watt per channel is irrevelent!!

[hybridauth_Facebook_664715932]

Hi all,
I consider myself a bit of hifi hobbyist. Had a decent set up for almost 20 years. Until recently I upgraded my whole system and now in process of educating myself to more technical side of things, thanks to you guys.

In my old set up I had MF E10 amp with BW DM601 speakers. E10 was rated @ 40 watts per channel and it was really loud, even when we had parties I never had to go past 11 o clock on the volume knob. There was no difference in terms of loudness when I upgraded the speakers to CM5.

However, with my current amp, which is evo50a rated @ 55 watts p/c @ 4 ohms running the same CM5s I found it atleast 30% less louder than the MF E10. Considering that the evo has 15 watts more p/c I would have thought it would be louder, not that it matters at all. Even with the smaller pmc 21s evo 50a is nowhere as near as loud as MF E10. Hence I found that the watts per c/h is irreverent to how loud a system can sound.

Your indepth elaboration on this matter will be appreciated.
Thanks for reading

 

[Frank Harvey]

Not completely irrelevant, but certainly not the be all and end all.

 

[expat_mike]

Hence I found that the watts per c/h is irreverent to how loud a system can sound.

It appears that you are claiming that a system will sound just as loud, regardless of whether you supply the speakers with 0.000001W, 1W, 10W or 100W etc.

Amazing!

Have you patented this technology yet?

 

[Anderson]

You said your MF was rated at 40wpc and the new one is 55wpc @4ohms. You really have to quantify the output of the MF amp, what impedance is the 40w at?

For practical purposes there's no difference between the amps, you would need a 450wpc amp to be twice as loud as the MF.

http://www.axiomaudio.com/power

 

[hybridauth_Facebook_664715932]

Hence I found that the watts per c/h is irreverent to how loud a system can sound.

It appears that you are claiming that a system will sound just as loud, regardless of whether you supply the speakers with 0.000001W, 1W, 10W or 100W etc.

Amazing!

Have you patented this technology yet?

May be not completely irreverent, but is definitely not an indication as to how loud a system will sound.

 

[expat_mike]

*biggrin*

 

[Vladimir]

How loud and with how much distortion at what position on the volume knob an amplifier gets depends on its input sensitivity and power.

Input sensitivity is the amount of power needed from a source component to drive an amplifier to its maximum power output without clipping.

If an amplifier has input sensitivity of 500mV and your standard CDP chucks out 2V in peaks, that amplifier will be already at its maximum power without clipping at a position on the volume knob sooner than 100%. Turn the knob any further and that amp will enter clipping. How sooner depends on the volume pot type, if its linear or logarithmic. If an amplifier has input sensitivity of 150mV, it will enter clipping even sooner on the volume knob. Usually already entering clipping at 10 o'clock position.

Ideally you want an amplifier with 1V input sensitivity with 2V digital sources, which leaves you plenty of usable space on the volume knob without clipping and plus extra 1V for turning it up louder on quieter tracks.

Amplifiers with input sensitivity of under say 500mV are simply trying to sound more powerful than they actually are. You turn the knob at 9 o'clock and they are so loud, you think wow this 50W amp rocks! No it doesn't. Turn the knob further and you don't get more clean power, you get clipping. It's an illusion of power.

Opposit of that an amplifier with 150W and 1V input sensitivity needs to be turned up further on the volume knob for the same amount of loudness and will give the impression of less power and less excitement or PRaT etc. It will feel dull and lazy, despite the fact it actually sounds the same as the 50W amp before pushed into clipping.

 

[Broner]

Normally Davedotco responds to questions such as these. To save him the trouble I would like to point out that there are three main issues here:

1) The volume knob can be deceptive. Loudness of the system at a certain position of the volume knob means nothing. Some manufacturers make sure that only a slight twist of the knob already causes a significant rise in loudness. This gives people the idea that the amplifier is really powerful and good. That’s great for sales, but it doesn’t really tell you how powerful it is. Other amplifiers may not cause such a vast increase in loudness initially, but when turning the knob a little further the system keeps getting louder and louder while other amplifiers have little power left.

2) A 40 watt amplifier can drive a system just as loud as a 55 watt amplifier. At least: it should be barely/not noticeable to the listener.

3) Loudness is a poor measure of how powerful an amp really is. The power of an amp shows itself in other ways.

By the way, the numbers on the EVO50a are slightly different than what you mentioned. The power is rated at 8 ohm, not 4 ohm. The MF E10 might also not be as powerful as advertised: http://www.hifi-review.com/150160-musical-fidelity-elektra-e10.html.

