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Volume control
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Old 6th June 2019, 02:46 PM   #1
Mark 461 is offline Mark 461
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Default Volume control

I've always wondered when connecting external speakers to a computer. Do you turn the volume from the computer to the max and adjust using the external speakers volume control or vice versa? I've heard it's supposed to be lower than the max to prevent distortion. Is this why realtek drivers default to 67 percent volume. Can someone explain this?
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Old 6th June 2019, 02:53 PM   #2
sSound is offline sSound
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To achieve the lowest noise, its best to add the most gain in the first stage, in this case your computer, so maxing the computer output and controlling the volume with your speakers will produce the least ammount of noise. However you may end up overloading the speaker's input, so you may want to back it up a bit.

If you are math inclined you may want to look at Friis gain equation, which basically says what I just said about noise.
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Old 6th June 2019, 02:58 PM   #3
Mark 461 is offline Mark 461
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Thanks for the response. Is this true for digital sources as well or only analog?
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Old 6th June 2019, 04:44 PM   #4
kipman725 is online now kipman725  United Kingdom
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I have a computer where distortion jumps above 63% volume dramatically. I would recommend at least doing a loop back measurement using something like right mark audio analyser or REW to check you don't have the same problem. Of course doing a simple loop back you can't tell if its the input or output but as the consequences of clipping are much more severe than a loss of SNR I would recommend this check.
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Old 9th June 2019, 01:44 AM   #5
Mark 461 is offline Mark 461
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Okay thanks a lot
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Old 9th June 2019, 03:03 AM   #6
abraxalito is offline abraxalito  United Kingdom
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The answer does depend on what player you're using on your computer. Some players can add digital gain - you definitely don't want those set to maximum or the output will clip. Ideally you want to set the computer volume to 0dB - no gain, no attenuation.

You can check by creating a full-scale (0dB) sine waveform in Audacity and monitor your DAC's output for clipping on a 'scope as it plays out. Or just listen to hear when distortion occurs as you raise the volume.
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Old 14th June 2019, 04:18 PM   #7
Mark 461 is offline Mark 461
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Thanks for your advice.
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Old 17th June 2019, 12:36 PM   #8
soundcheck is offline soundcheck  Germany
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It's not that easy.

As a matter of fact, the goal is to run the highest possible DAC
output voltage for lowest noise to achieve your maximum listening level.

And that max DAC output voltage very much depends on a well done DAC->amp->speaker integration.

You need to know your:

1. max listening level
2. speaker sensitivity
3. amp gain
4. DAC output voltage(s)


1. A maximum safe listening level should be about 85dB over a longer period.
2. Now you look at your speaker sensitivity.
Many of them run in the 88-92dB/W area. As a rough estimate - you'll
need just 1W amp power. Let's assume you own a 4R speaker. That'll
lead to 2V output voltage to achieve that 1W. That's the amp output voltage!
3. Many average amps run in the area of factor 20-30 on the gain side.
4. Typical max output voltage of a DAC is 2V - single ended - it doubles for XLR.

As you see that insanity lies in the typical amp gain. It'll make 40 to 60V from that max DAC-out voltage. We could almost live with a unity gain amp though.

And that means you need to drive your precious audio signal into the noise floor to cope with that insane amp gain. Basically you'll amplify a much noisier signal.

No matter if you run volume control on your amp or DAC/PC - analog or digital. You need to get your "gain" structure properly in place first.

Look for amps with variable gain-stages. NOT to be mixed up with amp volume control - that's something else! Usually that amp-volume control attenuates
the incoming signal!

With a properly dialed in amp_gain->speaker_sensitivity chain you'll be able to run your 32bit DAC digital volume control at rather audiophile levels.

BUT. You'd still need quite VC range though.

You'll face the recording levels/mixing level issue. The means you'd need up2 12-15dB headroom just to cope with the different rec level of CDs. That leaves you with e.g. just 0.5V DAC @85dB listening level for extreme "loud" recordings. Because you need the 2V to get the quietest recordings playing loud enough.

But. Again. If your have your gain-sensitivity setup dialed in properly, you've taken a big step into the right direction.

That's why I can live with a digital volume control on the DAC/PC quite well - since years.

Good luck.


PS:
As part of a proper integration. You need to find out what max input voltage your amp accepts.
There are amps that allow levels below that DAC-out 2V only.
If you'd blow these high DAC-out levels into an amp with e.g. 1.5Vmax on the input, you'll face nasty distortions of course.

Last edited by soundcheck; 17th June 2019 at 12:59 PM.
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Old 26th June 2019, 03:35 AM   #9
Mark 461 is offline Mark 461
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I'm not too sure I understand this. From what you're saying, amp gain and speaker sensitivity go hand in hand. The amplifier uses the DAC's voltage as a reference, to determine how much power to output. Reducing the DAC's voltage decreases the amp output power but at the price of increased noise?

So, after finding out the amplifier's max input voltage and the DAC's max output voltage before distortion, and reducing the DAC's output voltage to match the amplifier's max input voltage, results in the highest audio quality? This seems awfully complicated can't you just use digital in and avoid all of this?
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Old 27th June 2019, 08:34 AM   #10
phofman is offline phofman  Czech Republic
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"using digital in" does not circumvent any of the stages, it just moves them from one device to another.

It's actually quite simple.

The D-A conversion has some fixed floor noise, the same for tiny signal or signal close max attainable level. Therefore the max. attainable level will produce the lowest noise RELATIVE to the signal. That is what you want to use.

Then comes the analog attenuation (analog volume control), feeding the amplifier behind. The analog attenuation reduces both the signal as well as the DAC noise, but adds a bit of its own noise. The amplification behind amplifies both the signal and the noise. Also, the amplifier adds its own noise. The higher the amplifier gain, the more noise it adds.

Therefore you want to keep the amplifier gain at minimum, to add the least amount of noise.

An ideal situation for the lowest signal/noise ratio:

DAC - no attenuation

analog volume control - no attenuation

amplifier - just enough gain to attain the required listening level.

But every recording is different and you need some volume control. So in half-reality you pick just a bit higher amplifier gain and fine-tune with slight analog attenuation, as needed.

But in full reality you have no control over your amp gain and must use its analog volume stage for all the control. Still, keep the DAC output at max, of course below limiting.
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