Technical FAQ

Can a cheap USB charger disrupt the audio signal, or even damage an Electronic Ear?

Indeed, using a poor-quality USB charger is not without consequences for a demanding audio system. Through its lack of proper isolation and filtering, a cheap charger can generate interference that manifests itself as parasitic noise or ground loops. This interference, often imperceptible on the surface, propagates all the way into the audio signal and ends up even in the headphones, thereby degrading the listening experience and sound fidelity.

To remedy this problem, it is advisable to opt for certified chargers or power supplies that guarantee better electrical isolation and incorporate noise-filtering mechanisms. In a professional environment, it may also be wise to use USB isolators or anti-noise filters, which break the ground-loop path without affecting data transmission.

In short, investing in quality equipment — even if the initial cost is higher — proves to be a worthwhile solution in the long run, as it prevents interference and ensures optimum audio quality, particularly for sensitive equipment such as the Tascam DR07.

In any case, it is best, as far as possible, to avoid recharging a portable player during listening sessions and to favour a player that has its own built-in power supply.

Can an amplifier such as the Samson QH4 be added in order to get around the power limitation that prevents driving more than two headphones simultaneously? Is this solution viable? Is there a risk of damaging the N427c Ear by proceeding in this way?

No, I do not consider this solution viable, for several reasons, both technical and operational.

Intrinsic limitations of the N427c Ear. Adding an amplifier such as the Samson QH4 will not compensate for the limitations inherent in the N427c Ear. Although this amplifier makes it possible to distribute the signal to several headphones, it does nothing to increase the output power supplied by the Electronic Ear. Forcing the unit to drive more than two headphones via this method risks overloading its circuits, which can lead to premature wear or even irreversible damage. In this context, it would be preferable to opt for a solution or a piece of equipment designed from the outset to support safe multipoint distribution, such as the N426c or N425/30.

Drawbacks of adding an amplifier. Even if, in theory, coupling a low-impedance output (such as that of the N427c) to an amplifier's high-impedance line input guarantees efficient signal transmission, the practical reality is quite different:

Increased wiring complexity: Adding an amplifier requires the use of additional cables and adapters to interconnect the various pieces of equipment. Each additional connection increases the number of potential points of failure. Risk of interference and degradation: Over time, the cables and adapters may develop contact or oxidation problems, or be subject to electromagnetic interference. These nuisances can result in intermittent cut-outs, signal degradation, or even unexpected failures. Complicated maintenance and diagnosis: Multiplying the elements in the signal chain considerably complicates fault diagnosis in the event of a malfunction, increasing the maintenance burden and the risk of errors during installation or troubleshooting. Optimal approach and recommendations. It is essential to carefully weigh the risk/benefit ratio before modifying a configuration that was originally optimised. Our equipment is designed to operate with a minimal number of compatible accessories. This approach reduces redundant power supplies and limits potential disturbances, thereby ensuring stable and reliable performance. Like our competitors, who seamlessly integrate a mixing, amplification and redistribution suite, we favour simplified, optimised solutions in order to avoid multiplying the points of failure.

Freedom of choice and a word of warning. That said, we recognise that some experienced users prefer to explore alternative configurations according to their specific needs. However, it is essential to stress that such choices are made at their own risk. An unconventional approach may offer additional flexibility, but it also exposes the user to unforeseen technical problems and to potentially more complex maintenance.

In conclusion, although the idea of using an amplifier to get around the limitations of the N427c Ear may seem appealing in theory, operational reality shows that this solution carries major drawbacks that compromise the reliability and durability of the installation.

Other recommended equipment

The audio player:

The Tascam audio player is a recommended option for those looking for a high-quality audio player. Tascam offers a range of professional audio players that provide advanced features and excellent sound quality.

These audio players are renowned for their reliability, ease of use and exceptional sound quality. They are suitable for a variety of applications, whether for playing music in a studio, at live events or for home use.

It is important to select a model capable of playing and recording in HD 24-bit/48 kHz format.

Why choose 48 kHz / 24 bit?

Professional audio quality: the standard for cinema, television and post-production.

Increased dynamic headroom: 24 bits make it possible to capture the finest details without background noise.

