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signal to noise ratio

1800 Views 20 Replies 8 Participants Last post by MichaelJHuman, Feb 13, 2008

jlafrenz

Discussion Starter · Jan 19, 2008

I have recently been comparing amps and of course I am looking for something with a clean sound. I am well aware that the higher the dB rating for signal to noise ratio means there is less audible signal noise, and there for, a cleaner amp. I am wondering if there is a point at which the difference is inaudible?

1 - 20 of 21 Posts

M Code

· #2 · Jan 19, 2008

If you are referring to the signal-to-noise specification for a component audio power amplifier, I would not worry so much about this.

Yes..

It is a crucial specification but if it is a well-respected, established audio quality brand it will do fine.

The key specification is really input sensistivity for full-rated power output..

This should be matched to whatever preamp/controller and its respective output voltage you going to be using it with..

Just my $0.02..

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jlafrenz

Discussion Starter · #3 · Jan 19, 2008

Thanks for the response. I will admit that I am not familiar with input sensitivity and what to look for. I did a google search and did not clear much up for me. What do I want to look for as far as input sensitivity? On amp ratings I see input sensitivity/impedance and then it is stated in volts/ohms. Do I want higher or lower numbers here? or am I missing a bigger picture?

jlafrenz

Discussion Starter · #4 · Jan 21, 2008

Any takers?

MichaelJHuman

· #5 · Jan 21, 2008

It would vary by listener, I would guess. I stopped worrying about receiver specifications years ago. They never gauranteed great sound in my opinion. And there are other specs that are important. But no real agreement on the whole topic of the importance of specs, which ones are important, at what point the differences are inaudible and whether specs should be peferred over listening tests.

JorgeLopez11

· #6 · Jan 21, 2008

Quote:
Originally Posted by jlafrenz /forum/post/0

I have recently been comparing amps and of course I am looking for something with a clean sound. I am well aware that the higher the dB rating for signal to noise ratio means there is less audible signal noise, and there for, a cleaner amp. I am wondering if there is a point at which the difference is inaudible?

IMO 99.9% of current designs have a S/N ratio so good all of them can be considered "clean".

SOME of them may have a very particular sonic signature that SOME people tend to prefer ("warm" versus "analytic", for instance), but that does not have anything to do with the S/N spec.

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jlafrenz

Discussion Starter · #7 · Jan 21, 2008

Seems like a reoccurring theme... Demo the amps and let your ears decide. This is what I well end up trying to do. I still would like to know more about these ratings for my own personal knowledge. When it comes to input sensitivity and impedance, are higher or lower number better?

Bob Lee (QSC)

· #8 · Jan 21, 2008

Quote:
Originally Posted by M Code /forum/post/12863767

The key specification is really input sensistivity for full-rated power output..

This should be matched to whatever preamp/controller and its respective output voltage you going to be using it with..

They do not need to match; the preamp should be capable of output equal to or--preferably--greater than the amp's input sensitivity spec.

jlafrenz

Discussion Starter · #9 · Jan 21, 2008

When looking at amps I see that some have an input sensitivity of 1.0v and others have 1.4v. Which is the better rating and why?

MichaelJHuman

· #10 · Jan 21, 2008

I believe a lower input sensitivity on an amp can be beneficial. I believe 1.0 means you need 1 volt of input to drive the amplifier to it's maximum unclipped output, where 1.4 means you need 1.4 volts.

DonoMan

· #11 · Jan 21, 2008

Quote:
Originally Posted by JorgeLopez11 /forum/post/12884741

IMO 99.9% of current designs have a S/N ratio so good all of them can be considered "clean".

SOME of them may have a very particular sonic signature that SOME people tend to prefer ("warm" versus "analytic", for instance), but that does not have anything to do with the S/N spec.

For your first point, no, hiss can still be heard with a lot of todays equipment. My Pioneer Elite 91 isn't bad but is audible slightly. My Emotiva LPA-1 has more and the noise can actually bother me if I forget to turn it off before bed.

Your second point is just wrong. It's in your head and in the heads of everyone claiming that.

JorgeLopez11

· #12 · Jan 21, 2008

Quote:
Originally Posted by DonoMan /forum/post/0

For your first point, no, hiss can still be heard with a lot of todays equipment. My Pioneer Elite 91 isn't bad but is audible slightly. My Emotiva LPA-1 has more and the noise can actually bother me if I forget to turn it off before bed.

Are you sure it is just hiss or hum?

Quote:
Your second point is just wrong. It's in your head and in the heads of everyone claiming that.

Mmmmm... Can you tell me why I am wrong on this?

DonoMan

· #13 · Jan 21, 2008

Quote:
Originally Posted by JorgeLopez11 /forum/post/12886961

Are you sure it is just hiss or hum?

Mmmmm... Can you tell me why I am wrong on this?

Hiss/hum are part of SNR. Any kind of noise is included. Hiss/hum are the most common.

