LM833 any good?

[Wynand]

Hi!

I'm looking to build a preamp for an audiosector LM4780 kit.

Would the LM833 be a good op amp to use. If not what should I use?

[Wynand]

Another Q

Would it be better to put a buffer before and after a vol pot?
Rather than just after?

[forr]

I used an LM833 in a Bainter notch filter and it badly oscillated. I replaced it with another sample, same behaviour. A NE5532, a JRC 4560 or an MC1458 did not show this problem. The LM833's were used in subsequent Sallen & Key 12 dB/o filters and worked ok. As I want to rely on secure parts only, I prefer not to use LM833's if I have other devices at hand. I have not understood why this op-amp which has a very classic scheme and should have a large phase margin was unstable within the Bainter's circuit.

~~~~~~ Forr

§§§

[peranders]

Originally posted by forr
I used an LM833 in a Bainter notch filter and it badly oscillated.

... but did you analyze the frequency properties before you chose it? Accordning to datasheets I think this opamp is rather unsuitable for this. Maybe your pcb had some influence on this? Prober decoupling etc.?

[Wynand]

Anybody Else?

[peranders]

What I ment was that LM833 is decent so why not use it if you already have it but you have also newer types you might consider.

My answer is based on "normal" demands. If you have golden ears LM833 really nothing will be good enough. LM833 has similarities with the famous NE5534 which isn't as bad as some people claims.

[peranders]

Originally posted by Wynand
Another Q

Would it be better to put a buffer before and after a vol pot?
Rather than just after?

It's often better to have 10-47 k pot before the buffer then you'll have a real low ohmish output. If you put it after the opamp you might use a 1 kohms pot instead.

[Wynand]

Sorry about the quality of the picture

Will this buffer circuit work.

Are there any improvements to be made?

Would 1uF and 47K be ok?

[Russ White]

LM833 is fine for you aplication.

Do as peranders said and make sure you bypass the chip correctly. I would use something like a 47uf low ESR lytic with a 100nf film cap on each rail.

On input I would use 100K from input to GND and 1-2.2uf MKP for the input cap. It is always most safe to use the input cap, but if you are sure you will only use sources with no DC offset at the output then omiting the input cap will give you the best result (lower distotion).

Have fun!
Russ

[Salas]

Just 2 days ago it so happened I was servicing my first CD player (bought in 1987). A Denon DCD 1400. It sill plays ok, but I cleaned it and changed its pickup with a nos one I had bought years ago and kept as a spare. It had JRC 4580D opamps as I/V and buffer originals. I thought of playing around a bit. I fitted chip bases and listened to various substitutions. 5532, 2604, 2134. Oh, nothing sounded musical enough. Then I saw a couple of LM833 in my inventory. I recalled that they were favorites of mine among cheap ones but I did not use them in a preamp when I was testing out, back in 1990, because they exibited enough offset. But here the outputs are ac coupled! So I fitted them. Well, here it is again! The most musical outcome from using a cheap op amp! Nice encompassing sound with far more, but easy detail than the others. Tonality is superb without that midbass heavey B.B. sound. Second best was 5532 with good detail but thiner presence. The noise of LM833 proved as good as with 5532 also. The LM833s stayed in there and I grin each time I check a cd wearing my Grados. The old chick got a facelift and she's still kicking :-)