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Low volume from power amp

antcollinet

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Certainly not debating you as you are clearly more knowledgeable than I in this, but asking the question so that I can understand what you are explaining:

At -100 the volume is muted, that is the minimum, and +2 is the maximum (102 db range total). As I turn the volume up, I get to -30 which is 70db higher than the minimum (or ~70% of the volume range) just to get to normal listening levels. With other systems, at 30-35% of the volume range the system is plenty loud.

Unless the volume range isn’t linear, which I doubt, I don’t understand how at -30 I’d only be at 1/8 of output volume.
That is a difference between dB and % - they are not the same. dB is a logarithmic scale. I currently have my DAC at 0dB, and my amp (an AVR) set to -15dB - that is a loud listening level right now - higher than i'd normally listen to music, (and on vinyl which is probably only putting out 0.5V average from the pre-amp.

If I now turn the dac down to -30....... it is very quiet - less than background listening level. Only about 40dB spl - about 10dB above background noise level.

Try it - go down 10dB to -40dB level. You should perceive an approx halving of the volume. Go back to -30. Then go up to -20, you should percieve that as double the -30 level (stop increasing if the music starts to distort). Go up to -10 - it is going to be seriously loud now - only listen there for a few seconds - and again don't go there at all if you sense any distortion in the music.

EDIT : One thing to be aware of - +10dB is 10x power. So if you're normal listening level is 2W (not unusual) then +10dB from there: -20dB in your case, is 20W. Another +10dB (-10dB for you) is 200W.

Yes, you need 10x the power to achieve a perceived doubling of volume.
 
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PK1

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That is a difference between dB and % - they are not the same. dB is a logarithmic scale. I currently have my DAC at 0dB, and my amp (an AVR) set to -15dB - that is a loud listening level right now - higher than i'd normally listen to music, (and on vinyl which is probably only putting out 0.5V average from the pre-amp.

If I now turn the dac down to -30....... it is very quiet - less than background listening level. Only about 40dB spl - about 10dB above background noise level.

Try it - go down 10dB to -40dB level. You should perceive an approx halving of the volume. Go back to -30. Then go up to -20, you should percieve that as double the -30 level (stop increasing if the music starts to distort). Go up to -10 - it is going to be seriously loud now - only listen there for a few seconds - and again don't go there at all if you sense any distortion in the music.

EDIT : One thing to be aware of - +10dB is 10x power. So if you're normal listening level is 2W (not unusual) then +10dB from there: -20dB in your case, is 20W. Another +10dB (-10dB for you) is 200W.

Yes, you need 10x the power to achieve a perceived doubling of volume.
Makes perfect sense! And I knew db is a log scale, somehow didn’t put 2 & 2 together in this context!

I’ll give it a try. Thanks for explaining.
 

Talisman

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It often happens that old school audiophiles have a sort of "fear" about using the volume, it also happens that when some products use a logarithmic potentiometer instead of a linear one, many complain about a lack of power, when in reality they should only " simply" turn the volume knob a little more....
Just out of curiosity, have you actually tried simply turning up the DAC volume further and seeing if the power you expect comes through? It seems like something trivial to do....
 

staticV3

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That's interesting, I didn't know these things existed.
For educational purposes, why would this make a difference vs. the USC connection?
It's possible that the issue is caused by the DAC having a somewhat broken UAC2 implementation which doesn't want to play nicely with your iPad.

In contrast to a desktop DAC, the Hifime UT23 for example is an extremely simple USB device with no UAC2 controls whatsoever, which should make it more likely to work well with the iPad.
 

antcollinet

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It's possible that the issue is caused by the DAC having a somewhat broken UAC2 implementation which doesn't want to play nicely with your iPad.

In contrast to a desktop DAC, the Hifime UT23 for example is an extremely simple USB device with no UAC2 controls whatsoever, which should make it more likely to work well with the iPad.
Pretty certain it is the -30dB the DAC is set to.

Amp sensitivity is 4.6V for 200W at 8ohm, 25dB gain. Which is 40V output.

Dac is at -30dB. 0dB is 4V. So dac is outputting 0.126V for a full scale input. Amp is outputting 2.24V = 0.63W. And bear in mind the music won't be at 0dBFS for very much of the time, more like average -10dB

There is no power shortage from the amp - we just need to get the DAC turned up somewhat
 
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