OpAmp selection for XLR output.

[jrc4558]

Good day!
I have build an addition to my Condor cab sim to be able to drive an XLR input on the board in my studio. It basically consists of a non inverting buffer powered by a bipolar +/- 15VDC supply. I used a LF351 opamp and did layout for a single opamp 8 pin chip. The output is really quiet and very muddy. I suspect that LF351 is having hard time driving the low impedance line of XLR input. What would be a suitable subsitution, aside from NE5334, that could drive a balanced line well?
Thanks!

[Sir H C]

5534.  That is the one that is set to do 600 ohms.  Maybe some new ones, but most op-amps are not able to drive such low impedances.

[d95err]

Try a 5532 then, it's got a standard dual opamp pinout.

I'm building a Condor too, and I'm thinking about adding a balanced output. Is your output balanced, or is it just a buffered unbalanced XLR out?

[Ardric]

There are special chips designed for the purpose of driving a long balanced cable.  The SSM2142 was common once.  Some newer chips are TI's DRV134 and the spiffy THAT1646.  They are hi-fi and current hungry.  Powering them properly can be a problem for battery-powered fx.

If you go buffered but unbalanced, what about the 'ol LM386?

[David]

Constantin:

Check this link:  http://colomar.com/Shavano/intro_opamp2.html

Down toward the bottom of the page is a schematic for a DI with XLR output.  It looks a little sketchy, and I'm thinking it's intended for bipolar power.

[Seljer]

I think to make it run off a regular 9v battery, all you have to do is connect the other end of that 470k resistor and the noninverting input of the bottom opamp to 4.5V

heres another slightlighly fancies DI box http://sound.westhost.com/project35.htm

[David]

Good call, Selj!  Yeah, I'd probably go with that one too.

[jrc4558]

Cool guys! I actually am running the whole thing off of a bipolar 15VDC supply, just to get some of that high headroom. The Condor part is at unipolar 15VDC, which the input FET really likes too! So the current consumption is not an issue.
I though about LM386, but it was a very low input impedance (50k if i remember correctly), so it will need a buffer in front of it anyway. So I thought this will be plan B.
Ok, I will try to find some of those NE5534s and swap the LF351 out.
Will report with results!
Again, thanks for all opinions and advice!

[David]

Whoa, cowboy!  Hold up, thar!     If you're planning to build one of the DIs Selj or I suggested, I'd recommend using a 5532 since they require 2 op-amps.  The 5534 needs external compensation if you run it at a gain less than 3.  The '32 has no such constraint.

Let us know how it works out.  I may need to do something similar myself.