Technology

But sophisticated technology must not be rocket science and efficient adjustments should not take hours. Therefore we understand even the most elaborate circuit as a means to an end: producing an outstanding quality of sound (although we have to admit that the technology itself is a great source of delight, too).

In the end it is detail which makes the crucial differences. The following part offers a closer look.

Another popular form of meter is the LED chain which can be produced fast and easily. Unfortunately it has a disadvantage, too: Because of the chosen driver units the change between two values always happens abruptly. A single LED in the chain can therefore only show an imprecise value in a defined interval. Hectic flicker indicates that the actual value must be somewhere in between.

elysia solves these problems by introducing the  analog dynamic display that combines the benefits of both VU meters and LED chains. This meter is based on LEDs, too, but a special circuit design makes it possible to show interim values by modulating the brightness of the LEDs. This means a true analog way of showing the operation of the compressor: It is very fast, but with fluent transitions. The user gets an important tool for precise gain reduction monitoring – finally the relationship between acoustic and visual perception feels just right.

The special problem with bass is that in case that the B string is played it produces frequencies as low as 30 Hz, which is equivalent to a period of 33 ms between the waves. The result is that a fast attack setting will have its effect on every wave anew, producing unwanted artifacts.

Longer Attack settings reduce distortions significantly, but now the compressor reacts too slowly on fast impulses. The intended compression now turns into an expansion, because the fast and loud impulse is not processed while the level of the sustaining signal will be reduced. A slap-style bass displays this phenomenon very well.

This is where elysia’s Auto Fast function comes into play. If you set the attack to 80 ms and then engage the Auto Fast mode, the attack time will automatically be shortened on fast and loud signal impulses (e.g. string hits fingerboard when slapping). The compressor quickly reduces the signal and prevents the signal from 'slipping through'. Afterwards the attack time directly and automatically returns to its original setting. In Auto Fast mode the compressor can be very fast, but only when it is really needed!

The release characteristics behave in a very similar way. Again referring to our bass example, you often have to accept compromises when looking for the right release setting. If you set it too fast, you will create distortions, if you set it too slow, you will loose drive and loudness. Again, the Auto Fast mode is the solution. It will shorten the release parameter for a short moment and then reset it to the original value.

This function only influences the time parameters on short and loud impulses, in all other cases the original settings stay untouched. In both channels, attack and release each have an Auto Fast switch of their own, providing a great deal of flexibility in using it depending on the situation. Especially when processing/mastering complex and difficult material you have a very effective new tool at your disposal.

In the majority of cases small capacities are integrated into the amplifier stage in order to slow it down. The idea behind this is to reduce the amplification of high frequencies. Sometimes further external capacitors are added into the negative feedback path to achieve this. The problem is that these capacities have a negative effect on the sound quality of the signals that pass these stages.

The corollary was designing a circuit doing without capacitors that would affect the frequency spectrum. Intensive research finally led to a concept that has all the advantages but none of the handicaps of a classic op-amp: the current feedback amplifier. The current is directly modulated by the negative feedback and therefore avoids the time delay in the differential amplifier. The overall signal delay is clearly shorter and the phasing will stay intact even in high frequency areas.

Featuring an enormous slew rate and true reproduction of impulses, the amplifier can handle frequencies up to several MHz. The enjoyable results are clean high frequencies, a very good projection of details and open as well as natural dynamics. In addition, this amplifier can be tuned to work at a very low harmonic distortion level or also add a pleasant amount of K2 if wanted. Therefore some of our amplifier stages have experienced further fine tuning depending on their particular purpose. The resulting sonic quality is beyond any doubt and shows that classic analog design is still state-of-the-art for audio processing on the highest level.

Further on we placed additional MKP capacitors into many parts of the circuits in order to provide the current needed locally in a very fast manner. The voltage for the electronics is precisely kept at +/- 30 Volts. The voltage regulation is built out of discrete circuits, keeping the noise of the power supply so low that one can hardly measure it at all. At -114 dBu it is much lower than the background noise of the complete unit itself.

The measured hum is cancelled by 40 dB better than standard voltage regulators are capable of. This is an important condition for clean and clear sound results. If there were higher degrees of noise and hum in the voltage supply, the amplifier stages would have to compensate for that and could not fulfill their actual duty as well as intended.

The diode rectifiers have their influence on sound, too, because they have to recharge the electrolytic capacitors for a short moment and have to provide current for all circuits while doing so. Therefore elysia uses very fast and acoustically tested diodes for that purpose.

Also, we chose a toroidal transformer completely capsuled in MU metal. The production is laborious and therefore expensive, but it keeps the magnetic stray field on a negligible level. The transformer could therefore be placed inside the unit, keeping the connection to the power supply electronics as short as possible. An over-dimensioned measure of 140 VA guarantees that the transformer is always able to provide the electrolytic capacitors with much more current than they will actually need.

Another advantage of this technology is the distinct reduction of problems that result from physical component tolerances. When developing analog audio equipment, a 100% equal design of two stereo channels can rarely be realized. In addition, even the best components available have tolerances that result in the real values of two channels slightly differing from each other even if the controller settings are exactly the same. This problem especially affects equalizers and compressors needing equal settings in order to achieve a clear spatial projection and a stable stereo middle.

If these methods of signal processing are integrated into a high grade M/S matrix the component tolerances will then have their effects on the M and S signals. But this does not have negative effects on the later decoded stereo image, because in M/S mode the mono shares of the left and right signal are both using the same channel for processing! There is no further need for a 100% exact match of both channels (which can’t be done anyway), and level variations between left and right channel belong to the past from now on. It is hard to get along without this feature once you have discovered what it can do for you.

