Understanding Audio Dynamic Range / SNR (Part 1)

[617]

Amir, admit you love being a youtube celebrity. "WHAT's up guys, welcome to audio science review, be sure the smash that like button, and be sure to hit subscribe and click the little bell so you're the first to watch our debunkings EVERY week.

 

[rodrigaj]

Thank you for posting these videos. Very informative and educational.

 

[Invinoveritasty]

Amir, You may singlehandedly changing the industry. The power of the internet coupled with subject matter expertise is an incredible one-two punch. Thank you.

 

[MetalDaze]

All these nuggets of "we'll cover that in a further video" really makes me look forward to the further videos!

Great explanation and presentation, per usual.

Cheers & feel better

 

[sam_adams]

Hello Amir,
very good explanation of the db-Scale.
In this case, i have an idea what would be very interesting for an additional measuring problem:
Most High-Ender saying that the correct polarity of the mains plug is absolutely necessary for minimum potential difference between audio components. And wrong polarity of the mains plug would have a major negative impact in the soud quality due to massive compensating currents. For me, i have tried it but i cannot hear any difference depending on the mains plug polarity. Is there something relevant to measure or my ears are too weak?
Greetings, Walter

You may be referencing the inter-chassis currents in unbalanced systems that are the result of the stray capacitance between the power lines and the chassis. An understanding of this phenomenon and how to measure and mitigate them are explained in this tech note from Bill Whitlock of Jensen Transformers: Hum And Buzz In Unbalanced Interconnect Systems - Jensen AN-004.

 

[Lambda]

it but i cannot hear any difference depending on the mains plug polarity. Is there something relevant to measure or my ears are too weak?

If there is no problem you can't fix it

And wrong polarity of the mains plug would have a major negative impact in the soud quality

Can you even plug Australian plug in the other way around?

We have this stupid plug:

So there is no "right" or "wrong polarity" in most of Europe:
Equipment is build so it don't matter if phase and neutral is swapped.

But sometimes there can be "compensating currents" Massive is very relative.
maybe 0,5mA is typical.

This is an other excellent read about the topic:
http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

 

[PeteL]

Amir, this is another great video! Thank you for the opportunity to learn from you; I think you’re doing a great service to the audio community and future audio fans!

In all the modern amplifiers I’ve used, I’ve found the only two differentiators that I can subjectively hear are dynamic range (hiss from efficient speakers) and damping factor. I have a question about dynamic range as it relates to when you combine electronics.

Please pardon the question if it’s a dumb one but I did search for answers and was not able to find them. Let’s say you have a DAC pre-amp with 120db of dynamic range, and you marry that to an amplifier with 100db of dynamic range, is there a way to estimate the system’s dynamic range?

I assume it would be the lesser of the components at 100db, but then I wonder what impact the interconnects have, and is there any effect on noise and thus dynamic range of having the two units sitting near each other? Are there other factors that impact dynamic range in this situation?

Your insight and knowledge are greatly appreciated. Thanks again!

Your system dynamic range will never be more than the smallest in the chain, but keep one thing in mind, in your example, assuming a dac-preamp, linked to a power amp of 100 dB (at full power?), it does not mean that your power amp is effectively the limiting factor in your chain, in your use case. The Dac preamp has a volume control, it's "dynamic range" whether the volume is analog or digital, is a best case scenario . For the digital part the best dynamic range is normally at no attenuation, for analog the relation is not as direct, input noise floor get's attenuated with the signal, but it's not fully constant neither, there is a sweet spot, normally quite high up because it has self noise. (edit: or based on measurments here, when the signal level is effectively 2V unbal, 4V bal but same idea, there is an optimal value). Now you also have the recording dynamic range, environment noise, but I won't get there, amir measure equipments. Assuming your power amp is matched at full sensitivity with your preamp, this one won't move, but this is not necessarily the case, full volume on your preamp can be more than your full input sensitivity, your preamp can lead your amp to clip, or can be less, you have unused dynamic range. So gain structure matters.

