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Discussion Starter · #1 ·
My AVR displays everything in "reference level" increments (-15DB, for example, is 15 below reference level)..


My question is, how on earth can the AVR know what the level of the input signal is going to be? So, in my situation, I have a HTPC connected via HDMI on an ATI 5XXX series card. (let's use the example of music, but it stands for movies as well). In Winamp, I have a volume slider. I also have Winamp specific sliders (that can boost the level by 12 DB, IIRC). Finally, I have a Windows master volume slider..


If I have the AVR set to 0DB (reference level), what do I need to set the PC at to input the right "amount" of signal to drive "real" 0DB output. For example, I could set the AVR to 0DB, but then set the master volume in Windows to 5%, that's certainly NOT reference level. I'm assuming that it would be everything (except Winamp boosts) set to 100% (WinAmp and Windows Master Volume)?


It's hard when you have 3 (or 4) volume controls between the source and your speakers; I'm just not sure what I'm actually outputting compared to reference level..


Thx!
 

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Assume the input was digital. Assume a movie followed the THX standard (not all do,) of having an average level of -20 dBfs (20 dB below digital peak). In that case, 0 dB would play each channel at a peak of 105 dB IF each channel is calibrated to play at the proper level.


For any source where the average level is not 20 dB below full scale, your SPL would vary from THX reference.


For analog, it's probably more complicated, as the voltage output level from the player and the receiver's gain structure must meet the THX standard. If the player's voltage on full scale signals does not match the standard, or the receiver's gain structure does not match the THX standard, it won't matter if the movie was mixed using the THX standard, IMO.
 

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Quote:
Originally Posted by mjfink /forum/post/19507883


It's hard when you have 3 (or 4) volume controls between the source and your speakers; I'm just not sure what I'm actually outputting compared to reference level..

That is one reason why you want to avoid multiple volume controls between source & amp. Or, in the case of a PC, if you cannot avoid volume controls, at least disable them (for unity gain).


AJ
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by MichaelJHuman /forum/post/19508251


For any source where the average level is not 20 dB below full scale, your SPL would vary from THX reference.

Do you happen to know what PC HDMI is calibrated at? Is "100" on the MV from a PC 20dB below full scale?
 

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Quote:
Originally Posted by mjfink /forum/post/19507883


My AVR displays everything in "reference level" increments (-15DB, for example, is 15 below reference level)..


My question is, how on earth can the AVR know what the level of the input signal is going to be? So, in my situation, I have a HTPC connected via HDMI on an ATI 5XXX series card. (let's use the example of music, but it stands for movies as well). In Winamp, I have a volume slider. I also have Winamp specific sliders (that can boost the level by 12 DB, IIRC). Finally, I have a Windows master volume slider..


If I have the AVR set to 0DB (reference level), what do I need to set the PC at to input the right "amount" of signal to drive "real" 0DB output. For example, I could set the AVR to 0DB, but then set the master volume in Windows to 5%, that's certainly NOT reference level. I'm assuming that it would be everything (except Winamp boosts) set to 100% (WinAmp and Windows Master Volume)?


It's hard when you have 3 (or 4) volume controls between the source and your speakers; I'm just not sure what I'm actually outputting compared to reference level..


Thx!

You are confusing a Gain control with a Volume control..

When using a player or component with a gain control its purpose is to control the its gain as not to overload the next stage it is connected. Also it is pertinent to note that depending upon the player or component, it has its own unique optimum setting for signal-to-noise.. If the gain is set too low than the noise generated by its own circuitry may be audible and not covered by the audio source signal itself.


A good rule of thumb is to set the gain controls @ between 50-70%. Regarding the amplifier's (or AVR) digital display indication this is usually referenced to its rated output level. For example, if the amplifier is rated @ 100W/CH it takes an input signal of 1V (RMS) to drive the amplifier to 100W output into 8 Ohms, and the display should indicate 0 dB.. If boosted it will read + xx dB if decreased then it will read - xx dB.


The other critical factor is acoustic energy being output the input > amplifier > loudspeaker chain, and here the measurement is done using an SPL meter.


Just my $0.02...
 

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If the signal going into the receiver is not a movie, "reference level" has little or no mieaning.


If the signal going into the receiver is digital, there's nothing that you should adjust. No digital system can go higher than 0 dBFS. If you try to encode material digitally that exceeds this level you get ugly sounds. If you're transferring digitally, it is not possible to exceed the 0 dBFS level because digital just doesn't do that.


If you're feeding a line level signal and you "really" want to know, you'd need to play a test disk with a known level test signal (at say =20 dBFS or -30 dBFS) and use and SPL meter to determine the output (volume slider) level that gives you 85 or 75 dB with said test signal, when your master volume on the receiver is at zero. Otherwise you'll never know, and for the most part probably shouldn't worry about it anyway, unless you're overdriving the inputs or find you can't get loud enough . . .
 
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