Recorder models compatible with the HD 24-bit/48 kHz format:

here are a few options to consider:

TASCAM DR-05 (and DR-05X/DR-05XP) Type: Portable stereo recorder

Advantages:

Built-in omnidirectional stereo microphones

Recording in 24 bit / 48 kHz and 96 kHz

WAV format

Compact

USB interface for direct transfer to PC/Mac

Indicative price: ~$105–110 (DR-05XP)

Link: TASCAM DR-05

TASCAM DR-40 (and DR-40X) Type: Portable 4-track recorder

Advantages:

4 recording tracks (2 built-in mic tracks + 2 XLR/1/4" inputs)

Recording in 24 bit / 48 kHz and 96 kHz

Overdub mode, low-cut filter, limiter

USB interface, ideal for home studio or live use

Indicative price: ~$120 (DR-40)

Link: TASCAM DR-40

TASCAM SS-CDR250N Type: Professional network / CD / SD recorder

Advantages:

Recording in 24 bit / 48 kHz and 96 kHz (WAV/MP3)

2 SD/SDHC/SDXC slots + USB + CD-RW

FTP function for automatic transfer

Balanced XLR inputs/outputs

Ideal for fixed installations

Indicative price: ~$500–600 (depending on retailer)

Link: TASCAM SS-CDR250N

TASCAM DA-3000 Type: Stereo master recorder / high-definition AD/DA converter

Advantages:

Recording in 24 bit / 48 kHz, 96 kHz, 192 kHz (and DSD up to 5.6 MHz)

Analogue XLR/RCA inputs/outputs + digital AES/EBU, S/PDIF, SDIF-3

BurrBrown PCM1795 converters (very low distortion)

Recording to SDHC or CF card (up to 512 GB)

Fanless → absolute silence

Ideal for mastering, archiving and professional studios

Indicative price: ~$1,200–1,500 (depending on condition and retailer)

Link: TASCAM DA-3000

Conclusion:

For portable use: DR-05 or DR-40

For professional network/CD use: SS-CDR250N

For mastering / professional studio: DA-3000

Device for listening tests:

Interacoustics is a company specialising in the supply of equipment for diagnostic audiology and balance testing. They offer a wide range of equipment for hearing assessment, balance testing, vestibular rehabilitation, real-ear measurements of hearing aids, and so on.

Here are a few options to consider: AD259, AD226 and AD629

Interacoustics diagnostic audiometers offer high accuracy and reliability for carrying out comprehensive hearing tests, including threshold tests, speech tests, impedance tests, and so on.

This equipment is used by healthcare professionals to assess and treat hearing and balance disorders. It is advisable to consult the official Interacoustics website for detailed information on the various devices available, their features and technical specifications.

The Digital Ear

Digital or analogue — Alfred TOMATIS Forum

Question: Why, in the context of applying your method, do you recommend the use of the analogue system rather than the digital one?

Answer from Alfred Tomatis: The appearance, some years ago, of digital sound in the modern world inevitably raised a great many questions among the professionals who apply my method. I understand this perfectly, and I owe it to them to clarify what I have already told them on several occasions. It remains to be determined what the impact of such a product is when introduced into our field — Audio-Psycho-Phonology — and whether it is usable, or at the very least compatible, with our kind of work. That is precisely where the real and crucial heart of our debate lies. The task is to demonstrate the effects of capturing and transmitting sound material on the nervous system, for it is indeed at that level that we operate the moment we speak of sounds. Indeed, one can appreciate that having at one's disposal a process that is technologically unrivalled and of such high calibre truly demands that we look seriously into this research. All of this leads us to establish the fundamental differences that exist between the neurophysiological effects of the sounds emitted by the one system and the other. Their activity, at the level of the brain, is different. It is therefore necessary to investigate why, from the point of view of cortical recharging, the processes diverge.

Experiments carried out in certain laboratories, in particular in Japan, have shown that the projections onto the cortex did not have the same configuration. Those produced by listening to analogue sounds were more extensive across the cerebral map than those arising from listening to digital sounds. The effects produced by these two forms of sound emission must therefore be studied in depth. The brain receives them in very different ways. By its very structure, it is an analogue system. The human nervous system has a specificity that makes it a means of communication, an information highway whose transmission system has well-defined characteristics. It functions in an analogue form that the laws of evolution have forged since the dawn of time.

We are familiar with the mode of action of digital signals on the nervous system, and in particular at the level of the cochleo-vestibular apparatus. Likewise, we are not unaware of the harmful effects that may arise at the cardiac level, nor of those that go so far as to call into question the intimate mechanisms of memory. One must take to heart the idea that the brain is literally seized in its entirety. It does indeed operate as a whole. There will not be a single one of its atoms that is not called upon. It must also be made clear that the natural sound of a voice or that of an orchestra is captured by one or more microphones. These are always analogue sensors. The role played by the microphone is, in effect, that of a kind of transformer that converts the natural sound perceived through the air into an electrical signal proportional to the sound perceived. This transformation is analogue in nature. A loud perceived sound corresponds to a strong electrical signal. This is then processed electronically.