 

[testp]

this is an interesting topic to come back to in future, I've always wondered, what is the sinad/SNR when i listen to CD roughly at 70- 80 dB loudness, do i get 16 bits then or only when i listen at 96 dB, probably the latter... also do i miss anything when i listen at 70-80 dB??

 

[Chromatischism]

. 3. The way to go, is not by getting a more expensive (and quit) system, but find a house with a dedicated room in the basement. That would be really nice and quite.
4. Well equipped sound recording studios, have a silent room, isolated (floating floor) that can reach very low levels of background noise.

I find rooms above the 1st floor tend to be quieter as well and work better than basements for bass impact due to the suspended floor. Often times the HVAC equipment is in the basement which is a huge source of noise.

 

[Lambda]

also do i miss anything when i listen at 70-80 dB??

Are you missing something if your not close enough to the TV to see individual pixels?

Short answer, Yes your maybe missing something.

Longer answer would be. are you missing something of value?
is it maybe better for your enjoyment and immersion not to be able to resolve everything.

 

[nimar]

this is an interesting topic to come back to in future, I've always wondered, what is the sinad/SNR when i listen to CD roughly at 70- 80 dB loudness, do i get 16 bits then or only when i listen at 96 dB, probably the latter... also do i miss anything when i listen at 70-80 dB??

Recently came across this which speaks to this idea. What’s the dynamic range of your listening environment https://www.audiocheck.net/blindtests_dynamic.php?dyna=54

 

[testp]

Are you missing something if your not close enough to the TV to see individual pixels?

Short answer, Yes your maybe missing something.

Longer answer would be. are you missing something of value?
is it maybe better for your enjoyment and immersion not to be able to resolve everything.

yeah, that's exactly it.. sometimes i find spotify from my phone more interesting than more resolving setup, even though i know it sounds more correct there..

 

[Angsty]

Some remarks:
1. Electronic NR (Noise Range) is very high today, and can reach values way over 120dB.
But our environment is way worst. Urban background noise (you can check it easily with an application and your cell phone), is about 50 dB in a good day. Late night or a nice quiet neighborhood. Taking that as the noise floor, would ask to amplify the volume to some more significant levels. Lets say
90dB plus. 90-50 dB would leave you with a more practical 40 dB dynamic range, rather than 130 dB of an AP measurement screen.
2. There is a level of how loud you can go, with the Amp's max power and speakers efficiency. You may have a police visit after a neighbour's complain. So, after all, there's a limit, way more tangible than electronic dynamic range, over an AP test bench.
Not to say, that most CD's are recorded PCM 16 bit, equals to 96 dB dynamic range.
If you are a vinyle guy, it is way below 75dB. A 60 dB (rumble figure) is more practical.
3. The way to go, is not by getting a more expensive (and quit) system, but find a house with a dedicated room in the basement. That would be really nice and quite.
4. Well equipped sound recording studios, have a silent room, isolated (floating floor) that can reach very low levels of background noise.
An other limit of dynamic range is the compression that is used during the recording. Most studio practice some, and it is a standard equipment on every audio mixer. Some are using it aggressively. It makes the process way more easy that way.
Some manufacturers are proud of having ADC's or DAC's with the access of 24bit. Well, it is mostly to say that the top (high bit) 16 bit are linear and noise free. A true 24 bit equals to 144 dB! No home speaker can play that loud, or the low end would be soaked deep in the noise floor.
So after understanding the limits, that 133 dB measurement, is for display, not of any practical use.

Remember that the 133 dB value was for the analyzer itself, not for a tested audio component. One would want the SINAD of the analyzer to be much greater than that of a tested component or measurement problems would ensue.

In that same vein, having an audio reproduction system which exceeds the source by 10 dB or more would be ideal for transparency, despite the limitations of the listening environment. But, as you implied, an imperfect listening environment is like throwing away bits of SNR.