 

[Vladimir]

Roksan Kandy K2BT
Input sensitivity: 510mV
Gain: Preamp 5.7dB and Poweramp 31.6dB, Total 37.3dB
Power output: 140W in 8 ohms
SNR: Line 110dBa (at rated power)
THD: <0.005% 1kHz - 8Ω
Price: £945

Roksan Caspian M2
Input sensitivity: 240mV
Gain: Preamp 9.3dB and Poweramp 30.7dB, Total 40dB
Power output: 85W in 8 ohms
SNR: Line 108dBa (ref. 500mV)
THD: 0.002% 1kHz, 0.015% 20kHz 10W - 8Ω
Price: £1650

 

[dim_span]

Roksan Kandy K2BT Input sensitivity: 510mV Gain: Preamp 5.7dB and Poweramp 31.6dB, Total 37.3dB Power output: 140W in 8 ohms SNR: Line 110dBa (at rated power) THD: <0.005% 1kHz - 8Ω Price: £945 Roksan Caspian M2 Input sensitivity: 240mV Gain: Preamp 9.3dB and Poweramp 30.7dB, Total 40dB Power output: 85W in 8 ohms SNR: Line 108dBa (ref. 500mV) THD: 0.002% 1kHz, 0.015% 20kHz 10W - 8Ω Price: £1650

Interesting thread ....

how does an Amp like a pioneer SA-9800 fit in (where it is dual ... ie. the 1st few Watts are in A-Class and the rest in B-class

herewith the specs (click on the specs button):

http://www.thevintageknob.org/pioneer-SA-9800.html

 

[Vladimir]

Class A or AB or B has nothing to do with this. Class A amps also enter clipping when they run out of power, just like Class AB designs. Only benefit in full Class A tpology is it doesn't sound as horrid (less crossover distortion).

That Pioneer is 150mV on the Tape and Aux. If you plug your CDP on it it will sound very loud and powerfull early on the volume knob and run out of power before half way. When it runs out of juice it will be in Class B so the pleasant Class A distortion wont happen in this case. It will distort like all clas AB designs, by hardening the sound and manifesting harshnes.

 

[dim_span]

Class A or AB or B has nothing to do with this. Class A amps also enter clipping when they run out of power, just like Class AB designs. Only benefit in full Class A tpology is it doesn't sound as horrid (less crossover distortion).

That Pioneer is 150mV on the Tape and Aux. If you plug your CDP on it it will sound very loud and powerfull early on the volume knob and run out of power before half way. When it runs out of juice it will be in Class B so the pleasant Class A distortion wont happen in this case. It will distort like all clas AB designs, by hardening the sound and manifesting harshnes.

thanks ....

 

[hybridauth_Facebook_664715932]

How loud and with how much distortion at what position on the volume knob an amplifier gets depends on its input sensitivity and power.

Input sensitivity is the amount of power needed from a source component to drive an amplifier to its maximum power output without clipping.

If an amplifier has input sensitivity of 500mV and your standard CDP chucks out 2V in peaks, that amplifier will be already at its maximum power without clipping at a position on the volume knob sooner than 100%. Turn the knob any further and that amp will enter clipping. How sooner depends on the volume pot type, if its linear or logarithmic. If an amplifier has input sensitivity of 150mV, it will enter clipping even sooner on the volume knob. Usually already entering clipping at 10 o'clock position.

Ideally you want an amplifier with 1V input sensitivity with 2V digital sources, which leaves you plenty of usable space on the volume knob without clipping and plus extra 1V for turning it up louder on quieter tracks.

Amplifiers with input sensitivity of under say 500mV are simply trying to sound more powerful than they actually are. You turn the knob at 9 o'clock and they are so loud, you think wow this 50W amp rocks! No it doesn't. Turn the knob further and you don't get more clean power, you get clipping. It's an illusion of power.

Opposit of that an amplifier with 150W and 1V input sensitivity needs to be turned up further on the volume knob for the same amount of loudness and will give the impression of less power and less excitement or PRaT etc. It will feel dull and lazy, despite the fact it actually sounds the same as the 50W amp before pushed into clipping. 

Thanks for that, good info

 

[drummerman]

Yes, there are boring watts and exciting watts ...

... watts that make you go emotional and watts that that put you to sleep ...

 

[Vladimir]

Further reading.

 

[hybridauth_Facebook_664715932]

EVO50a are slightly different than what you mentioned. The power is rated at 8 ohm, not 4 ohm. The MF E10 might also not be as powerful as advertised: http://www.hifi-review.com/150160-musical-fidelity-elektra-e10.html.  [/quote]

Evo 50a is rated @ 55wpc @ 4ohms and 80wpc @ 8ohms

 

[Vladimir]

55wpc @ 8ohms

80wpc @ 4ohms

 

[fr0g]

Watts per channel (real WPC) makes a huge difference.

Going from a 60 WPC Arcam to a 200 WPC Lyngdorf demonstrated this pretty clearly back when I ran them.

Weedy 40/50/60 WPC amps manufacturers figures aren't gonna mean much.

 

[JoelSim]

My neighbour will tell you it isn't.

 

[Broner]

[quote ]

Evo 50a is rated @ 55wpc @ 4ohms and 80wpc @ 8ohms

[/quote]

Nope, you've got it backwards.

