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CD player and USB streaming

•  Channel isolated double mono
•  Uncompressed Stereo Digital Signal
•  TDA1540D converter in ceramic housing
•  Synchronized oscillators of the TDA1540D
•  Dynamic correction of the shift register
•  Frequency compensation of the TDA1540D
•  Class A operation of the TDA1540D

The result of this interaction is the audible achievement of a spatial and temporal precision. It is no longer necessary to ask the question of deep bass registers, of nuances or transparency of reproduction - the discussion about top performances in terms of sound is over here. Rather, new standards are set for continuity and naturalness of reproduction. Simply put, compared to the best digital playback devices, whether CD or streaming, a metronom sounds lively and authentic.

Simultaneous data format

No compression, no artifacts and no quantization errors. The simultaneous data format is an uncompromising data format for analog conversion - while traditional digital playback devices use the I2S data format, which compresses the stereo channels into just one signal. With the simultaneous data format, the stereo channels are processed separately and uncompressed in a separate converter chip per stereo channel. The converters do not have to re-allocate the bundled signal to the stereo channels. Stress-free, these can fulfill their actual task, plus: negative interactions, because both stereo channels are processed in the same chip, do not occur. From digital to analog output, a channel-separated dual mono setup is possible.

Digital Analog Converter TDA1540

For an analogue converter that produces without embedded filters and amplification stages, you have to resort to first-rate technology. Current chip architectures perform static analog conversion without remedying the resulting errors - but reduce manufacturing costs.

While two 16-bit TDA1541A converters were used in the predecessor, the principle of active metronome correction could be transferred to a 14-bit converter. Since this converter has a still more than 40% more complex structure of the shift register, The TDA1540 is known for its unsurpassed natural timbre.

Active correction metronome

The converter-internal shift register, which takes over the analogue conversion of the data from the bitstream, as it were, as a manual transmission, is controlled by internal oscillation. This is disadvantageous without metronome correction with a fixed frequency and not in dependence on the received data window. ThThrough the active metronom module on the converter, the oscillation of the shift register is adapted dynamically to the data window, a frequency compensation is performed and the converter output is set in class A.

Active correction metronom 14

The oscillator and shift register in the TDA1540 are controlled externally. A dynamic control depending on the data input, specifies the analog conversion in a new order of magnitude.

metronom base units

Basic restored units are supplemented with metronom modules and modern components of the highest quality. Thanks to new remote control module and digital input, a metronom also leaves nothing to be desired in terms of functionality and convenience.
Thanks to metronom 2.0 with the TDA1540, analog conversion is set into a new era. With the possibility of USB streaming, further digital playback devices with common delta-sigma converters become obsolete.
Work on your existing devices

Revox B225

The most sophisticated metronom CD player and DAC. Biggest features thanks to new building blocks. Convinced with discrete single transistors in the adjustable output stage also as a solo cast on active speakers and headphones.

Revox B225
•  Revox B225 metronom 2298€buy
+ USB digital input - DAC 258€buy

Bang & Olufsen CDX

Inside, the CDX is much the same as the Philips CD 104. Thus, the CDX with its timeless design is the right choice for lovers of TOP loaders.

•  B&O CDX metronom 2198€buy

Philips CD304

With its anodized aluminum front and tube display, the CD304 fits well with standard format hi-fi devices.

Philips CD304
•  Philips CD304 metronom 1998€buy
+ USB digital input - DAC 258€buy

Philips CD104

The CD 104 is the organ donor of the 304 and many other CD players that have crystallized over 30 years as the best CD players of all time.

Philips CD104
•  Philips CD104 metronom 1948€buy
+ USB digital input - DAC 258€buy

Philips CD100

For real enthusiasts, the first CD player, fully restored, remote controllable and with top sound performance.

Philips CD100
•  Philips CD100 metronom 2298€buy

List of all suitable basic devices

HiRes in comparison

Gladly it seems that the hi-fi development has made huge leaps in the past 30 years. If you believe the advertising for digital playback devices, every year is continuously offered a better and better playback. Such claims are readily accepted, as the restless hi-fi prospect 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 !?

Revox B225, USB-in module

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.

