High bit compared

Gladly it seems that the hi-fi development has made huge leaps in the past 30 years. If one believes the advertising for digital playback devices, every year an ever better reproduction is offered. Such claims are readily accepted, but the restless hi-fi interested is constantly looking for improvements. If one takes the advertising statements literally, one should come to the conclusion that the reproduction of music on a new hi-fi system is better than the original !?

Philips TDA1540 14 Bit DAC

In advertising, higher and higher bit numbers play a decisive role. They should suggest tonal advantages. The stultifying principle is: "The higher the numbers, the better the result." It is all too often concealed that the numerical values ??extracted from the technical context have no significance.

Measuring data

A direct correlation between isolated measurement data and good sound can not be found. You can not locate good sound by competing numbers about the harmonic distortion or extension of the frequency range. In digital playback devices today they find arguments such as quantization of bit numbers and sampling frequency. It just means cutting production costs and removing from the original music recording. The invention of the CD was an epochal event. It delivers the sound of the master band directly into our own listening room. It was the crystallization of the efforts of the engineers of that time. In comparison, the new generation of digital playback devices only offers an increase in the data rate. The lifespan of these formats will be short-lived. What we need is an accurate understanding of the pros and cons of these formats to develop new ones - which are in line with our sense of hearing.

High bit technology in the CD player

Here are the characteristics of a metronom 14 CD player, which has two of the tried and tested converter TDA1540, brought into a comparison with a modern high bit converter. This high bit converter is installed in CD players in the four-digit euro range, but is just as in video players for around 100 euro to find.

High Bit DAC

On the left side of the picture, a transistor for the muting is visible at the top and bottom, which last sit in front of the cinch sockets at the output. To the left of the edge of the picture are a transistor for the signal path in front of it, to the right of each channel there are 2 black resistors and 1 capacitor forming an analogue low-pass filter. There is no preparation by further amplifiers necessary. Thanks to the DC control, a coupling capacitor in the signal path is superfluous. With its integrated digital filters, its amplifiers, and the removal of harmful DC current, this converter eliminates the need for many other components, resulting in significant cost savings. In the high-priced reproduction devices surprisingly still further amplification stages and voltage followers (Buffer) are found, partly also with tubes. Their task is to give the device an individual touch by changing the original signal. With sound neutrality, such measures have nothing to do.

On paper, the converter developed 30 years after the TDA1540 has advantages: a higher bitrate, a larger dynamic range and the developer-attractive "finished" audio output with a defined 2 Volt output. This is practical in that it does not need its own development. However - and this is one of the decisive disadvantages - no longer possible. Other advantages allegedly relate to resolution and dynamics - but only theoretically and also not to be confused with the amount of detail or fine drawing. For example the higher sampling frequency of 192khz: The higher resolution refers to an extension of the frequency to 96khz (Nyquist, sampling frequency equal to at least twice the playback frequency) - A frequency extension in which no usable information in the digital music end product are included, which is not recorded in the recording of music by physics underlying microphones and which can not be detected by the human auditory sense. Only dither can be found in the extended frequency - in the digital data processing finally added digital noise. On the other hand manufacturers of audio electronics turn in the indication of ever larger values of the distance of noise to the signal as quality feature.

Music achieves a maximum dynamic range of 80 dB. The human voice has a dynamic range of 40 dB. The dynamic range of the TDA1540 with its 94 dB already offers a large unusable reserve and achieves a practical 118 dB dynamic range. With the digital music reproduction it has no effect to increase the dynamic range on the paper ever further. Especially if a natural timbre is put into the background. An advantage is offered in the studio alone in the digital signal processing, it facilitates the sound engineer the work, for example to avoid overloads in the final product. Also the size of the data window (1 bit, 28 bit, 32 bit) with which the digital music is transported is not related to a better musical result. Unlike an increased sampling frequency, an increased bit rate does not harm the rendering result, at least - it's of no use.

See also: Xiph.Org Foundation

The Xiph.Org Foundation is a non-profit corporation dedicated to protecting the foundations of Internet multimedia from control by private interests.

Comparison in hearing test

Advantages on paper suggest a superiority, but they do not bring anything to the listener. For an objective comparison, first of all identical conditions have to be created. Both players, the metronom with TDA converter and the comparator with high bit converter, reproduce the same recording by playing two identical CDs. Both players have the same output level and are tested with the same cabling on the same music system. The most time-consuming part of this experiment is to play both CDs at the same time, as the metronom with its CDM-1 drive and the Play buttons on both devices press simultaneously about 1.5 seconds earlier. The reason for the somewhat lame newer technology is the upsampling of the digital signal to the higher bit rate. If both devices are running synchronously, they can be compared at the listening position by switching the playback source on the remote control - free from all technical and spatial differences. In order to keep the result free from prejudices, suggestions and "background events", the audience does not know which device to listen to. Finally, the display of the input source on the amplifier is covered.

The hearing test is now very short. The difference is immediate, clear and repeatable at any time. Clearly striking is the larger, yet taut sonority of the "old" technology. Not only the amount of details, but also their precision and naturalness is not only "a little bit better" across the entire frequency spectrum. On a flowery description of nuances can therefore be omitted gratifyingly in this hearing comparison.

The reasons for the sound differences are the digital chips themselves and the way they are integrated into the CD player. The result of this comparison is a "resounding slap in the face" for modern audio electronics and speaks against any manipulation of the digital signal through over- and upsampling or compression. The advantages of a high bit lie only in the cheaper production through higher integration and thus a reduced number of chips and components in the finished devices. With a disadvantageous connection of the playback to the computer, moreover, a music-carrying medium also wants to be rationalized away - even if a data transmission via the computer with its standardization of a dedicated solution is disadvantageous. But constructive weaknesses of the music chain can be "purged" using psychoacoustic manipulation in a digital way.