Pre-amp voltage. What is the norm?

Discussion in 'Archived Threads 2001-2004' started by Shawn Shultzaberger, Jan 4, 2002.

  1. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    All the talk about pre/pro has got me wondering. In the car audio world a head unit (pre-amp) that is putting out 4v-8v is quite good. Those with 1v or less aren't considered worthy.

    In the home audio world is the higher the pre-amp output voltage the better? I remember reading about someone on the internet who was running 32v to his amps. I couldn't believe how high that was. It seems excessively high. And I know he was doing it with a unit that ups the voltage coming out of the pre-amp. I think they call it a line driver or something?

    I checked to see what my Outlaw 1050 put out but it doesn't say.

    I would just like to learn more about this.
     
  2. Peter Johnson

    Peter Johnson Stunt Coordinator

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    The standard for a CD player is 2V. A power amp almost never requires more than 300-500mV to reach rated output. There is no need for gain in a preamp for a line level source (ie, not a turntable), hence some preamps are passive...basically only being a variable resistor.

    Higher is not better.
     
  3. Shawn Shultzaberger

    Shawn Shultzaberger Supporting Actor

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    Very cool. I did not know this. Thanks for the info!
     
  4. Wayne A. Pflughaupt

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    Shawn,

    I don’t know what the output voltage of a typical home theater/stereo pre amp is, but I expect that Peter is right, it doesn’t take a lot of voltage to drive a home amp.

    I do know this: In the ’80s and through the first half of the ’90s, most car stereo head units put out substantially less than 2v. The high-output level car head units are a recent phenomena. They came about as a means to reduce or eliminate the inherent noise problem in many sophisticated car systems.

    Balanced signals would have done the trick, but to be “done right” it would have required a new, universal protocol for signal connections. It never happened. You had some manufacturers using double RCA cables for each channel, and some using bulky pro-standard XLR connectors, still others using multi-pinned XLRs or DIN cables, etc. Some manufacturers had their own proprietary multi-pinned connectors, and others offered “conversion kits” for unbalanced equipment, utilizing balancing transformers at each end of the signal (after the head unit and again before the amplifier) – more stuff in the signal chain, not to mention to find a place for. Bottom line, nothing was compatible and balanced car audio gear never took off. To top it off, I’m not even sure if there ever was a head unit with balanced outputs.

    The idea with high-output head units was to get the signal level so high it would be way above any noise picked up by the unbalanced signal topology. This way the old, standard RCA connector could be used, thus conquering both noise and compatibility issues at the same time.

    So it should make sense, Shawn, that high-output home pre amps are unnecessary and therefore no indication of component quality.

    Regards,

    Wayne A. Pflughaupt
     

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