The original Wyetech Labs Topaz 211A amplifier was the culmination of our research & development into the sound quality of various topologies and valve types. Three years of experimentation were needed to learn the secrets of design and implementation in order to build one of the finest sounding amplifiers ever to reach the marketplace.
Tube or valve amplifiers present an opportunity to "go back to the future" so to speak. The solid state (SS) market has long since reached its maturity. It is exceedingly difficult to improve the sound quality of SS amps to the point where the "Law of diminishing returns" is dominant.
Solid state amps are becoming ever more complex, with the use of integrated circuits, digital logic, multi-layer printed circuit boards (PCB's) and computer aided automated design (CAD). It has reached ever more complicated levels of circuitry to the point where an SS amp with 10 times the number of components of an equivalent valve amp can be sold for one-tenth the price.
So why is there a valve revival in the audio world, when other factors such as specifications of tube amps will never be able to reach those absurd levels found in SS amps. One reason is that many valve amps with distortion figure as high as 2% sound much better than state-of-the-art SS amps with 0.0001% distortion! Another reason is because tube amp designers are not trying to hopelessly compete with SS amp specifications and are instead concentrating more on sound quality. At Wyetech we have concentrated our effort on taking advantage of those qualities which valves are known to exceed in. One predominant advantage is that it is far easier to operate a valve in its linear excursions than it is to do so with transistors. Another overlooked advantage is what I call power to weight heat ratio. A tube with a plate dissipation of 100 watts can be operated at that level while a transistor rated at 100 watts will self-destruct at 4 watts without proper heat sinking. Even with enormous heat sinks a fan is almost a necessity to cool one transistor operating at a 100 watts of power dissipation.
What makes our 211A amplifier stand above the crowd, ultimately, is the quality of the sound it reproduces. There is no magic involved in achieving this aim, only a genuine desire to use only those techniques that lead to improved sound. The first decision was to choose tubes over solid state. When comparing a simple triode valve with a 3-element transistor, the tube usually wins when it comes to linearity! However, do not think we are dead against solid state - on the contrary: with low level signals such as phono amplifiers, it is much easier to design a good SS phono stage than it is to do the same with tubes (the load is usually much less complex, being of a resistive nature for the most part). We are talking only about amplifiers interfaced with speakers - an extremely complex reactive load.
There is a generally accepted principal that goes like this.....The fewer elements and the simpler the circuit is, the better chances are of getting it right! Choosing a valve circuit allows us to take full advantage of this principle, since it is also well known that to do a given job, fewer tubes are required than transistors.
The Wyetech Labs 211A amplifier does its job using just 4 tubes for a complete stereo amplifier. There are 3 stages in each channel. All stages are single ended, self-biased and consist of absolutely no (NFB) negative feedback of any kind, either local or global. All stages operates in class A1 and only the best coupling capacitors and output transformers are used. This coupling contributes the most to the sound of an amplifier, and we have chosen these particular high quality parts wisely - as you will find out when you listen to this amplifier! Note that the 3 stages are pure triode and the equivalent solid state circuit would equal 3 transistors per channel. The first and second stage uses double triodes that contain both channels inside each tube envelope. The third stage consists of a single 211 directly heated triode valve operating at 1200 volts in self bias mode. This is one of the most linear triodes ever employed in amplifier designs to date. It is of the thoriated tungsten filament design noted to be the best sounding kind.
Feedback: to be or not to be
The issue of feedback! We are not absolutely against feedback, though our experience has taught us that feedback affects the sound, regardless of the amount used. Our aim is to correct any irregularities noted in the original circuit without feedback. We have focused our energies on building circuits that keep these irregularities to an absolute minimum, so that error correction can be avoided altogether. We have only been able to attain this by using pure triodes in the signal path. The benefit of having done so is to experience a completely open sound stage with absolute precise imaging. We have noted good results when using feedback & pentodes in regulating power supplies. We have chosen to leave these out of the signal path. You be the judge and let your ears decide!
