• 11-21-2003, 03:09 PM
    topspeed
    Receiver's volume indicators...what do they mean?
    This is dumb question and I'll be the first to admit it...

    A receiver's or preamp's volume attenuator essentially restricts power flow (at least that's how I understand it from past threads), right? So when a receiver is showing "-db" which gradually increases to "0db" is it showing you the reduction in resistance? What does it mean when you go to the positive db's (i.e. +5db)? If you're running an external amp does that mean the preamp's internal amps are pushing extra power above and beyond the amp's? What about when there is no external amp?

    I've never been able to figure this out. Some say that "0db" is reference level, but that's ridiculous because unless the darn thing had a built-in mic and autocalibration (like Pioneer now has) it would never know due to differences in speaker efficiencies. The only thing I can figure is that it's completely arbitary and different with every manufacturer, which is completely inane but just about right for the world of audio :)

    Any ideas?
  • 11-21-2003, 06:48 PM
    trollgirl
    Somebody correct me if I'm wrong...
    as I usually seem to be. I think the 0dB mark means zero attenuation, which is to say, full rated power. On power amps I've owned which had power meters (like my sorry-I-sold-it Proton AA-1150) the meters read 0dB at 50 watts, the rated power.

    Laz
  • 11-23-2003, 10:18 AM
    poneal
    My receiver's manual indicates that 0db is the max rated output for the receiver. While 0db may be the max rated output, it doesnt mean that this is the loudest it can go. My reference level is -15, so the manual says. But -15 is pretty loud so I usually just keep it between -40 and -30.
  • 11-23-2003, 03:08 PM
    topspeed
    Quote:

    Originally Posted by poneal
    My receiver's manual indicates that 0db is the max rated output for the receiver... My reference level is -15, so the manual says. But -15 is pretty loud so I usually just keep it between -40 and -30.

    Does your receiver go to +db? Mine goes to like +25db I think (too lazy to look up the manual right now). Also, why would your manual state -15db is reference level when it doesn't calculate for speaker efficiencies? Obviously, a speaker rated at 86db @ 1 meter driven by 1 watt is going to be far quieter than a 93db rated speaker.

    Like I said, it doens't make sense.
  • 11-23-2003, 09:59 PM
    Pat D
    They're just arbitrary markings for reference.
    Quote:

    Originally Posted by topspeed
    This is dumb question and I'll be the first to admit it...

    A receiver's or preamp's volume attenuator essentially restricts power flow (at least that's how I understand it from past threads), right? So when a receiver is showing "-db" which gradually increases to "0db" is it showing you the reduction in resistance? What does it mean when you go to the positive db's (i.e. +5db)? If you're running an external amp does that mean the preamp's internal amps are pushing extra power above and beyond the amp's? What about when there is no external amp?

    I've never been able to figure this out. Some say that "0db" is reference level, but that's ridiculous because unless the darn thing had a built-in mic and autocalibration (like Pioneer now has) it would never know due to differences in speaker efficiencies. The only thing I can figure is that it's completely arbitary and different with every manufacturer, which is completely inane but just about right for the world of audio :)

    Any ideas?

    You are correct that an ordinary volume control can only attenuate the signal. Well, you have figured out much of it, and it is best to treat the scale (including the "0" point) as arbitrary. One wonders how accurate the relative numbers are, for example, whether reducing 10 dB actually does that or is even close.

    First of all, there are no standards for this sort of thing, nor the taper of the volume control. Volume controls are different.

    Second, there is the output of your source component, typically a CDP. This is not the same for every CDP, although the standard is 2 volts output at digital "0," which is the loudest it can go. But over the years, I have seen reviews of players where the maximum output is anywhere from 1 to 4 volts or so, although it is usually closer than that.

    If you have a multi-player, such as a DVD or SACD player, then the output for each format they handle (CD, DVD, SACD) is probably not exactly the same either!.

    Third, there is the input sensitivity of your receiver or preamp. Indeed, this may vary with each input, such as a CD input or a tape input.

