It is important question. May be his standard and my standard is different. Extreme low THD for me is below 0.0001%. If we talk about different thing, the conclusion always wrong.
You seems do not understand the characteristic of many amplifiers. An amplifier can have low distortion at 1 kHz but very high distortion at 20 kHz. There are also some amplifiers who have low distortion at all audio frequency, it usually used 2 or more pole compensations. THD also change with level of output power. It affected the sound.
If you do not understand about amplifier characteristic, it is useless to discuss about THD.
Sorry, but I am finding it difficult to understand what you have said. (I appreciate English is probably not your first language.)
You wrote: "Other member of the group suggested him to change the speaker with better speaker".
So which spkrs used SB Acoustics drivers? The ones he first had ... or the ones he changed to? I ask because I use SB Acoustics 'Textreme' drivers in my spkrs - and I find them exceptional.
Good point. 👍 However, I would suggest standards between different people are generally different.
Whereas for me ... it's probably 0.01%. 😀 However, what is important to me is that H2 makes up most of the THD.
And even if we talk about the same thing ... it's possible to be at cross-purposes. 😵
If you say so. After all ... I'm just a boomer, dumb, white guy.
Totes agree! 👍
The first speaker that he had is cheap speaker according to him. I do not remember the type of the drivers, but he said it was from SB Acoustics.
Aah, OK. Well maybe it used different drivers to the 'Textreme' drivers that I used. Which are certainly not cheap! 🙄
Adding some series R to the power amp output can change the speaker response. Some people claim it sounds more tube like. When I tried years ago I didn't hear much (any?) difference but there is some science as to why it might, which is better than a lot of the theories around tweaks.
I completely agree. when I started looking at my DIY amps with a spectrum analyzer (soundcard with REW) it became very clear that THD is a lessor issue. This is why I added the +N to my earlier post. Get them both low and you hear what is supposed to be there. I guess also because i listen a flea watt levels these days this may be a bigger issue.
Nevertheless, NEVE consoles, which still sell for large sums of money, use either opamps in the channel strips, sum buses and filter and FX loops, or discrete opamps.
And completely digital mixing is better why?
I know Phil Newell pretty well http://philipnewell.net/index.html and the last time we talked he moaned big time about the rubbish consoles he was obliged to install on a frequent basis.
Of course it does - as it effectively increases the amp's Zout. SS amps have a very low Zout ... tube amps ... not so much.
I expect it will. But a far more preferable way of getting an ss amp to sound more tube like, I suggest - is to go Class A.
Some do... some don't. I have a few that have DF in the teens. I have several below 100. I have a few that claim that they reach high triple digits.
What does the operating class of the amplifier have to do with "tube like" sound? I'm asking from curiosity. I'm not challenging your assertion. My experience differs from yours, or at least I have some additional thoughts.
I have several solid state Class A amplifiers that all have (what I would consider to be) very different distortion profiles along with very different parameters that many would consider "important" to the "sound quality". I have a few that are "3rd dominant". There are also tube amps that are 3rd dominant. When I run a few of the amps balanced / bridged (cancelling most of the H2), I'd say the ones that sounded more "tubey" before running them balanced/bridged still sound "tubey" (to me). So, to me... it's not always even H2. It's certainly (to me) not DF.
I can also take a 'very low distortion' Class D or a Class A/B amplifier that some would consider "boring" perhaps and use an "H2 generator" to add some "salt" using that analogy from another member. To me, perhaps not to others, but to me, that provides an excellent "tubey" character. I can then alter the "H2 generator" and it might sound (to me) pretty terrible. There seems to be a range... or a nuance.
Sure, if I'm looking for the "tubby" (not tubey) "bloom" in the bass that may come from some tube amps perhaps paired with the wrong speakers or vice versa... I might intentionally alter the DF. I've never heard that mod make any difference in the "air" or other superlatives that sometimes go along with "tube-like".
I don't know the operating class of the M1.OT, but at least in that historic situation... it was shown that all that's required to match the sonic profile of a well-regarded tube amp is to null the difference to match the sonics identically (to certain trained listeners and certainly from a measurement POV).
If we generally agree that a "tube-like" character can be desirable, and that it can come from a certain set of parameters, then to me... it doesn't matter what topology is used to achieve that end result. I don't personally think Class A brings it closer (in many cases), and to me it may not even be the best choice depending on one's desires, but I just have fun with it. Don't get me wrong... the VAST majority of the amps I own and have built are Class A. I just don't know that it's the operating class that makes them more or less 'tube-like'.
