Low volume from power amp

[antcollinet]

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.

 

[PK1]

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]

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]

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]

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

 

[ubiq]

Hi fellows
I've had the same experience the OP had, and in need of a suggestion: I've compared

a MOON (SIM Audio) 340IX (2x100W / 8 ohms, gain 37db) coupled with its PREAMP DAC streamer MOON 390 (gain max 10db)
VS
a NCx500 power amp (380W / 8ohms, gain 22.8) linked to a streamer/preamp Cambridge CXN100 in XLR (I suppose it outputs 4v, but I've been unabled to find the information, anywhere).

Same speakers. So I was expected for the NCx500 380W to "audibly" sounds a bit louder than the Moon 100W, even knowing the difference of power is not a X3 of the perceived sound, but a mere +4,5db, so not a lot (correct me if I'm wrong)

Boy, what a disturbing difference in the volume perception !

With the Moon, volume knob at between "11 & 12 o'clock" was plenty loud (so halfway of the volume course), the max I could put before I start to hear some "saturation". It was very loud (private dance party level) but not TOO loud (painful). It means half of the volume knob course is lost, but psychologically it was very satisfying :-/

With the NCx500, I was obliged to turn the volume knob of the CXN 100 to "95" to reach a loud level, but still not as loud as the Moon. Like the OP described with some other preamp, sound was low level @"75", so of use from "75" to "95". I admit I didn't dare to turn to "95+" - "100" as I was in a store, so not my devices....
I've had some nice explanations from the NCx500 manufacturer, very similar of those from @antcollinet, so I think I understand the "why". A little. But my brain is thick : I can't help thinking the NCx500 is unabled to play as loud as the 2X100W...

All this report to ask you the following :
I plan to use the NCx500 with a Wiim Ultra (RCA to XLR, amp in high gain), and I think the Wiim will behave the same way the CXN100 did.
- Do I have to accept to use the volume knob between "96" and "99" for dance party level (btw, what do u think "100" will cause?), and between "75" and "95" for casual listening (meaning the first 3/4 of the volume knob is useless) ?
- Is there a way (hardware or software) to change the way the volume is handled ? I mean, how can I be sure to be able to push the NCx500 to its limit? By adding a device (preamp) ?

Thank you for your answers or suggestions. Be kind.

 

[staticV3]

Hi fellows
I've had the same experience the OP had, and in need of a suggestion: I've compared

a MOON (SIM Audio) 340IX (2x100W / 8 ohms, gain 37db) coupled with its PREAMP DAC streamer MOON 390 (gain max 10db)
VS
a NCx500 power amp (380W / 8ohms, gain 22.8) linked to a streamer/preamp Cambridge CXN100 in XLR (I suppose it outputs 4v, but I've been unabled to find the information, anywhere).

Same speakers. So I was expected for the NCx500 380W to "audibly" sounds a bit louder than the Moon 100W, even knowing the difference of power is not a X3 of the perceived sound, but a mere +4,5db, so not a lot (correct me if I'm wrong)

Boy, what a disturbing difference in the volume perception !

With the Moon, volume knob at between "11 & 12 o'clock" was plenty loud (so halfway of the volume course), the max I could put before I start to hear some "saturation". It was very loud (private dance party level) but not TOO loud (painful). It means half of the volume knob course is lost, but psychologically it was very satisfying :-/

With the NCx500, I was obliged to turn the volume knob of the CXN 100 to "95" to reach a loud level, but still not as loud as the Moon. Like the OP described with some other preamp, sound was low level @"75", so of use from "75" to "95". I admit I didn't dare to turn to "95+" - "100" as I was in a store, so not my devices....
I've had some nice explanations from the NCx500 manufacturer, very similar of those from @antcollinet, so I think I understand the "why". A little. But my brain is thick : I can't help thinking the NCx500 is unabled to play as loud as the 2X100W...

All this report to ask you the following :
I plan to use the NCx500 with a Wiim Ultra (RCA to XLR, amp in high gain), and I think the Wiim will behave the same way the CXN100 did.
- Do I have to accept to use the volume knob between "96" and "99" for dance party level (btw, what do u think "100" will cause?), and between "75" and "95" for casual listening (meaning the first 3/4 of the volume knob is useless) ?
- Is there a way (hardware or software) to change the way the volume is handled ? Adding a device?

Thank you for your answers or suggestions. Be kind.

Gain dictates loudness, max output power dictates headroom.

The Hypex setup has less gain, so will play quieter all else being equal.

It has more output power though, so you can play at higher volumes before the Amp conks out.
But only if you can provide enough input voltage to the Amp.

The WiiM Ultra has a maximum output voltage of 2V, which a standard NCx500 Amp with 26.7dB of gain can turn into (2*10^(26.7/20))^2/8=234W at 8Ω.

