Years of experience have shaped the founder's preferences towards one technique versus another. Although this page does not contain any trade secrets, it does explain the audio design preferences of the founder.

Feedback

Most commercial amplifiers available today work in what is called closed loop. We conducted many subjective listening sessions of several amplifier prototypes and clearly demonstrated beyond any doubt that a non linear amplifier whose loop is closed does not sound as well as a linear amplifier with a similar band pass and gain in a closed loop (and sometimes even in open loop). Although the difference is hardly measurable -- if measurable at all -- this phenomenon seems quite logical. As the founder likes to say: "When the closed loop reacts, it's because it's done or it was about to do something wrong". In other words, what is important is that closed loop correction comes in somewhat too late. Also, our subjective listenings lead to a result contrary to classical theories: it is really better to have a small feedback correction gain.

Darn Speakers

We also learned that many amplifiers available today are designed and tested using a resistive load that is nowhere close to simulate a speaker's true electrical charactersitics. In fact, in the unnatural environment of a laboratory, these amps are capable of displaying quite impressive characteristics. However, add the most crucial link in the audio chain -- the speaker -- and the equation is immediately changed. This partly explains why all amplifiers display outstanding charactersitcs and yet all sound so different.

Throughout the years, we have carefully studied the interactions between the amplifier and the speakers to keep them minimal. Along with the two assertions above, our research lead us to design our patent-pending output stage used in our Pleyel amplifier.

We're grounded

Many of our competitors in the amplifier field seem to make an important mistake in their design: dereferencing the music signal from ground to power supply lines and back to the ground for the output stage. This is a terrible thing to do, for at one point of its path, the signal actually depends on a power supply line... which is not a pure constant in dynamic (as ideal theory predicts it). Some manufacturers will argue that excellent regulation and filtering are key to success but no matter how good a regulation is, the supply lines will fluctuate as the power demand changes on it. These slight variations - however small they are - do alter a sensitive signal referenced to it, especially in the input stages.

Our Pleyel reference amplifier never dereferences its input signal, which is always and only referenced to the ground from input to output (when in unbalanced mode). Thanks to surface mount technology, the ground path of the Pleyel is a solid 2-oz copper plane which is no bigger that 30mm x 20mm (about 1.2" by 0.8") which makes it virtually equivalent to a single point. Because of this, the Pleyel is not sensitive to the power supply fluctuations allowing its design to be based on a simple bridge+capacitor old time favorite.

"Band with" an attitude

Aside from the only capacitor in the input, the Pleyel Amplifier modules start their bandwidth at zero hertz. That is right, they amplify from DC all they way to about 380KHz (by bypassing the input filter). Because it is preferable to remove any possible continuous residue from the source, the input circuit contains a 6.8uF polypropylene capacitor which is the only capacitor in the entire amplifier chain. Subjective listening with and without the capacitor has proven to be an equally supreme experience and therefore the capacitor was kept in order to avoid possible speaker and amplifier damage if connecting a source with continuous residue. The final bandwidth with the input cap is 10Hz..380kHz at +0/-1dB.

The Class

All stages of our Pleyel amplifier operate in Class A except for the output stage which operates in our new ultra-linear open loop Class. This patent pending technology reduces the interaction of the speaker's EEM with the amplifier. Moreover, because it operates in open loop, the speaker self-induced EEM does not cause erratic transients from the amplifier.

Of course, a clever and innovative design would be nothing with poor or even average quality parts; that's why we did not cut corners selecting only the best components for the Pleyel 250 amplifier. You'll be pleased to find in our product the finest audiophile parts such as Vampire's 24k gold plated phono jacks and speaker binders, a generous audio toroidal power transformer, only film metal resistors and polypropylene input capacitor -- among others.