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Who designed the Radford ZD22 preamp?
Who designed the Radford ZD22 preamp?
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Old 12th December 2016, 07:01 PM   #1
DouglasSelf is offline DouglasSelf  United Kingdom
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Default Who designed the Radford ZD22 preamp?

Generally regarded as the most advanced preamp of its day. (1973 on)

But who designed it? Anyone know?
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Old 14th December 2016, 10:35 AM   #2
Konzentr8 is offline Konzentr8  United Kingdom
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Possibly John Widgery ? don't know for sure though he was involved in a lot of their early / classic designs.
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Old 14th December 2016, 12:28 PM   #3
irribeo is online now irribeo  Netherlands
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Befor Richard Hay left he was working alongside Arthur Radford designing successors for ageing valve amplifiers, or so some claim. He probably left just before SS Radfords were introduced ? John Widgery after Radford continued with valve designs didn't he? Woodside??
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Old 14th December 2016, 02:08 PM   #4
Konzentr8 is offline Konzentr8  United Kingdom
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Yes John Wigdery created Woodside when Radford retired but he was apprenticed at Radford when younger and is credited as being heavily involved in creating some of the early / classic designs at Radford , unfortunately i can't dig up any thing more specific.
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Old 14th December 2016, 02:16 PM   #5
Mooly is offline Mooly  United Kingdom
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Who designed the Radford ZD22 preamp?
Ah, the venerable Radford...

I haven't the answer but somewhere such as Radford Revival might be worth contacting. Someone somewhere may know something.

Contact Us | Radford Revival
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Old 15th December 2016, 05:29 PM   #6
DouglasSelf is offline DouglasSelf  United Kingdom
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Thanks for your replies everyone, I will try Radford Revival.
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Old 15th December 2016, 08:52 PM   #7
irribeo is online now irribeo  Netherlands
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Radford Revisited:

"Curiously, although Radford is well remembered, Bailey seems to have been overshadowed and largely forgotten. Yet the four HFN articles were credited to Bailey and Radford, with Bailey’s name given priority. If you read the articles the first few paragraphs make plain that Bailey’s contribution was vital in identifying the problems, and in devising the solution in the form of the pentode-triode phase splitter stage. This becomes even clearer when you read the WW article by Bailey.

A similar fate seems to have happened to another design for which Radford has remained well known. Many people recall that Radford patented a design for the ‘transmission line’ form of loudspeaker. Yet if you look at Wireless World, then again you find an article by Bailey[6] describing the loudspeaker, mentioning it is patented, etc. Bailey also developed the early Radford solid-state amplifier designs – with details appearing in Wireless World – but these failed to gain the reputations of the earlier valve designs."
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Old 18th December 2016, 03:34 PM   #8
DouglasSelf is offline DouglasSelf  United Kingdom
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I have (indirectly) consulted John Widgery and the answer is that the ZD22 and associated power amplifiers (ZD100) were designed by Jens Landvard, a Scandinavian free-lancer.

He is unknown to Google.
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Old 18th December 2016, 04:22 PM   #9
Mooly is offline Mooly  United Kingdom
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Who designed the Radford ZD22 preamp?
Wow, that is probably not the answer that any of us would have expected.

Thanks for updating the thread with that though.
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Old 16th June 2019, 04:33 PM   #10
goran7 is offline goran7  Sweden
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The name of the Hedley Radford designer is Jens Langvad from Denmark.

He was also the designer of the Hedley Radford LDO3 ultra low distortion generator.

This oscillator had distortion below -120 dB at 1 kHz.

K2 -124 dB and K3 -126 dB typically.

-110 dB at 20 Hz and -100 to -106 dB at 20 kHz sample dependent.

K4 and up < -135 dB down.

As seen on the HP3580A spectrum analyser connected to the distortion out of the DMS3.

The oscillator used the sample and hold technique to provide almost bounce free settling after changing frequency.

With a Vactrol, MCD521, as the active gain control element.

Sweeping the frequency dial up and down showed barely any visible change in amplitude.

I met Jens Langvad and Artur Radford at the AES convention in London spring 1975.

I bought a LDO 3 and DMS 3, Distortion Measuring Set, on the spot as nothing available then had such low inherent distortion.

Having used the HP334A for a couple of years with its typically 0.008 % (<-80 dB) inherent limit at 1 kHz and getting the Radford being another - 40 dB down was nice.

I still have the hand drawn schematics of the LDO 3 oscillator signed by Jens Langvad.

Göran Finnberg

Agent for Hedley Radford Instruments in Sweden from 1975 to 1980.
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