Does the amplifier amplify the noise?

[Flakboy115]

Hello, I am new to the forum and not a expert on audio but I have read a lot about headphones DACs and amplifiers and one thing that always bothers me is that there is this tendency that people say the DAC does not matter, or at least that the amplifier is more important than the DAC.

Let's look at the following thought experiment: Imagine we have a crappy DAC that is very noisy and an amplifier that is perfect aka 0% distortion and no measurable noise. If we put a 1khz sine wave into the dac, we get let's say -100dB of noise across all frequencies (white noise is defined as not bandlimited after all). If we put a 1khz sine wave into the amp we have a clean spike at 1khz and nothing else.

If we plug the noisy DAC into the perfect amp, theorhetically it should just perfectly copy the sound of the noisy dac and just amplify the amlitude right? This means that all the noise will be proportionally amplified as well since the amplifier should not be able to tell what is noise and what is sound (or does it? *vsauce theme plays*). I know that in general, there are methods of reducing noise but they are all based on some form of low pass filtering which in our case, we obviously can't do because then our amplifier has no treble.

My conclusion would be that the bad SNR of a noisy DAC can't be removed by an amplifier, no matter how good. Of course, in the case of a perfect dac with a noisy amplifier, the amplifier would add noise to the perfect signal (that is rather obvious). So the DAC and the amp should in theory have similar noise performance so that "no performance gets wasted".

Thanks for reading and feel free to point out flaws in my train of thought.

 

[MakeMineVinyl]

An amplifier will amplify anything presented to its input jacks. It will also add noise/distortion of its own, but with a good design these would not be a concern.

 

[DVDdoug]

This means that all the noise will be proportionally amplified as well since the amplifier should not be able to tell what is noise and what is sound

Correct!

Imagine we have a crappy DAC that is very noisy and an amplifier that is perfect aka 0% distortion and no measurable noise.

'Sounds not-crappy to me!

there are methods of reducing noise but they are all based on some form of low pass filtering

It's usually more sophisticated than that but (open ended) noise reduction usually works best when you have a constant very-low-level background noise... When you don't really need it. And for best results it has to be "tweaked" for the particular situation (typically you give it a "noise fingerprint" of noise-only) so it works best on audio files and not so good with real-time processing.

My conclusion would be that the bad SNR of a noisy DAC can't be removed by an amplifier, no matter how good.

"Links in a chain."

 

[Holmz]

Hello, I am new to the forum and not a expert on audio but I have read a lot about headphones DACs and amplifiers and one thing that always bothers me is that there is this tendency that people say the DAC does not matter, or at least that the amplifier is more important than the DAC.

Let's look at the following thought experiment: Imagine we have a crappy DAC that is very noisy and an amplifier that is perfect aka 0% distortion and no measurable noise. If we put a 1khz sine wave into the dac, we get let's say -100dB of noise across all frequencies (white noise is defined as not bandlimited after all). If we put a 1khz sine wave into the amp we have a clean spike at 1khz and nothing else.

If we plug the noisy DAC into the perfect amp, theorhetically it should just perfectly copy the sound of the noisy dac and just amplify the amlitude right? This means that all the noise will be proportionally amplified as well since the amplifier should not be able to tell what is noise and what is sound (or does it? *vsauce theme plays*). I know that in general, there are methods of reducing noise but they are all based on some form of low pass filtering which in our case, we obviously can't do because then our amplifier has no treble.

My conclusion would be that the bad SNR of a noisy DAC can't be removed by an amplifier, no matter how good. Of course, in the case of a perfect dac with a noisy amplifier, the amplifier would add noise to the perfect signal (that is rather obvious). So the DAC and the amp should in theory have similar noise performance so that "no performance gets wasted".

Thanks for reading and feel free to point out flaws in my train of thought.

We can also flip the thought experiment scheme 180 degrees.

There are people that swear by such-n-such brand of a multi k$ DAC, and then shove it through some amp that makes it warm with lots of distortion. They usually talk about the “purity” of the DAC and simultaneously talk about the amp beIng musical and not clinical\, or just gloss over that the purity is intentionally lost.

 

[jcarys]

You have come to the correct conclusion. Noise is noise is noise, it doesn't matter whether it comes from the recording, the playback source, DAC, amp or speaker. They all add to the total noise (or fancy word, nonlinearity) from the original. I'm not sure where you are hearing that an amp is more important than a DAC, but you can ignore those people. What they may be getting at is that you can now buy a cheap DAC that performs beyond the ability of human hearing quite easily, while it takes a bit more effort to get an excellent amp that performs right on the edge of what a really gifted human can hear in perfect conditions. And no matter how fantastic the playback chain is, your speakers are usually going to have more noise than everything that came before them.

