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80hinhiding said:

I'm having a terrible time moving forward with my build because I don't have clarity on what constitutes a professional line input for a mixing console. 

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TI INA217 or THAT 12xx-series.

You're welcome.

Hi Adam

have a look at Doug Self's book on low-level audio design.  Its a goldmine of practical circuits, including a 5534/5532 base Line Input.

Also, IIRC there is Steve Doves excellent series on Professsional Mixing Console Design that is hanging around somewhere on the Internet. - Found it here:

http://www.vintagewindings.com/gen%20pop/8299543VW8335/ProAudio1/Steve%20Dove%20Console%20Design.pdf

Best regards

Mike

80hinhiding said:

Ahem, I have had both on my radar already.  It's not that simple Andy.

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It's not that hard if you want is clean linear wideband signal capture.  Many console makers use the canned off the shelf solutions these days. Back when I was designing consoles we had to roll our own, but not very hard.

If you are looking for some audio voodoo, research effects circuitry, and be more specific with your inquiry....

JR

A linear input does not impart any tone on the signal...

This is an old argument,  but do you cook with a clean cooking pot, or one that imparts some common flavor every time?

FWIW this is a fairly common pursuit in some circles, but I long ago decided to put a bypass switch on all intentional nonlinearities, and avoiding non ideal transfer functions I don't want...

Sorry I am the wrong guy for advice if you don't want a clean basic audio path. I haven't designed an effect since the early 80s.

JR

> With so many options I'm stalling.

Pick one and move on with your life. Technical stall is not getting music on tape (MP3).

> Are they all suitable options to be considered professional?

Neil Young is a professional musician. One of his hits (such as Neil has hits) was allegedly recorded on a classroom-type Wollensak in a hotel room. I was around for another band's small release which has an amazing afterlife as a samples source; that was plain UN-balanced inputs on a Tascam board. "Walk Away Rene" was mid-level hi-fi stuff in a basement. You can hear the duck-tape around the inserted flute solo. 13 weeks on the charts, #220 in Rolling Stone Greatest Songs.

PRR said:

You can hear the duck-tape around the inserted flute solo.

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Best quote nominee.
Best,
Bruno2000

80hinhiding said:

Ahem, I have had both on my radar already.  It's not that simple Andy.

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You asked, "What constitutes a professional line input?" and the answers I gave met that criterion.

The thing is -- what's inside those parts is the same as a 5532- (or any other op-amp) based differential input stage. They roll in precision resistors, laser trimmed at the factory, so CMRR is much better than anything you can do with discrete resistors around a 5532. (When you read the data sheets, all op-amps will claim > 100 dB CMRR, but that doesn't include the effects of the external resistors, which must be well matched to actually meet that figure.)

So if you hate the tone of a THAT input stage, you'll hate the tone of a 5532 input stage, too. (5534 is basically the same except you can trim the offset and change the compensation.) I'm sure you hated the tone of the TL072 input stage.