Just curious... the "power output in the range of 20Hz to 20kHz (both channels driven)" for my receiver is 54W + 54W (8ohms harmonic distortion <0.5%). At 35W output the distortion drops to < 0.03%. I've looked at the specs for various receivers and amps and noticed the THD values can be 0.5%, 0.4% with many lower than that. At what value is there an audio difference in THD? What does the distortion sound like?
THD...Can you hear it now?
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swechsler
Frog Whisperer
When I first started getting into audio in the mid 70s, the general guideline was that 0.5% or less was considered inaudible. And you're almost never running your amp at its peak output anyway. And even more important, your speakers will most likely introduce way more distortion (audible or not) into the signal than the electronics.
This really depends on the music you listen to. A trained flutist with good ears can hear 3%. Flutes have very low harmonic content, nearly all fundamental tones. On busy music, it is much higher. If you are at 1%, it's more than adequate. Worrying about tiny numbers doesn't do any good. I remember when Technics was advertising. 003% or such THD. The receivers sounded terrible, thin, with no bass. However people wanted the low distortion rating because it was "better", even when it was audibly worse
damacman
Resident Psycho
Anyone that believes they can detect distortion levels anywhere near what conventional wisdom tells you is audible owes it to themselves to prove / disprove that. There exists media out there for just such purposes. I shall warn you though, you'll get your feelings hurt.
Imagine choosing a pair of eyeglasses based on the details you could make out on a woman's dress at 5,000ft. These right here are a magnitude sharper.
Imagine choosing a pair of eyeglasses based on the details you could make out on a woman's dress at 5,000ft. These right here are a magnitude sharper.
ejman
Super Member
I think the audibility of distortion depends on the frequency and the harmonic content of the distortion. Even high levels of 2nd harmonic distortion in the low bass at 5-10% may be difficult for most untrained listeners to discern while 1% of 5 or 7th harmonic in the low to mid treble would be quite annoying.
Pyrrho
Super Member
The answer is going to be complicated if it is accurate and precise. The amount of distortion it takes to be audible depends on many factors, including the frequencies of the distortion, as well as the frequencies that are not distortion (as having a wide range of frequencies that are part of the signal can mask the distortion; it is generally easier to hear distortion of pure test tones than complicated sets of frequencies that is typical of actual music). Generally speaking, human hearing is more sensitive to midrange frequencies than to frequencies at or near the limits of the frequency range that can be heard, so subwoofer distortion, for example, can be quite high (relatively speaking) without it being audible. So there is no simple number to give you; it depends on what frequencies we are discussing, as well as what frequencies are part of the signal that isn't distortion.
'We, the people' don't hear everything the same way..
And, I, personally do not believe anybody hears what 'the machines' hear..
Take the written specs with a grain of salt, listen to what you hear..
If it sounds distorted, start by adjusting the volume down a bit..
Then take things a step at a time, to figure out the source of that unpleasant sound.. based on your ears.. (not what is 'written')
And, I, personally do not believe anybody hears what 'the machines' hear..
Take the written specs with a grain of salt, listen to what you hear..
If it sounds distorted, start by adjusting the volume down a bit..
Then take things a step at a time, to figure out the source of that unpleasant sound.. based on your ears.. (not what is 'written')
Lavane
Lunatic Member
A small single ended tube wmp I built puts out 5.5wpc @ 5% distortion at full output. At lower volumes.its around 1%-2%. It has the worst specs of all my amps. I can't hear it. The frequency response is 40hz to 18khz. I don't notice anything missing in the low end when listening to it. But then a lot of the speakers I have roll off from around 30hz to 40hz anyway.
I have to really crank the volume on that little amp to hear any distortion.
I have to really crank the volume on that little amp to hear any distortion.
As is apparent from this ^^^ comment, there's more to an amps/recievers fidelity than just the THD spec. I suspect that more than just a few folks bought the lowest thd amp without really listening to the music coming out of it.
stereofanboy
Addicted Member
I had a boombox with 10% thd that was turned all the way up on several occasions. It sounded like ass on those occasions.
gslikker
Super Member
Most of my restored vintage amps do "sound right", even low power ones like Pioneer SA700. A small few do not.
They just give the "do not want it as my main system" feeling, one is a Beomaster 2300 and one is a ITT stereo 3700. I should try to measure distortion but there are so many things to do....