Comparison in hearing test

Benefits on paper suggest a superiority, but they do not bring anything to the listener. For an objective comparison, identical conditions must first be created. Both players, the metronom with TDA converter and a comparator with high bit converter, give the same recording quality again. Both players have the same output level (+ -0.5dB) and are tested with the same cabling on the same music system. If both devices are running at the same time, 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 of prejudices, suggestions and "background happenings", 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. You notice the bigger and still tighter sonority of the "old" technique. Not only the amount of details, but also their precision and naturalness is not just "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 such distinct sound differences are in the analog converter chips and how they are connected to the data sets in the devices. The result of this comparison is a "resounding slap" for modern audio electronics and speaks against any manipulation of the digital signal through HiRes over- and upsampling or compression. The advantages of a HiRes lie only in the cheaper production through higher integration and thus a reduced number of chips and components in the finished devices. With a collection of playback by the computer, also wants the music-carrying medium CD away streamlined - even if a data transfer via the computer against a dedicated solution in the CD player at a disadvantage.

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 frequencies - it means cutting production costs and removing the original music recording.
The invention of the CD was an epochal event. It took many months of effort by a specially formed team of international engineers - unthinkable today. It became possible to transport the quality of the masterbands directly into our own listening room. In comparison, the new generation of digital playback devices only offers an increase in the data rate. The lifetime of these devices will be short lived. What we need is a good understanding of playback devices that fit our sense of hearing.

HiRes Technique in CD Player

Here are the characteristics of a metronom CD player, which has two converter TDA1540, compared to a modern converter for HiRes. This HiRes converter is installed in playback devices in the four-digit euro range, but is also found in equipment for less than 100 euros.

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. On the signal path in front of it are located on the right next to each stereo channel 2 black resistors and 1 capacitor, which form an analog low-pass filter. It is not necessary to prepare by further amplifiers. 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 direct 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.

Philips TDA1540 14 Bit DAC

Philips Analog Converter

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 in theory and also not to be confused with the amount of detail or fine drawing. The higher resolution refers to an extension of the processed frequency response to 96khz (Nyquist, sampling frequency equal to at least twice the playback frequency) with the example of 192khz playback. - 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 sense of hearing. To find in the extended frequency response 'Dither' - in digital data processing in the final mastering always added digital unnatural noise - necessary to conceal the re-quantization interference of the increased sampling frequencies.
On the other hand, manufacturers of audio electronics in the indication of ever greater values of the distance from noise to the signal as a quality feature.

Dynamic range

Music achieves a dynamic range of 80 dB depending on the instrumentation. The human voice has a dynamic range of 40 dB. The dynamic range of the TDA1540 already offers a not really usable reserve with 94 dB and achieves further control reserve in the practical application, even if before the usual -9dB headroom for digital and analog is reached.

A jackhammer generates 120 dB of sound pressure, standing next to it you can not understand a 40dB loud calling person. Without previously worn ear protection even 5 minutes after not yet. The indication of the dynamic range for HiRes products is rather theoretical - not to say that it is out of touch with reality. When playing music, there is no effect to increase the dynamic range on paper to non-representable or audible values. When I put important features such as a natural timbre in the background, I find that misleading.

An advantage through higher Headroom is in the studio alone in the signal processing. This facilitated the work of a 'modern sound engineer' e.g. To avoid oversteer in the final product - an activity that was previously successfully carried out by experienced professionals.

The size of the data window (bit) with which the music is digitally 'transported' is not related to a better musical result alone. Unlike an increased sampling frequency, an increased bit rate at least does not harm the rendering result - it has no use whatsoever; the mathematical dynamics gain is of a purely theoretical nature.

Revision versus Modification

The topic has often been discussed, but rarely defined exactly: what exactly is the difference between revision and modification?

Revox B225, Relay output

A revision means putting a working CD player back to its original state. If he does not play because of a defect, it is a repair. The necessary measures of a revision, which leave the original state, but of course very time consuming, for example, includes the removal of cold solder joints. This is done by expert, careful desoldering and attaching new silver solder. Mechanical parts are made feasible by adjusting and maintaining them with appropriate means. The list of the important steps of a faithful revision can be continued indefinitely.

Revox B225, balanced XLR output with transformer (optional)

But even the replacement of aged components in a CD player blurs the line between revision and modification. For example, capacitors are affected by aging. Many of the original types used in previous devices are no longer available for good reasons. The component market has long since replaced them with significantly improved capacitors.

