How Much THD Is Bad?

[Aaron Bilger]

So I have a Crown XLi 800 amplifier I use on my HI-FI speakers and wanted to know how bad is THD 0.5% on those kind of speakers i'm not going to say what kind but it's what anyone would use in a Home Theater or even my PA speakers I use when I want to play loud?

 

[WaynePflughaupt]

I’ve always heard that THD isn’t audible until it gets higher than ~3%.

Regards,
Wayne A. Pflughaupt

 

[lovinthehd]

Consider that it's a rating, not necessarily what it always does at all levels. Your speakers likely have significantly more distortion....

 

[Aaron Bilger]

I’ve always heard that THD isn’t audible until it gets higher than ~3%.

Regards,
Wayne A. Pflughaupt

Consider that it's a rating, not necessarily what it always does at all levels. Your speakers likely have significantly more distortion....

Thanks I was wondering so most tests are done at 1℅ distortion right before clipping or something I know this is for a car amp but not sure about amplifier for home/DJ use?

 

[MR.MAGOO]

If the Total Harmonic Distortion sounds bad, it is!

 

[Mike Ruby]

Distortion is not all the same. Most tube amps and some class A amps don't produce the odd order harmonic distortion that most solid state amps produce.

 

[slipperybidness]

General rule when designing a power amp is to keep THD less than 0.1%, and that should be attainable. In general, up to 1% is likely acceptable (maybe starting to get audible).

But, the THD for the electronics will be much lower than THD for the speakers.

Very general statement: for most modern SS amps (i.e. well designed amps), THD will be fine as long as you aren't pushing the amps past their limits.

 

[Mike Ruby]

I thought this was an interesting thought that I dug out of my 20yr old pass labs aleph 3's owners manual( 30watt/8ohm 1%. To quote Nelson Pass
There has been a failure in the attempt to use specifications to characterize the subtleties of
sonic performance. Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.
Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest
THD, or the highest slew rate, or the lowest noise, has not become a classic or even been
more than a modest success.
For a long time there has been faith in the technical community that eventually some objective
analysis would reconcile critical listener's subjective experience with laboratory measurement.
Perhaps this will occur, but in the meantime, audiophiles largely reject bench specifications as
an indicator of audio quality. This is appropriate. Appreciation of audio is a completely
subjective human experience. We should no more let numbers define audio quality than we
would let chemical analysis be the arbiter of fine wines. Measurements can provide a
measure of insight, but are no substitute for human judgment.

 

[slipperybidness]

I thought this was an interesting thought that I dug out of my 20yr old pass labs aleph 3's owners manual( 30watt/8ohm 1%. To quote Nelson Pass
There has been a failure in the attempt to use specifications to characterize the subtleties of
sonic performance. Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.
Historically, that amplifier offering the most power, or the lowest IM distortion, or the lowest
THD, or the highest slew rate, or the lowest noise, has not become a classic or even been
more than a modest success.
For a long time there has been faith in the technical community that eventually some objective
analysis would reconcile critical listener's subjective experience with laboratory measurement.
Perhaps this will occur, but in the meantime, audiophiles largely reject bench specifications as
an indicator of audio quality. This is appropriate. Appreciation of audio is a completely
subjective human experience. We should no more let numbers define audio quality than we
would let chemical analysis be the arbiter of fine wines. Measurements can provide a
measure of insight, but are no substitute for human judgment.

Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.

Right, but the JOB of an amp is NOT to sound "nice". The JOB of an amplifier is to ACCURATELY REPRODUCE THE INPUT SIGNAL AT THE OUTPUT (WITH A LARGER AMPLITUDE).

To put this into a form similar to that comment from above:
products with higher power, wider bandwidth, and lower distortion will produce a more accurate signal at the output

If you want to get a "nicer sound" then the component to do that JOB will be in the chain BEFORE the amplifier.

 

[Mike Ruby]

I find my old pass amp to have more resolution than my bryston 9BSt. Pass amp doesn't have as much power but just compresses when you hit its limits (30 watt/channel 8ohm 60 watts/4 stable on a short) I really don't think you can mistake the difference between the two with a good source.
It's terribly inefficient, it idles at 240watts doing nothing but heating my home and it takes 30 minutes before it heats up and the measurable distortion goes down. It was interesting to listen to the performance change as it reached ideal operating temp. Ultra simple circuit that was very well executed.

