Autosound 2000 Presents Test CD #104

Autosound 2000 Presents Test CD #104

Autosound 2000 Presents Test CD #104 MUSIC AUDIO amplifier level setting disc  

Music 

Audio CD 

CD 

$124.99
Packaging
Track 1 - This track is a sample from Sheffield Lab's Sonic Detour" by Freeway Philharmonic. It is a digital clone and is intended to serve as the audio reference for the entire disc.

Tracks 2 through 6 were specially recorded by sampling the speaker terminals of a medium sized car audio power amplifier. The purpose of these tracks is to demonstrate the subjective increase in loudness that can be obtained by providing a specified amount of gain overlap at the power amplifier of an audio system. This unique disc provides a method to evaluate this critical system operating parameter without trial and error. The process is easy and can be done at normal listening levels. Although gain overlap can increase the usable loudness of a system, it is a compromise. For every dB of increased loudness, there is an equal decrease in the signal to noise ratio at lower listening levels. There is also an increase in peak distortion at high listening levels. Good system performance is a result of optimizing the tradeoffs. The following tracks were each recorded with gain overlap increments of 5 dB. By listening to these tracks, you can determine the amount of gain overlap that is right for your listening tastes and your system. In order to experience the full effect of the increased loudness, the volume control of your system should not be adjusted from one track to the next. Be sure to start at a low level because Track 6 is considerably louder than Track 2. If listening is done at too high of a level, your own system distortion may mask the actual differences in these tracks. Most people find that the best compromise is 10 dB of gain overlap Track 4. (Note: Because each succeeding track is louder than the previous, it may not be easy to judge the distortion increases equally. After observing the loudness differences, skip to Tracks 31 - 36 to evaluate the distortion compromise.)

Track 2 - This track demonstrates 0 dB of gain overlap. The gain of the playback amplifier was adjusted so that the absolute highest musical peak just approached the threshold of clipping. There should be no audible distortion and the only difference between this track and Track 1 is the transfer function of the amplifier.

Track 3 - This track demonstrates 5 dB of gain overlap. The subjective loudness is 4.9 dB above Track 2. The distortion is very minute (less than 0.3% averaged for the duration of the music) and is not audible. The peak voltage at the input of the amplifier was 1.8 times the amplifier's actual sensitivity for full output. This amount of gain overlap can be reproduced by setting amplifier levels using Tracks 13 through 18.

Track 4 - This track demonstrates 10 dB of gain overlap. The subjective loudness is 9.4 dB above Track 2. This amount of gain overlap is usually considered optimum. Peak distortion on most program material occurs for less than 3% of the program duration and is rarely audible to most listeners. The peak voltage at the input of the amplifier was 3.16 times the amplifier's actual sensitivity for full output. This overdrive ratio can be reproduced by setting the amplifier levels using Tracks 19 through 24.

Track 5 - This track demonstrates 15 dB of gain overlap. The subjective loudness is 13.3 dB above that of Track 2. This amount of gain overlap can be acceptable for those who want to play their systems very loud. Peak distortion on most program material occurs for about 15% of the program duration and can be heard by most listeners. The peak voltage at the Input of the amplifier was 5.6 times the amplifier's actual sensitivity for full output. This overdrive ratio can be reproduced by setting amplifier levels using Tracks 25 through 30.

Track 6 - This track demonstrates 20 dB of gain overlap. The subjective loudness is 16.2 dB above Track 2. Peak distortion on most program material occurs for about 40% of the program duration and can be heard by anyone. This amount of gain overlap will produce the absolute maximum loudness from a system. Increasing the overlap beyond this amount will produce slightly more distortion with virtually no more loudness. The peak voltage at the input of the amplifier was 10 times the amplifier's actual sensitivity for full output.

