COLIN WONFOR: Q&A regarding their new HB100 mono power amps

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HP: Gentlemen, you’ve been designing amps and preamps for over 30 years. Is it still a challenge and ..... are you having fun?

A: Colin has been designing electronic professionally for over 40yrs. He has done this for a living. His many designs include power control and power supplies Linear, Resonate, Switch Mode and even Thyristor power supplies. The out power of these range from a few milli-watts low noise to 5.5MW. Audio is for him just extensions to the designs, but with rewards of good sounding music and audio which he loves and as played with and designed for over 50yrs.

Q: Is it still a challenge ?

Oh yes and fun to learn new things and get the sound you need for close to perfection.

Q: So, a life time’s wok?

A: You mean 'work' rather than 'wok' - surely?

Q: Err, yes. Sorry about that.

A: Yes, a life time's work.

Q: What constitutes "success" in the HB100's design?

A: The Q20, HB50 and HB100 are based on the same topology; a push pull class “A” with a dynamic sliding bias. Nothing unusual there you may say but ..... the proof is in the listening. The Q20 has only one pair of matched complementary transistors in the output rated at 32A and 120V 200W each channel. The HB50 has four pairs and the HB100 has eight and in bridge mode to reduce any hum loop and keep the power supply HT rail low. The entire set of output transistors are matched at 40C as well as the drivers. The driver transistors are designed to work up to 100+MHz.

Q: Which means ….. what?

A: This helps to make their driving abilities easy into the output transistors.

Q: It seems to us here that most designers stick with one concept and run with it for their entire career. So, how did EWA come to use such a varied approach to their amp designs?

A: Yes ….. correct …. most designers use the same concept on all their designs. In contrast I do this only on a family of designs i.e. Sabre 1, Claymore, Claymore 2 and Claymore S but not the Sabre 2 (a baby amp).

Q: What about the Quatra?

A: Ah yes, the Quatra. This was a current dumping amp and the TOCA and Iridium were SECA designs. Here at EWA we’ve improved the latter with better parts and power supply designs.

Q: Is the HB100 being musical the result of it being simple?

A: Yes KISS designs I love. The circuit is simple but lots of time and thought have gone in to it to achieve the results I want.

Q: If you had to pick one out of many amplifier design aspects, such as stability, load tolerance, good phase response, no slew rate limiting and so forth, what was your #1 factor for the HB100?

A: All those and more for the HB100 but....

Q: But?

A: But ..... cost is also a limiting factor. If I could persuade buyers to spend £80k on a mono amp then I could go mad with a well OTT design.

Q: Really?

A: Really!

Q: In 2017, have we reached a point where amplifiers won't be getting much better or does amplifier design have a long way to go towards perfection?

A: New components and mixed design concepts will affect how all amps will be designed.

Q: Which means ….?

A: It means it is - and always has been - a learning process.

Q: Can amplifiers have a "personality" outside of a particular system or does a system determine an amplifier's sound and if so, what "personality" does the HB100 have?

A: It seem most people think my amps have a personality; my personality ‘cos I’m big, warm, powerful.

Q: And …?

A: And I’m 6'4" and 125Kg

Q: What is the personal favorite amp that EWA have designed and why?

A: I love the SECA 50. It is life-like, magic, warm but not dull. Dynamic; not pitch-scream, and easy to enjoy music.

Q: Foot tapping?

A: Always!

Q: Generally, how important is Class A bias?

A: Mmm… complex. (imagine Colin stroking his chin; looking far away into the distance). I would say very, in SECA. It’s a shame Class “T” and “D” sound so poor in comparison

Q: Is there anything else you can say about the Class A situation? One of the things you were talking about a while back was noise; high order harmonics and things like that.

A: Currently we are designing a SECA pre with a super-overload range. We made one in the 1980’s and Inca Tech had a ID1P but components are so much better now, so the fun begins. (Colin chuckles at this point)

Q: Is reliability a major design goal for EWA?

A: Yes I never want to see my products returning ‘cos of unreliability, and with luck like most of the Claymore models they will work for 40yrs plus - if not misused.

Q: What is the EWA philosophy on power supplies? Should they be tightly regulated and how was your decision applied to the HB100?

A: PSU should be designed for purpose, the amps should be a PSU with a dynamic output normally set to zero until the signal is applied, then it should be follow regardless of shape or frequency and referenced to zero.

Q: In terms of the chassis design having an influence on the HB100, is it simply the shielding factor, or is there more to it?

A: Yes and more. Yes shielding is very important, but internal layout - like the tracks – are much more important.

Q: You are very careful about the resistors you use. How can one low tolerance 47 Ohm resistor sound different from another one?

A: In a few words, temperature, tolerance, inductive value, noise, construction, material used and ….. where it is used.

Q: Okay, what about capacitors?

A: Read above; very very important.

Q: Generally, what's your take on digital amps?

A: All lies. Music mangled. Just lies and to me it sounds crap. Sorry guys.

Q: What's next on your plate for future projects; an HB preamp perhaps?

A: A hyper preamp is under construction. We have two prototypes.

Q: Where do EWA see the future of audio heading?

A: With luck back to real sounding music and not these digital lies we have.

Q: Where does EWA see itself 5 or 10 years from now? Do you think that both of you can radically influence the way future amplifiers are built? Do you see yourself becoming famous, perhaps like another Mr. Mark Levinson?

A: Hey I thought I was more infamous than Mark. Upset now. Seriously though, we want to pass the flag on to a new generation learning from the past but using the future technology to improve how things are done.

Q: That's about all the time we have. Is there anything else that you would like to share gentlemen?

A: Yep. Keep analogue alive and dump the digital lies he he. (We end here with the resonant sound of Colin’s characteristic deep, comforting and booming laugh)



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Thank you. Neil McCauley / Editor in chief


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