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Topic: Do preamps need to be level-matched (Read 10382 times) previous topic - next topic
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Do preamps need to be level-matched

Do pre-amps need to be level matched in order to compare them?

Do preamps need to be level-matched

Reply #1 –
Depends on how you are comparing them.

Do preamps need to be level-matched

Reply #2 –
Quote from: Rich B on
Do pre-amps need to be level matched in order to compare them?


If you listen to two otherwise identical systems, but one is even 1 or 2 dB louder, the louder one will often be perceived as better, even if the level difference isn't perceived as such.

Do preamps need to be level-matched

Reply #3 –
Quote from: julf on
Quote from: Rich B on
Do pre-amps need to be level matched in order to compare them?


If you listen to two otherwise identical systems, but one is even 1 or 2 dB louder, the louder one will often be perceived as better, even if the level difference isn't perceived as such.


That's why I'm asking about pre-amps. Wouldn't pre-amps be at the same level so a straight swop would suffice? Or must one still level-match pre-amps like everything else, like power amps, and receivers, speakers, etc?

Do preamps need to be level-matched

Reply #4 –
Even if you have set the volume knobs identically on two different preamps, this does not guarantee equal gain (you have been told this already).

Do preamps need to be level-matched

Reply #5 –
Quote from: Rich B on
Do pre-amps need to be level matched in order to compare them?


Only if you want  to allow for the possibility that the two preamps may  be found to sound the same.

If you don't match levels adequately, the preamps will sound different, and that is the goal of most audiophile listening evaluations.

Many find even false audible differences to be very satisfying because it confirms their belief that they have golden ears, know how to select better sounding gear, and are generally classy dudes.

Do preamps need to be level-matched

Reply #6 –
Quote
Wouldn't pre-amps be at the same level


I don't see why they should be. The simplest reason why not is that the volume control knob is usually one of their functions.

Passive pre-amps might, in a perfect world, output the same level as input. Mine, according to its specification, puts out slightly less through the passive output and slightly more through the bufferred output.

Anyway... Aren't some pre-amps actually designed to pre-amplify?
The most important audio cables are the ones in the brain

Do preamps need to be level-matched

Reply #7 –
Quote from: Rich B on
That's why I'm asking about pre-amps. Wouldn't pre-amps be at the same level so a straight swop would suffice?


No, different pre-amps have different amounts of gain.

Do preamps need to be level-matched

Reply #8 –
Quote from: Thad E Ginathom on
Passive pre-amps might, in a perfect world, output the same level as input. Mine, according to its specification, puts out slightly less through the passive output and slightly more through the bufferred output.


But if it has a buffered output, it isn't really passive, right?

Do preamps need to be level-matched

Reply #9 –
Quote from: julf on
Quote from: Thad E Ginathom on
Passive pre-amps might, in a perfect world, output the same level as input. Mine, according to its specification, puts out slightly less through the passive output and slightly more through the bufferred output.


But if it has a buffered output, it isn't really passive, right?


It has a choice, bufferred or passive. The passive is passive enough that it works without power supply --- or, at least, the signal passes through it, although switches like tape output controls do not.

Not sufficiently educated to go beyond that myself, but, for the record, it is a McCormack TLC-1, a piece of equipment that was well known a couple of decades ago, and that I bought second-hand for entirely subjective reasons.

The most important audio cables are the ones in the brain

Do preamps need to be level-matched

Reply #10 –
Quote from: Thad E Ginathom on
Quote from: julf on
Quote from: Thad E Ginathom on
Passive pre-amps might, in a perfect world, output the same level as input. Mine, according to its specification, puts out slightly less through the passive output and slightly more through the bufferred output.


But if it has a buffered output, it isn't really passive, right?


It has a choice, bufferred or passive. The passive is passive enough that it works without power supply --- or, at least, the signal passes through it, although switches like tape output controls do not.

Not sufficiently educated to go beyond that myself, but, for the record, it is a McCormack TLC-1, a piece of equipment that was well known a couple of decades ago, and that I bought second-hand for entirely subjective reasons.



This reference should pretty well settle whether the proposed UUT is passive:

Stereophile Line drive  technnical tests


However, even ideally passive devices can have frequency response and input/output level losses.

Do preamps need to be level-matched

Reply #11 –
Quote
Do pre-amps need to be level matched in order to compare them?
Seriously, Rich?  If you are comparing sound, how can you have a difference in sound level?  Unless sound-level differences are what you are listening for...

You want to control the variables as much as possible and keep the conditions the same as much as possible...  If you are comparing the fuel mileage of two cars, you can't test one uphill and the other downhill! 

Do preamps need to be level-matched

Reply #12 –
I know that level differences can result in audible differences. I've been told that a 1-2 dB difference is enough to result in a more 'full' sound. People who report equipment sounding brighter, how does a level difference result in added brightness, assuming there were level mismatches?

Do preamps need to be level-matched

Reply #13 –
Quote from: Arnold B. Krueger on
This reference should pretty well settle whether the proposed UUT is passive:

Stereophile Line drive  technnical tests


I mentioned specifications. Just for the record, I think it was that review that I was thinking of, and not any Specification published by McCormack, at least, not in the manual. Error regretted.
The most important audio cables are the ones in the brain

Do preamps need to be level-matched

Reply #14 –
Quote from: DVDdoug on
Quote
Do pre-amps need to be level matched in order to compare them?
Seriously, Rich?  If you are comparing sound, how can you have a difference in sound level?  Unless sound-level differences are what you are listening for...

You want to control the variables as much as possible and keep the conditions the same as much as possible...  If you are comparing the fuel mileage of two cars, you can't test one uphill and the other downhill! 



