2139f508   
   From: IainNG@kolumbus.fi   
      
   "Patrick Turner"  wrote in message   
   news:a41f22e9-1495-434f-927a-c558e305c589@l14g2000pro.googlegroups.com...   
   ?   
   >   
   > > Was Arthur Radford a " penny pincher " ???   
   >   
   >> Or perhaps Arthur Radford reasoned that   
   >> for a commercial amp, overkill just added to the cost   
      
   >What a frightful attitude!   
      
   Who knows?   
      
   > Driving at 1kHz at 100W, my STA 100B has THD 0.09%   
   > Not too shabby, I am sure you will agree:-)   
      
   >This is very hard to believe, considering most of the power is in   
   >class B and that typical THD with no GNFB is 6%+ for UL amps like this   
   >one. With 20dB GNFB you'd reduced THD to maybe 0.6%. I might believe   
   >0.09% THD at 10 watts, but not at 100W.   
      
   All Radford amplifiers, the STA 15, STA 25 and STA 100   
   had a published distortion fig of 0.1% at rated power output.   
      
   > The STA100 has 20dB of NFB and is unconditionally stable.   
   > The manual also states that it can run continuously and at full   
   > power into shorted or open loads.   
      
   >Very silly talk indeed. at full power? There is no power produced with   
   >a short circuit load or an open circuit.   
      
   Probably means when driven with a signal that would produce   
   full power when working into a load.  I have the documentation   
   filed away somewhwere. I will make a pdf.   
      
   > OP was given as 21 years continuous use.   
      
   >Is that all? I've seen many hot running PTs in old junk run for 70   
   >years OK.   
      
   Note: "continuous"   
      
      
   >> Both he, and his associate Dr A R Bailey, had close   
   >> connections with the studio at which I worked in the UK.   
   >> We used Radford STA25 amplifiers and Tannoy Lancasters   
   >> as the standard monitoring set up in probably thirty   
   >> rooms. The studio control rooms had STA 100s.   
      
   >Maybe most power levels were quite low in the Tannoys. Tannoys have   
   >sensitivity of 95dB/W/M, no?   
   >Maybe average levels were only 0.5W per channel.   
   >Hence good sound.   
      
   In those days, before Tannoy had a professional   
   division, many UK studios also used Lockwood speakers,   
   with Tannoy Gold 15" monitors.  I doubt that Gary Glitter   
   was mixed at 0.5W per channel :-)   
      
   The BBC had a monitor speaker built by Kef, (impedance   
   25 Ohms) that had a special 25 Ohm Radford amp built in   
   on a shelf at the bottom.   
      
   Besides being a designer of test equipment and audio   
   amplifiers, Arthur Radford, together with Dr Arthur Bailey   
   also did pioneering work on the acoustic transmission line   
   loudspeaker, and published an article in Wireless Word.   
      
   http://en.wikipedia.org/wiki/Acoustic_transmission_line   
      
      
      
      
   Iain   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)