Interview

Australian writer John Murt interviewed Ayre designer Charles Hansen in late 1996.

Charles, what background did you bring to Ayre Acoustics?

Previously, I had founded Avalon Acoustics and was designer of the Ascent and Eclipse loudspeakers. My degree is in physics, and prior to Avalon, most of my work experience had been in electronics.

Why another audio product in a market that already seems oversupplied?

Our commitment at Ayre is to manufacture products that are not only outstanding performers, but also offer superb value. There is something special that is available from music that is reproduced on a truly high-performance system _ one can experience the performers' intent more fully and deeply. The problem is that most of these systems cost enormous sums of money! At Ayre, we believe that by applying creative circuit design and carefully tuning these designs by ear, we can build components that capture the magic of music and yet are still affordable.

The Ayre V-3 supports a number of interesting circuit topologies, including the employment of choke-input power supply filtering. This traditional form of filtering was used decades ago in valve amplifiers -- why use it in the V-3 when there are other more cost effective methods of power supply filtering?

The benefits of a choke-input filter are two-fold. First, in conjunction with the filter capacitors, you now have a two-stage filter which is more effective at filtering out the RF noise that is present on all AC power lines. Secondly, the chokes store energy in their magnetic fields and slowly release it to the capacitors, so that there is a continuous charging current. Without the chokes, the capacitors are charged with short-duration, high-current pulses _ it's like having an internally generated source of RF noise. These types of high-frequency noise seem to have a large impact on the perceived sound quality.

Australian line voltages run around 240/250 VAC at 50 Hz. What lengths have Ayre Acoustics gone to ensure that there are no mechanical buzzes emanating from the power transformer?

This is a problem that many manufacturers have, and we spent a lot of time on this one! Toroidal transformers have a very low radiated field, but they can be prone to mechanical vibration. It turns out that this problem is exacerbated by the choke-input filters we use. We ended up using a special impregnation process to stabilize the core, as well as a shielding material with a very low magnetostriction coefficient. The net result is a transformer that is quieter than just about anything out there, even under adverse line conditions.

The V-3 uses a fully-balanced-bridge topology from input to output _ this would normally reflect in carefully matched components throughout. How has this been achieved?

Most components are readily available with a one-percent tolerance. The glaring exceptions are the active devices, which can vary quite a lot. Therefore, every transistor that comes in is individually tested and graded. We then match them up into pairs. This is particularly important since the V-3 uses no negative feedback. In fact, feedback was developed for just this reason. In the 1930's the telephone company needed a way to make the gain of their repeater amplifiers uniform, even though the tube characteristics varied from sample to sample. Feedback allows for the characteristics of the amplifier to be set by ratio of resistor values, which are much easier to control than the characteristics of the active devices.

Ayre Acoustics contracts circuit board assembly to outside suppliers. Although this is not a new concept, as a few other highly specialized audio manufacturers do the same, why are Ayre taking this approach?

There are two advantages to this approach. One is that it allows us to concentrate on what we do best, which is the design process. Building circuit boards is what they do best. That's all they do, and they are experts at it. Second is that we can quickly adjust production levels as sales increase. When we double our sales level, we don't have to install a second production line _ we can just order twice as many circuit boards.

Selection of components is a critical factor in producing the final sound of today's electronics. What supplies and components are used in the Ayre V-3?

I would compare this to the process of preparing a great food dish. You have the recipe, or the circuit, and you have the ingredients, or the parts. The best ingredients for one recipe may not be the best ingredients for another recipe. With that in mind, I will say that we use Cardas wire and Roederstein resistors. We have been very happy with the sound we get from these components _ very natural and very musical.

In the laboratory, the V-3 measures very similarly to many tube amplifiers. Can you explain that?

I think the common factor here is the relative level of negative feedback. With a low or no feedback design, you tend to get numbers like 30 or 40 kHz bandwidth, one or two percent distortion at full power, and a damping factor of 10 or 20. This is irrespective of whether the design is tube or solid-state.

Similarly, the frequency roll-off is around 25 kHz, with rise times in the order of 14 micro-seconds. Is the V-3 bandwidth limited, and if so, why?

The upper frequency limit of the V-3 is set by the output impedance of input stage in conjunction with the input capacitance of the output stage. Again, the use of feedback would extend the measured frequency response, but at what sonic cost? The other approach is to use a lower output impedance driver stage, and we did try that during the development of the design. We added a source-follower driver stage to the input circuit, and it measured better but it sounded worse. I think that, in this case at least, simpler is better.

The Ayre K-1 preamplifier is shortly to be announced to the Australian market. The K-1 will support similar design topologies to the V-3, please elaborate.

The K-1 has the same basic circuit layout as the V-3. Specifically, the input stage is a cascoded complementary-differential circuit, which directly drives the output stage, which is a complementary source follower. This basic circuit is so simple yet performs so well, that we use it everywhere, from the phono stage to the power amplifier. Naturally, we select the optimal devices for each application.

Will the Ayre K-1 offer a phono section? What is the company's viewpoint with regards to vinyl, and how will this be reflected in the preamplifier?

Yes, the K-1 will have an optional phono stage. I believe that digital has a long way to go to catch up to analog. Hopefully, the new DVD format will result in a higher resolution digital audio standard, because digital is so darned convenient that it's not going to go away. But analog is not going to go away either, thank goodness! We've really done an all-out effort with the phono stage, which hasn't been done by anybody else for quite some time. I'm quite pleased with the result _ it has very high gain and extremely low noise, so it is suitable for even the lowest output moving coils. Yet the gain is user-adjustable, so that it can be used with moving magnets as well. The resolution is almost shocking _ I think that many people will be surprised at the amount of information that is available in a good analog medium such as vinyl.

The K-1 offers a remote volume control. Is this a mechanical or an electronic type?

We spent a lot of time looking at this aspect of the design. For a balanced circuit, you must precisely match the two phases if you want to retain the advantages of balancing. This rules out ordinary potentiometers, and leads one to stepped attenuators. There are several methods for implementing stepped attenuators _ mechanical rotary switches, relays, and electronic switching. We listened to all of them, and by far the most transparent was a good mechanical rotary switch. We took the implementation of this to the limit, using a solid-silver-contact switch made by Shallco. It has 46 positions, so that the steps are very fine, while the remote function is handled by a stepping motor. The result is what is probably the best volume control ever produced. The remote operation is just an added bonus for we lazy types!

Future products coming down the road?

We will do a little brother to the K-1 preamplifier at about two-thirds the price. Also, a big brother to the V-3 power amp _ these will be big monoblocks, as we've had a lot of requests for that. I have an interesting idea for a digital-to-analog converter. I think we will be able to set a new standard for digital playback, yet have it be priced realistically.

Ayre Acoustics have a definite viewpoint on marketing their product. Please elaborate.

We're not interested in making another "me too" product. There are plenty of good products around. If we can't make something that is significantly better than what is already out there, what's the point? But it also has to be affordable. If there are only six people world-wide that can buy it, what's the point of that?