We'd probably also agree that not all tube amps sound the same, but I think we're probably on the same page when it comes to enjoying that "tube-like" character.
Like I said... I can barely hear (compared to those golden-pinnae types) anymore, but it's certainly fun to learn what people consider important about amplifiers. I'm just happy I can see well enough to still solder a few things. My little ugly ducklings are still mine, so I'm likely heavily biased toward thinking they all sound marvelous.
Cheers!
The tube sound is caused by a bad design or under damped/noisy tube amp , or/and paired with new types of loudspeakers with low Z and low sens made for SS amps.
Alnico magnets , paper cones , 2n order , 8 ohm+ = tube friendly, it will not sound tuby.
Place the same amp with a modern carbon fibre smaller driver , 6 ohm, 3rd order , neodymium magnet = salad.
Many SS amps also suffer from the same problems, at low wattage they reveal the horrendous mess on high sensitivity loudspeakers.
The most tubby like SS amps are class D, Class T. If you listen to a good power tube amp there is no difference much from a well designed SS amp, it converges away from tubbiness/aggressiveness and towards definition/resolution and fun.
---------------------------------------- this is a quote from N. Pass (https://www.passdiy.com/project/amplifiers/the-plh-amplifier):
The JLH was designed at a time when “the tube era was in decline” and the new generation of designers were pulling out all the stops to create big science amplifiers - pure voltage sources with high power and infinitesimal distortion – complex circuits with lots of feedback.
36 years and a little progress later, we can perhaps appreciate the simple charm of the JLH topology as an exercise in minimalism, but if you haven’t listened to one, you might be very surprised by the quality of sound, which is extraordinarily good within it’s power limitations. If you have efficient speakers and you like to listen to two-channel sound at reasonable levels, the JLH is still in the top rank.
---------------------------------------
The gain of input is reduced and input voltage cut from 15 volts (I am just extrapolating) , but it has the effect of CCs at audio frequency, NEW higher gain input stages directly on the max rail power act in open loop at low and high signals (I suppose) as a RIAA, = the bass gain becomes low with voltage drop, and as HIGH frequency needs LESS voltage gain to have the SAME power, the gain is higher and progresses as the frequency climbs, (I am not talking about above 20khz), So this is corrected by feedback (by whatever means it is applied at the input of that stage).
This is clear that THD/Power is a Designing tool when designing one component the designer try to achieve lowest THD with the intended design circuit, it is one factor of quality.
Alnico magnets , paper cones , 2n order , 8 ohm+ = tube friendly, it will not sound tuby.
Place the same amp with a modern carbon fibre smaller driver , 6 ohm, 3rd order , neodymium magnet = salad.
Many SS amps also suffer from the same problems, at low wattage they reveal the horrendous mess on high sensitivity loudspeakers.
The most tubby like SS amps are class D, Class T. If you listen to a good power tube amp there is no difference much from a well designed SS amp, it converges away from tubbiness/aggressiveness and towards definition/resolution and fun.
---------------------------------------- this is a quote from N. Pass (https://www.passdiy.com/project/amplifiers/the-plh-amplifier):
The JLH was designed at a time when “the tube era was in decline” and the new generation of designers were pulling out all the stops to create big science amplifiers - pure voltage sources with high power and infinitesimal distortion – complex circuits with lots of feedback.
36 years and a little progress later, we can perhaps appreciate the simple charm of the JLH topology as an exercise in minimalism, but if you haven’t listened to one, you might be very surprised by the quality of sound, which is extraordinarily good within it’s power limitations. If you have efficient speakers and you like to listen to two-channel sound at reasonable levels, the JLH is still in the top rank.
---------------------------------------
The gain of input is reduced and input voltage cut from 15 volts (I am just extrapolating) , but it has the effect of CCs at audio frequency, NEW higher gain input stages directly on the max rail power act in open loop at low and high signals (I suppose) as a RIAA, = the bass gain becomes low with voltage drop, and as HIGH frequency needs LESS voltage gain to have the SAME power, the gain is higher and progresses as the frequency climbs, (I am not talking about above 20khz), So this is corrected by feedback (by whatever means it is applied at the input of that stage).
This is clear that THD/Power is a Designing tool when designing one component the designer try to achieve lowest THD with the intended design circuit, it is one factor of quality.
This sentiment echoes and rhymes all over the forum, throughout history, and across all timelines and parallel universes. 🤣
My best guesses remain the same:
The amplifier needs to be matched to the speaker hardware. Maintaining a flat 0.01 ohm output resistance up to the kHz range is what happens when a high feedback factor is maintained, probably for the sake of specmanship, or following the advice of amplifier experts and "blameless" design techniques, when in actual fact, speaker distortion may be needlessly 10× higher.
