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Thread: Can a pre-amp make a power amp sound better?

  1. #46
    Senior Member bigshot's Avatar
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    Quote Originally Posted by eljr View Post
    Don't get me wrong, it's the best way to compare but most people don't even do this part right. They listen for a few minutes then make the switch and listen for a few minutes.
    When I do comparisons of players and DACs, I feed the tracks in sync into two inputs to my preamp, level match and then switch back and forth quickly. My preamp's input switch is very quiet, so it's almost like the music playing continuously with no click between. Just a very quiet short thud. Some switchers are better suited to A/B testing than others.

    Long listening periods are not only subject to problems with auditory memory, it can also be skewed by your ears adjusting. You can create a clearly audible response imbalance and hear the problem easily with quick switching. But if you listen to the imbalanced sound for a while, the ears will acclimate to the imbalance, and then the balanced one will sound wrong. It's like being under red lights for a long period of time. You can walk into a neutral colored room and for a little bit it will seem greenish.
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    [QUOTE=bigshot;1652524Long listening periods are not only subject to problems with auditory memory, it can also be skewed by your ears adjusting.[/QUOTE]

    Same with visual when you're comparing video (or any other source) color balance. If you look at Version A for a goodly period, Version B seems off when you switch. The after viewing Version B for awhile, Version A seems off. It's why your eyes (or brain, actually) adjust to tungsten illumination so that white looks white to you, but is yellow when shot with daylight balance film.

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    Quote Originally Posted by tterrace View Post
    Same with visual when you're comparing video (or any other source) color balance. If you look at Version A for a goodly period, Version B seems off when you switch. The after viewing Version B for awhile, Version A seems off. It's why your eyes (or brain, actually) adjust to tungsten illumination so that white looks white to you, but is yellow when shot with daylight balance film.
    Wish I could delete my post, because you said the same thing.

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    Senior Member millionrainbows's Avatar
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    Quote Originally Posted by Mandryka View Post
    If you use a DAC, the output stage uses amplification. No need for a preamp if the DAC is suitably matched to the power amp. I'm assuming you have digital volume control and only one input. The problem is in the words "suitably matched" -- I don't know how to tell apart from trial and error.
    This is like matching the impedance of electric guitar pickups to the input of a guitar amplifier. This can make all the difference in the sound, and whether it sounds weak and thin, or full and rich. Power amps differ, and so do DACs, so a preamp adds flexibility to the match. Yes, trial and error is called "using your ears."
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    Senior Member bigshot's Avatar
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    DACs don't differ because they take input in the digital realm. Impedance only exists in analog. And impedance is only an issue with power amps, not preamps that operate at line level. If you know how the stuff works, you know what to look for.
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    Senior Member millionrainbows's Avatar
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    Quote Originally Posted by bigshot View Post
    DACs don't differ because they take input in the digital realm. Impedance only exists in analog. And impedance is only an issue with power amps, not preamps that operate at line level. If you know how the stuff works, you know what to look for.
    \

    Of course, we are talking about what happens when the digital data is transferred into the analogue realm, and is OUTPUT into a power amp or preamp. Of course this can vary, just as "line level" is a generalization which can vary also. I'd say a preamp is a good way to accommodate the differing "line levels" we may encounter from different CDs and files.
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    Line level has nothing to do with impedance. Impedance is an issue with transducers.
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    Senior Member millionrainbows's Avatar
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    Quote Originally Posted by bigshot View Post
    Line level has nothing to do with impedance. Impedance is an issue with transducers.
    That's misleading. Line level is the specified strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles.
    Line level sits amongst other signal strengths such as those from weaker audio signals i.e. microphones and instrument pickups, and stronger signals, such as those used to drive headphones and loudspeakers. The "strength" of these various signals does not necessarily refer to the output voltage of the source device; it also depends on its output impedance and output power capability.
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    Quote Originally Posted by millionrainbows View Post
    \

    Of course, we are talking about what happens when the digital data is transferred into the analogue realm, and is OUTPUT into a power amp or preamp. Of course this can vary, just as "line level" is a generalization which can vary also. I'd say a preamp is a good way to accommodate the differing "line levels" we may encounter from different CDs and files.
    But then you have the problem downstream of matching the output of the preamp to the power amp.

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    From wikipedia
    As cables between line output and line input are generally extremely short compared to the audio signal wavelength in the cable, transmission line effects can be disregarded and impedance matching need not be used. Instead, line level circuits use the impedance bridging principle, in which a low impedance output drives a high impedance input. A typical line out connection has an output impedance from 100 to 600 Ω, with lower values being more common in newer equipment. Line inputs present a much higher impedance, typically 10 kΩ or more.

    The transmission line effects are reflections causing overshoot/undershoot (signal distortion) when the cable's characteristic impedance does not match with the driver/receiver impedance, but since the propagation delay through the cable is extremely small compared with the audio wave's slope, this does not matter.

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    Senior Member bigshot's Avatar
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    Line level for inputs is standardized. If it says "line out", it should work fine without any alteration. Line out is line out. (The exception being phono cartridges.) The level going out from and amp to speakers isn't standardized. You can have 4 ohm speakers or 8 ohm speakers that require a completely different kinds of power from the amp, and there are headphones that have high sensitivity and low impedance, and ones that have low sensitivity and high impedance. The transducer sets the impedance requirements. That's what I am trying to say.
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    Senior Member millionrainbows's Avatar
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    Quote Originally Posted by tortkis View Post
    From wikipedia
    As cables between line output and line input are generally extremely short compared to the audio signal wavelength in the cable, transmission line effects can be disregarded and impedance matching need not be used. Instead, line level circuits use the impedance bridging principle, in which a low impedance output drives a high impedance input. A typical line out connection has an output impedance from 100 to 600 Ω, with lower values being more common in newer equipment. Line inputs present a much higher impedance, typically 10 kΩ or more.

    The transmission line effects are reflections causing overshoot/undershoot (signal distortion) when the cable's characteristic impedance does not match with the driver/receiver impedance, but since the propagation delay through the cable is extremely small compared with the audio wave's slope, this does not matter.
    Quote Originally Posted by bigshot View Post
    Line level has nothing to do with impedance. Impedance is an issue with transducers.
    Nonetheless, line level DOES have SOMETHING to do with impedance. Bigshot's statement was not true, plus, it was misleading.
    Last edited by millionrainbows; Jun-17-2019 at 16:06.
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    You're a funny person. Do you act this way with your friends in real life? Are you this desperate?
    Last edited by bigshot; Jun-17-2019 at 08:38.
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    Senior Member millionrainbows's Avatar
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    Quote Originally Posted by bigshot View Post
    You're a funny person. Do you act this way with your friends in real life? Are you this desperate?
    If you're going to be "Mister Objective," then you'd better be accurate, not misleading.
    "The way out is through the door. Why is it that no one will use this method?"
    -Confucious

    "In Spring! In the creation of art it must be as it is in Spring!" -Arnold Schoenberg

    "We only become what we are by the radical and deep-seated refusal of that which others have made us." -Jean-Paul Sartre

    "I don't mind dying, as long as I can still breathe." ---Me

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    Tag, you're it.
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