A third alternative is the use of voltage controlled amplifiers (VCAs). In most cases these are special integrated circuits (ICs) that vary their amount of amplification depending on the control voltage. The main benefit is a comparatively linear character curve. In addition, they can also be used as amplifier stages, giving them a very broad range of application (e.g. in noise gates). Even so VCAs are not often found in high end gear. One reason is the limited number of manufacturers and product models that can meet the sophisticated demands of the audio market. Furthermore, these components are integrated circuits that cannot be modified in terms of sound. Finally, the ICs contain active stages that have a fixed (and often too low) quiescent current rate that can result in unpleasant distortion on high input levels.

Because of the specified downsides elysia has developed a new gain reduction component: the fully discrete Passive Current Attenuator (PCA). This circuit transforms the incoming signal into a current and is then able to reduce this current controlled by voltage. The control voltage can be compared to that of a VCA and benefits from a calculable characteristic curve. The core consists of sixteen discrete transistors being kept at a defined temperature by an exclusive heating system that avoids unwanted fluctuations.

The aim was to create a musical gain reduction stage that could meet even the highest demands concerning audio quality. Countless experimental setups and auditions were needed to finally achieve this goal. Unlike industrial ICs the PCA works purely passive – it has no internal amplifiers and only reduces incoming signals. Not until the signal leaves the PCA, a downstream amplifier stage converts the current into voltage again, and the make up gain is added by setting the correspondent control. The characteristic curve of the control voltage was optimized for mastering applications resulting in precise but gentle gain reduction performance. If more keen and spirited kinds of sounds are on the agenda, the alternative feed forward mode offers them at the simple push of a button, too.

Further advantages of the PCA are its enormous bandwidth and its extreme fast control speed. Even huge level changes are done in just a few microseconds – an important premise for a fast and flexible compressor. The PCA plays an important role in the overall sonic character of the alpha compressor. It enriches the music with natural overtones by producing a healthy amount of K2 and K3. The sound characteristics become fuller and especially inspire digitally mixed productions with that certain something.

elysia sets the quiescent current at 14 mA which is an unusual high value for audio circuits. Doing so, the transistors will always be conductive, even when there are small resistor loads and high amounts of current. Crossover distortions cannot occur. For comparison: The total current consumption of a typical audio op-amp NE5534 is 4 mA and the quiescent current about 2 mA. The measurable crossover distortions of these op-amps are very small, too. However, this can only be realized by high amounts of feedback that need more signal stages, having negative effects on the fidelity of the signal in turn.

To guarantee pure class-A mode elysia utilizes power transistors normally used in power amps in the output stage. The sonic result is a clear increase of immediacy and dimension – all signals sound more present and massive. With a value of 2 watt each, the emitter resistors are also over-dimensioned in order to improve the projection of details even further.

A better choice in terms of speed would be a FET limiter, for example. But the need to work very fast remains and the FET limiter may cause sharp and audible edges in the signal. Moreover, the set time constants will have a noticeable influence, too: if the release time is too long, for example, the limiter will also reduce signals that would actually not have been too high in level and therefore degrade the original signal structure.

elysia’s Soft Clip limiter was developed to solve these specific problems. It is specialized on reliably catching short and transient-like signals. But the technical principle is different from that of classic 'brickwall' limiters that completely avoid further level increases beyond a certain threshold. It is better to compare it with an analog tape machine that drives loud impulses into saturation, and by doing so acts like a kind of 'natural' limiter. The Soft Clip limiter is built out of discrete transistors and similar to analog tape its characteristic saturation curve results in rounding peak signals rather than cutting them off. This makes it an effective tool especially when the source material contains variable peak values.

With the T16 Heater elysia presents a system that arranges constant conditions and reduces the thermal fluctuation to a minimum. This system was inspired by high-precision measuring instruments. It features up to 16 discrete transistors in a massive copper ring that is warmed up to a definite temperature.

A bordering ceramic cap the isolates the copper ring and keeps it from cooling down quickly and prevents exceeding heat emission into the housing at the same time. Once the system has reached its working temperature, it only needs little current to keep it at the same level. An electronic control circuit is responsible for a small variance of only a few degrees. The procedure is known from high end tube gear: the alpha compressor should be granted an adequate warm-up-time in order to experience it absolute top form.

The filter used for this application is an all pass variant with flat frequency response that changes its phasing correspondent to the setting of the frequency controller. When the signal that went through the all pass is afterwards mixed to the original again, signals that are in phase will be amplified and out-of-phase signals will be reduced.

This is how the special frequency response of the filter comes off. Because the filter signal is mixed to the original, the genuine structure and impulse-response can be contained to a large extent. None of the amplifiers will be shortened in their frequency response, which results in an open and dynamic sound. By simultaneously boosting and cutting the selected frequency-areas it is much easier to influence the character of a track ('bright' vs. 'dark') compared to using other types of equalizers.

VOVOX sound conductors transmit the whole frequency range with minimal losses. This means sound becomes brilliant and tangible. At the same time, the bass range becomes more powerful and precise. Due to their special design, these cables are able to transmit hard peaks very directly. Music becomes more brisk, dynamic and powerful.

During the record and the replay, VOVOX sound conductors enhance the spatial reproduction of music. Even in very complex situations, the sound remains transparent with clear contours. Often a significant enlargement of the stereo base is observed. As the sum of many different effects, there are also noticeable improvements to the ‘charisma’ of music: The clarity and immediacy of the sound signals offer an aura of calmness, solidity and sovereignty.