 is not going to sound much different. I tested both of these in a circuit that I designed. You can read about it here:

http://www.muzique.com/lab/null.htm

Both chips performed similarly and had quite low noise. The LM4562 will be slightly better, if you are looking to reduce noise and distortion. It is still available in a DIP package like the 4558 and 072.

Best regards, Jack

[Silvio55]

So if I remove the input buffer and increase the input bias resistor to get higher input impedance then a TL072 would perform better, right?

[antonis]

Right but alter input cap value, also..
(for 1M bias resistor 10nF should be fine - of course, you'll need to lower it down to 1.8nF if you wish to maintain "original" HPF responce..)

[Silvio55]

Right but alter input cap value, also..
(for 1M bias resistor 10nF should be fine - of course, you'll need to lower it down to 1.8nF if you wish to maintain "original" HPF responce..)

Cool! Thanks!