I've always made decisions in my system based upon listening. My point being that specs don't always correlate into better sound.

 

[M Code]

Though there are differences in amplifiers depending upon brand/model/price...
IMHO...
The bigger variable is the loudspeakers..
Evaluating/concluding about an amplifier's sonic capabilities based upon lab tests and/or published specs has minimal merit...
Each loudspeaker depending upon its electrical design and x-over can/will load an amplifier differently which results in varying audibile performance delivery... A loudspeaker presents a complex, inductive load to the amplifier which is significantly different than a bench-test load resistor... Many of the advised audible differences in amplifiers is not the amplifier design/topology but rather the threshold settings of current/protection circuits or power supply limitations...

Just my $0.02...

 

[Jeffrey S. Albaugh]

If you have the lossless formats (DTS HD Master, Dolby True HD), with modern test equipment you cannot measure THD. Translation: They have 0 THD. Unmeasurable. How much better can it get then that?

 

[Aaron Bilger]

If the Total Harmonic Distortion sounds bad, it is!

If you have the lossless formats (DTS HD Master, Dolby True HD), with modern test equipment you cannot measure THD. Translation: They have 0 THD. Unmeasurable. How much better can it get then that?

Though there are differences in amplifiers depending upon brand/model/price...
IMHO...
The bigger variable is the loudspeakers..
Evaluating/concluding about an amplifier's sonic capabilities based upon lab tests and/or published specs has minimal merit...
Each loudspeaker depending upon its electrical design and x-over can/will load an amplifier differently which results in varying audibile performance delivery... A loudspeaker presents a complex, inductive load to the amplifier which is significantly different than a bench-test load resistor... Many of the advised audible differences in amplifiers is not the amplifier design/topology but rather the threshold settings of current/protection circuits or power supply limitations...

Just my $0.02...

I find my old pass amp to have more resolution than my bryston 9BSt. Pass amp doesn't have as much power but just compresses when you hit its limits (30 watt/channel 8ohm 60 watts/4 stable on a short) I really don't think you can mistake the difference between the two with a good source.
It's terribly inefficient, it idles at 240watts doing nothing but heating my home and it takes 30 minutes before it heats up and the measurable distortion goes down. It was interesting to listen to the performance change as it reached ideal operating temp. Ultra simple circuit that was very well executed.

I've always made decisions in my system based upon listening. My point being that specs don't always correlate into better sound.

Amplifiers with similar measurements are not equal, and products with
higher power, wider bandwidth, and lower distortion do not necessarily sound better.

Right, but the JOB of an amp is NOT to sound "nice". The JOB of an amplifier is to ACCURATELY REPRODUCE THE INPUT SIGNAL AT THE OUTPUT (WITH A LARGER AMPLITUDE).

To put this into a form similar to that comment from above:
products with higher power, wider bandwidth, and lower distortion will produce a more accurate signal at the output

If you want to get a "nicer sound" then the component to do that JOB will be in the chain BEFORE the amplifier.

Ok so then is there a way for me to quiet down the pink/white noise I hear when I turn the volume up on the amp I hear from the speakers. Now all amps will do this to some extent but my amp is beside me and my speakers are beside me at my computer desk and if I turn the volume up and not playing any audio then is there any kind of way to quiet that pink/white noise whatever that noise is it is faint when at normal use but then I connect my preamp no change in pink/white noise until I turn the volume up halfway to match a certain loudness to work with other settings and subwoofers?

 

[slipperybidness]

Ok so then is there a way for me to quiet down the pink/white noise I hear when I turn the volume up on the amp I hear from the speakers. Now all amps will do this to some extent but my amp is beside me and my speakers are beside me at my computer desk and if I turn the volume up and not playing any audio then is there any kind of way to quiet that pink/white noise whatever that noise is it is faint when at normal use but then I connect my preamp no change in pink/white noise until I turn the volume up halfway to match a certain loudness to work with other settings and subwoofers?

