Preamp difference : if it's not the frequency, not the slew rate, and not the harmonics, what is it ?

[RoadrunnerOZ]

I think the effects of mic placement in a studio would far outweigh any differences in a preamp. Also try putting a linear phase EQ on a single high attack sound like snare or hats and listen to the result - then compare it switching to normal EQ - the linear phase sucks the life out of the sound in the mid to high areas and audible ringing can occur especially at low frequencies. A lot of software EQ’s have a linear phase button these days. Linear phase can work when say double miking a guitar cab or other instruments but completely not necessary for single miked.

 

[vintageampfixer]

I think the effects of mic placement in a studio would far outweigh any differences in a preamp.

Yes, as eloquently written by Dr Floyd O'Toole: "All things being equal, and if one has the option, of course get the phase correct - at least at the one point in space where it can be done!! However, this presents problems for two-eared listeners in multiple seats in reflective rooms (solve this one and a Nobel prize awaits)." but I'll say once more, the OP specifically said preamps.

In a comparative listening test of preamps, once assumes there should be minimal changes in the rest of the signal chain, so effects of mic and loudspeaker placement are effectively eliminated, right?

 

[Cqwet Dbdfte]

Phase interaction is a "thing", it can be additive or subtractive. Funny how old 50's recordings with single mic can sound so "real". Constructing a stereo image from multiple isolated tracks may be interesting, but would never be a true acoustic representation, if one was even possible, as electronic sources lack an acoustic analog, making "bin aural" representation a moot point, and seem to be quite rare anyways.

 

[RoadrunnerOZ]

Yes, as eloquently written by Dr Floyd O'Toole: "All things being equal, and if one has the option, of course get the phase correct - at least at the one point in space where it can be done!! However, this presents problems for two-eared listeners in multiple seats in reflective rooms (solve this one and a Nobel prize awaits)." but I'll say once more, the OP specifically said preamps.

In a comparative listening test of preamps, once assumes there should be minimal changes in the rest of the signal chain, so effects of mic and loudspeaker placement are effectively eliminated, right?

Any line test of preamps should be done by a listening test on well recorded music on decent speakers and each person in turn at the same listening position - you can put all the test signals you like and analyse with all the distortion and spectrum analysers under the sun and end up nowhere. A simple piece of music using say just vocals and acoustic guitar for one test, another with full orchestra and another with full rock band would sort of cover the ground for doing line tests.
I’ve blind tested gear (being looked at with purchase in mind) in studios for years by getting someone else to set up the patch (or by making a switch box and not seeing which I/O lead pair is going into which socket pair) and seeing which piece of gear I prefer, doing the same with other engineers and musicians.
For testing preamps with mics, mounting two identical matched pair mics together (I have several close mount adjustable dual mounts) and feeding each mic into the respective preamps, recording vocals and/or guitar, drums, bass and seeing which sounds best when soloed. For mic preamps it’s almost pointless putting line signals through for comparison if they’re never going to be used with a complex mixed signal but only single source from a mic.

 

[RoadrunnerOZ]

Phase interaction is a "thing", it can be additive or subtractive. Funny how old 50's recordings with single mic can sound so "real". Constructing a stereo image from multiple isolated tracks may be interesting, but would never be a true acoustic representation, if one was even possible, as electronic sources lack an acoustic analog, making "bin aural" representation a moot point, and seem to be quite rare anyways.

Yeah in some cases less is more - I’ve found for example that the more mics you put on a drum kit the more cluttered the sound can get. By starting with the overheads and then bringing up the other mics one by one to get the right balance is a good way to start rather than getting each drum and percussion piece to be full on sounding great and then trying to mix them and then introduce the overheads and room mic. I’ve had great results using just 3 or 4 mics in total.
Phase cancellations with multiple mics is another issue - when recording I usually get a rimshot at the very beginning or stick hits and can then later look at the track beginning of all the tracks and align them to the snare. I measure the overheads if spread to be the same distance from the snare or X-Y them - at the same distance from the snare as the floor Tom mic.

