shooter said:
Have to disagree. A passive volume control adds distortion as phase distortion. As a general rule, its the impedance limitations of the typical high end volume pot that causes the poor reproduction of dynamics and high frequency loss, also keep in mind that even the slightest unevenness in frequency response or phase distortion will add a false sense of dynamics since the apparent volume of the playback will vary as the pitch of the music varies, these factors add muddiness to the sound. There are better pots than others but even the best has degrees of the above.
I must admit I'm no expert in electronics. I just strive to learn as much as I can because I really like to know how thing work and why. and it also helps me to make more informed buying decisions
. I must admit that this concept of phase distortion is new and bizarre to me . I mean, to my knowledge, resistor, unlike coils and caps, are those passive components that don't induce any phase irregularities, but I may be wrong. could you post a link to an article describing in more detail how passive volume ctrl contributes to phase distortion? I once read about phase distortion in cables when there got so hot around Tellurium Q cables. from what I found phase distortion is a problem but in a many hundred miles long lines. nothing to do with lenghts associated with speakers. so I can't see how a resistor could make problems here? furthermore, as I mentioned before coils and caps do induce phase shifts of various degrees but it's down to proper design to cancel those shifts out at the output...
shooter said:
Reagarding dithering, yes its quantization steps and has nothing to do with SNR. The idea about dithering is to de-correlate the quantization error from the audio signal. If the dither noise is added to the 24 bit sample after the level control and befor the re-quantixation to 16 bits, the quantixation erro can be fully cecorrelated from the signal. This means instead of distortion there is noise, the music in undistorted.
There is a different method and the more elaborate dithering shape the noise in such a way that is is mainly at higher frequencies where the human ear is less sensitive. This means the audible noise is much lower.
:shifty: :cheers:
and what if you're listening to music at so low volume levels that dither becomes a problem?
I was doing some maths today. I'd rather not repeated here as there's too much explaining what's what. anyway, it turns out you can enjoy a massive orchestral work with 25dB dynamic range from a typical 80Wpc class AB amp and 85dB/1W/1m sensitive speakers. it's going to be at full tilt but no clipping and volume level should reach at 4m 102dB peak from two speakers and 77dB low, which quite nicely represents situation in the middle of a big concert hall. however, if you're listening to more dynamically restrained music or just let the music play in back ground you won't be able to listen at full tilt as it's going to be too loud. with 10dB dynamic range you'll get 102dB peak and 92dB low. this is quite loud. 85dB for a long time will cause hearing loss and you have to raise your voice in order to talk. so you'll attenuate about 10dB for loud but quite comfortable listening (unless you're masochist
) and about 20dB or more for background listening. this, I think, should cause no problems.
another story is with very sensitive speakers. say 100dB. for the symphonic work you'll attenuate by 20dB in order to match volume levels from first example (123dB peak and 98dB low is waaaay to loud for anybody to bear without incurring penalties). this gives 30dB attenuation for low dynamic range music and 40dB or more for background music.
but. this may be remedied. if you choose low gain power amp with high sens speakers. in my case 2Wpc (!) will be capable of the same performance as 80Wpc with 85dB sens speakers. you won't have to attenuate too much so you won't have to be worried too much about dither noise.
so. digital volume ctrl can be good with the right components down the chain. it's all down to careful picking what's best. it seems like it's bad idea to match hi gain amps with sensitive speakers.
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