1 Topic by Johannes AU (edited by Johannes AU 2021-12-14 08:29:46)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Topic: I have a question about dB and amp output in W (stupid indeed)

Actually it is a question during a discussion with friends during the weekend.

We discuss about morden amp, display a -dB value when we turn the volume knob counterclockwise, for example, my Yamaha WXA-50 produce 70W at full power at -0dB, and minimum is -80dB, so what is the output in W related to the -dB value applied?

I do not know how to answer them, but I myself also wants to know the rough idea of that relationship though I do not care the -dB value and just turn to the comfortable listening level.

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen

2 Reply by ning (edited by ning 2021-12-13 09:48:14)

  • ning
  • DAW Mastermind
  • Offline
  • Registered: 2019-06-08
  • Posts: 579

Re: I have a question about dB and amp output in W (stupid indeed)

This is not correct.  First of all db is not the correct unit to use here. either dbu or dBV should be used to indicate level.
Secondly, Yamaha WXA-50 won't produce 70W at 0dbu. That solely depends on the impedance of the thing you are connecting to the amp.

The correct way to calculate it is, get the absolute dbu or dbv value, translate that to vrms (by simple math, or online calculators http://www.sengpielaudio.com/calculator-db-volt.htm ), then vrms^2/impedance is the output power.

In real life the impedance of your speaker varies in different frequency/power.  so there's no way to measure precisely unless you hook multimeter to measure both voltage and current at the same time.

3 Reply by Johannes AU (edited by Johannes AU 2021-12-13 09:59:33)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

ning wrote:

This is not correct.  First of all db is not the correct unit to use here. either dbu or dBV should be used to indicate level.
Secondly, Yamaha WXA-50 won't produce 70W at 0dbu. That solely depends on the impedance of the thing you are connecting to the amp.

The correct way to calculate it is, get the absolute dbu or dbv value, translate that to vrms (by simple math, or online calculators http://www.sengpielaudio.com/calculator-db-volt.htm ), then vrms^2/impedance is the output power.

In real life the impedance of your speaker varies in different frequency/power.  so there's no way to measure precisely unless you hook multimeter to measure both voltage and current at the same time.


ning, I understand the above, what I cannot answer my friends because dB is not the right value depending on impedance of speakers (also varies at real time), so can we just take the Yamaha shown value of dB as a rough idea of treat it as kind of percentage?

I did use the online calculator before the RME arrives, it is a wonderful tool indeed.

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen

4 Reply by Johannes AU (edited by Johannes AU 2021-12-13 10:15:53)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

Ar ... suddenly an idea came in mind, could be that -dB value at the Yamaha is the attenuation value of the input at the pre-amp section of the Yamaha/any other intergrated amp?

Stupid me .....

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen

5 Reply by KaiS (edited by KaiS 2021-12-13 11:03:14)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,150

Re: I have a question about dB and amp output in W (stupid indeed)

Johannes AU wrote:

Actually it is a question during a discussion with friends during the weekend.

We discuss about morden amp, display a -dB value when we turn the volume knob counterclockwise, for example, my Yamaha WXA-50 produce 70W at full power at -0dB, and minimum is -80dB, so what is the output in W related to the -dB value applied?

I do not know how to answer them, but I myself also wants to know the rough idea of that relationship though I do not care the -dB value and just turn to the comfortable listening level.

The correct answer is:

The dB value your Yamaha WXA-50 shows is an attenuation value related to full volume setting.


Trying to calculate the power in W from this value is not possible, as you would need to know:

• The Voltage of the input signal, which you can’t know as the voltage of a music signal is changing all the time - music is no steady state signal like a sinewave.

• The Yamaha’s max. gain / amplification factor, which is unknown and can’t be found in it’s specs.

KaiS's Website

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

KaiS wrote:
Johannes AU wrote:

Actually it is a question during a discussion with friends during the weekend.

We discuss about morden amp, display a -dB value when we turn the volume knob counterclockwise, for example, my Yamaha WXA-50 produce 70W at full power at -0dB, and minimum is -80dB, so what is the output in W related to the -dB value applied?

I do not know how to answer them, but I myself also wants to know the rough idea of that relationship though I do not care the -dB value and just turn to the comfortable listening level.

The correct answer is:

The dB value your Yamaha WXA-50 shows is an attenuation value related to full volume setting.


Trying to calculate the power in W from this value is not possible, as you would need to know:

• The Voltage of the input signal, which you can’t know as the voltage of a music signal is changing all the time - music is no steady state signal like a sinewave.

• The Yamaha’s max. gain / amplification factor, which is unknown and can’t be found in it’s specs.

Thank you KaiS and ning, you both woke me up from confusing discussion with my friends, they misleaded me to think something meaningless .........

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen

7 Reply by Curt962 (edited by Curt962 2021-12-13 17:56:36)

  • Registered: 2019-01-07
  • Posts: 1,462

Re: I have a question about dB and amp output in W (stupid indeed)

Johannes!

