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.
Common amplifier design operate in a closed loop configuration. This means that there is a feedback loop where a fraction of the output produced by the amplifier is compared to the input signal and any residual error is injected back into the amplifier to compensate. We conducted more simulations, test prototypes and subjective listening sessions than we can count which 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, this phenomenon seems quite logical.
We have spent an incredible amount of time during the design of our amplifier stages to achieve the most linear possible transfer function in open loop. Birdland Audio's Solid-TubeTM technology is a result of this relentless quest for linearity, and the purity of the sound quality is a testament to that nutured research.
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.
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 is actually referenced to a power supply line which is not a pure constant in dynamic (even though ideal theory claims it to be). 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 always fluctuate as the power demand changes on it. These slight variations - however small - will add noise to a sensitive signal if, referenced to the power rail. This is especially true 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 (even in our in unbalanced designs). Thanks to surface mount technology, the ground path of our Pleyel amplifiers can be reduced to 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.
Aside from the only capacitor in the input, the Pleyel Amplifier modules start their bandwidth at zero hertz. That is right, the design amplifies from DC all they way to about 300KHz. 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..300kHz at -3dB.
All stages of our Pleyel amplifier operate in Class A except for the output stage which operates in our new ultra-linear Solid-TubeTM technology. This technology reduces the interaction of the speaker's EEM with the amplifier. Moreover, because it operates the local feedback gain is extremely low gain, it operates almost in open loop, and as a result, 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.