    Fourth, the CDs, etc., are not all recorded at the same level, and anyway, music is generally constantly changing, so the output in the soft parts is much less than in the loud parts and transients.

    Five, as you note, there is the senstivity of the speakers. Speakers vary in sensitivity. As well, what level the amp will clip also depends on the speaker's impedance, which itself varies with frequency.

    Six, input the sensitivity of most power amps is less than 1 volt, meaning they require less than a volt to drive them to their maximum rated output. Compare this to the 2 volt CD standard maximum output and you can see why you have to have to be careful with the levels. For example, if the amp is clipping, then it's too loud, no matter what the volume control setting is.

    I've probably not listed everything . . .
  • 11-24-2003, 06:57 AM
    poneal
    Quote:

    Originally Posted by topspeed
    Does your receiver go to +db? Mine goes to like +25db I think (too lazy to look up the manual right now). Also, why would your manual state -15db is reference level when it doesn't calculate for speaker efficiencies? Obviously, a speaker rated at 86db @ 1 meter driven by 1 watt is going to be far quieter than a 93db rated speaker.

    Like I said, it doens't make sense.

    Yes, my receiver goes from negative to positive. I've never had it over +10db and that was just playing around to see how loud the receiver goes. It was loud :-). The manual says to use -15db as the start for sending pink noise through the speakers for speaker level calibration. I don't have an SPL meter so I just let the receiver do its thing. Maybe for Xmas I will get an SPL meter. I have no idea why the -15db reference, just kinda took it as the way to do it. Now if I get an SPL meter for Xmas, then I don't have to use the -15db and can set the speakers at whatever reference level I want. Hope this clarifys things a bit. Paul.
  • 11-26-2003, 09:23 PM
    trollgirl
    Let me tell you a story about +dB...
    When my daughter was a toddler, she liked to play with the buttons and switches of my audio gear. One day, I came home, powered everything up, and punched the PLAY button of my CD player. I didn't know that the preamp's gain knob was ALL the way up. When the sound began, I moved (maybe) the fastest in my life, and saw the needles of the power meters drift back from 400 watts (50 watt rated). +dB indeed - the speakers were always a little raspy after that...

    Laz
  • 11-26-2003, 10:25 PM
    happy ears
    Amazed they still worked
    Boy that must have been a shocker, amazed that you did not destroy part of the crossover or tweeter.
  • 11-26-2003, 11:13 PM
    topspeed
    Yeeouch!!!
    Quote:

    Originally Posted by trollgirl
    When my daughter was a toddler, she liked to play with the buttons and switches of my audio gear. One day, I came home, powered everything up, and punched the PLAY button of my CD player. I didn't know that the preamp's gain knob was ALL the way up. When the sound began, I moved (maybe) the fastest in my life, and saw the needles of the power meters drift back from 400 watts (50 watt rated). +dB indeed - the speakers were always a little raspy after that...

    Laz

    Raspy indeed! Would you like some eggs to go with those fried voice coils?
  • 11-27-2003, 04:59 AM
    skeptic
    I tried posting a reply to this once before but somehow my computer got locked up.

    The markings on a volume control on a preamp and the meters on a power have some significance if they are correctly calibrated by the manufacturer.

    On a preamplifier, the manufacturer will specify "sensitivity" for different inputs such as 100 millivolts (mv) input for 1 volt output for aux, tuner, cd, tape, etc and 2 microvolts for 1 volt output for phono or microphone. Assuming it is correctly calibrated, when the volume control is set to 0 db, the referenced input will give the referenced output. The volume control is not a power restrictor, it is a "gain" control. Technically it is a variable voltage divider between two of the gain stages whether gain is supplied by transistors or tubes. Because the overall gain can be anything from negative infinity to more than one, the volume control can accurately be said to go into positive numbers (above 0 db.) The most common type of volume control in the past has been the rotary logarithmic potentiometer. Linear slider types with a lograthmic taper are also available on some recievers. However, in all digital models, the visual fluorescent or LED digital readout in db may be the only way you have of knowing how high or low the volume control is set. Until you are accustomed to what those numbers mean on any particular receiver, meaning its range, it's best to be cautious at first. By the way, so called passive preamplifiers can only have gain of 0 db or less. They are not really preamplifiers because they don't amplifiy voltage or current, they only attenuate it, so their gain is always zero or less.