Tweaks
The issue of tweaking! It has been said that the best tube amps should have adjustable bias pots for each output valve. Due to the necessity of balancing the output winding for minimum distortion, and to avoid saturating the iron core, this is precisely so in push-pull amps. This does not apply in the case of single ended outputs, which have air-gapped transformers to avoid saturating the core while balancing is not applicable. (Except in the case of multiple output devices in parallel, which we have also avoided to maintain absolute purity). The major disadvantage to any adjustments is the aging of circuit elements over time, necessitating re-adjusting for optimum performance. Our choice was to opt for self-biasing which negates this factor while maintaining other advantages - not the least of which is softer clipping. It also allows the user to change any tube at any time without consequence. So the tweaks can still get their kicks without degrading or altering the circuit design elements! It allows us to give a longer warranty and still be able to sleep at night.
Wiring: quality inside is also important
The issue of wires! Why all the fuss about interconnects - when the worst possible wiring is found inside most amplifiers! Most amps do not even use wires - they use PCB's (printed circuit boards), which contain thin copper foil that has been etched into a wiring pattern. The use of real point-to-point wiring is obviously a large advantage over PCB foil. We start by using quality Teflon coated silver-plated OFHC copper in all critical signal paths and power lines. We employ VCB's (vector circuit boards) throughout our amplifier. This allows us to outperform all the sonic advantages of PCB's while avoiding all their disadvantages. VCB's allow the same density of component placement while simultaneously decreasing the length of the signal path (through the use of point to point wiring). The VCB is built using swaged terminal post. Next goes the point to point wiring, after which the component elements are soldered to the terminals. This allows the replacement of any circuit element quickly and without affecting the wiring. (Unlike PCB foil that has a tendency to self-destruct with heat from a soldering iron!)
PCB foil is inherently inferior over using quality wire. Interior wiring is even more important to the overall sonics than external interconnects. You will not find any commercial solid state amplifier that does not use PCB foil, and for good reason! The number of elements presently used in most SS amplifiers outnumber those in valve amps by a factor approximating 10 to 1. To hand wire this number of elements would be prohibitively costly!
Classic Status: Built In
Reliability and longevity were once design goals when valves were king back in the early 60's. The best of amps back then were using similar technology to what we employ in our amplifier for superior mechanical construction. Our use of VCB's with swaged terminal posts and point-to-point wiring, along with polypropylene caps and the use of inductors in the power supply, have all contributed to meet our design goals. We build an amp that will be easily repairable to meet original specs and with a longevity to ensure attaining "classic status."
Today, most products have built-in obsolescence. When you buy a Wyetech Labs product, you can be assured that you are not only in possession of a work of art, but something that will keep on working precisely for decades to come.
Matching of Output Devices
In all the high power SS AMPS you will find multiple parallel output devices which range from two to forty-eight (or more) per channel. You will often hear manufacturers stating that they have employed matching output devices. There is no such thing as perfectly matched devices - even when they share the same silicon chip substrate. They must choose a tolerance range in order to match up component devices, and this range is almost always greater than 10% (while some consider close matching at 30% tolerance). What you will not hear from these manufacturers is how close they match these devices. THE REAL FACT IS that any pairing of devices leads to a degradation in one form or another over what can be obtained by using a single device!
Our goal was to design the best sounding amplifier - and make a statement of the highest art that our combined knowledge and experience could produce. This forced us to revert to the purity of SINGLE ENDED topology using only a SINGLE OUTPUT ELEMENT per channel! No one can go against the laws of physics.
Power Amps: Tubes (Hollow State) vs. Solid State
The least mentioned of all areas where tubes excel is in the area of heat dissipation. A valve will radiate all its heat without any help (the 211A dissipates over 100 watts per tube if you include the filament & plate). I do not even want to contemplate the contortions needed to get rid of that kind of heat from a single solid state device! If these 100 watts had to be dissipated via heat sinks the total weight of the heat sinks might well exceed that of the 211A output stage transformer.
Valves (triodes) are also known to be exceptionally linear in properly designed circuits and do not require feedback to attain this linearity. The most profound reason of all why some people choose Valves over Solid State cannot readily be explained. That is that the best Triode designs breathe more life into the music than what seems possible with silicon. They are also known to be mood-enhancing (they glow in the dark!).
Push-Pull vs. Single Ended
There are many outstanding amplifiers that can be designed in either single ended or push-pull configuration. However, if the designer wants to reach as far towards perfection as he can possibly attain, then the laws of physics shall apply and he would have no choice but to use single ended mode.
