There are many consumer audio products on the market with sophiscated digital designs, such as multiple codec support, internet function, HD display...

There are large amount of elaboration of digital specification from manufracturer, but hardly found official detail about THD+N characteristic and analog performance, and some open case test say the analog circult paths in some product are not audio signal friendly, e.g. undersize/bad coupling capacitor, high noise power supply, sometimes even class B amp stages with distortion.

does it mean that
1. Manufracturers are hiding weakpoint?
2. The IC inside them as negligible THD+N defects?
3. Consumer digital audio never get good analog performance?

Think about iPod, TV HD Media Player with analog out and consumer grade Disc (CD,DVD,BD) players

You should give more details, and perhaps one specific case, so we can see what are you talking about, because now you are talking in general.

Audio technology has progressed to the point where it is not uncommon to find relatively inexpensive electronic gear that has very good technical performance. Frankly, their performance is so good that the technical specs would be boring to read.




You seem to be saying what many of us know to be true - people do sighted evaluations and then pontificate the existence of sonic problems that may be the consequence of listener prejudice, not listener sensations.

I would characterise the typical audio sound quality evaluation that one sees on the web as a report that someone listened to something, and then wrote down their free associations and their reflections on the emotions that they felt at the time. No way to tell if the gear had anything to do with any specific perceptions - perhaps they had too many drinks over lunch or dinner. Who knows?



Maybe there are no sound quality weak points to hide.




Pretty likely.



So general as to be easily dismissable on the grounds of excess generality.



Many of these products such as the iPod are sonically innocious, as commonly used. One of the worst complaints I've heard about the iPod is that if you use highly sensitive earphones with it, you can hear a faint noise when the music isn't playing. Last time I looked, it is far more important what you hear *while* the music is playing...

Another possible explanation is that many manufacturers now lack the equipment, know how or desire to perform audio performance measurements. They're just picking parts, putting them on circuit boards, giving a quick listen and assuming they are performing as advertised by the parts manufacturers.

I've visited any number of manufacturer facilities over the years, and as a rule they are at least reasonably well equipped. One exception might be small high end manufacturers, particularly those who sell "snake oil" products. Another exception might be companies that produce equipment that is basically the chip vendor's demonstration board, or "reference design". This happens not infrequently with bottom-end audio interfaces, for example.



I've tested 100's of pieces of consumer audio gear over the years, and designed and built some of my own. There are just too many ways to make a mistake. The actual gear is better than what you'd get that way. People generally at least nominally test what they sell.

While I agree in theory, spec don't mean much at all. Creative, Sony; all companies have published spec which ended up being wishful thinking at best: they publish the chips' spec, but in real-world tests, none of the hardware ever performs up to 98db s/n for instance which was a favourite of Creative to broadcast for their portable players. Driving no loads, they can get pretty good, but spec, manufacturing, single ended vs. push/pull designs have a lot to do with how signals actually reach the ears of listeners.

As for ic and that goblety gook, it only goes so far as: balanced is generally better than unbalanced and shielded is better than unshielded. Those tests, however, are easy to prove and have nothing to do with subjective listening. Where subjectivity comes in (take a look at headfi) is where a manufacturer claims something: everyone believes it, then hears it. this happens all the time. Spec, I have come to learn, means absolutely nothing, unless it has to do with vital parts like a stepped attenuator versus volume pot, optical versus analogue and balanced versus unbalanced, etc..

I have a bottom-of-the-line Sherwood home-theater receiver and I can hear noise (even with a digital input selected) from the speakers when there is no program signal (maybe some 60Hz buzz, and some sort of "digital whine").

It's not too bad, but I was kind-of surprised when I first hooked it up... I expected "silence" from a modern "digital" receiver... At most, I would have expected some amplifier hiss with my right-up to a speaker.

I mostly notice it when I walk near one of the speakers, but from my chair I can tell if the unit is on or off. (Sorry.. no blind testing was done. ) I haven't looked at the specs... I'll bet the specs "look good". Maybe my speakers are too efficient, or maybe my living room is too quiet!

I never hear any distortion (unless its present in the program source).

Volume turned up or down?

Is there any media cued up to play?

What speakers?



I also use a Sherwood, but its just a stereo model. My speakers are fairly inefficient. No noticable noise in the room.

However, I do hear buzz via my headphones. All of the audio in this system is routed through my Sony TV (volume control, source selection), and its the weakest link.

Why I produce this post is because some review critized/merited some music player (from ipod to chinese models) and AV devices analog design and performance, they might be nonsense but drived me to think about it more seriously, as a physic electonics courses inspiried me.

"Keep your PCB design neat and it works better, don't forget capacitors!"

I doubt it is the DAC that is making the noise. I have a 3000USD Pioneer surround amplifier and I still have slight noise from the speakers without signal (have to put my ear to the tweeter for it to be audible) Nothing unusual about that, The noise floor is probably so low it doesn't matter when you play music. The noise can come from grounding issues, other electric household items in your house.. etc. Probably nothing with your amplifier or its design.