 

[MajorFubar]

Hence I found that the watts per c/h is irreverent to how loud a system can sound.

It appears that you are claiming that a system will sound just as loud, regardless of whether you supply the speakers with 0.000001W, 1W, 10W or 100W etc.

Amazing!

Have you patented this technology yet?

You're just being pedantic and bloody awkward for awkward's sake. It's pretty obvious what he was meaning. God there are some times when contributors on internet forums irritate the hell out of me.

 

[lindsayt]

My overall favourite sounding amp boasts a whopping total of 2 watts output.

It never clips when I use it with my biggest speakers, even at loud volumes. It runs out of puff with my least sensitive speakers. Horses for courses.

There is a slight inverse corelation in valve amps between sound quality and power output. The lower the power the better they sound. That's assuming quality of design and engineering. I've seen some technical bods talk about linearity and valves, with the most linear ones happening to be the lowest powered ones. And some technical discussion about output transformers, with them being easier to engineer for lower powered amps.

Solid state amps seem to be another kettle of fish when it comes to sound quality vs power output. With some great sounding solid state amps being high powered designs and some being mid powered.

 

[Vladimir]

BTW few months ago I heard on BBC radio that a British engineer invented a real world current based (not voltage based) amplifier. This bypasses all the issues with amplifiers ability to drive speakers. This probably requires specially designed output devices for current.

Can't wait to see a commercial version of this unit, which may not be for audio initially.

 

[Vladimir]

To put it simply, voltage determines how loud an amp goes and current determines how well the amp will maintain its voltage with different speaker impedances.

Ohms law is V = I * R. Voltage = Current * Impedance (resistance). P = V * I[/b]. Watts = Volts * Amperes.

When you set an amplifier at certain volume to play music, you are setting voltage. Music signal is voltage.

Now as speakers play, due to the nature of music, impedance changes constantly. Everytime it goes low, say 4 ohms, the amplifier needs to raise current to maintain voltage, otherwise voltage rails sag, amplifier clips, tweeters blow.

(how the ideal amplifier works)

16V = 2A * 8Ω - (16V * 2A = 32W in 8Ω, low THD)

16V = 4A * 4Ω - (16V * 4A = 64W in 4Ω, low THD)

16V = 8A * 2Ω - (16V * 8A = 128W in 2Ω, low THD)

16V = 16A * 1Ω - (16V * 16A = 256W in 1Ω, low THD)

(how the cheaply designed amplifier works)

16V = 2A * 8Ω - (16V * 2A = 32W in 8Ω, low THD)

15V = 3.75A * 4Ω - (16V * 3.75A = 60W in 4Ω, begining slight voltage sagging, high THD)

13V = 6.5A * 2Ω - (16V * 6.5A = 84.5W in 2Ω, clipping)

10V = 10A * 1Ω - (16V * 10A = 160W in 1Ω, new tweeters)

So basically for an amplifier to maintain voltage stability, it needs a good power supply. If you want louder music, you need amplifier that delivers more voltage, and to do that properly, the power supply needs to get bigger for more current delivery.

 

[andyjm]

To put it simply, voltage determines how loud an amp goes and current determines how well the amp will maintain its voltage with different speaker impedances.

Ohms law is V = I * R. Voltage = Current * Impedance (resistance). P = V * I. Watts = Volts * Amperes.

When you set an amplifier at certain volume to play music, you are setting voltage. Music signal is voltage.

Now as speakers play, due to the nature of music, impedance changes constantly. Everytime it goes low, say 4 ohms, the amplifier needs to raise current to maintain voltage, otherwise voltage rails sag, amplifier clips, tweeters blow.

(how the ideal amplifier works)

16V = 2A * 8Ω - (16V * 2A = 32W in 8Ω, low THD)

16V = 4A * 4Ω - (16V * 4A = 64W in 4Ω, low THD)

16V = 8A * 2Ω - (16V * 8A = 128W in 2Ω, low THD)

16V = 16A * 1Ω - (16V * 16A = 256W in 1Ω, low THD)

(how the cheaply designed amplifier works)

16V = 2A * 8Ω - (16V * 2A = 32W in 8Ω, low THD)

15V = 3.75A * 4Ω - (16V * 3.75A = 60W in 4Ω, begining slight voltage sagging, high THD)

13V = 6.5A * 2Ω - (16V * 6.5A = 84.5W in 2Ω, clipping)

10V = 10A * 1Ω - (16V * 10A = 160W in 1Ω, new tweeters)

So basically for an amplifier to maintain voltage stability, it needs a good power supply. If you want louder music, you need amplifier that delivers more voltage, and to do that properly, the power supply needs to get bigger for more current delivery.

At the risk of being pedantic, the force on a loudspeaker cone is due to the magnetic flux produced by the current in the voicecoil interacting with the magnetic flux of the magnet. Loudspeakers are current driven devices, not voltage.