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February 2013 Issue
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WITH BRIO

Firstly may I introduce myself. I am Terry Bateman, the designer of the Rega Brio amplifier reviewed in the November 2012 issue of Hi-Fi World.

   Yes, the story is true as regards the power amplifier circuit. It was about 22 years ago I came by a collection of Wireless World magazines covering the 1960s and first half of the 1970s which ‘road mapped’ evolution of the transistor amplifier circuit which started in 1961 with the Toby & Dinsdale circuit (based on the work of H.C. Lin) and saw the work and designs of Bailey, Walker, Hood, Leak, Nelson-Jones, Sugden & Baxandall et al, which evolved into the classic circuits which are in use today.

   As well as having a keen interest in valve amplifiers such as the Stereo 20, Quad 22 & Radford STAs etc. I also like researching the transistor amplifier circuits of the 1960s and the 1970s, which led me to the idea that I used in the Brio-r amplifier. The work done by Hood in the late 60s and early 70s was the inspiration for the circuit. I have to point out when I was researching and developing the circuit, which was to be used in the Brio-r, I used valve amplifiers such as the Stereo 20 and Mullard 5-10 etc to compare the prototype against.

   As stated in the review, the earlier incarnations of the Brio were already very good but I felt the power stage could be further improved with the research I’d been doing on transistor amplifiers and so the Brio amplifier you reviewed came about.

   Personally, I’ve got my hands on good examples of the Quad 33/303, later (silicon) Leak ST30+/70, Rogers Ravensbourne, Sugden A21/C51/P51 and Revox A78 amplifiers to chart and research the evolution of the second-generation (silicon-based) commercial transistor hi-fi amplifiers in the UK in the latter part of the 60s and first half of the 70s. I’m also looking at the kits like the PW Texan and Hood Hi-Fi News 75 Watt amplifiers. As part of this research I’d like to take the prototype of the Brio-r power amplifier and replicate the subjective listening tests Hood did in 1969-71 between this and say something like the Mullard 5-10 using a passive pre-amplifier.

   I also felt the review of the DAC you did a couple of months ago was a cracking piece. Speaking as its designer, the review really got a handle on what the Rega DAC was all about.

   Finally, I have a few Troughline tuners in the collection so I enjoyed the recent article on the Troughline. I agree with the safety letter in the November issue though.

Regards,

Terry Bateman

 

The Rega Brio amplifier was designed very much with an ear on good

designs from the past, says its designer Terry Bateman.

 

Thanks for that Terry. I’m suitably impressed you have heard such a wide range of amplifiers and love the design history; it’s so important to have a good over-view. So many design engineers I meet (which I like to do) have heard few products outside their own personal cocoon, whose boundaries often do not extend far. It’s what Alex Garner of Tannoy named the “not invented here syndrome”. Meaning it isn’t worth knowing about if not invented ‘here’. Such parochialism doesn’t help one little bit. 

   The only confusing factor about old designs is old components. Even Quad admitted to me a little sheepishly in the end that had they not had a blind belief that components are passive and don’t affect sound quality then some earlier products could have sounded much better. 

   Worse, not only did old designs have poor components, those components age, especially electrolytic capacitors. So what we hear today from an old design may misrepresent what it can do. People rebuild Quad 33/303s with new bits and report amazing results, for example. It’s an interesting conundrum: to rebuild or not to rebuild? 

   The Rega DAC review – ah yes, the scintillating ear of Rafael Todes and his candid commentary does tend to impress us all. I am glad you appreciate his perceptive insights. Rafael can hear jitter before I measure it! NK

 

Quad 303 power amplifier was beautifully made and very reliable, but

may have sounded better with quality components.

 

ALL THE ANGLES

Perhaps I should have been more careful in my argument in citing small VTA changes as more important than small VTF changes (Hi-Fi World Letters, August 2012).

I was trying to argue that minor VTF changes do not matter so long as the pickup is not mistracking and that it was a waste of time to set VTA to hundredths of a gram - but that it was the geometrical relationships of stylus to groove (or internal cartridge geometries) that are more important than fine adjustments.

I cited VTA because many of us are familiar with it and it was being changed by altering VTF.  I cited using VTF as a simple way to fine tune geometrical relationships by ear if your tonearm does not have micro adjustments built in, as most do not. Trying to fine adjust the height of a tone arm without fine height control is a thankless task.

Many audio advances are done without first knowing the scientific logic behind them. Indeed there are many things we do in set-up and design that are ‘good’ but we don’t really know why. But repeatable results are surely meaningful. So asking me to produce a detailed explanation in a simple letter to a magazine is hardly necessary and probably a waste of space. I could just as well ask for Mr. Beal to provide a clear explanation of why my procedure is not true.

By the way I only referenced the old issue of Stereophile to make the point that this was not a new idea not as support for my point. I wrote the Stereophile article and citing oneself as a reference is certainly circular and irrelevant.

In all but a few corners (such as Rega) fine VTA adjustment has been accepted and heard by many as significant and should be readjusted when VTF is changed. Indeed if one wants to take it to extremes (as some do) it needs to be altered for different manufacturers and different record thicknesses which I honestly rarely do.

I strongly believe that VTA precision is a minor factor in tuning our record systems and fine tuning of geometry is much more significant. I’m always open to being shown differently – it won’t be either the first or last time – but so far I haven’t seen or heard anything to alter my mind.

On another note, a thank-you and a bit of nostalgia. I was looking through some old Hi-Fi World DIY supplements (I save almost everything audio) and in issue 31 from October 1997 I found an article on using sticky tape on speaker fronts to smooth diffraction caused by minor gaps. My main speakers are SEAS Froy 3 kits (with custom 18” woofers below 85 Hz) and while the fronts were professionally constructed that only means they were paid for, not that they were well done. My gaps were larger than would be optimum, to say the least. Well I tried the sticky tape and it gets my recommendation. It definitely smoothed up the high end. Thank you. I miss those supplements; they were the impetus to my first purchase of your magazine.

Allen Edelstein

New Jersey,

USA

 

The cutter head has a specific cutting angle, set to 15 degrees in the USA

and 22 degrees in Europe. The Vertical Tracking Angle of a cartridge must

be similar to avoid distortion. 

 

When people get pernickity about Vertical Tracking Angle, I always recall reading a white paper from Benjamin Bauer, of CBS Labs, about the phenomenon of lacquer springback and how it alters the intended cutting angle, confusing the issue completely. Quite what the final modulation slant is on an LP then becomes an unknown, at least to any useful degree of accuracy. This is one confusing factor.

   Another one is that most cartridges have a VTA of around 30 degrees, way above the correct value of 22 degrees. A change of 8 degrees at the headshell to correct this means moving the arm pillar down 32mm, an impossibly large amount. 

   And finally (!) I have yet to become convinced that correct VTA in a cartridge is strongly linked to sound quality. Other factors have greater influence it seems to me, having measured VTA and then listened to the product, for hundreds of models over more than 20 years or more (don't like to think about this!). Even Ortofons nowadays don't come with measurably correct VTA, as they once did (e.g. VMS20E), but it doesn't seem to affect their sound quality. And I know Ortofon listen carefully to all they produce. As you say, other issues are at play. Best to relax and enjoy the music, methinks! 

NK



 

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