From: phil_a@tpg.com.au   
      
   "Patrick Turner"   
      
   I said...   
   > Amp has wear and tear and looks 20 years old, but it sure ain't from 1965.   
      
   You said...**  Those 3 PCBs are a dead give away.   
      
   Well yes, but it is know as a Fender "Deluxe Reverb" reissue.   
   The full name on schema is "Deluxe Reverb Amplifier". No need to nit pick   
   Phil.   
      
   ** Fender models go by their face plate names.   
      
   There IS a "Deluxe Reverb" and also there  IS  a " Deluxe Reverb-Amp".   
      
   Hundreds of models exist with only small name variations between them -  eg   
   there are distinct models called " Twin Reverb", "Twin Reverb-Amp" and "The   
   Twin" which even owners mix up all the time.   
      
   No nit picking happening on my part.   
      
      
   > This tiny amount of NFB does hardly anything to flatten the   
   > signal at the speaker. The signal response at has a 6dB peak   
   > at 100Hz and +6dB at 2kHz, relative to 1kHz level. So the   
   > Vo merely outlines the speaker Z which is to be expected..   
      
   **  Err   -  no   
      
   Regular guitar ( and most other) speakers don't double impedance with a one   
   octave change in F above 1kHz. It takes 2 octaves, at least.   
      
      
   >The rise in Z above the minimum Z at about 300Hz is due to   
   > increasing XL in series with RL of speaker, and the eventual   
   > increases in ZL IS 6dB per octave.   
      
   ** Not so.   
      
   You need to do an impedance test and stop assuming.   
      
   The *soft* iron pole pieces of a speaker magnet have LARGE eddy current   
   losses and so the impedance rises much less rapidly with F than if   
   transformer lams were used.   
      
   Look at almost  ANY published speaker impedance curve :   
      
   http://www.electrosmash.com/marshall-mg10   
      
   Bottom of page:   
      
   7.5ohms at 250 Hz ( = minimum) then   
      
   9ohms at 1 kHz   
      
   18ohms at 5.5 kHz   
      
   36ohms at 16 kHz   
      
      
      
   ...  Phil   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)