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Understanding the Clayton Audio Design: An Interview with Clayton Audio’s Wilson Shen

A Brief Interview with Wilson Shen of Clayton Audio
by Dave and Carol Clark of Positive Feedback Online


A full review of the new M200s appears in issue 33 and 34


So what is different from the older models as compared to the newer models?

Comparing the S40 to M200 is like going from M100 to M300. We have kept the core of the circuit design of M100 and S40 to make M200 and M300—but as true balanced power amps. We did improve the power supplies and we have new custom made transformers for the M200 and M300.

We miss the low-bias setting, why the omission?

We tried to keep it simple and do not have a bias hi/low switch in M200. But we do in M300 because of its higher output.

So what is the story behind (or inside) the new models?

M100 and S40 are great in overall sound performance; the balanced design of M200 and M300 increased the dynamics and reduced the signal noise.

We keep it in truly balanced differential mode throughout to eliminate the RCA single ended option which needs an adapter circuit. Those who don't have a balanced output in their preamp may choose M100, or S2000, S100, and S40 stereo models. The M200 has a conservative power output of 200-watts @ 8 ohms and 400-watts @ 4 ohms.

The major circuit of M100/S40 is a three stage design. The first stage is differential amplifier, second stage is voltage gain amplifier and last stage is current gain amplifier. Three stage designs are very common for use in power amplifier designs. We keep the circuit simple to achieve natural sound, and through extremely careful component selection, make the circuit ultra stable and reliable to not be effected by high temperature and age.

Tell us about your past.

I got my EE degree in 1978. I joined RCA Taiwan for two years. I designed and maintained an ATE machine; Auto testing equipment for production color TV. During those days color TV was one of the hottest major electronic commercial products.

I then joined IBM in 1981 as mainframe hardware engineer. I was trained in Japan at IBM Fujisawa Lab and in Australia IBM. I worked on special projects for Singapore IBM and AT&T. I also worked closely with Motorola power designs where, as a special project manager in 1990, I was involved in projects with TI semiconductor for their initial set up for the production of memory chips. I designed the Taiwan Air Traffic control systems; TAA, which is like our FAA here in US. I developed Banking Network Systems and Hospital Patient care systems.

I moved to the US at the end of 1993. One of reasons was I was getting tired of that kind of high tech, crazy busy life. But I will agree the pay was good.

How did Clayton Audio come about?

Designing amplifiers, a good amplifier, was my hobby. I had earlier developed antenna amplifiers and worked closely with both IBM and Motorola with amplifier design overseas as well. During the first year in the US, IBM in St. Louis contacted me asked me to join them to continue this path, but I turned them down. In 1995 a friend in Taiwan wanted me to be in charge of his new established airline company which had six new Boeing 737s. But I choose to stay here, because I wanted to do something I really wanted to enjoy and raise my three kids here.

I also did not need to let someone tell me what I already knew that time; High-end, handmade audio does not make much money! Fortunately I also worked as a consultant for some other electronics manufacturers (who will remain unnamed). 

Why only class A?

I believe only a class A designed amplifier can sound good, and a lot people in this field knew that too, But how to overcome the heat been generate by class A amp is not an easy task. One needs electronic professional skills and years of experience with amplifier design of all types to be successful. Going from my hobby to becoming a commercial success is a big step. In the spring of 1994 I setup my labs here in St. Louis, Missouri. I actually spent about 15 months studying and dealing with various major suppliers, including semiconductor manufacturers for all materials I required. My monaural amplifier, the M70, came out in May 1996.

Why balanced?

All our amps are pure class A designs. The M70, M100, and S40 were all single-ended designs. The M70/M100 only has the XLR accommodation for those with balanced preamps. In the year 2000, we designed the S2000 and M2000 balanced amplifiers, both weighing so much we had to crate them carefully. Each one needs six or eight hands! Not easy shipping, and are all custom ordered.

Now we have M200 and M300: two popular true balanced versions of our custom S2000/M2000. Music lovers can now enjoy the dynamics and detail with these new balanced class A power amplifiers.

I believe that class A is the only way to use a balanced design to achieve a power rating of over 200-watts. To correctly design and make a pure class A 100-watt power amplifier in single ended mode is difficult and challenging, but not impossible. It is very difficult to get the power transistor operating in both high current and high voltage within the specification in my design. But when you want to enjoy the big dynamics and detail of performances from an over 200-watt per channel pure class A amplifier, you need a true balanced design. We use dual amplifiers to achieve our 200-watt balanced rating. Everything is in mirrored pairs. All parts and circuits are symmetrical for truly balanced operation.

What sets your vision of class A apart from that of others in the community? Parts, execution, what?

A great circuit design is essential to a good amplifier. Not only is this the heart of the core circuit design, but the power supply and control circuit design are equally important. Nothing is overlooked in the design (synergy) of my amplifiers.

Correct and the most careful parts selection is very important for an amp to sound right in all audio frequency spectrums, and for best stability and reliability of its design. Different types of parts in a circuit are required and their selection can make quite a difference. A resistor is a good example. Some areas need more precision in a resistor's ohm value, and some areas need stability with regards to temperature.

In my high-end audio designs, there is no way I could use best parts to fix a bad design and still call it a GREAT HIGH END MASTERPIECE.

The M200s run pretty hot.

A class A amp is very hot! We use our huge heat sink and output transistor array to keep the temperature setting at 55 degrees over the room temperature. The bias circuit is very stable and will not allow for shifts. In our design we would rather it break down to than shift. I still have and use the first pair of M70s, after 10 years the bias still right! Although hot, you will not burn your hands touching the heat sinks.

For the design and production of an amplifier, you need special testing equipment to measure the units to make sure the performance is within the specifications. But amplifiers are for human ears to listen to musical performances. I like what I hear, as do our Clayton Audio friends!



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