WYRED 4 SOUND amps.

ttt...

Pycroft wrote: »

Also, is there a suggested website to learn the difference between Class A, B, C, D, etc. amps? If I remember when I was reading tubes, there are different types - push/pull, etc. Does it have something to do with this?

Power amplifier circuits (output stages) are classified as A, B, AB and C for analog designs, and class D and E for switching designs based upon the conduction angle or angle of flow, Θ, of the input signal through the (or each) output amplifying device, that is, the portion of the input signal cycle during which the amplifying device conducts. The image of the conduction angle is derived from amplifying a sinusoidal signal. (If the device is always on, Θ = 360°.) The angle of flow is closely related to the amplifier power efficiency. The various classes are introduced below, followed by more detailed discussion under individual headings later on.

Class A
100% of the input signal is used (conduction angle Θ = 360° or 2π); i.e., the active element remains conducting[5] (works in its "linear" range) all of the time. Where efficiency is not a consideration, most small signal linear amplifiers are designed as Class A. Class A amplifiers are typically more linear and less complex than other types, but are very inefficient. This type of amplifier is most commonly used in small-signal stages or for low-power applications (such as driving headphones). Subclass A2 is sometimes used to refer to vacuum tube Class A stages where the grid is allowed to be driven slightly positive on signal peaks, resulting in slightly more power than normal Class A (A1; where the grid is always negative[6]), but incurring more distortion.

Class B
50% of the input signal is used (Θ = 180° or π; i.e., the active element works in its linear range half of the time and is more or less turned off for the other half). In most Class B, there are two output devices (or sets of output devices), each of which conducts alternately (push–pull) for exactly 180° (or half cycle) of the input signal; selective RF amplifiers can also be implemented using a single active element.

These amplifiers are subject to crossover distortion if the transition from one active element to the other is not perfect, as when two complementary transistors (i.e., one PNP, one NPN) are connected as two emitter followers with their base and emitter terminals in common, requiring the base voltage to slew across the region where both devices are turned off.[7]

Class AB
Here the two active elements conduct more than half of the time as a means to reduce the cross-over distortions of Class B amplifiers. In the example of the complementary emitter followers a bias network allows for more or less quiescent current thus providing an operating point somewhere between Class A and Class B. Sometimes a figure is added (e.g., AB1 or AB2) for vacuum tube stages where the grid voltage is always negative with respect to the cathode (Class AB1) or may be slightly positive (hence drawing grid current, adding more distortion, but giving slightly higher output power) on signal peaks (Class AB2); another interpretation being higher figures implying a higher quiescent current and therefore more of the properties of Class A.

Class C
Less than 50% of the input signal is used (conduction angle Θ < 180°). The advantage is potentially high efficiency, but a disadvantage is high distortion.

Class D
These use switching to achieve a very high power efficiency (more than 90% in modern designs). By allowing each output device to be either fully on or off, losses are minimized. The analog output is created by pulse-width modulation; i.e., the active element is switched on for shorter or longer intervals instead of modifying its resistance. There are more complicated switching schemes like sigma-delta modulation, to improve some performance aspects like lower distortions or better efficiency.

Additional classes
There are several other amplifier classes, although they are mainly variations of the previous classes. For example, Class G and Class H amplifiers are marked by variation of the supply rails (in discrete steps or in a continuous fashion, respectively) following the input signal. Wasted heat on the output devices can be reduced as excess voltage is kept to a minimum. The amplifier that is fed with these rails itself can be of any class. These kinds of amplifiers are more complex, and are mainly used for specialized applications, such as very high-power units. Also, Class E and Class F amplifiers are commonly described in literature for radio frequencies applications where efficiency of the traditional classes in are important, yet several aspects not covered elsewhere (e.g.: amplifiers often simply said to have a gain of x dB - so what power gain?) deviate substantially from their ideal values. These classes use harmonic tuning of their output networks to achieve higher efficiency and can be considered a subset of Class C due to their conduction angle characteristics.

The only "horn" like speakers I've heard them on are Tannoys(horn loaded tweet), and Sonist(waveguide ribbon). I've also heard them on Acoustic Zen Crescendos and they've never sounded harsh with W4S gear in the signal path.

SolidSqual wrote: »

I heard my W4S 1000s on a Klipsch Heresy speaker and I wanted to kill myself. I'm told the Heresy needs more tubey warm amplification.

Not a glowing review...

Some people don't like horns to begin with because they are very "in your face" with extreme detail sometimes to a fault. I think that tubes tones down these characteristics a bit, lending horn and non-horn lovers to enjoy them alike. However, I am a stickler for detail, low noise, and clarity in my listening, and so I enjoy the horn sound even without tubes.

Thanks for the thoughts and I will continue to be skeptically interested in hearing a W4S amp with my speakers.