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

[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]
====
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

 

[Cqwet Dbdfte]

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

JR

I vaguely recall Consumer Reports were sued by Bose and lost due to some negative subjective remarks, which highlights the perils of subjectivism.
Music interpretation can (should) be emotional, opening the door variability and inconsistency, and has to be taken with a few pinches of salt.
I have little experience with Peavey, a friend had one, a little guitar amp he said had insufficient power output. I measured it with a dummy load, and it met the stated output, like 50W, but it did not sound "loud". I suspected too low even order harmonics, but did not do a deep dive into to causes.

 

[Mr. Moscode]

Just my two cents,
On panning, hard left or hard right are the only positions of zero phase , Center in stereo is kinda there but still subject to anomolies of stereo speakers room acoustics etc. That is why theatre sound developed the center speaker. to increase the clarity of dialog. So there are few real choices for pure punchy reproduction until you get to the bottom frequencies where the two speakers function together as a single array. (That will depend on the spacing of the speaker pair.) So to pan outside of the hard left and right creates "fuzz" in the mid and high frequencies, and the real question is how much fuzz do you want. In a mix you can use that to contrast with the stuff that is in your face clear. Futher, adding of time delays choruses, Haas effect etc. can make mid and hi stuff clearer, but it is at expense of low and mid low frequencies which will add comb filtering that ruin any phase linearity. To add to the complication, people hear things differently. Some are able to isolate sounds, hearing around all the fuzz. To others it is just one big din. Others have one ear that hears things different from the other so they will favor one side over the other. So trying to come to a consensus is sometimes impossible. So unless there are individual speakers in all over the place - super Atmos surround? (Has anyone heard playback in George Massenbergs's Blackbird room) We make the best decision in the given situation with the given listeners.

Why do you think panning alters phase? Have you measured it? All panning does is change the levels in the channels used.

Personally I don't like instruments hard panned to one side or another for the reason you bring up, unequal response of ears, especially in the older folks. And with earbuds or cans it's worse.

 

[Mr. Moscode]

Quite so for absolutes. But where there are phase shifts in some frequency ranges, I think they'd be audible.

I don't follow ... a DC-coupled amplifier doesn't necessarily have a frequency response from 0Hz to whatever

DC coupled may be different from a DC amplifier. If flat to DC there is no low frequency cutoff frequency, ergo, no phase shift unless there is an anomaly in the design that introduces phase shift, like EQ.

Audibility of phase shift is so context dependent. Fast complex music would mask it unless it's intentional, like a Hammond Leslie spkr which changes phase with a rotating horn and is a Doppler frequency shifter. Instruments have phase shift in overtones in different ranges or registers, so . . . there you go.

 

[vintageampfixer]

Instruments have phase shift in overtones in different ranges or registers, so . . . there you go.

Of course. So if the intention of recording is to have an accurate copy which can be replayed and hopefully sound as close as possible to the original then whatever the characteristics of the sound being recorded - from a duck quack to a Hammond with a Leslie speaker - wouldn't one strive for the recording process to not colour that and if that's the case then shouldn't anything which changes the tonal quality - the timbre of the original - avoided where possible?

If on the other hand, we're considering the end output as divorced from the original source - the mix, processing and production become the product rather than fidelity to the original, then perhaps it doesn't matter.

 

[abbey road d enfer]

DC coupled may be different from a DC amplifier.

How?

Audibility of phase shift is so context dependent. Fast complex music would mask it unless it's intentional, like a Hammond Leslie spkr which changes phase with a rotating horn and is a Doppler frequency shifter. Instruments have phase shift in overtones in different ranges or registers, so . . . there you go.

The discussion here is audibility of fixed phase-shift resulting from high or low-pass filtering.
Of course, varaiable phase-shift is audible because a dry signal is mixed with the phase-shifted signal, which results in variable notches. So again, what is perceived is frequency response variations.

 

[abbey road d enfer]

Instruments have phase shift in overtones in different ranges or registers, so . . . there you go.

Can you elaborate on that? Phase-shift is a relative notion. What is the reference?

 

[RoadrunnerOZ]

The use of external preamps to record whether feeding to a recording console or direct to an audio interface is generally chosen to improve on the mic preamps available in the existing recording gear - an inferior pre would never be chosen in the first place. Finding the best is a matter of comparing with known benchmarks and listening to the recorded result.