Can you tell me how 2 amps that are flat throughout the audible range and have negligible distortion figures can possibly sound warm, analytical, or otherwise different?

Bob Lee (QSC)

· #14 · Jan 21, 2008

Quote:
Originally Posted by jlafrenz /forum/post/12886053

When looking at amps I see that some have an input sensitivity of 1.0v and others have 1.4v. Which is the better rating and why?

If you have, say, an iPod or portable CD player driving the amp directly, then the 1.0 volt input sensitivity might be the better choice.

If you have something with a stronger output driving the amp inputs, then the higher one should be fine.

M Code

· #15 · Jan 21, 2008

Quote:
Originally Posted by Bob Lee (QSC) /forum/post/12885786

They do not need to match; the preamp should be capable of output equal to or--preferably--greater than the amp's input sensitivity spec.

That why the Preamp/controller needs to have adequate output level capability..

If the output level is too low...

Then its noise floor will increase significantly as its gain is increased.

Additionally one must consider the dynamic range swing as well...

Also one must consider the amplifier's input gain stage too..

If set too high and the output swing of the Preamp is too high..

A couple of things may happen..

Clipping may occur either in the output stage of the preamp, and/or overdriving the amplifier's input stage..

End result.

Is that clipping can be detrimental especially for loudspeakers, such as high frequency tweeters..

The challenge today is when mixing components of different brands and country of origin, design philosophy differences may exist...

A good example, is for a CD or DVD player's audio output level. The standards specify 2V (RMS) as the norm but in reality, it may be as low as 0.5V or as high as 2.5V. This is one of the reasons that in the higher end consumer products (AVRs & processors), often there is an input adjustment panel so that each source will have an equal, perceived loudness.

Just my $0.02..

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JorgeLopez11

· #16 · Jan 22, 2008

Quote:
Originally Posted by DonoMan /forum/post/0

Can you tell me how 2 amps that are flat throughout the audible range and have negligible distortion figures can possibly sound warm, analytical, or otherwise different?

Ok. I think we agree on this. That's why I said SOME people prefer a particular amplifier sonic characteristic, regardless of its S/N ratio spec.

The most notorious claims are related to "warm" or "musical" amps usually opposite to "cold" or "analytical" amps even if those amps are flat or has the same S/N, THD... you name it. It is the usual tube versus SS debate.

I do not subscribe to this POV.

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WakJob

· #17 · Feb 13, 2008

I was about to post the same question.

So all things being equal, if:

Amp 1

SNR: > 107 dB below rated power into 4Ω

Input Sensitivity: 1.23 volts (+4 dBu) for rated power into 4 ohms

Amp2

SNR: > 100 dB below rated power into 4Ω

Input Sensitivity: 1.15 V (+3.4 dBu) for rated power into 4 ohms

Is either amp significantly better when fed by a descent home theater preamp?

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FMW

· #18 · Feb 13, 2008

Firstly, the signal to noise ratio has nothing to do with the signal. It refers to the difference in db between the signal and the component's internal noise. You could consider anything with a S/N ratio of 75 db or more to be quiet under normal listening conditions.

If two amplifiers have the same S/N ratio, frequency response curve and inaudible distortion, they will sound the same as long as they are being used within their design parameters. If there is an audible difference between two amplifiers, then the causes of that difference can be measured. In fact inaudible differences can be measured.

FMW

· #19 · Feb 13, 2008

Quote:
Originally Posted by WakJob /forum/post/13096578

I was about to post the same question.

So all things being equal, if:

Amp 1

SNR: > 107 dB below rated power into 4Ω

Input Sensitivity: 1.23 volts (+4 dBu) for rated power into 4 ohms

Amp2

SNR: > 100 dB below rated power into 4Ω

Input Sensitivity: 1.15 V (+3.4 dBu) for rated power into 4 ohms

Is either amp significantly better when fed by a descent home theater preamp?

Not for that reason. Both have inaudible noise floors. One amp could be better than another if it is more powerful than the other and if that power is necessary for the application.

FMW

· #20 · Feb 13, 2008

Quote:
Originally Posted by JorgeLopez11 /forum/post/12889766

Ok. I think we agree on this. That's why I said SOME people prefer a particular amplifier sonic characteristic, regardless of its S/N ratio spec.

The most notorious claims are related to "warm" or "musical" amps usually opposite to "cold" or "analytical" amps even if those amps are flat or has the same S/N, THD... you name it. It is the usual tube versus SS debate.

I do not subscribe to this POV.

Yes. Amplifiers should not have a sonic characteristic. Designers aim to have the amplifier increase the amplitude of the waveforms without changing their shape or adding any additional waveforms. Fortunately, they succeed at this almost every time. If you like to alter the frequency response of the system then a tone control or equalizer will do that for you. It is a better solution than a "colored" component because it is adjustable.

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