The subjective feeling is both of these receivers employ "funny" technologies, the B&O apart from other things uses LDR/lamp for volume regulation, and the ITT has a vintage Philips chipset for analog control of volume, tone controls, loudness and balance by remote control. The ITT is just what it is, I recapped it too, the B&O maybe I want to spend some time on.
They just give the "do not want it as my main system" feeling, one is a Beomaster 2300 and one is a ITT stereo 3700. I should try to measure distortion but there are so many things to do....
The subjective feeling is both of these receivers employ "funny" technologies, the B&O apart from other things uses LDR/lamp for volume regulation, and the ITT has a vintage Philips chipset for analog control of volume, tone controls, loudness and balance by remote control. The ITT is just what it is, I recapped it too, the B&O maybe I want to spend some time on.
Thorsten R.
Super Member
Years ago when I sat in our workshop working on a Pioneer CT-F850 I made some trials. I had just tuned the recorder, it was still connected to the Nakamichi T-100. A good headphone was the control gear.
I monitored the recording and levelled the recording level until I read a thd of 3 %. I noticed that there was a slight distorsion however it was not very disturbing, not unpleasant. As we know this is a magnetic distorsion similar to that which occurs in a tube amplifiers transformator when in overdrive.
Then I monitored only the electric path of the recorder. Of course the volume at the headphone was always the same. When I read 0,1 % distorsion level on the Nakamichi I tore the headphone from my ears. That was significant!
I monitored the recording and levelled the recording level until I read a thd of 3 %. I noticed that there was a slight distorsion however it was not very disturbing, not unpleasant. As we know this is a magnetic distorsion similar to that which occurs in a tube amplifiers transformator when in overdrive.
Then I monitored only the electric path of the recorder. Of course the volume at the headphone was always the same. When I read 0,1 % distorsion level on the Nakamichi I tore the headphone from my ears. That was significant!
Buying by spec is still very common. People will pass over a great 50 watt amp to buy a crappy 100 watt amp that is a gutless wonder. My favorite demo in my early days was to use a good little 20 watt receiver against a far less competently built receiver rated well north of 100 watts. The sound was fuller, and had more bass. The THD was ten times higher (like .1%) and people just couldn't wrap their heads around it. Oh, the little one was half the price, but it did have larger siblings.
It was hard for some people to let go. They would buy the clearly inferior sounding product because of brand loyalty or over reliance on specifications that didn't mean what they thought.
Artie
Super Member
Yup. The more negative feedback you dial in, the lower the THD number, and the more you quash the dynamics. People paid attention to THD numbers but not dynamic range.
I remember, back in my audio sales days, a tech rep saying that the best a cassette deck could do was around 10% THD. But I've heard, and still have, great sounding cassettes.
That would depend on how you define dynamic range. Negative feedback does not reduce dynamic range in the conventional sense.
Anyone overly concerned about THD numbers should listen to a single ended tube amp sometime. They measure absolutely terribly, but they tend to sound pretty nice.
I've listened to amps with comparatively high distortion numbers that I thought sounded good, and ones with relatively low numbers that I thought sounded bad. Some had tubes, some had transistors.
it does increase amplifier damping though. Sometimes the "looseness" that a higher output impedance (lower feedback) makes for a "fuller" sound, but IME depending on the speakers it can get very flabby in the bass department.
I've listened to amps with comparatively high distortion numbers that I thought sounded good, and ones with relatively low numbers that I thought sounded bad. Some had tubes, some had transistors.
it does increase amplifier damping though. Sometimes the "looseness" that a higher output impedance (lower feedback) makes for a "fuller" sound, but IME depending on the speakers it can get very flabby in the bass department.
Yes, quite true. I wonder if that also explains the criticism we sometimes hear about amps "having thin bass". I'm sure those amps have a flat response to down well below 20Hz, but their high damping factor would restrict the "bass flap" that other amps might allow, giving the impression of thin bass.
Just a guess.
setup1
Super Member
Artie
Super Member
It has always been my understanding that higher amounts of negative feedback contribute to higher compression. The louder an output signal, the greater amount that's negatively fead back into the differential input stage. Thus, suppressing the input signal. But, I may have that wrong.
Bill Ferris
Lunatic Member
, 