The Electronic Ear that we use within the framework of Audio-Psycho-Phonology is an analogue processing device. This device corresponds to certain features of the functioning of the human ear in its listening mechanisms. It is adapted to the transmission of sound towards the cortex and then throughout the body by means of certain networks that I have named the "integrators". This whole system functions on an analogue rhythm, corresponding to the neurophysiological responses of the human organism. It must therefore be understood that, within the framework of our therapeutic work, one can only use a set of devices (Electronic Ears, headphones, microphones, etc.) functioning in an analogue mode. This is in order to ensure maximum cortical recharging. On the therapeutic level, it is necessary to take into account the requirements of the human nervous system, which, for its part, has not followed the same processes of progression as present-day technology. The brain must be regarded as a gigantic network whose purpose is to bring together all the cells so that they act in unison — in accordance, of course, with their own attributions, which individualise them within a functional programme. It follows that the use of digital sound, within the framework of our therapeutic work, under the Electronic Ear, cannot be contemplated at the present time.

Can the smart card be used?

Even when the keypad is locked? Yes.

The keypad locks access to the Alfred TOMATIS parameters (channel, delay, precession, gating, balance); however, the standard keys of the Ear remain functional (volume increase, start, stop, etc.).

The Ear includes 2 microphones

What are their functions?

A. MIC — external microphone to be connected to the socket located on the rear panel, on the left-hand side of the Electronic Ear (source). It is used for active phases such as repeating words. Its activation key is located on the left of the keypad in the Source section; we will also use the standard UP/DOWN keys to adjust the volume. The microphone remains "open" continuously as long as its setting value is greater than 0.

B. MIC is an internal microphone located on the right-hand side of the Electronic Ear, used during a conversation between teacher and patient connected to it, like an intercom. To adjust the output volume, simply press the UP/DOWN keys (arrows) and hold down the MIC key during the conversation. On the display screen, you will know at all times, through the word ON, that the microphone is connected. Another way to ensure this option is working is to check the AP zone. When you produce a sound, you will see the LEDs move up and down. We will also use the standard UP/DOWN keys to adjust the volume.

What is the power consumption of the Electronic Ear?

For an Electronic Ear connected to its accessories such as headphones and AP?

The consumption corresponds to that of a 30 W computer.

Normal or easy gating?

What is the purpose of normal or easy gating?

We will find this option in MENU / OPTIONS / ENTER / DOWN ARROW / GATING / NORMAL OR EASY for the (older) NN0425-00 and NN0426-00 models.

NORMAL GATING = Allows use with any sound source (in position 40).

EASY GATING = For use with low-quality sound sources (in positions 45 to 50).

For the (new) N425 and N426 models it appears by default at 40% (positions 10 to 50). Vocabulary note: Position: a mathematical value that expresses sound sensitivity. Gating: the switch from channel 1 to channel 2 at the moment when the sound is higher (sound volume). Delay / precession = these are the timing parameters.

Line input volume

I need my Electronic Ear to switch from channel C1 to channel C2, but I have to increase the input volume (line input) a great deal. Is this normal?

YES.

It depends on the sound sources used (worn cassette, poor recording, etc.) and on the quality of the player in terms of the sound signal.

So it will be possible to adjust the outgoing sound using the bone-conduction and air-conduction parameters, taking the patient's comfort into account. This adjustment is left to the teacher's judgement.

Filtered music

Which pieces of music (by Mozart) can be filtered?

The MNF ALC pieces are the CDs on which we can apply filtering.

Individual Station AP4/2, AP4/4 or AP8/4

Does it override the Ear with regard to bone conduction, air conduction and balance? The Ear has no influence on balance; it is the station that performs this function, since there is no electrical connection for balance between the Ear and the station. As regards bone conduction and air conduction, it will attenuate the sound volume of the parameters set on the Electronic Ear. *Example*: if the volume is at 4 (40%), and you want to maintain this percentage, you will need to set the potentiometers to 10 (100%) on the station. *Other examples*: taking the previous case: if you were to set the potentiometers to 5 (50%) on the station, you would obtain 50% of the 40% preset on the Ear, i.e. 20%.

AP cord

AP connection cable — C2-5: what is its function?

This cable, about 4 metres long, allows an AP to be connected to an Electronic Ear. It can also be used to make the connection between two APs.

Headphone extension cable

Model C3-5: what is its function?

To extend the headphone cable by about 4 metres, or more if needed.

It also offers the possibility of connecting the APs to one another and between the Ear and the AP. This cable is made to order only.

How many APs?

Can be connected to an Electronic Ear?

So as not to lose effectiveness, it is preferable to connect at most, and only occasionally, 2 APs to an NN426 and 3 to an NN425.

The maternal voice kit, EVM

What is it? What is it for?