That's about 60% of the Amp's maximum theoretical output power, or 85% of the maximum theoretical perceived loudness (output power and perceived loudness do not scale linearly).

In other words, the Amp is gain-limited.

Amp designers who use the NCx500 module have the option to design their own buffer modules, which can change the Amp's effective gain.

For example, your NCx500 Amp seems to have a lower than default gain of 22.8dB, which when coupled with the WiiM Ultra, would result in (2*10^(22.8/20))^2/8=95W at 8Ω maximum output power.

That's 25% of the Amp's maximum theoretical output power, or 65% of the maximum theoretical perceived loudness.

In other words, even more gain-limited.

In a situation where you're gain-limited and missing loudness, even with everything turned up to the max, you can insert an additional preamp been the source device and your Amp.

This will boost the voltage and allow your Amp to output more power.

In a situation where your Amp is gain-limited, but you're still getting enough loudness for a satisfying listening experience, you do not have to do anything.

A gain-limited Amp does not compromise sound quality.

 

[EJ3]

All I can think of is to ensure the source and DAC are at 100% volume. I lent a coworker recently an Apple dongle, who said he wasn't really impressed with the sound. I asked him how he controlled the volume, to which he said he didn't want to take the iPhone past 30-50%. That meant the aux device he was outputting to had to work too hard to amplify the signal.

Is that a battery saving technic?

 

[ubiq]

@staticV3
Hi, and thank you. Makes sense. I should have add that I plan to use the high gain switch of the amp (29db) with the Wiim, of course.
And to add a simple preamp like a ToppingL70 if it's not enough... Will see

 

[staticV3]

Is that a battery saving technic?

Battery drain is the same with 10% or 100% volume.

Most likely, Chroma's coworker thought that sound quality would suffer if pushed above 30-50% volume (it doesn't).

 

[MCH]

Battery drain is the same with 10% or 100% volume.

Are you sure? I don't have an apple dongle, but in all my dongles power consumption depends on volume (measured) and more so headphones impedance, what intuitively also makes sense to me.

 

[staticV3]

@staticV3
Hi, and thank you. Makes sense. I should have add that I plan to use the high gain switch of the amp (29db) with the Wiim, of course.
And to add a simple preamp like a ToppingL70 if it's not enough... Will see

An L30II would be plenty enough preamp

 

[ubiq]

An L30II would be plenty enough preamp

Y!

 

[staticV3]

Are you sure?

My Apple A2049 playing music into a high impedance Line input draws 18mA at min volume (1mVrms Peak) and about 18.5-19.0mA at full volume (1000mVrms Peak)

Compared to the total current draw of an iPhone's internals, this 0.5-1.0mA difference is irrelevant and will not affect battery drain.

 

[MCH]

My Apple A2049 playing music into a high impedance Line input draws 18mA at min volume (1mVrms Peak) and about 18.5-19.0mA at full volume (1000mVrms Peak)

Compared to the total current draw of an iPhone's internals, this 0.5-1.0mA difference is irrelevant and will not affect battery drain.

I bet the high impedance of the input is what makes it not change much in your case

 

[antcollinet]

Are you sure? I don't have an apple dongle, but in all my dongles power consumption depends on volume (measured) and more so headphones impedance, what intuitively also makes sense to me.

If you are driving headphones that would make sense. Headphones are a relatively low impedance so consume more power at higher level.

@staticV3 is driving a high impedance line input - power almost zero - so even if you double it by doubling the volume, it is still almost zero.

 

[EJ3]

My Apple A2049 playing music into a high impedance Line input draws 18mA at min volume (1mVrms Peak) and about 18.5-19.0mA at full volume (1000mVrms Peak)

Compared to the total current draw of an iPhone's internals, this 0.5-1.0mA difference is irrelevant and will not affect battery drain.

I do not have anything like that as a setup (so I am basically clueless on this particular subject) but I just thought someone might have the 'idea' that it might be a battery saving technic.
I have heard a number of people say that they thought that sound quality suffers if they push the volume, so likely you are correct there.

 

[Chromatischism]

Is that a battery saving technic?

For this individual, I think it was mostly leftover knowledge from a bygone era of analog preamps.

 

[EJ3]

For this individual, I think it was mostly leftover knowledge from a bygone era of analog preamps.

Wherever that knowledge came from, it was/is certainly wrong in this application.
Sometimes (if you know that what your going to do won't actually harm the gear you are using) you need to venture past what you believed with other gear. (Or ask a few people with what you have or something similar to what you have).
Whenever you start messing with a new type of gear: you need to recalibrate what you know, as what you already know doesn't necessarily apply to the new stuff.