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I can't find a straight answer to this on the Internet.
When a preamp is set to -15db, is it really attenuating the signal? Or is 0db more like a "Reference" level, and doesn't mean the source signal is coming out at the same voltage?
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Interesting. Thanks all. My pre/pro goes from -50db to +15db (or was it +20?). It really doesn't make sense to me to have a stage to attenuate the signal before amplification - unless I start thinking about what it would take to build a system that had no attenuation from source to speaker. Definitely not practical
I suppose in theory you'd want to build out a system where, if you took the quietest source you listen to at the maximum level you want to listen at, the amp and preamp are maxed without distortion. All other source levels and volumes would be handles by volume attenuation?
Definitely seems impractical - so I guess a big amp section and large attenuation for volume control makes sense to be able to use the equipment in a wide range of configurations and sources.
In nearly any separates with a preamp and an amp.. THE CD player signal at 2 volts is far higher than most amps could possibly use.
IMO ALL preamps playing music from a standard CD player are attenuating the signal.
Well, maybe not if you like playing at 110dB...
Try connecting your CD player direct to your amp.. But remember you ARE likely to blow up you speakers or amp doing it.. from too much signal.
Wayyy back before CD.. ALL signal devices were standard at 0.5 volts..
THen CD came along and for some crazy stupid reason raised CD output signal to 2 volts..
NO preamp or amp makers ever actually adjusted for this.
(I have no idea why not) But it is true. ALL the companies I know of, preamps and amp combos all have way more amplification than they need. And all attenuate the signal from digital sources to amp.
SOME old source devices having the earlier 0.5 volt standard will not.
I think I'll pass on blowing up my gear, thanks!
Ravel's "Bolero" starts very quiet and builds slow and steady over several minutes until it reaches full volume.If you can play the song all the way through without it getting too loud then you might need a preamp with gain.
If it gets louder than you would ever normally listen to your system before the end and you have to push stop, then you don't need a preamp with gain.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/06/16
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I have a consumer grade Panasonic receiver that uses dB for the volume control. I think it is very cute, although it must seem totally baffling to the average person IMO.
While I don't pay much attention to it, I do think that 0 dB is it's MAXIMUM output and everything else is an attenuation (from MAXIMUM output with NOMINAL 2 volt p-p input).
As Einstein already stated, it's all RELATIVE!
(see, I don't even know what I'm talking about anymore!! Maybe, this link has more info.)
It would be interesting to verify just how that logarithmic scale functions, but with a consumer grade audio device, there's basically a just right volume, otherwise all you do is expose the nonlinearities inherent in the equipment.
rkeman brought up some good points. I would add these:
I think -15db which I assume is a volume control setting means 15db below the rated gain/ output of your preamp. We can't put a number on that because the source output level and impedance play a role. Then of course we are playing music too which is always varying in level.
You can plug your source into your power amp and you'll probably find that with today's hi out low z sources it will overdrive your power amp meaning your preamp is almost always attenuating the source. Be very careful if you do. I recommend a quiet passage of classical music if you do with thevremote in hand to be able to hit stop. (Using CD not vinyl or tuner) That's why I now use a passive line stage by the way.
Also I've seen preamps that have anywhere from 12-27 db gain and I'm sure the are others outside that range.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Probably. Preamplifiers attenuate a line level signal most of the time, because these sources typically produce 500mV to 2V. In any particular case (e.g. a -15dB setting in this preamplifier), the fixed gain of the preamplifier circuitry (usually 10dB or so) and relative level of the volume control references to 0 gain (usually "0dB")would have to be determined in order to know if the setting is actually amplifying or attenuating the input.
" these sources typically produce 500mV to 2V." That certainly has been the case in the past but I have noticed the voltage output of many, if not most, CD players and DACs has typically creeped upwards. I just did a random check on a handful of current players and DACs. The lowest output voltage I found was 2.5v and the highest was 5v. This isn't, of course, a comprehensive piece of research. However as someone using power amps with a 0.5v input sensitivity I have been noting this upward trend for some time. I am also surprised to find that some of the largest Japanese manufacturers no longer quote output voltage in their specifications.
this is becoming a problem of sorts. My Conrad Johnson has a goodly amount of gain and the DAC has at minimum 2.? volts. The volume control becomes a hair trigger.
I would say you could go with a passive but it all depends on your amplifier. Some sound good with passives while others not so good.
charles
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