Thanks, all. I suspect that Walt may have the answer, that 0dB is the point at which further power brings an increase in noise or distortion.
Rick http://photo.net/photos/RickW ----- Original Message ----- From: Mark Roberts <[email protected]> To: Pentax-Discuss Mail List <[email protected]> Cc: Sent: Thursday, February 2, 2012 6:57 PM Subject: Re: OT question for electronics geeks Rick Womer wrote: >I have this nifty new receiver, which sounds great--a huge improvement over my >38-year-old Pioneer. > >What puzzles me is the volume control: Minimum volume is -90dB (mute), and >maximum is +15dB. > >Huh? > >What is zero dB? Is it an arbitrary point? Is it linked to some undisclosed >property of the unit? > >I can tell you that 0dB is too loud to be in the room with using the tuner, >barely tolerable with a CD, and just a bit loud with an LP. > >Otherwise, the scale makes no sense to me. For all practical purposes, in this instance 0dB is an arbitrary number. They could be referencing the signal level between the pre-amp and power amp stages, at the output of the volume control. But even then we don't know what reference they're using for 0dB. The old standard was 0dBm = 0.7 Volts RMS into 600 Ohms. This was back in the days of vacuum tubes when everything was transformer coupled and power transfer was important to know. A more modern standard is dBv which is just 1 Volt RMS into the typical high impedance solid state input stage of an amplifier (loading is so slight at the impedances you're likely to encounter that you don't need to specify impedance precisely). But even that doesn't tell you anything useful unless you know the voltage gain of your power amp. Come to think of it, it doesn't tell you anything useful even if you *do* know ;-) So, for all practical purposes, in this instance 0dB is an arbitrary number. -- Mark Roberts - Photography & Multimedia www.robertstech.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