 

[NiagaraPete]

May the source be with you.

 

[antcollinet]

.....there is this tendency that people say the DAC does not matter....

Just a small correction. No-one says that the DAC doesn't matter. What you are probably hearing is people saying is which "well measuring" dac you choose doesn't matter.


Of course if you pick a DAC with audible noise and distortion, then that is going to be sub-optimal.

 

[Larry B. Larabee]

My conclusion would be that the bad SNR of a noisy DAC can't be removed by an amplifier,

In the above case if the dac produced noise in the ultrasonic region that folded over into the audible frequency range would that noise be eliminated if the amplifier was bandwidth limited to, let's say 100khz instead of something crazy and useless like 500khz.

 

[Killingbeans]

This means that all the noise will be proportionally amplified as well since the amplifier should not be able to tell what is noise and what is sound

Yes. If you have problems with hiss from your speakers, it can be the residual noise from your amp, or it can be the noise floor of your source being amplified.

 

[radix]

I try to increase the SINAD as I go away from the speakers. So, get your source the cleanest, then your preamp/dsp (if you have one), then your amp, then your speakers. I guess one could also extend that to the room (i.e. use room treatment).

 

[RayDunzl]

And no matter how fantastic the playback chain is, your speakers are usually going to have more noise than everything that came before them.

Do speakers (passive) make noise?

 

[ahofer]

As I understand it, a DAC has a pretty high “line” output of around 2 volts, so most people listen to the DAC signal attenuated by the preamplifier, then amplified at the main amp. Whereas phono cartridges particularly moving magnet, with output of 3-6 millivolts) have to be amplified a lot in the preamp stage, and small amounts of noise do indeed get blown up more.

(corrected for obvious mistake)

 

[tvrgeek]

Hello, I am new to the forum and not a expert on audio but I have read a lot about headphones DACs and amplifiers and one thing that always bothers me is that there is this tendency that people say the DAC does not matter, or at least that the amplifier is more important than the DAC.

Let's look at the following thought experiment: Imagine we have a crappy DAC that is very noisy and an amplifier that is perfect aka 0% distortion and no measurable noise. If we put a 1khz sine wave into the dac, we get let's say -100dB of noise across all frequencies (white noise is defined as not bandlimited after all). If we put a 1khz sine wave into the amp we have a clean spike at 1khz and nothing else.

If we plug the noisy DAC into the perfect amp, theorhetically it should just perfectly copy the sound of the noisy dac and just amplify the amlitude right? This means that all the noise will be proportionally amplified as well since the amplifier should not be able to tell what is noise and what is sound (or does it? *vsauce theme plays*). I know that in general, there are methods of reducing noise but they are all based on some form of low pass filtering which in our case, we obviously can't do because then our amplifier has no treble.

My conclusion would be that the bad SNR of a noisy DAC can't be removed by an amplifier, no matter how good. Of course, in the case of a perfect dac with a noisy amplifier, the amplifier would add noise to the perfect signal (that is rather obvious). So the DAC and the amp should in theory have similar noise performance so that "no performance gets wasted".

Thanks for reading and feel free to point out flaws in my train of thought.

Yes, there are those who say the DAC does not matter. Their belief. Some of us know that is not true. I know the Atom DAC+ has a smoother midrange and less "glare" than my Schiit, Topping, Muse, or Focusrite.

You are correct in your thinking. Amplifiers amplify. It takes magic to remove noise or distortion. For that you need to leave ASR and go to the glossy page magazines where the reviewer raves about speaker jumpers. ( advertised on the back page of course)

Personally, I think small amplifiers have been solved and many good ones, but I don't own $5000 headphones. Not sure you are going to get a cleaner head amp than the Topping or JDS. Even my Schiit. I hear nothing wrong and they all measure at levels that are hard to believe.

 

[AnalogSteph]

The crux of the matter is that, absolutely speaking, the standards for DACs these days are quite high. You do not have to look very hard at all to find one that provides better dynamic range than any existing acoustic recordings of music. If the amplifier following sports a volume control, you want something like 90+ dB worth of dynamic range... maybe 103 dB with headroom for EQ and stuff. Demands are higher if you insist on driving fixed-gain power amplifiers directly, you're generally looking at 110+ dB at this point, plus potentially some more to make up for level/gain mismatch in the whole DAC / amp / speaker chain. But even that is not at all unaffordable these days.

Standards for frequency response flatness and periodic filter ripple tend to be fairly high as well, although a few exceptions with somewhat poor filter choices exist. You have to try pretty hard for a DAC to have audible levels of distortion, too.