OK, now we may be getting somewhere. I believe what you are describing is noise, not THD.

In particular, can you tell if the noise is coming from the tweeters?

My goal is to be able to pause my source and turn all of my gains (volume knobs) to the very highest setting, then put my ear right on the tweeter, and hear complete and total silence.

I can't always achieve that, but it is certainly my goal. If I can't achieve that, then at the very least I want to turn the volume to the max level that I will be listening, then pause the source, and have complete silence.

When you have audible noise or hiss, this tends to be a problem with the gain structure of your system. Depending on your setup, there could be some other issues at work here.

If you want help and advice, I suggest listing out your equipment, how it is connected, the cables in use, and what your specific problems and goals are. The answer may be as simple as adjusting the gain down on that amp.

This is a PC setup? How are you connected from the PC to the audio chain? At a first guess, the problem likely lies with PC or the PC connection, not likely the amp.

EDIT: I see that amp has a sensitivity switch on the back. What setting do you use? Have you tried the other setting?

 

[Aaron Bilger]

OK, now we may be getting somewhere. I believe what you are describing is noise, not THD.

In particular, can you tell if the noise is coming from the tweeters?

My goal is to be able to pause my source and turn all of my gains (volume knobs) to the very highest setting, then put my ear right on the tweeter, and hear complete and total silence.

I can't always achieve that, but it is certainly my goal. If I can't achieve that, then at the very least I want to turn the volume to the max level that I will be listening, then pause the source, and have complete silence.

When you have audible noise or hiss, this tends to be a problem with the gain structure of your system. Depending on your setup, there could be some other issues at work here.

If you want help and advice, I suggest listing out your equipment, how it is connected, the cables in use, and what your specific problems and goals are. The answer may be as simple as adjusting the gain down on that amp.

This is a PC setup? How are you connected from the PC to the audio chain? At a first guess, the problem likely lies with PC or the PC connection, not likely the amp.

EDIT: I see that amp has a sensitivity switch on the back. What setting do you use? Have you tried the other setting?

My amp is on the 0.775v sensitivity and I did some testing first test was to disconnect the signal wire from the computer and then turn the amp all the way up and there was no issue there and then I connect my phone up the the amp from the signal and no issue there I connect a different phone for the signal and no issues there and last was to connect it to a different PC and no issues there it is my PC it's a desktop PC and it does not have a separate sound card it uses on board sound and here in a week I will be buying me a new sound card and I really hope that fixes that. If you wanted to know what sound card I will be buying it is a CREATIVE LABS Sound Blaster Z PCIE.

 

[lovinthehd]

Try the 1.4V sensitivity instead and see if that reduces noise (as in signal to noise ratio, its not THD). Probably a sound card issue....

 

[Aaron Bilger]

Try the 1.4V sensitivity instead and see if that reduces noise (as in signal to noise ratio, its not THD). Probably a sound card issue....

Ya I would say since I don't have a sound card it's on board audio it sucks I will be upgrading to get a sound card.

 

[slipperybidness]

Yup, onboard audio can be crappy, poor power supply and noisy environment. I prefer an external DAC over sound card, even dac in my avr is fine.

Pass the signal out of chassis in the digi domain, even if just optical out from mobo or cheapie sound card

If you insist on a sound card then get one that is well shielded. I would be looking at the Asus Xonar sound cards.

Try the other sensitivity setting on the amp. Thats free and may solve your issue

 

[Aaron Bilger]

Yup, onboard audio can be crappy, poor power supply and noisy environment. I prefer an external DAC over sound card, even dac in my avr is fine.

Pass the signal out of chassis in the digi domain, even if just optical out from mobo or cheapie sound card

If you insist on a sound card then get one that is well shielded. I would be looking at the Asus Xonar sound cards.

Try the other sensitivity setting on the amp. Thats free and may solve your issue

I just did try the other sensitivity and it does the same but a little less sound issue but when I have a preamp connected that is not enough signal.

 

[mtrycrafts]

Distortion is not all the same. Most tube amps and some class A amps don't produce the odd order harmonic distortion that most solid state amps produce.

May want to read this, para Harmonic content:

https://en.wikipedia.org/wiki/Tube_sound