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What are Amir's Volume Settings for a Product Review?

Tom C

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I've sometimes wondered how volume control settings correspond to the levels Amir shows his measurements at. So, like when we look at the dashboard for a balanced output DAC test and see 4 volts out, SINAD -119dB, is that at maximum volume, or just turn the dial until output reads 4 volts, and that could be max or 3/4 or 1/2 or whatever for that unit? I realize he likes to show the readings at 2 volts output for a unit with unbalanced connections, and readings at 4 volts output for units with balanced connections so we can compare apples to apples. But a lot of times in a system there are several controls for volume, both hardware and software. So if I want to set and forget a unit by placing the output at the knee of the power output curve, for example, is there a way to tell at what volume setting Amir found that to be when he tested?
 

amirm

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There are a lot of considerations depending on class of product and its capabilities.

In general, DACs are tested with 2 volt RCA/4 volt XLR per Sony/Philips spec since introduction of CD players. Digital input to the DAC is at full scale (0 dBFS). If the DAC has volume control, I adjust that to get this output level. With most desktop DACs this means maximum volume if they have such a control.

DAC output of AV products is not standardized so I adjust their volume to get the above values. For them, I also run a THD+N vs output level so you can see performance at other levels.

Amplifiers are measured at 5 watts output, 1 kHz tone, 4 ohm load. Integrated amplifiers with volume controls are adjusted for gain of 29 dB per THX spec and input level adjusted to get this output.

If a product can't produce the above output levels, then whatever it outputs is shown. For dongles sometimes this is is just 1 volt and so that is what you see.
 
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Tom C

Tom C

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There are a lot of considerations depending on class of product and its capabilities.

In general, DACs are tested with 2 volt RCA/4 volt XLR per Sony/Philips spec since introduction of CD players. Digital input to the DAC is at full scale (0 dBFS). If the DAC has volume control, I adjust that to get this output level. With most desktop DACs this means maximum volume if they have such a control.

DAC output of AV products is not standardized so I adjust their volume to get the above values. For them, I also run a THD+N vs output level so you can see performance at other levels.

Amplifiers are measured at 5 watts output, 1 kHz tone, 4 ohm load. Integrated amplifiers with volume controls are adjusted for gain of 29 dB per THX spec and input level adjusted to get this output.

If a product can't produce the above output levels, then whatever it outputs is shown. For dongles sometimes this is is just 1 volt and so that is what you see.
Thank you Amir. You truly are the best!
 

GXAlan

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Amplifiers are measured at 5 watts output, 1 kHz tone, 4 ohm load. Integrated amplifiers with volume controls are adjusted for gain of 29 dB per THX spec and input level adjusted to get this output.

What does that typically translate in terms of input level? How would the numbers change if you used 2.0V for input and then turned up the volume to equal 5W of output?
 

NTK

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What does that typically translate in terms of input level? How would the numbers change if you used 2.0V for input and then turned up the volume to equal 5W of output?
The THX spec of 29 dB gain means the output voltage is the input voltage multiplied by 28.2 (= 10^(29/20)) times.

For 5 W at 4 ohm load, the amplifier output voltage is 4.47 Vrms. Dividing 4.47 by 28.2 gives us 0.159 Vrms input. (See Marantz PM-90 review)

Marantz PM-90 Measurements RCA Vintage Stereo Amplifier.png


If you want an input of 2 Vrms and an output of 5 W at 4 ohm load (= 4.47 Vrms), the amplifier gain needs to be reduced to 4.47/2 = 2.24X = 7 dB.

Therefore, if for example an amplifier has a maximum gain of 29 dB, you'll need to set the volume knob to -22 dB (i.e. 22 dB less than full gain) when your input is 2 Vrms and your desired output is 5 W at 4 ohm.
 
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