Opa2134.

[fap]

G'day all, this is my first post here. I have used the OPA2134 dual op amp in a few preamp projects with good results.

Is the op amp still widely available? I believe that Burr-Brown have stopped making it. Any comments? Regards, Felix.

[SY]

Mouser's got thousands to ten thousands of the various 2134 flavors. It doesn't look like much of a shortage.

[jrockhead]

Digikey has something like 30,000 ready to ship. How many you want kid?
Focus.TI says the 2134 is Active Status. Its my favorite fet input op amp.

[fap]

G'day mate, yes they are indeed a very nice dual op amp. In my various DIY Elliott Sound Products projects (P06, P88 and P99), I've used a mixture of different dual op amps like the old faithful NE5532's and LM833's, however I wouldn't mind 'upgrading' a few projecs to use the OPA2134. Regards, Felix.

[stratus46]

Originally Posted by fap

G'day mate, yes they are indeed a very nice dual op amp. In my various DIY Elliott Sound Products projects (P06, P88 and P99), I've used a mixture of different dual op amps like the old faithful NE5532's and LM833's, however I wouldn't mind 'upgrading' a few projecs to use the OPA2134. Regards, Felix.

The only thing that concerns me about that opamp is the asymmetrical slew shown on page 7 of the data sheet "LARGE-SIGNAL STEP RESPONSE". That glitch at the negative zero cross just doesn't seem right. I use them and don't have any sonic complaints but it bothers me.

G²

[fap]

G'day mate, that's quite interesting. I don't know if I'd ever actually 'hear' it, but it is a fact that the the OPA2134 being a FET input device will be about 6 db? 'noisier' than comparable dual op amps like the (bipolar input) NE5532!

For this reason I tend to use NE5532's in my DIY phono stages, but having said that, my main system DIY phono preamp uses OPA2134's and it seems pretty quiet to me! Regards, Felix.

[jrockhead]

Hi Felix, I use the 2134's with Rod's P97 preamp and with the standard gain as he recommends the preamp is quiet as the proverbial mouse. With a shorted input and the volume knob all the way up I hear a slight hiss, that's all.

What I did notice about the P97 board is it only has about 40 to 50 db of channel separation. Not enough in my estimation.I then bought a second board and piggybacked it so only one channel per board. Now the preamp has 100 db's of channel separation or crosstalk if you will. And that's across the whole audio band, not too shabby.

I originally tried LM4562's in this preamp and they sounded a little too crisp for my taste. The BB's gave it just the right smoothness, must be the FET inputs on the 2134's.

[fap]

G'day mate, interesting stuff. I've never built the P97, only the P88 and that seems fine. Yes I've frequently wondered about channel crosstalk issues as for example with the P06 phono stage where one half of each op amp handles one channel and the other half the other.

However I've never 'heard' or noticed anything untoward, thankfully. Regards, Felix.

[Andrew Eckhardt]

Originally Posted by stratus46

The only thing that concerns me about that opamp is the asymmetrical slew shown on page 7 of the data sheet "LARGE-SIGNAL STEP RESPONSE". That glitch at the negative zero cross just doesn't seem right. I use them and don't have any sonic complaints but it bothers me.

G²

The distortion curves might tell more about what it does at audio speeds, especially with less than 100p on the output. Maybe it wouldn't be the best for something like a DAC I-V converter (or anywhere else it might see edges). If you look at the PCM1704 datasheet filter circuit you'll see TI didn't recommend it, but did use it for the output filter.

[jrockhead]

Originally Posted by fap

G'day mate, interesting stuff. I've never built the P97, only the P88 and that seems fine. Yes I've frequently wondered about channel crosstalk issues as for example with the P06 phono stage where one half of each op amp handles one channel and the other half the other.

However I've never 'heard' or noticed anything untoward, thankfully. Regards, Felix.

Well, the problem with the P97 is not so much the dual op amp although I'm sure it does have an effect. Most of the problem was the closeness of the PCB traces in the tone amp section. Lots of coupling there. Next was the use of a single pot to do the balance function. Quite clever scheme but I changed it to a dual pot so each channel has its own resistor{pot} to ground to shunt the signal.

And of course having two boards one inch apart adds mightily to the separation.With the single stereo board I noticed the music blended together into a nice sounding mush. Not offensive but just did'nt blow my dress up if you understand my meaning.

Now the instrument and voices are quite distinct and just pop out of my speakers, most enjoyable to say the least! I would have to say now that channel separation, lots of it, is one of the things that make a good pre amp.