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[Nathan Riddle]

Time to put to rest the preamp differences game.

Audible Difference? Inside An ABX Console Test
Blindly comparing the input stages and A/D converters of two consoles through Dante to see if either actually sounds better.

https://sites.google.com/entertainmenttechnology.org/mixer-test

[John Roberts {JR}]

That time came and went a couple decades ago...

 Good luck sticking a fork in it. 

JR

[Miguel Dahl]

And who are these people in the test panel? Friends with a beer in their hand at a party, audio professionals, or just "randoms"?

For me a hammer is a hammer, for carpenters there's different kinds of hammers.

[Tim Hite]

Looks like the real winner here is the 2018 MacBook Pro speakers. . .

[Frank Koenig]

And who are these people in the test panel? Friends with a beer in their hand at a party, audio professionals, or just "randoms"?

There are many variations on how you can do this experiment but I would expect the result to be much the same. There MIGHT be a few dB difference in noise, which might matter for something specialized like nature sound recording, but even in that instance the noise is likely to be dominated by the noise of the preamp built into the condenser mic. (From the point of view of a preamp designer the worst case for noise I know of is small diaphragm dynamics, such as lavaliers, that have very low sensitivity.) Phase shift or nonlinearity in the ADC won't amount to a hill of beans. If you really want to go looking for trouble look at how the ESD/EMI circuitry in front of the first gain stage affects certain picky microphones or how the preamps "round-off" as certain engineers find it necessary to flirt with clipping. BTW, aluminum electrolytic blocking caps (properly polarized) in the signal path sound fine. They're like testis in men -- most preamps have a pair -- unless they're trannies (use a transformer to insert phantom power). --Frank

[Peter Morris]

That time came and went a couple decades ago...

 Good luck sticking a fork in it. 

JR

“Like”

 …..  not really wanting to get into this debate, but what amazes me is - when you take a lovely analogue signal and for want of a better analogy, chop it up into little pieces 1/96000 of a second long, measure the size of those pieces; and then start adding, subtracting, multiplying and dividing those pieces (numbers) and eventually reassembling those numbers into an analogue signal … THEN... so many people want to attribute the whole sound of this system to the initial sound of the Mic-pre.

FWIW

https://www.audiomasterclass.com/newsletter/the-famous-5-preamp-everything-you-need-to-know

The chip used above was based on a design by my good friend Graeme John Cohen – He did this in 1984!

http://leonaudio.biz/double.balanced.mic.amp.notes.pdf

[John Roberts {JR}]

“Like”

 …..  not really wanting to get into this debate, but what amazes me is - when you take a lovely analogue signal and for want of a better analogy, chop it up into little pieces 1/96000 of a second long, measure the size of those pieces; and then start adding, subtracting, multiplying and dividing those pieces (numbers) and eventually reassembling those numbers into an analogue signal … THEN... so many people want to attribute the whole sound of this system to the initial sound of the Mic-pre.

FWIW

https://www.audiomasterclass.com/newsletter/the-famous-5-preamp-everything-you-need-to-know

The chip used above was based on a design by my good friend Graeme John Cohen – He did this in 1984!

http://leonaudio.biz/double.balanced.mic.amp.notes.pdf

I was not familiar with Cohen's (RIP) work until fairly recently but used the topology decades ago. In 1981 I published a kit article for a high performance phono preamp in Popular Electronics, using a variant on the topology using JFETs instead of bipolar devices for the front end gain stage. (I also sold a MC version kit using low noise bipolar transistors).
http://proaudiodesignforum.com/images/pdf/Roberts_Low-Noise_Low-Distortion_Phono_Preamplifier_Popular_Electronics_March_1981.pdf

Some old timers here may recall the potted "transamp" mic preamp modules, that also used that topology. I rolled my own console mic preamps using some even quieter Japanese transistors I found (ROHM 2sb737, 2sd786).

So indeed transformer-less console mic preamps were already far better then microphones some four decades ago.     

JR

[Frank Koenig]

Another subtle way that a "cheap" preamp might differ from an expensive one (I'm grasping at straws here) is common mode rejection. As long as there are passive components outside the chip the matching of those components for symmetry will affect the ability of the amplifier to reject noise that is common to the plus and minus inputs. This is unlikely to make a difference until the day a mic cable magnetically couples with some power cables in a way that introduces a lot of common mode hum.

Other differences might include the implementation of digital gain control and what sort of dance between actual gain steps, input pads, and downstream digital trim is programmed. It gets more complicated when gain sharing between consoles. I haven't looked into this but I don't think they're all the same -- yet. Thankfully the problem of "zipper noise" (the audibility of gain steps when making changes in the presence of signal) was solved some time ago.

--Frank

PS: Having brought up common mode rejection I thought I better go look at some specs. The XR-32 claims 80 dB at 40 dB gain which is damn good. They must be using chips that include all the critical parts and are trimmed from the factory. I looked at Yamaha and A&H and they don't even bother giving CMRR specs. Guess I'm so last century.  Never mind. -F

[Roland Clarke]

A dear friend of mine Mike Skeet, sadly no longer with us, used to build project box mixers using virtual earth amplifiers.  He originally used the SSM2017 but later used the SSM2019.  He did many remarkable classical recordings with these and sound quality was always extremely good. 

This is a link to an article about one of his matrix mixers and has a couple of pics of the said amps.

http://www.saturn-sound.com/Curio's/the%20practical%20research%20file%20of%20mike%20skeet%20-%20paper%20no%206.htm

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