If on the other hand, we're considering the end output as divorced from the original source - the mix, processing and production become the product rather than fidelity to the original, then perhaps it doesn't matter.

The recording console and/or digital audio interface used to record various mic and line sources is usually the same equipment used for mixing - there is no divorce from the original sound/source. The addition of various inline effects or compressors is to enhance the original sound. The fidelity to the original sound is not lost in this process. What happens at the consumer end depends on the format they have and the reproduction equipment they use.

"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.

Phase differences at different frequencies will naturally occur in any piece of gear - this doesn’t necessarily mean phase distortion will occur. In parametric equalisers you can get phase distortion occurring at the crossover points (Low/Low Mid, Low Mid/Hi Mid, Hi Mid/Hi - but you don’t usually use these in the recording path. Phase distortion can also occur when splitting a recorded sound and processing it on dual effects processor channels, or dual miking an instrument where tiny differences (or large) in positioning can cause phase errors.
The quality of what is recorded depends on the “sound” (and quality) of the mic and the integrity of the first contact preamp(s) that will pass this to the record medium.

 

[jeremynothman]

The use of external preamps to record whether feeding to a recording console or direct to an audio interface is generally chosen to improve on the mic preamps available in the existing recording gear - an inferior pre would never be chosen in the first place. Finding the best is a matter of comparing with known benchmarks and listening to the recorded result.

The recording console and/or digital audio interface used to record various mic and line sources is usually the same equipment used for mixing - there is no divorce from the original sound/source. The addition of various inline effects or compressors is to enhance the original sound. The fidelity to the original sound is not lost in this process. What happens at the consumer end depends on the format they have and the reproduction equipment they use.

Phase differences at different frequencies will naturally occur in any piece of gear - this doesn’t necessarily mean phase distortion will occur. In parametric equalisers you can get phase distortion occurring at the crossover points (Low/Low Mid, Low Mid/Hi Mid, Hi Mid/Hi - but you don’t usually use these in the recording path. Phase distortion can also occur when splitting a recorded sound and processing it on dual effects processor channels, or dual miking an instrument where tiny differences (or large) in positioning can cause phase errors.
The quality of what is recorded depends on the “sound” (and quality) of the mic and the integrity of the first contact preamp(s) that will pass this to the record medium.

Hmmm

Well I can agree with the first and last statements, that the sound and quality is defined by transducers and preamps, I can’t really agree with the rest.

Pretty much all recording engineers, perhaps excepting those working in classical music, utilise parametric EQ on the way in, and accept the resulting phase anomalies - but of course, this should be a secondary course of actions after mic choice and placement.

Also, using different tape machines or converters and different consoles for mixing to the recording process is more or less par for the course. While there are some exceptions, this was especially highlighted by the ‘90s concept of “record on a Neve, mix on an SSL”, and I still think it stands for most pop/rock engineers, that they tend to prefer to record on a more colourful console, and mix on a console/in a DAW with superior routing and cleaner signal processing. The use of different studios with different acoustic spaces and speakers for tracking and mixing is more or less par for the course

 

[RoadrunnerOZ]

The preference i have experienced in recording is to record flat and not apply EQ or compression (unless absolutely necessary) on input path but on the monitor or mixdown path - leaving a clean untouched recording and applying the EQ etc later.
You can’t un-EQ or uncompress a recording. Any EQ applied is usually for remedial purposes like to clean up room sound or instruments such as Toms ringing.
With the ability to have unlimited tracks with EQ, compression etc in a modern DAW there is mostly no need to pre-treat a recording. Anyway that’s a preference that is down to the individual engineer but I know very few who use record path EQ - maybe limiters to prevent input clipping or compression for poor vocal or acoustic guitar techniques - or if using a mic pre that has particularly nice EQ that complements a particular mic.
The use of a different console/studio/engineer for mixdown is more common in the commercial environment where the client can afford it, but in the smaller studio/home studio environment this is not usually the case. It all comes down to budget.

 

[jeremynothman]

I think this is a question of philosophy. All the engineers I’ve worked with (amongst them Grammy, Emmy and ARIA award winners gladly EQ and compress to tape wherever they consider useful. For some of them that looks like 10dB of gain reduction on room mics and 5dB on bass or acoustic guitars, and for others it’s only for tracking vocals or tickling the meters. Ultimately, isn’t everyone trying to make it sound like a record? If I have a good monitoring environment and good hardware and in front of me, I want to use it, because frankly, it tends to be more characterful than what I have in plugin world