Never mind levels.  What you REALLY need are Exotic Wooden Dampers under your Yamaha!  wink

Qat:  One of the only words where the Q is not followed by a U, but the audio qualities of Qat Wood are amazing!  big_smile

Oh Manoman!  That'll have your Guests wondering!!  smile

Yours in the Best BS,

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

8 Reply by Johannes AU (edited by Johannes AU 2021-12-13 18:14:00)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

Curt962 wrote:

Johannes!

Never mind levels.  What you REALLY need are Exotic Wooden Dampers under your Yamaha!  wink

Qat:  One of the only words where the Q is not followed by a U, but the audio qualities of Qat Wood are amazing!  big_smile

Oh Manoman!  That'll have your Guests wondering!!  smile

Yours in the Best BS,

Curt

Actually I do not mind the levels, in general I listen to my Yamaha at -50dB to -35dB, not more than that. The discussion between friends make me confused and asked a stupid question here.

The Yamaha is sitting on exotic wooden dampers since day one, it is the desk big_smile Natural cork sheet are more exotic to me in damping.

Qat wood? cost more than my system many folds, not necessary .... tongue

It can be an endless road if chase for something "perfect", first cables, second power conditioners, third room treatment, fourth another set of equipment approved by golden ears ... then actually no time to enjoy music even money spent.

My humble system with the renowned RME dac serves me very well, The RME have the Guests wondering ALREADY.

Music! Music! Music!

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen
  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

ning wrote:

This is not correct.  First of all db is not the correct unit to use here. either dbu or dBV should be used to indicate level.
Secondly, Yamaha WXA-50 won't produce 70W at 0dbu. That solely depends on the impedance of the thing you are connecting to the amp.

The correct way to calculate it is, get the absolute dbu or dbv value, translate that to vrms (by simple math, or online calculators http://www.sengpielaudio.com/calculator-db-volt.htm ), then vrms^2/impedance is the output power.

In real life the impedance of your speaker varies in different frequency/power.  so there's no way to measure precisely unless you hook multimeter to measure both voltage and current at the same time.

Don't get me wrong, I am not argue with you, never ever.

The 70W figure is from the manual also the spec at their webpage, I quote 70W because my speaker impedance is 6 ohms, lowest 5 ohms.
https://usa.yamaha.com/products/audio_v … oduct-tabs

But of course we all know that figure is for reference only, I assume it can only produce 50W (could be even less) in normal use, will not expect too much from a small package like the WXA-50.

It look nice together with the RME dac and Mac mini smile silver/grey/black.

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen
  • ning
  • DAW Mastermind
  • Offline
  • Registered: 2019-06-08
  • Posts: 579

Re: I have a question about dB and amp output in W (stupid indeed)

it says 70 W + 70 W (6 ohms, 20 Hz-20 kHz, 0.06% THD, 2-ch driven) but you can go beyond that at the cost of clipping (worse thd).
the official spec also listed 90 W + 90 W (6 ohms, 1 kHz, 0.9% THD, 1-ch driven), whose thd is still acceptable (< 1%).
But even this 90W does not indicate the full volume output power (volume knob at maximum).
So the best way is to measure by a meter.
For instance, tune your volume knob to normal listening level. remove the speaker cable. use multimeter to measure the ac voltage.
use V^2/R to get the power.
it's possible that you consume much less than 50W. My daily studio monitor has maximum rating at 50W. But my listening level is 30 db lower than full allowed volume so that's 1000x less power.
the wattage is not relate to attenuated volume db number in linear way. turn your knob down and the power will be exponentially lower.

11 Reply by Johannes AU (edited by Johannes AU 2021-12-14 15:58:06)

  • From: Hongkong
  • Registered: 2021-06-30
  • Posts: 720

Re: I have a question about dB and amp output in W (stupid indeed)

ning wrote:

it says 70 W + 70 W (6 ohms, 20 Hz-20 kHz, 0.06% THD, 2-ch driven) but you can go beyond that at the cost of clipping (worse thd).
the official spec also listed 90 W + 90 W (6 ohms, 1 kHz, 0.9% THD, 1-ch driven), whose thd is still acceptable (< 1%).
But even this 90W does not indicate the full volume output power (volume knob at maximum).
So the best way is to measure by a meter.
For instance, tune your volume knob to normal listening level. remove the speaker cable. use multimeter to measure the ac voltage.
use V^2/R to get the power.
it's possible that you consume much less than 50W. My daily studio monitor has maximum rating at 50W. But my listening level is 30 db lower than full allowed volume so that's 1000x less power.
the wattage is not relate to attenuated volume db number in linear way. turn your knob down and the power will be exponentially lower.

Thank you very much, ning smile

The Yamaha is less warm at same SPL with the new Oberon 1 which is 3dB more sensitivity than the former Spektor 1, it work with less load (-5dB more than before).

Pacifist, dumb, not stupid
Listen music out from a box which sounds
Reading words on paper/ screen