Home Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Propeller Head Plaza ]
[ Alert Moderator ]

RE: "Accuracy": not simple, alas

So as to make things concrete, I will talk about objective measurements, although I believe that subjective perceptions are ultimately more important. I will also confine myself to electronics, indeed only mono electronics, just to keep things simple. Even simpler, a line level amplifier.

One can characterize the performance of this device in three basic ways, noise, frequency response, and distortion. Oversimplifying, these separate concepts do not interact. Noise corresponds to output when there is no input. Frequency response corresponds to differences between input and output that are proportional to the input (linear), and distortion corresponds to differences between input and output that are not linear. All three of these categories can be further broken down since the effects will depend on frequency. You can not characterize the distortion of this amplifier by a single number. You will need a table of dozens of numbers. You find this in over simplified detail on a spec sheet or in more detail in the "measurement" section of articles in magazines. Now if you are comparing a few amplifiers and you are working with a few dimensions, say two to keep it very simple, you can plot the measurements on a piece of graph paper. At the origin you would have the "perfect" amplifier. I think most would agree that such a device, were it to exist, would be what you called "transparent". You could plot other devices as points on the paper. Now if you took a ruler you could measure the distance on the paper between two points and it would provide a measure of similarity. If you measured the distance between the point corresponding to the device and the origin you would have a "distance" that characterized how transparent the device was.

Here you see already the difficulty. If there is only a single dimension all the devices will plot on a line and it will be clear which device is more transparent than the other. But as soon as you have two axis a question of scale comes up. If you expand one axis and contract the other the ruler will place more emphasis on the attributes associated with the first axis and less on the attributes associated with the second axis. There is no obvious way to compare a given amount of noise vs. a roll-off of high frequencies above 10 kHz, for example.

Consistent ordering is simple. If I rank devices and always come up with the same order of preference, no matter what tests I perform, my ordering is consistent. This is possible, at least for some audiophiles who aren't suffering from audiophile neurvosa and if a small range of reference recordings are used for comparison. If many recordings are used or if many listeners get to express their preferences, it is unlikely that consistent results will be observed.

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar

This post is made possible by the generous support of people like you and our sponsors:
  McShane Design  

Follow Ups Full Thread
Follow Ups
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]