This accessory is a microphone preamplifier; it transforms the electrical signals from the microphone (-48 dB) into electrical signals (line -10 dB) that can be recorded on a tape recorder, a Fostex, an Alesis, etc.

It is needed to record the maternal voice (VM) under good conditions (raw voice).

*Microphone + EVM + Fostex = Recording of the maternal voice* cannot be used for active voice sessions; it does not replace the Ear, but it makes it possible not to tie up one of them just for recording the VM. *Microphone + Fostex + Electronic Ear = Active voice session*

The keypad does not work!?

Technical problem: the keypad does not work, it is locked; how can I unlock it?

"For the NN425 and NN426 models (large version), put the unit into standby mode (the red light comes on), then press the following keys in succession, in the order indicated, depending on the type of keypad."

"Bone -> Line -> Delay BC -> Delay AC"

"Bone -> Line -> Delay -> Precession"

"Trans -> Line -> Attack -> Delay"

the last lamp of the VU meter will light up briefly.

This will indicate that the unlocking has been carried out correctly.

Otherwise, lock the keypad to prevent the client from making incorrect adjustments.

Go to:

MENU-KEYBOARD / LOCK-ENTER key; the keypad locks access to the TOMATIS parameters (air conduction, bone conduction, balance).

It is always possible to increase the microphone, headphone and sound-source volume, as well as to use the keys needed to start and stop the Electronic Ear.

Returning a unit for repair

When returning an Ear for repair, what equipment should be included?

It is only necessary to return the Ear, without having to include the power supply and the cables, which would add to the weight of your parcel.

What are they for?

Types of smart card:

Siemens (older card compatible with the older NN0425-00 and NN-0426-00 models). These can only record a single state of the parameters (like a snapshot).

The I2C (new — 402, 425, 426, 427, 430) works like a memory card, with the capacity to store up to 60 sessions. (See the instruction manual of the Electronic Ears for recording, as well as the NNcard manual.) They work like a memory card and have the capacity to store up to 60 sessions. (See the Electronic Ear manual and the NNcard software manual for recording.)

They have the option of recording the Tomatis parameters without being able to set the session time through the Electronic Ear, or of recording up to 60 sessions and their durations using the computer program called NNcard, compatible with the latest models with a USB port (since August 2007). Each type of smart card can be used with the Electronic Ear models of the same generation, namely the 402, 425, 426, 427 and 430.

What equipment is needed to start up a centre?

1 or 2 N425

1 x N426c or N427c

10 x adult headphones

2 x children's headphones

2 x AP8/4

1 x AP4/2 or AP4/4

2 or 3 Tascam

1 x test device

1 x headphone tester

1 x EVM

Digital resolution

The digital resolution of the CDs and of the CD or SDHD players must be 24 bit/48 kHz, which corresponds to the professional audio standard.

By way of comparison, a resolution of 16 bits or 24 bits represents image quality due to the number of pixels in an image. Audio offers us only 2 choices: 16 bits (low quality) or 24 bits (high quality), rather like the comparison between normal and metal cassette tapes.

The sampling frequency of 44, 48, 88 or 96 kHz is comparable to speed. In audio, one can compare the quality of a maxi 45 rpm single containing a single track per side (professional format) with an album cut on a 33 rpm record containing 5 to 6 tracks per side, used by the general public. The two vinyl "platters" have the same diameter, so on the same surface more information will be cut per minute with a 45 rpm than with a 33 rpm: by spinning faster, more material is used to store the information, which ensures greater reproduction fidelity. One could thus accept that going from 45 to 33 rpm is already a process of compression, but a mechanical one.

The same is true of reel-to-reel tape recorders such as the Revox B77, which offered 2 speeds, 9.5 or 19 cm/s; at the time it was considered that the speed of professional recordings should be 19 cm/s.

But this comparison is not representative enough for the layperson; let us compare instead with a washing machine. If I myself have correctly understood how the basic model works, depending on the fabric one chooses the temperature and the programme (which determines the wash, rinse and spin cycles, etc.), but which essentially determines the wash time and therefore the speed?

Simply for the sake of comparison, the temperature is equivalent to the resolution: 16 bits = 30°, and 24 bits = 40°; and the programmes: Eco = 44 kHz, normal = 48 kHz, long = 88 kHz, special = 96 kHz.

If you wash a garment at low temperature for a short period it will not be entirely clean; likewise, at the right temperature but on the wrong programme for too long, it will be clean but certainly very creased, or even faded or misshapen.

Conclusion: With music too, it is important to have the right temperature (24 bit) to guarantee the richness of the sound, and the right speed (48 kHz) so as not to distort or wash it out (a metallic or harsh sound).