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Inverse RIAA Network schematics


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6/4/1998 2:30 AM
nic
 Inverse RIAA Network schematics
Say can anyone lead me to schematics for phon graph preamps???  
 
Thanks a lot  
nic
  
6/4/1998 12:00 PM
Clyde
Various editons of the RCA receiving  
tube manuals have different schematics  
for phono preamps. See if you can  
lay your hands on one.
  
6/4/1998 12:46 PM
nic
whwere would I look for one of them???
  
6/5/1998 10:58 AM
J Epstein
I could fax you the RCA one from the RC-24, also there is a nice one at :  
http://www.geocities.com/TimesSquare/1965/phono.html  
 
which I have built and I think it sounds good.  
 
-j
  
6/5/1998 11:10 AM
J Epstein
By the way, as I understand it, an "Inverse RIAA Network" is an EQ network used to simulate the EQ applied in disc cutting. In other words, a phono preamp contains an "RIAA EQ Network," and you would use an "Inverse RIAA Network" to test the frequency response and accuracy of a phono preamp itself. You do that by running a test signal through the _inverse_ RIAA, then the preamp with its "forward" RIAA, and measure what comes out. The more it resembles the frequency response in, the more accurately your preamp's RIAA EQ is measured to be.  
 
The reason this is needed is because phono cartridges/disc cutters are not a linear reproduction chain, and frequency pre-emphasis and de-emphasis is needed for good results. Same thing as a tape deck, by the way, but different EQ is used.  
 
There is good material on phono preamp circuitry in "Valve Amps" by Morgan Jones.  
 
-j
  
6/4/1998 1:01 PM
Mike D.
try MachMat's Analogica. Tons of hi-fi schems http://www.avvt.com/machmat/tubes/tubes.htm
  

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