 

[Angsty]

You may be referencing the inter-chassis currents in unbalanced systems that are the result of the stray capacitance between the power lines and the chassis. An understanding of this phenomenon and how to measure and mitigate them are explained in this tech note from Bill Whitlock of Jensen Transformers: Hum And Buzz In Unbalanced Interconnect Systems - Jensen AN-004.

I’m struggling to understand how the mains plug polarity matters to audio quality if the mains power is rectified and filtered to DC in the power supply.

 

[Francis Vaughan]

Most High-Ender saying that the correct polarity of the mains plug is absolutely necessary for minimum potential difference between audio components. And wrong polarity of the mains plug would have a major negative impact in the soud quality due to massive compensating currents. For me, i have tried it but i cannot hear any difference depending on the mains plug polarity. Is there something relevant to measure or my ears are too weak?

Like most things proposed by audiophools, there is a tiny tiny nub of fact that that is totally misunderstood and blown into something just plain wrong.
In most household wiring you have active, neutral and ground. It is common to tie neutral to ground at some point. Just where and how varies from county to country. In Australia we tie them together in the main breaker panel, known as the multiple earthed neutral or MEN system.
This means that the neutral wire in the power cable is tied to earth, and the active swings above and below earth potential. Mostly this is of academic value so far as equipment is concerned. It still gets fed AC and transformers transform voltages down to useful internal potentials with full galvanic isolation. (This includes switch mode supplies.)
The only place you could see the slightest change is in how transformers are wound. The outermost layer of a given transformer winding can act as a partial shield. If the outer layer is the end connected to neutral it is at close to the same potential as the earthed case of the equipment. That may provide a tiny bit of additional immunity to mains born interference getting into the gear. And I do mean tiny. But it is the sort of thing one does in designing gear as generally good practice.
A mis-wired power outlet or power cable could swap active and neutral, and thus defeat the effect. Maybe, just maybe, this might matter to some bit of gear in some places with bad mains interference.

A mis-wired system that connected active to the case ground could result in massive currents between gear. But that isn’t some sort of high end audiophool optimisation. It is a lethal situation that can and will kill you. You cannot rely on audio interconnects to carry fault currents and to trip breakers.

As a general bit of guidance, anyone spouting rubbish such as you heard can be safely ignored on that, and on any other audio subject they may propound on.

 

[MC_RME]

It should be noted that this video is about Signal to Noise Ratio (SNR), not Dynamic Range (DR), which uses a -60 dBFS test signal to uncover noise modulation.

 

[scott wurcer]

I’m struggling to understand how the mains plug polarity matters to audio quality if the mains power is rectified and filtered to DC in the power supply.

There needs to be some control of discussions that can involve "cheater" plugs and things like defeating the safety ground. Codes and practice vary around the world. Our lab was balanced by local code with each alternate bench wired on a different phase of 220 but it was common practice to use a cheater on some TEK scopes with capacitive leakage on their mains transformer. Talk about magic smoke!

 

[MC_RME]

Living my life split between Germany and Thailand I know both sides. Very good electric net in Germany (which is not always the case, but mostly), with PE working as it should. And a completely PE free wiring in Thailand, where even Neutral is not on earth/ground level. Connecting different units the sparks fly, and touching metallic surfaces while standing on the ground with bare feets successfully wakes me up in the morning

I don't think one can discuss cheater plugs and ground loop breaking openly. It always ends up with tips that are extremely dangerous and might get you sued if something happens. The alternative is what every manufacturer does, strictly advice against those. But that's no discussion, it's just a repetition of what you can read everywhere.

 

[Ron Texas]

This stuff is important, but instead of classifying it as reviews it might need it's own category like tutorials or technical papers.

 

[amirm]

This stuff is important, but instead of classifying it as reviews it might need it's own category like tutorials or technical papers.

We only have one home page. It is mostly reviews so the title fits.