Amp power and SNR measurements

[Groove01]

You're judging by wattage rating alone? Weird.

Helpful

 

[Chrispy]

Helpful

Rather know the original logic/thought....he seems to make some odd assumptions in any case.

 

[Groove01]

Rather know the original logic/thought....he seems to make some odd assumptions in any case.

Maybe just ask that…

 

[Cbdb2]

because their speakers self noise will dominate,

Speakers dont make noise by themselfs

 

[EngineerNate]

You're judging by wattage rating alone? Weird.

No?

 

[EngineerNate]

Speakers dont make noise by themselfs

Sorry meant distortion "noise", since the speakers are almost always the weakest link on that front.

Got mixed up with microphone self noise, been watching a lot of Julian Krause.

 

[Cbdb2]

At the end of the day with no standards in amplifiers as far as gain, it it is difficult to have a test scenario that is 100% proper.

Gain depends on power output, dont you mean sensitivity, the input voltage for full output?

 

[Chrispy]

No?

No? Yes? Dunno. Might at least sort of line up some other common aspects/specs than wattage alone or the weird "PA" thing.

 

[amirm]

Gain depends on power output, dont you mean sensitivity, the input voltage for full output?

No. I am testing at 5 watts so sensitivity for full power is not the number but of course, they are related.

 

[Cbdb2]

That's not taking into account the fact that to get high power levels often means paralleled output devices, which inherently increases noise as well.

Almost all the noise in an amp comes from the input stage and the power supply.

 

[Cbdb2]

No. I am testing at 5 watts so sensitivity for full power is not the number but of course, they are related.

I think I got it. The input voltage to get 5 watts out depends on sensitivity so its different for diffrent amps, ie no standard.

 

[EngineerNate]

Almost all the noise in an amp comes from the input stage and the power supply.

Yes I was talking about this with an EE friend and he said much the same.

How much does scaling power capability make making the power supply quiet harder?

 

[EngineerNate]

No? Yes? Dunno. Might at least sort of line up some other common aspects/specs than wattage alone or the weird "PA" thing.

When I say PA amps I'm generally referring to big rack mount units, often with fans, generally meant to be installed in pro sound applications. Behringer A800 or a Crown K2 for example.

Generally speaking I don't see near kilowatt output from hifi stuff outside big sub amps and super niche stuff that costs as much as a car.

 

[David_M]

For decades (70s), even till today, the FTC has always mandated SNR to be measured at 1W for all amplifiers into 8 ohms. That way, all amps of various wattage could be easily compared to one another. The other SNR measurement was at full load. This has been and still is the golden standard. SNR measurements at 5W rating are unique to Amir only.

 

[wwenze]

Yes I was talking about this with an EE friend and he said much the same.

How much does scaling power capability make making the power supply quiet harder?

A 3000W power supply can be as quiet as a 300W unit. With SMPS there are standards to conform to regardless of wattage, with linear regulators they're too quiet to begin with. (Noting that Topping and Benchmark both use SMPS for their amps and the end result has high SNR)

 

[babadono]

Sorry meant distortion "noise", since the speakers are almost always the weakest link on that front.

almost always...no ALWAYS..in sound REPRODUCTION at least

 

[amirm]

For decades (70s), even till today, the FTC has always mandated SNR to be measured at 1W for all amplifiers into 8 ohms.

There is nothing in FTC about SNR.

This has been and still is the golden standard. SNR measurements at 5W rating are unique to Amir only.

I assume you mean THD+N. If so, that was a de-facto practice, not a standard. It was for a time when 50 watt amplifiers were powerful and speaker sensitivity was very high due to large cabinets and such. Today, neither assumption is correct. We have tons of power in amplifiers and small cabinets have made speakers much less sensitive. Furthermore, noise would dominate 1 watt measurements with little contribution from distortion. At 5 watts, they both play a strong part and hence the reason I chose.

 

[LSPhil]

Even when we want to compare two voltages, for example 2V vs 1V, the difference is 6dB. But compare two powers, 2W vs 1W, the difference is 3dB. Yea audio is weird.

If I double the voltage, that corresponds to a +6 dB increase.
At the same time, the power also increases by exactly the same +6 dB.
That’s because power is proportional to the square of voltage — so doubling the voltage results in four times the power, which equals +6 dB (since 10 × log₁₀(4) = 6 dB).
For example, the TPA3116 runs happily at 24 V and delivers about 60 W into 4 Ω, while its bigger brother, the TPA3255 runs happily at 48 V, cranks out around 240 W into 4 Ω.
Same family, just one clearly had a few more cups of coffee before going to work

 

[antcollinet]

If I double the voltage, that corresponds to a +6 dB increase.
At the same time, the power also increases by exactly the same +6 dB.
That’s because power is proportional to the square of voltage — so doubling the voltage results in four times the power, which equals +6 dB (since 10 × log₁₀(4) = 6 dB).

Exactly - the whole point of the definition of dB being 10x.... for power and 20x..... for voltage/current - is that it results in the same db.

3dB increase in voltage (x √2 )- results in 3dB increase in power (x2) for the same load.
6dB increase in voltage (x 2) - results in 6dB increase in power (x4) for the same load.