So you can get an amplifier with average THD specs due to an early pole, which rolls off the open loop gain, and low gain to start with, BUT, listening performance surpasses expectations because the designer understood how speakers work.
I don't know YOUR loudspeakers but mine have less THD ... 😎
With modern drivers (Purifi, Bliesma, ScanSpeak etc) it's actually not so easy to measure driver THD cause its buried in the reference microphone noise for lower levels. You can build speakers with 0,02% THD for normal listening level (between 80 and 90dBSpl).
So we are getting there that the whole listening chain has THD below recognition of the ear.
And is this important?
I rather have low THD as not. Most THD tests are absolute worst case scenarios (e.g. 1kHz sine) which have nothing to do with how we can detect THD in music.
But THD shows clearly if your amp or speaker works well and where they leave their area of linearity! THD over frequency tells a lot how feedback works. THD structure also tells about feedback amount and how the amp works in the background.
Nevertheless if we can hear it or not - THD is one of the most important measurements cause it has a lot of information in it.
Because I've actually done the work. Routed a software generated 24 bit tone through these systems and performed a software based spectral analysis, so no AD/DA conversions or op amps. The tone returns as mathematically perfect as it leaves. Are consoles following the general trend of all electronic devices towards consumables? Sure. On the other hand I also gave away a 'real' Studer 24 channel desk, from what I can tell the same model PS Audio purchased for Octave Records. A Mida/Behringer X32 might not have the same demonstrated service life but absolutely demolished the Studer in terms of I/O interfacing, audio performance, on board DSP, interface programming and lack of service requirements at 1/30 the price. I'll take that rubbish all day long.
This is not distortion, this is how the different instruments musical tones are formed.
A bass guitar 440Hz differs from a piano 440Hz due to the levels of harmonics and fundamental each instrument generates.
And the fact of fundamental level being lower than the harmonics, it's totally normal.
It happens with the piano lower frequencies.
The A0 note in a piano has fundamental frequency of 27.5Hz and its level is way below its harmonics
The resonant wood close to the strings cannot vibrate at lower frequencies so it cannot propagate high SPL low frequencies.
That's simply how piano sounds.
On the other hand, an A0 played in a pipe organ, depending on where you are listening from, may have the fundamental level higher than its harmonics.
Moving the point of listening may severely decrease the fundamental level since there are standingwaves for a such low frequency.
That's how a pipe organ sounds at a specific place of listening.
The problem is that the information is all scrambled together in a way that makes it useless for estimating the degree of distastefulness of an audio device. The correlation is very, very weak (except maybe if THD is very bad then the sound is probably bad too).
Well, there is an old thread about sound quality vs. measurements, over 20.000 posts long across 10 years, with no agreement or conclusion!
I doubt anyone can bring up something not beaten to death there.
https://www.diyaudio.com/community/threads/sound-quality-vs-measurements.200865/
My position on the matter is that using any single measurement for evaluation how audio component/system will sound is futile. However, a comprehensive set of measurements is good indication of how equipment could sound, and is the only way to confirm that engineering design goals were met. There is uncertainty related to personal preferences and synergy with other audio chain components.
Harmonic profile is the key factor when distortion is relatively high but becomes irrelevant with ultra low distortion amplifiers.
For me, both measurements and subjective impressions must be in agreement.
Perfect. As in any analysis. Single variable doesn't lead to a conclusion, but it doesn't mean that specific variable isn't important.
My body temperature is currently 36.5C. Am I healthy? I may be or not. Temperature will not determine that. But temperature is a super important variable.
Perfect again.
RIAA does not have low voltage gain at low frequencies. That’s where the highest gain is.
This is completely incorrect.
I suggest you forget all this nonsense about RIAA. It has no relevance to transistor output stages. As for your second statement, I refer you to Ohm’s Law.
So? Nelson Pass claims that amplifiers that have a certain distortion profile sounds better. He then makes amplifiers that have that distortion profile and tells people they sound good. There's nothing wrong with that. That's marketing in a nutshell.
But fundamentally, his assertion about sound quality versus HD profile is rooted either in opinion or his personal experience. He's entitled to his opinion and experience, but the fact that Nelson Pass says X does not automatically make X valid.
If you're curious about the correlation between sound quality af THD, I suggest that you read up on the science on the topic. An AES membership is pretty affordable and gives you access to many scientific papers on the subject.
Tom