Dereux Amplifier: le STÉRÉOPHONE

Fabrice Albanese, connoisseur and restorer of tube amplifiers, has offered us this beautiful example of the Dereux amplifier.


(Dereux was promoted to "Essai d'Analyse et de Synthèse rationnelle des sons dans les espaces réverbérants au moyen de l'Orgue Electro-Statique")


The STEREOPHONE is an interdependent reproducing unit comprising the Amplifier-Loudspeaker-Reverberator-Space chain, in which a volume similar to a U-shaped pipe serves as an intermediary between the loudspeaker and the listening space.


We only have the amplifier on display, and we hope to be able to trace the other parts as well. There is a photo of such an installation with an organ for a church or concert hall.

Brochure text:

Unleash the magic of the orchestra through the miracle of the Dereux STEREOPHONE

thanks to the servo-control of the amplifier to the acoustic reactions of the space.


By its automatic adaptation to the listening space, the STEREOPHONE has made the numerous adjustment knobs on the usual amplifiers superfluous.


Without any intervention on your part, whatever the size or nature of the room, the STEREOPHONE alone will ensure the most marvellous reproduction with a purity, a naturalness and a dynamism that the old methods could not offer you.


Moreover, the way to convince you of this is very simple: Ask to listen to a comparison of the same disc between the STEREOPHONE and the best high fidelity system, whatever its price.

Our purpose is not to assert the superiority of the STEREOPHONE, which you will immediately notice, but to explain it to you as simply as possible.



It is an interdependent reproducing unit comprising the Amplifier-Loudspeaker-Pre-reverberator-Space chain, in which a volume similar to a U-shaped pipe serves as an intermediary between the loudspeaker and the listening space.

Although the pre-reverberator is generally called a "pipe" because of its analogy with a U-shaped pipe, it has none of the characteristics of a sound pipe

Its regime is that of a small reverberant space. There is always a standing wave whatever the ratio between the length of the system and the frequency emitted by the speaker.

by the loudspeaker. This standing wave follows the same laws as those of the reverberant listening space, but the wave being much more intense there, it could be used to control the amplifier by feedback from the loudspeaker under well-defined conditions.

The efficiency of the device is such that the gain of the amplifier can vary in the ratio of 1 to 10 depending on the frequencies and the acoustics of the room.


In the classic reproducers, improperly called high fidelity systems, there is a broken link.

The chain which, starting from the player, should lead to the listening room, ends at the loudspeaker.

It is easy to understand that the enormous difference in density between the membrane and the ambient air creates a brutal discontinuity from which all the reproduction defects come.

In the STEREOPHONE, the column of air in the pre-reverberator, which has a mass of 128 grams, allows the gradual transition from electrical to acoustic oscillation thanks to the ever-present standing wave.

To use a crude image, we can say that the loudspeaker-pre-reverberator tandem plays a role in electro-acoustics analogous to that of an automatic gearbox in the automotive field.


The consequences of eliminating this break are extremely important:

a/ - Hearing is practically identical at all points in the listening space.

b/ - The sounds of the different instruments no longer seem to emanate from the loudspeakers but are born in the space at points whose situation is linked to the pitch, timbre and relative intensity of the different instruments in the orchestra.

This phenomenon, which is typical of the STEREOPHONE, is similar to what is known in acoustics as the "ventriloquism effect".

c/ - Consequently, the hearing of monophonic discs acquires a spatial relief at least equal to that of a stereophonic reproduction in the usual devices. Hence the justified name of STEREOPHONE.

d/ - Because of their directional effect, the usual loudspeakers have a heterogeneous sound field, hence the adjustments of timbre in each channel, the balance etc...

These adjustments are tedious and, depending on the position of the listener, are absurd, since you have to leave this position to make the adjustment or take the amplifier with you.

The homogeneous sound field of the STEREOPHONE makes these adjustments unnecessary and

allows identical listening for many listeners.

el/- Finally, there is an inadmissible contradiction in the listener's mind between his mental representation of the orchestra and the point source offered to him by classical reproduction.

This contradiction, which has disappeared in the case of the STEREOPHONE, plays a large part in the artificial character of the speaking machine, even stereophonic, as many acousticians have pointed out.




It is not our intention to suggest that the quality of our production is superior to that of our competitors.

Practically all the serious companies present material of excellent quality.

Unfortunately, it has been more or less the same technique for thirty years.

When we introduced the electrostatic organ in cathedrals, we came up against problems that were far more difficult than those of phonographic reproduction.

All reverberant spaces follow the same fundamental laws, so we only had to adapt our technology.

We sincerely hope that the appearance of the STEREOPHONE on the market will shake up apathy and that other equally valid formulas will be born in other laboratories.

This emulation can only be beneficial to all.



For rooms up to 1,000 cubic metres including:

A double amplifier 15 W + 15 W permanent

Dimensions : Length 300 x Height 130 x Depth 240 min

Weight: 7 kg

Two reverberators, dimensions: 0.30 m x 0.30 m x 0.98 m

Brown or clear finish

Homogeneous response in space 30 - 14 000 cycles at + 3 db

A GARRARD SP 25 automatic turntable Original oiled teak base


Price without table: 2050 francs plus VAT

Reading table : 500 francs plus VAT


Distributed by : I. R. O.C. International Recording Organ.  S.A.