Radford MA50 Renaissance Class-A Power Amp Reviewed

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#75 lighter but I owned a Radford STA25 Mk III. It was 1978 and I was desperate to transcend the limitations of an ailing Rogers Cadet. Not that the Goodmans Eleganzas were all that hungry; I just knew that I had to run something with greater dynamics, better bass control and a sweeter midband. The Radford was the amplifier with all the street cred and a friend was willing to part with his. Little did I know that over a decade later I'd be reviewing its great-great-grandson. But had you told me this, I wouldn't have been surprised.

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I still own that STA25, which served as the heart of my system for five years. What I learned from it has only been made apparent during the past few years, since Arthur Radford allowed
Woodside Electronics to undertake the upgrading and manufacture of his classic. The STA25 Mk IV was a natural starting point, a modernised version of its ancestor. So, too, were the mono versions, dubbed the MA75s. These in turn led to the replacements for the STA25 Mk IV, the new STA35. And all of these begat the amplifier under review, the Class-A 50W monoblock MA50 Renaissance. And they confirmed the lessons imparted by the old
Mk III: that the basic circuit was so 'good' and so 'right' that it could evolve along with the rest of the electronics industry -- right into the Digital Age.

Back when Arthur was at the helm, items like trick cables and tweak resistors weren't even part of science fiction lore. Gold-plated sockets, ultra-low-impedance speakers, sophisticated
solid-state components for mere pence -- John Widgery, the 'heir' to the legacy, has addressed or exploited all of these and more in the time he's been entrusted with the Radford's development. He's now graced the amplifier with Class A operation and greater security with nasty loads by reworking the power supply to include solid-state regulation feeding the phase splitters. Other changes include a move to cathode bias, creating both the Class A operation and removing the need for manual bias controls, as well as a return to EL34 valves. Martin Colloms deals with these changes in full elsewhere in this review; I cite them only to reinforce the relationship to the venerable circuit of the grey-painted predecessors.

The empirical differences connect the MA50s to its current siblings while one key change actually links this to a long-departed ancestor. If my memory serves me well, this is the first amplifier in the STA series since the sought-after STA15 to do away with manual bias facility. It may be a minor point, but I know from discussions with dozens of valve amplifier manufacturers that this is the sole remaining cause of techno-fear in would-be tube converts. As non-technical as I am -- my skills are limited to soldering good enough for kit-building duties -- manual biasing never worried me, especially as most modern valve amplifiers provide meters (eg Raymond Lumley) or tell-tale LEDs (Beard, Radford) which make rebiasing no more of a challenge than setting record levels on a cassette deck. Still, if someone leery of tubes can be assured that an amplifier is virtually maintenance-free, then it's one less obstacle for the nervous one to overcome.

That aside, the ergonomics and operation of the MA50 differ hardly at all from most solid-state products. Radfords run warm even in low-powered, Class AB or B form; the MA50s give off
enough heat from each bank of four EL34s to make the mesh cage uncomfortable to the touch, hotter than the 150W Raymond Lumleys and almost as scalding as the 12-valved Beard P1000. These need breathing space, so allow room for two 17x16in radiators (including switches and terminals) if you're considering the MA50s.

As with other current Radfords, the MA50 is finished in black with gold trim, the cage covering all of the valves in the interests of safety. (If you want romance in the form of exposed valves, consider the presence of pets, children or maladroits before removing the protective cage.) The front sports only an on/off switch and a green 'on' indicator, while the back offers three-pin IEC mains input, fuse holder, a gold-plated phono socket and five-way binding posts for speaker connections. Switch-on is accompanied by a 'sproin-n-ng' sound, but the amp
settles down immediately. A half-hour is ample for pre-listening warm-up.

One curious aspect of the MA50s which had me worried when I tried them with the 3 ohm Apogee Divas was a smell of melting plastic or paint. Had I cooked the Radfords? Was a light show soon to follow? Naaah...it was the actual burn-in procedure, described in the literature as 'quite normal'. It disappeared after a couple of days, but did bring back horrible memories of faulty anachrophilia.

Although the Radfords will handle devilish impedances when the transformer is rewired to suit such loads, I opted for something a bit more in line with the capabilities of a 50W valve amplifier. The Radfords were auditioned with Celestion SL700s, the rest of the system including the Marantz CD-12 CD player, Oracle Delphi turntable, SME Series V arm, Audio-Technica ART-1 moving-coil cartridge, Audio Research SP-9 and Air Tight ATC-1 preamplifiers. Cables included Lieder speaker wire and Mandrake, Lieder and masTER LINK interconnects.

This was no blast from the past, as I learned through a side-by-side comparison with an STA25 Mk IV. Readers with experience of Radford products will recognise the mid-band, with
its rich, rounded sound and ample detail, but the extremities may cause some shock. Partly this is due to the extra headroom and greater dynamic capability provided by the extra power. You'd expect the bass to have greater impact, just as you'd expect a gain in maximum level and whatever else an extra 3dB can provide. But you cannot prepare for what the Class A operation and those extra decibels do for the edges of the frequency spectrum.

I've never had any complaints about the way Radford amplifiers handled the bottom octaves. I've tended to use Radford amplifiers with small monitors and I'm not all that bothered about life below 70Hz. But for those of you who don't believe that there's any bass to match the bass which damages bladders and induces nausea, YO! The Radford works with 'eavy metal!!!

Continue on to Page 2 for more about the MA50.

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