To clarify the differences between revision and modification, a comparison with cars is helpful. In classic cars, it is frowned upon to replace old parts with new ones. Subsequent installed disc brakes, a power-assisted steering, even a non-original rearview mirror are considered a taboo break. The highest law is to keep the car in its original state.

For a CD player, the question is different: may the old, long-dried capacitors be replaced? Or does the owner want to live with a device whose sound audibly deteriorates from year to year compared to the original state? The question is more theoretical. To leave a valuable CD player with only partially functional components convulsively in its original condition would mean that it is dawning on its certain death.

Lifetime capacitors

There is every reason to replace old ones with modern components in order to bring the original sound characteristics back to their original level. So here is the point where revision and modification inevitably merge. The preliminary conclusion of this consideration is: Anyone who wants to preserve the priceless merits of an early CD player (they start with the eternally built drives and end with the extremely solid, vibration-free mechanics) through the use of modern components and make good use of comes to a Modification not over.

Technical possibilities

Before I go into that, I would like to say in advance that I have great respect for the tremendous power of the Philips engineers who developed the compact disc and its players in the 1980s. The development had taken place in the Dutch Philips laboratories in Eindhoven. Many dozens of German, French and British engineers had spent years calculating, designing and designing until the silvery-round "digital revolution" finally worked. I would never be so presumptuous to suggest that with a few simple steps, a simple bridged circuit or the premature replacement of some components can improve a very high-quality CD player with just a few hours of work.

Revox B225, metronom analog board

To judge where something is possible and what not, you have to go back about 30 years. Let's start with a look at the components. In the past, only resistances of inferior quality were available. They not only had large tolerances of 10% and above, they also had a lot of noise. Their temperature behavior was questionable in practice, even a small warming reduced the resistance considerably. For the capacitors used at the time, deviations of more than 10% of the rated capacity were normal. In many places, components were therefore inevitably used whose accuracy was more in God's hands than on the drawing board of an engineer. The series variations of the devices were correspondingly large.

Revox B225, advanced remote control module

Today resistances are available with an accuracy of 1% and better. For capacitors, the same applies in principle. The quality of the components has progressed rapidly in these 30 years. Conversely, nowadays, with reasonable cost, it is no longer possible to construct a drive as elaborate as the CDM-0 or CDM-1 of a Revox B225. It would also cause too high a cost for a large-scale production.

The result is that so-called high-end vendors have inevitably fall back on DVD mass drives of cheap design, if they even want to offer CD players - instead umzuschwenken on cheaper to be produced network player. The missing inner values are compensated by noble housing and high expenditure for marketing and advertisement. Sometimes only a thick bottom plate makes it a seemingly heavyweight from the technical lightweight.

CDM-1 Laser Drive

What argument would argue against combining the best of the past and present worlds? Even looking at a photo shows that the mechanics of a Revox B225 are second to none and will probably never be produced again. These drives will still turn when the remnants of today's high-end players have long since been recycled as PET bottles and car bumpers.


The framework conditions under which products are developed in a group must also be considered when assessing the meaning or nonsense of a modification. Cost laws were the same then as they are today. An engineer can develop even more ingenious ideas - if the controller strikes with the arithmetic pin and explains the idea as too expensive for mass production, it is done quickly. Each group always calculates with the second or even third place behind the decimal point when using components.

After all, even a simple law plays a role: Behind every device and its development are people with their peculiarities. Who does not know the situation that a young engineer has a courageous idea or proposes an unusual path, but fails because of the incorrigibility of a superintendent gray in honor? Or that a small team of young developers is duping the desk bosses by providing a stage of development for a product, but that will not be pursued? With the same number of constructive peculiarities, especially the Philips analogue converter chips, this is the case. Some excellent possibilities of the CD player remained strangely unused even then. It took more than 30 years until today's metronome CD player.


The conclusion of these discussions from different perspectives: There could be found no argument against a technical upgrade of a CD player with modern, superior components. Likewise also no argument against improvements at places, which were not used with the original model for cost reasons. Nor does it make sense to leave introduced features for purely marketing reasons.