 

[abbey road d enfer]

"Extremely low" is more than zero so it means the effect is perceptible. I have to say, my ears might not be able to specifically attribute any effect to phase distortion or even detect it in the first place but by changing the phase relationships of different frequencies, you will eventually change the tonal quality of the sound. Consider an open A string being plucked; the waveform generated is close to a sine wave. If that A string is mounted on a sound box, the tonal quality changes because some harmonics are at different levels although the fundamental note remains an A. Now think about a trumpet playing the same note, the sound heard and the waveform are quite different although the fundamental frequency is the same. I'm not suggesting phase distortion will make a harp sound like clarinet but slight changes in the phase-frequency relationship will inevitably alter tonal quality - i.e. phase distortion is audible to some people and by reducing it, we clean up the sound.

You are talking about differences in harmonic content, which is clearly audible. That's the essence of timbre.
Many tests have been conducted with synthesized sounds where the position (phase) of the different harmonics have been varied. The resultant perceived tone differences were all attributable to the difference in peak factor.

 

[Cqwet Dbdfte]

I just wanted to point out a possible confounding issue affecting pre-amp sound, but as all know there are many pieces in the recording chain between the control room ears and the musical source. The weighted effect of a line level preamp ought to be minor compared to all other contributing factors. Making a list of these may be useful exercise. The more non-linear devices, (transducers) should have more weight in affecting the outcome.
Sadly, the majority of the listening public have been lulled into highly compressed storage formats and "musical" content with severe amplitude compression, which are not very challenging. Not saying striving for quality is a wasted effort, far from it, but real voices of concern may be few and far between. Sound reproduction would add more constraints than sound production, as the original source is not available for comparison. Sound production of course have more variables to deal with.
As has been pointed out, different people listen to different aspects of musical content, so getting a unified quality score may be a fuzzy target.

 

[abbey road d enfer]

Thank you for putting the thread back in the right track.

 

[JohnRoberts]

I just wanted to point out a possible confounding issue affecting pre-amp sound, but as all know there are many pieces in the recording chain between the control room ears and the musical source. The weighted effect of a line level preamp ought to be minor compared to all other contributing factors. Making a list of these may be useful exercise. The more non-linear devices, (transducers) should have more weight in affecting the outcome.
Sadly, the majority of the listening public have been lulled into highly compressed storage formats and "musical" content with severe amplitude compression, which are not very challenging. Not saying striving for quality is a wasted effort, far from it, but real voices of concern may be few and far between. Sound reproduction would add more constraints than sound production, as the original source is not available for comparison. Sound production of course have more variables to deal with.
As has been pointed out, different people listen to different aspects of musical content, so getting a unified quality score may be a fuzzy target.

[TMI] This (other weak links in the audio chain) is what drove me out of the hifi business in the mid 80s. After years of development I made a RIAA phono preamp that was in my judgement arbitrarily accurate. Then I received night and day different magazine reviews of the same exact review unit. My ASSumption (conclusion) was that the reviewers were hearing the differences in the rest of their personal review listening chains. In a vinyl playback signal chain pretty much every other element in that chain has larger variability than my precision preamp.

The reviewer with a questionable MM cartridge, lousy amplifiers, lousy speakers, lousy sound room, etc (He said my preamp made violins sound like sawing on wires. ) . He was most likely hearing his equipment not mine. Alternately the other reviewer with excellent phono cartridge, properly loaded with C, excellent loudspeakers, good amplifiers, and good listening room, heard his good gear. He favorably compared my preamp to one costing more than 10x. /TMI]
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Indeed almost everything is a weaker link compared to modern line level audio electronics.

JR

 

[vintageampfixer]

Indeed almost everything is a weaker link compared to modern line level audio electronics.

Are you saying the only buying criteria now are availability, price and feature set (probably in that order!)?

 

[JohnRoberts]

Are you saying the only buying criteria now are availability, price and feature set (probably in that order!)?

Nice straw man but no..... There is customer expectation bias associated with different brands. Back a few decades ago when I was selling a 36x24 split recording console for only $20k manufactured by Peavey, I had customers put tape over the Peavey name to not spook their customers.

The customer is always right, even when wrong.

JR