    Power meters don't really meter power output at all. They are invariably volt meters calibrated to tell you how much power the amplifier would deliver into an 8 ohm resistive load. 0 db is usually calibrated to coincide with the rated output of the amplifier however, since an amplifier can deliver more than rated power at least for brief periods, they include a region beyond 0 db. You can see that with the speakers turned off or even disconnected, the meters will continue to swing back and forth with the input signal even though it is obvious the amplifier is not delivering any power to anything. And of course, when the load is not 8 ohms resistive (it rarely is) all bets are off and you may actually be delivering more or less power than they indicate. (most speakers have impedences which vary all over the place at different frequencies. 8 ohms or whatever else the rating is, is nominal.)

    Are these meters and markings of much practical use or value? For most people under most circumstances, probably not.
  • 11-28-2003, 12:11 AM
    topspeed
    Thanks Skep!
    Brother, you are thorough! Just out of curiousity, is a noble attenuator different than what you described?
  • 11-28-2003, 04:20 AM
    skeptic
    Quote:

    Originally Posted by topspeed
    Brother, you are thorough! Just out of curiousity, is a noble attenuator different than what you described?

    I never heard of a "noble attenuator." Is that a type of attenuator or a brand?

    I said "By the way, so called passive preamplifiers can only have gain of 0 db or less. They are not really preamplifiers because they don't amplifiy voltage or current, they only attenuate it, so their gain is always zero or less." Actually the gain is 1 or less which means 0 db or less, 0 being the log of 1. As I recall, the voltage gain in db is -20 log V(out)/V(in).
  • 11-28-2003, 05:14 AM
    happy ears
    Power Meters
    Power meters may be nice to look at, otherwise they just tell you if you are using more or less power. Do not like power lights, drive me nuts with the lights out.

    I believe "Noble" is a brand or line within a company
  • 11-28-2003, 10:06 PM
    spacedeckman
    Easy answers
    0dB would mean maximum rated output. Easy concept, but not so easy in practice since it would depend on speaker load and input level. When you see +10dB, you are 10dB above THX reference volume, meaning that your receiver is a THX piece or using a similar scale.

    Noble is a brand, as is Alps.

    Space
  • 11-29-2003, 12:44 AM
    topspeed
    Quote:

    Originally Posted by spacedeckman
    0dB would mean maximum rated output. Easy concept, but not so easy in practice since it would depend on speaker load and input level. When you see +10dB, you are 10dB above THX reference volume, meaning that your receiver is a THX piece or using a similar scale.

    Noble is a brand, as is Alps.

    Space


    My receiver isn't THX certified so there may be some holes in that argument. Thanks for the info on Noble attenuators. I didn't know what it was either but the one on my PS Audio 4.6 pre was supremely accurate and of obvious quality. Never had one problem with it in 15 years, which is more than I can say of the volume control on my old Marantz 2230(?) which has a nasty tendency to get dirty easily thereby creating loud pops and crunching sounds as you dial up the volume. Great sound for a 30 year old receiver tho.
  • 11-29-2003, 01:37 AM
    happy ears
    Change Volume Control
    Topspeed, if the only problem with the old Marantz is the volume control, why not change it out. Have had this of type of problem with volume control and cleaning never seamed to work long term. Finding an exact match may be the tough part but when there is a will there is a way.

    There are many attenuators available from fairly cheap to exotic. Also what people have said above about power meters is what the problems are in accuracy.

    Have A Great Day
  • 11-29-2003, 05:54 AM
    spacedeckman
    topspeed, what holes?
    I said it is either THX or using a THX type scale. It wasn't "A", so it is obviously "B". The answer is the same, "0"dB being "reference volume" which is completely meaningless in real life.