Whether we are talking about tuning or a modification, the changes should be made according to professional standards. Being professional is a modification if it takes place on the basis of many years of experience and results in an increase in all the characteristics of a CD player. A quick guide from the Internet, to remove all filters from a CD player, is certainly not one of them. Sound effects, such as the unnatural emphasis on bass and treble, at the expense of a balanced transmission, expose themselves after some listening time itself as disturbing and alien. The claim of a metronom CD player is the neutral, natural and exactly the original reproduction of the music.

Digital misbelief resolved

Videos youtube:
Digital Audio: The Line Between Audiophiles and Audiofools
Digital Show and Tell (Monty Montgomery @


Why push back against 24/192? Because it's a solution to a problem that doesn't exist, a business model based on willful ignorance and scamming people. The more that pseudoscience goes unchecked in the world at large, the harder it is for truth to overcome truthiness... even if this is a small and relatively insignificant example.

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

Audio industry salesman have been promoting faster than optimal sample rates. The promotion of such ideas is based on the fallacy that faster rates yield more accuracy and/or more detail. Weather motivated by profit or ignorance, the promoters, leading the industry in the wrong direction, are stating the opposite of what is true.

Dan Lavry, Lavry Engineering, Washington: weblink

Since you have done a great job! That a CD player is capable of such musicality at all I have not believed so far. After many years and many CD players was the topic for me actually "eaten"; thank you very much, that you once again opened my ears (and I am comparing here on a high level - with a Studer professional machine and master tape copies). Such unity in the musical flow and above all, such a great presentation and physicality of instruments and voices I have never heard of a digital source. The intonation is consistent, from the bass to the highs, the timbres are rich and the timing just perfect!

A. Sandreuther, Nürnberg

Out of amazement, I came out only after some time. I remembered how much money I already spent on finding perfection. In relation to the devices that used to play for rankings "recommendations" of various hi-fi gazettes, my new 304 can not compete with them - in the price! I feel like a man who always blinked and then bought a new eyeglass cleaning cloth. Suddenly, I see clearly, before it was gritty and blurry. I should have come up with this idea earlier.

Gerhardt Wengenroth, Hemer

After unsuccessful attempts by ‘experts’ on my CD304, I came across you via internet research. Now it gives me great pleasure - thank you very much for that. I also noticed from your communication that you stand out pleasantly from the chatter of self-appointed specialists.

Hannes Scholten, Stuttgart
Founder of HiFi magazine 'Audio' and former editor in chief 'Stereoplay'

It was a surprise. Initially, the CD100 metronom was just ahead, but after extensive testing, the competition is over. Long-forgotten CDs are pulled out of the drawers. For example: The Ray Brown Trio Live at the LOA, ‘Summer Wind’, Concord Jazz CDD-4426, or: Paganini, Mendelsohn, Jaap van Zweden/Ronald Brautigem, Philips 422 230-2, and so on. All the best recordings with headroom. The most difficult CDs for many CD players, but the CD100 metronom presents these recordings with dynamics and detailed colour of the instruments. It has more energy, finesse and naturalness. Hats off, this sound quality was previously only heard when playing the master tape. The test was carried out with a professional audio engineer using QUAD ESL63s loudspeakers and Neumann KH310 monitors. Acc****** DP450 and Nag** CD were used as comparison devices.

The former management of Philips Audio in Hasselt

Work on your existing devices

For all CD players with CDM 0 or CDM 1 laser unit from Revox, Philips, Marantz, Grundig, B&O ...
Material sets are also available for self-installation: CD DIY set

Revision metronom basic
All necessary maintenance work will be carried out on the CD player you sent us. Replacement of all electrolytic capacitors. Renew the vias. Elimination of ground loops in the power supply unit. Check and repair of cold solder joints. Changeover to 240 volt mains voltage. Relocation of tantalum capacitors. The electrical and mechanical revision of the laser and the feed mechanism. The subsequent adjustment and calibration of the laser optics. The retrofitting of the basic sound components: metronom socket, power supply, tuned operational amplifier and output capacitors. The analog converters already built into the unit are retained. Replacement of defective laser units or ICs is not included.

Revision metronom basic 698€on request

Restoration metronom
Your sent CD player will be restored, aged solder connections will be renewed, power transistors will be exchanged and extended by all metronom upgrades. Analog converters TDA1540D in ceramic case are included besides hand selected components. Any modules like remote control, relays and more powerful opamps are included. A USB-in or XLR-out can be ordered additionally on request.

Restauration metronom 1498€on request