The amount of instantaneous dynamic range that you absolutely need in a DAC can be quite modest if it is followed by a volume control. It's the difference between peak SPL and desired noise floor at the same volume setting, plus the odd dB of headroom. If you find that you want peak levels in the low 90s dB SPL and a noise floor in the 4 dB SPL vicinity at the same time, your dynamic range requirements may only be 90-95 dB. 1980s CD player terrain.

This is why even a lot of relatively modest onboard audio chips of roughly the last decade are perfectly acceptable on the D/A side, including e.g. the lowly ALC887. Far from SOTA for sure but adequate for the intended use. My new computer sports a midrange level ALC1200 codec, rated 110 dB on the D/A side and 1.1 Vrms out... RMAA says 105 dB(A) in loopback (presumably limited by the A/D side), with negligible filter ripple on the D/A side. The thing sounds just as fine as my old Asus Xonar D1, I just have to turn up the volume a bit more since maximum output is lower.

There are lots of outputs that are at least acceptable on DAC performance but struggle with driving headphones adequately for one or more reasons - a headphone amplifier is my go-to recommendation then, since it allows addressing a wide range of shortcomings, including high absolute noise level, poor load driving, high output impedance and just not enough output level full stop.

DACs may vary quite a bit at levels of 0 dBFS or even beyond. Keep away from full-scale a bit, which is easily done on a computer (you may want to have playback volume levelling anyway, which has the side effect of turning down problematic hot recordings), and there's that problem sorted. Those who need a DAC specifically for a CD/DVD/BD player may have to look more closely (either avoid ASRC and certain DAC types or insist on digital volume control built-in).

Really, DACs are some of the most mature links in the chain. Tons of them are transparent. Now speakers and headphones on the other hand...

 

[Holmz]

In the above case if the dac produced noise in the ultrasonic region that folded over into the audible frequency range would that noise be eliminated if the amplifier was bandwidth limited to, let's say 100khz instead of something crazy and useless like 500khz.

Maybe, maybe not.
The IMD likely gets mostly folded into the ultrasonic range, but one needs to know where it is to work it out exactly.

 

[JSmith]

Some of us know that is not true.

Proof please... where is your controlled ABX result? Without same, it's simply your perception and you cannot prove it to anyone else.


JSmith

 

[BoredErica]

My question is, does difference between good and stellar dac really not make any possible audible difference? Say I have a dac and I hooked it into a power amp with high gain so the power amp can drive very sensitive speakers, and I want to not be able to hear noise with ear 1 inch from the tweeter in a noise controlled environment (house has sound isolation treatments or recording booth)?

For 99% of people that's a totally crazy use case, but I'm just saying. Are dacs *that* superb? Who cares what sinad an audio interface has, get the cheapest one with the right features/etc?

 

[Holmz]

My question is, does difference between good and stellar dac really not make any possible audible difference? Say I have a dac and I hooked it into a power amp with high gain so the power amp can drive very sensitive speakers, and I want to not be able to hear noise with ear 1 inch from the tweeter in a noise controlled environment (house has sound isolation treatments or recording booth)?

For 99% of people that's a totally crazy use case, but I'm just saying. Are dacs *that* superb? Who cares what sinad an audio interface has, get the cheapest one with the right features/etc?

In ^that example^, you would want to make sure that the amplifier without the DAC allows you ear to be within 25mm of the tweeter.

The noise and the distortion both make up SINAD…
I don’t like a hissing amp at all.
A non linear amp with lots of distortion can still sound good compared to a hissing amp.

 

[DanielT]

OT,
Old amplifiers can have humming transformers that sound in themselves. A humming sound that comes directly from the amplifier / transformaton ,. that is, no hum that is passed on in the chain to the speakers / headphones. There is a constant level of hum, regardless of volume. If you get annoyed at it, it's a matter of taste. That sound, hum, is drowned, most often, at increased volume.

I think the risk of this is reduced with ring core transformers.If I'm wrong about that, feel free to correct me.

Edit:
By the way, I have tried to reduce that type of hum on an old NAD3020 amp. With extra screws between chassis and transformer, rubber plates between transformer and chassis. It did not help.Used, a lot of sound for the money but new Hifi undeniably has its advantages.

More ideas about it:

Mechanical Transformer Hum

Hi All One of my BGW 750s transformer is emitting a predominantly 240 hz hum. I`ve researched the subject however, most solutions target DC induction on the powerline, which is not the case here as another identical, albeit younger amp on the same line is dead silent. I`m guessing some windings...

www.diyaudio.com

 

[JSmith]

My question is, does difference between good and stellar dac really not make any possible audible difference?

Depends... headroom is a thing, like 10 - 15db


JSmith