Well that's it. When doing a listening test there is a lot of checking things just to make sure, and level matching is one of the most important things. Whether the device is passive, active or runs off of batteries or cosmic rays, it can cause a change in levels and that can be audible.  Level match testing can uncover other things like reversed or defective cabling, etc.  You just do the setup and checks and once they are right, move on.

Do preamps need to be level-matched

Reply #16 –
Just a nitpick: You actually level match the system, not the individual component. The goal is not to have the units under test to output the same levels, but to listen to both units under test at exactly the same level.

Now, in most cases, level-matching the units under test is sufficient, because the remainder of the system can be assumed to have not changed. However, there are situations when the level is affected by the combination of two devices, because of the interaction of source and input impedances. If you measure the output level of the unit under test while the following device is disconnected, the level may change significantly when the following device is reconnected. Sometimes the same thing happens when a source switch is operated in the following device.

Well-designed gear doesn't act like that, but not everything is well designed, particularly when the word "audiophile" comes into it.

Therefore, as a general precautionary rule, measure the levels in exactly the system configuration which you are using for the listening test.

Do preamps need to be level-matched

Reply #17 –
In the case of amplifiers, one might be tempted to connect the signal source to both at once and then switch between listening to one output or the other. However, it is possible that one amplifier's input loads the source in a way that affects the sound, and unless you switch the source as well as the outputs you will never hear this.

Do preamps need to be level-matched

Reply #18 –
Quote from: pelmazo on
Just a nitpick: You actually level match the system, not the individual component. The goal is not to have the units under test to output the same levels, but to listen to both units under test at exactly the same level.

Now, in most cases, level-matching the units under test is sufficient, because the remainder of the system can be assumed to have not changed. However, there are situations when the level is affected by the combination of two devices, because of the interaction of source and input impedances. If you measure the output level of the unit under test while the following device is disconnected, the level may change significantly when the following device is reconnected. Sometimes the same thing happens when a source switch is operated in the following device.

Well-designed gear doesn't act like that, but not everything is well designed, particularly when the word "audiophile" comes into it.

Therefore, as a general precautionary rule, measure the levels in exactly the system configuration which you are using for the listening test.



The above is why I recommend that levels be matched by monitoring the voltage at the speaker terminals.

Do preamps need to be level-matched

Reply #19 –
Quote from: pdq on
In the case of amplifiers, one might be tempted to connect the signal source to both at once and then switch between listening to one output or the other. However, it is possible that one amplifier's input loads the source in a way that affects the sound, and unless you switch the source as well as the outputs you will never hear this.



I have been aware of this concern for about 40 years. The ABX RM-2 relay module supported switching line or phono level inputs, line level outputs, and speaker level outputs concurrently. I have never actually seen an instance of measurable input distortion given that both pieces of equipment were powered on, and operating normally.  Equipment that is powered off or clipping can cause this problem.

Do preamps need to be level-matched

Reply #20 –
Quote from: Arnold B. Krueger on
Quote from: pelmazo on
Therefore, as a general precautionary rule, measure the levels in exactly the system configuration which you are using for the listening test.
The above is why I recommend that levels be matched by monitoring the voltage at the speaker terminals.
Good advice and it's probably more precise than variations caused by listener's head movements.
Headphones and IEMs are also used for listening tests and level matching them is quite difficult. Any advice for that ?

Do preamps need to be level-matched

Reply #21 –
Quote from: Kees de Visser on
Headphones and IEMs are also used for listening tests and level matching them is quite difficult. Any advice for that ?

You mean tests which compare different headphones?

That's difficult. Precise matching may require in-ear microphones or other specialized equipment.

Do preamps need to be level-matched

Reply #22 –
Quote from: Rich B on
I know that level differences can result in audible differences. I've been told that a 1-2 dB difference is enough to result in a more 'full' sound. People who report equipment sounding brighter, how does a level difference result in added brightness, assuming there were level mismatches?


Subjective descriptions of the character of the sound are pretty useless anyway, but you might want to check out the Fletcher-Munson curves.

Do preamps need to be level-matched

Reply #23 –
Quote from: Kees de Visser on
Quote from: Arnold B. Krueger on
Quote from: pelmazo on
Therefore, as a general precautionary rule, measure the levels in exactly the system configuration which you are using for the listening test.
The above is why I recommend that levels be matched by monitoring the voltage at the speaker terminals.
Good advice and it's probably more precise than variations caused by listener's head movements.
Headphones and IEMs are also used for listening tests and level matching them is quite difficult. Any advice for that ?


Essentially the same: Match the voltages at the headphone jack.

Never ever use a SPL meter or microphone if there is any other option.

Do preamps need to be level-matched

Reply #24 –
Quote from: Rich B on
I know that level differences can result in audible differences. I've been told that a 1-2 dB difference is enough to result in a more 'full' sound. People who report equipment sounding brighter, how does a level difference result in added brightness, assuming there were level mismatches?


The answer to that question lies in that golden ear whipping boy, the Fletcher Munson curves:

Fletcher Munson Curve Explained



The strongest effect is that as the SPL goes up, the ear's low frequency sensitivity goes up faster than its mid frequency sensitivity. This creates the perception of more bass as the levels increase. IME this is about as clear as the nose on my face and I dispair when people don't understand this sort of thing.

However, this does not happen as strongly at high frequencies which creates a bit of mystery.  Why does playing music louder (to a point) create the impression of heightened detail and sheen?

I can't point out an answer for treble so easily, but I experience it frequently.  I think it is a matter of a shifting perspective on midrange sounds stimulated by the increase in bass. More bass has similar perceptual effect to having less midrange. 

I've long noticed that properly adding a good subwoofer to a system can improve the perception of high frequencies.