"Phono High" input for ceramic phono cartridges on Fisher tube receivers

monkboughtlunch

Super Member
These questions pertain to using ceramic carts via the "Phono High" input on the 400, 500C and 800C. Yes, I realize that a ceramic cart could be plugged into an Aux line level input (but that would not be optimum from an EQ perspective).

Only the 400 manual lists an input sensitivity for "Phono High." It's not listed in the 500C or 800C manual. But like the 400, the 500C and 800C also have "Phono High" inputs.
  • "Phono High" 14mV input sensitivity (Fisher 400 owners manual)
The 400 owners manual states:
  • Phono High is designed "for all ceramic cartridges with adaptors for magnetic inputs."
Questions:
  • 1. What does "adaptors for magnetic inputs" mean? Is that simply an RCA connector? Or does it mean something else?
  • 2. If a ceramic cartridge with an output of 0.5V (500mV) is presented to the Phono High input, will that overload the Phono High input? The sensitivity is listed at 14mV (0.14V) -- but the headroom before distortion for signals above that input sensitivity threshold are not listed.
  • 3. Additionally, how loud would a 500mV signal fed to Phono High be in relation to the relative loudness of FM tuner?
Below: Fisher Owner's Manual

sens.jpg

ceram.jpg
 
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I too have a vested interest in this response. I want to try different carts in my Garrard TT which means replacing ceramic with moving magnet. Their output voltages have a direct effect on how well the preamp/amp electronics handle the input voltages. In your case it's PHONO LOW versus PHONO HIGH which is moving magnet versus ceramic respectively. Like you said, you want to match as closely as possible the voltages of the cart and preamp.

To answer your #2, I believe PHONO HIGH wants a ceramic cart. PHONO LOW wants a moving magnet cart, HIGH and LOW refers to the voltage the preamp/amp sees.

Thorne
 
With a few exceptions, ceramic cartridges have very high output levels (on the order of a volt) and are, in essence, self-equalizing (because they are amplitude and not velocity sensitive). The output of most ceramic cartridges would have to be severely attenuated and de-equalized (to reflect the RIAA curve as reproduced by a MM or MI cartridge) to use even that "PHONO HIGH" input properly.

http://rec.antiques.radio-phono.narkive.com/N9DaqwXz/ceramic-phono-cartridges-need-equalization
 
One of the things I like about my '59 Fisher X-100 is its versatility. Besides having phono level trim pots for each channel on the front and all sorts of channel switching capability (L, R, mono, stereo), it also has inputs for two turntables, one at 50k and the other at 100k loading, plus ceramic.
 
The X-100 has an input sensitivity of 180mV for Ceramic (vs. 14mV for the 400, 500C and 800C). Seems like it was designed to accept a ceramic cart without an "adaptor for magnetic inputs"--unlike the 400, 500C and 800C.
 
Monk & Thorne. I go by this. If the output of the MM cart I'm using is 4.5mv or Less I use LOW INPUT. If it's 5mv or > I use High INPUT. If there is a ?????? as to the output of the cart, or if the ouput is right at the dividing line, Listen to both ports and use the one that sounds better with less distortion.
 
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