Note: It was even worse when I had a 6000USD Electrocompaniet power amplifier, it had a quite loud, audible hiss/hum. when it comes to noise issues, bigger and more expensive isn't always better

I'm not home right now, and I'll need to double-check that stuff. My front speakers are home-built. I can look-up the driver specs. I think they have above average efficiency, but they are not horns. They are tall, so when I walk around, my ear can get close to the tweeters. My rear speakers are old "floor standing" Pioneer units (maybe 5-way) and they do have at least one horn. These are hanging from behind my couch, so again the speaker-to-ear distance can get pretty close when I'm walking around. And like I said, I mostly notice the noise when I walk near the speaker.

Somebody gave me the Pioneer speakers.... Like the saying goes, "They don't make 'em like that anymore!" I've looked online for some specs, but couldn't find anything. Of course, I have taken off the grill to look! (And, I've had the back panel off to install some eye bolts for hanging.)

I wouldn't think it's the actual DAC, I assume it's the analog circuitry following the DAC.

I don't think there are any grounding problems. I guess I can try disconnecting all of the inputs/outputs except the digital input and speakers. That way, the only ground will be at the digital input. (Until my DVD player died recently, I had an optical connection, so there was no ground on that input... The new one has a coax connection.)

I don't think there's anything "unusual" generating noise on my AC line, but I will try unplugging the TV which is plugged into the same (or nearby) outlet.

BTW - This isn't really a problem I was trying to solve. I was just mentioning it to say that not all modern electronics are "perfect". The noise isn't "bad", and I can live with it.... When I listen to a DVD concert in 5.1 Dolby, the sound is awesome! And, these are not classical concerts... The crowd noise drowns-out any receiver noise!

One more example is some buzz sound will come out from speaker/ headphone/ line out when a backlight is illuminated. Which I think is the switching step transformer produced electricial noise

Some answers... and some surprising results......

Just for reference, the noise level is lower than some other household background noises... The fan/air noise from the central heating is louder... Water running in the kitchen (around the corner) is louder. Since the noise is such low-level and coming from all-around, the only way I can really identify the source of the noise (from my chair) is to switch the receiver on & off with the remote. Before, I mentioned buzz and whine... There is also a hiss component.

My receiver is a Sherwood RD-6108. The specs claim a S/N ratio of 92dB for the analog inputs. (There is no noise specification for the digital inputs.)

The noise is affected by the volume control, but it's non-linear. The digital display shows volume from "MIN" to "70". At "MIN", there is no (audible) noise. But at "1" it kicks-in and is constant to about "50" (I don't know if I've ever had it turned up that loud with program material.) Above 50, the noise gets louder as I turn up the volume. At high volume settings the whine dominates.

It doesn't seem to matter. However, there is some noise (whine?) coming from (or triggered by) the digital coax input. With the volume turned-up above 50, there is less noise when I disconnect the digital input! With nothing connected to the digital or analog inputs, the noise seems about equal from the digital & analog inputs.

I tried two DVD "players" (actually recorders) and I'm getting noise out of both. One of them is hooked to the cable-TV, and with the volume cranked way-up (with DVD playback paused) I could actually hear the TV broadcast sound leaking through from its built-in tuner!!! Clearly this is one source of noise. (But, I don't hear these noise components at normal volume settings.)

The front (home built) speakers appear to have sensitivity of about 98dB@ 1W, 1M. (I don't have a sensitivity spec, but I have calibrated frequency response curves for the drivers (and for the manufacturer's recommended design). My seating position is about 2 Meters from the speakers (~10' from the front, ~8' from the back). And, the tweeters are aimed directly at me.

I still think the noise I'm hearing at low/normal volume settings is coming from inside the receiver. The noise is present with nothing connected, so that should eliminate grounding issues. I never notice the noise getting better or worse when any household appliance is turned on or off. Unplugging the TV didn't make any difference either.

the physical background noise should not be an excuse to use more noisy circult, as some house are quiet enough, or using a earbud.

I use a 2008 dell PC -> headphone at quiet night for some classical music, a small hiss/ buzz is very audible. I have to make a NIMH battery Cmoy headphone amp with amplification factor of -20db (attenuation amplifier) to reduce noise, since battery with shielding is very pure power.

This concludes there are electricial noise from the PC.

You don't need an active circuit to get -20 dB of attenuation. A passive circuit will work just as well, and it is cheaper and more reliable.

I tried a resistor circult, result is not as good as active circult

And don't go off topic.

It was you who went off-topic in the first place.


And BTW way it is utter nonsense what you are saying! The battery, its "pure power", and shielding have got nothing to do with what you are getting.

Attenuation just decreases the output device's input sensitivity. The total noise level is always made up of an absolute component, constantly being about the same level regardless of input, and a relative component, that is dependent on the input signal (only the latter is commonly published as "SNR"). When you attenuate the input signal you can raise the source's amplitude far above its absolute noise component, so that all that is left is its true relative SNR. That's all.


It's not trivial to get a passive circuit to not modify the overall frequency response. Still it is certainly possible and wasting battery power for attenuation is mindless. Probably not for the certain mindset desperately wanting to believe that he is replacing dirty powers with "pure powers".