(Please note that for certain steps detailed in Tracks 7 through 30, the speakers may need to be disconnected from amplifiers to prevent speaker damage.)
Tracks 7 -12 are useful for setting the maximum level (clipping threshold) of electronic components. The best way to use this track is to start It the first component in the system (head unit) and then set the gain of each succeeding stage to the threshold of clipping by observing its output on an oscilloscope. If an oscilloscope is not available, good results can be achieved using a small hand-held amplified speaker such as the Radio Shack 277-1008C. With the volume adjustment of the hand-held amplifier turned down, adjust the level on the component until distortion just becomes audible. Then reduce the volume until the clipping cannot be heard. Then connect to the next component in the signal chain and continue. For more detailed instructions see the April-May 1992 and September 1994 issues of Autosound 2000 Tech Briefs available by calling 209-465-3450 Monday-Friday 8:30 AM until 4:30 PM.

Use Track 10 for most components, and for band-limited components such as crossovers, choose the appropriate track with the frequency in the fattest part of the pass-band. If these tracks are used to set amplifier gains, absolute minimum distortion and maximum signal to noise ratio will result. There will be 0 dB gain overlap.

Track 7 - 50 Hz @ 0 dBFS. This track is useful for adjusting the subwoofer section of a crossover. This track is also useful for measuring the output voltage of source units using a simple hand-held AC voltmeter.

Track 8 - 100 Hz @ 0 dBFS. This track is useful for setting the midbass output level on an electronic crossover.

Track 9 - 400 Hz @ 0 dBFS. This track is useful for setting the crossover output that covers this frequency.

Track 10 - 1 kHz @ 0 dBFS. This track is used to set the midrange output of an electronic crossover.

Track 11 - 4 kHz @ 0 dBFS. This track is useful for setting the high frequency (tweeter) output of an electronic crossover.

Track 12 - 8 kHz @ 0 dBFS. This track is useful for setting the high frequency (tweeter) output of an electronic crossover.

Tracks 13 through 18 are used to obtain 5 dB of gain overlap as demonstrated in Track 3.
Track 13 - 40 Hz @ -5 dBFS
Track 14 - 100 Hz @ -5 dBFS
Track 15 - 400 Hz @ -5 dBFS
Track 16 - 1 kHz @ -5 dBFS
Track 17 - 4 kHz @ -5 dBFS
Track 18 - 8 kHz @ -5 dBFS

Tracks 19 through 24 are used to obtain 10 dB of gain overlap as demonstrated in Track 4.
Track 19 - 40 Hz @ -10 dBFS
Track 20 -100 Hz @ -10 dBFS
Track 21 - 400 Hz @ -10 dBFS
Track 22 - 1 kHz @ -10 dBFS
Track 23 - 4 kHz @ -10 dBFS
Track 24 - 8 kHz @ -10 dBFS

Tracks 25 through 30 are used to obtain if de of gain overlap as demonstrated in Track 5.
Track 25 - 40 Hz @ -15 dBFS
Track 26 - 100 Hz @ -15 dBFS
Track 27 - 400 Hz @ -15 dBFS
Track 28 - 1 kHz @ -15 dBFS
Track 29 - 4 kHz @ -15 dBFS
Track 30 - 8 kHz @ -15 dBFS

Tracks 31 through 35 are the same as Tracks 2 through 6, however the levels of these tracks have been adjusted to compensate for the loudness increase. This allows for a more detailed analysis of the distortion. Without the loudness differences, better subjective comparisons can be made of the musical compromises resulting from gain overlap.
Track 31 - Reference track with 0 dB gain overlap (same as Track 2).

Track 32 - This track demonstrates 5 dB of gain overlap at the amplifier with the recording level lowered 4.9 dB to obtain the same subjective level as Track 31.

Track 33 - This track demonstrates 10 dB of gain overlap at amplifier with the recording level lowered 9.4 dB to obtain the same subjective level as Track 31.

Track 34 - This track demonstrates 15 dB of gain overlap at amplifier with the recording level lowered 13.3 dB to obtain the same subjective level as Track 31.

Track 35 - This track demonstrates 20 dB of gain overlap at the amplifier with the recording level lowered 16.2 dB to obtain the same subjective level as Track 31.

For CD Player

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