Does THD accurately predict good sound quality? And is subjective SQ useful to assess amps?

the high hat sounds is very fake, the singer voice is very distorted,
That's how it sound - these hihats ARE fake. Add Youtube compression ...
What you do with your tube is what I described with "adding glue" during mixing - you add distortion to make the sound less separated and "sterile" (means you hear LESS detail of a fake sound which makes it nicer).
But that's not High Fidelity, it's sound design 🤓

opening of Hotel california
Listen to that snare ... or bass drum ... it's horrible. But that's the sound of that time. I listened to the 2013 remastered version on youtube - there seem to be plenty of artefacts from video compressing around 20s. Spotify already sounds better.

It's totally fine to add distortion to make that more pleasurable.
But you should try to listen to a good recording in a great listening space with high resolving speakers ... or better not, it's hard to go back 😉
 
Another, the Sanctus of Mass in C minor, most system will 'rip it apart' it will sound like a soup,
In Bach I found also a part that is nearly impossible to sound right on any system: Zion hört (Choral) or in the first choral, its when the main motif is interleaved with the melody of like half a measure (maybe) it sounds like the score is wrong or deficient. However it is incredibly logical and very pleasant on a resolving system (I am lacking semantics to describe).
 
All this stuff about THD. I have seen amplifiers that measure superbly for THD. But there is no guarantee they can properly reproduce a sound stage. I know of one (which I believe has internal SMPS) that measure great in terms of THD but collapses the sound stage pretty completely (probably due to correlated noise that doesn't show up well on an FFT). Another amplifier measures even better for THD, really superb, the sound stage is lopsided. That type of thing can happen where there are layout issues that cause asymmetrical crosstalk. The problems make both of those amplifiers useless for me.
 
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IamJF, they are fake, however they really sound OK, they are acceptable filling loop samples, and the singer voice is full of depth effects but it is clear, I cannot hear any 'compression' except a lack of dynamics but the sounds are clear and full of definition. It is a tube buffer : it has 100% feedback and differential , I don't know where I am adding coloration or tube sound.

The remastered version I listen, maybe I am not very critical, but I enjoyed it a lot!
What do you mean by compression artefacts around 20s?? ? 20s?

To me spotify is horrible. I can't listen to OGG files, they are sounding worse than mpe128bit.

Youtube is a big hit from cd but it is still listenable.
 
andy then your speakers are passive

I'm afraid you are mistaken ... there is no way my spkrs can be called "passive". A good definition of an active spkr, I suggest, is that the amp channels are directly connected to the drivers - ie. there are no (passive) XO components in between them.

you are the first person to tell me that amps outside speakers are active speakers.

So what do you call a spkr which has one amp channel inside it (so you need to plug a mains cable into it) yet has more than one driver ... and so has a passive XO inside the box, to split the frequencies?

(I call this a powered spkr - but not an active one.)
 
The quick search on google all the internet beg to differ. Active and powered are interchangeable. Passive means it doesn't plays by itself. Active or powered means you can plug a pre output and it is going to sing.
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IamJF:
your proposition is still interesting for testing purposes. I remember after testing my dac if I could hear the difference between a recording of my Phono outputs and the real record playing.
I could not really tell even with the ADC/DAC added. The bass what maybe not as good, the clicks and pops were a little more annoying on the digital playback but I could not really fault it in anyway.

Now it is going to be very ugly, I can take wires to the amp outputs and plug them in the microphone input and record it, then play it through the non-tube (dac which I hate) and also give you a sample to listen to try to find a difference with the master sample on youtube. It means my sample will have travelled through my poor tube dac, my power amp, and my so so ADC. (3 devices, 2 volume controls (mic and amp), This is not going to take too much time to do.
 
I'll give you a lengthier definition:
* 'passive' spkrs need an amp channel to drive them.
* inside the box - if there is more than just one driver - there is a passive XO which splits the incoming music signal across the drivers.
* the key issue, to my way of thinking ... is that the amp channel is not directly connected to the drivers - the XO is in the way.
* whereas an 'active' spkr has one amp channel directly connected to its corresponding driver.
* hence, the frequency splitting happens before the power amp channels.
* these amp channels can be incorporated in the spkr enclosure ... or they can be external.
* in my case - they are external.

Here are my spkrs - which don't have an enclosure (with the Class A amp next to it):
To me, you've perhaps described a set up using active crossovers (even though I don't see those mentioned specifically above) for each driver instead of a passive network vs. what I'd consider to be an "active speaker" aka "powered speaker", but it's greatly appreciated that you clarified what you meant. That's what is wonderful... we can all sometimes use the same words and not understand them to mean the same thing. As long as we clarify, we can all be on the 'same page'.

From my limited time playing in the hobby and seeing advertisements, I've seen a number of "Active Speakers" (some advertised as monitors) that use passive XOs. They simply have an amplifier per channel (possibly 1 per driver, but not always that I can tell). They seem to vary quite a bit, but what does seem to be relatively consistent is that they have the amplifier 'in the same box' as the drivers. When I looked for any definitive information... as usual, I came up with nada.

Cheers!
 
I need to dust off the project I have sitting on my computer: Adding various distortion profiles to a track and have people blindly rate them by perceived distortion and listening pleasure. I’ve already written most of the code…
I finally found one of the studies I was trying to hunt down in response to this. Morning coffee and a fresh mind. 🙂 My memory is worse than my filing system (sadly); or my filing system is better than my memory (thankfully), and I haven't gotten around to reading everything in the 'library'.

https://www.diva-portal.org/smash/record.jsf?pid=diva2:1430978&dswid=-7023 (also attached)

This may be of interest. It doesn't likely go about the study in exactly the way you're considering, and your results would be unique to theirs, but possibly they could compliment them.

If you don't have a DOE, I'm never above stealing shamelessly... 😉 theirs was what I'd consider robust.

Completely unrelated - My favorite part of the entire document is "Finally, a gentle pet to the cats of Ankarskatavägen for being cats".

For others that like to "dig in" a little, the works that Lézin cites in the paper can also be quite informative.

As yet, I still haven't found a paper showing a preference for "amplifiers or a signal chain with lower distortion" that covers amplifiers in the "ultra low distortion range", but I'd love to add it to the collection of works I have yet to read if anyone out there happens to be able to point toward anything.

I also admit that I may need to read a few things several times before they sink into this addled brain. Some of it is quite a bit above my head. @Markw4 sent me a few scholarly works some time ago as an example (thank you again), and while I've read them at least twice each... I'm still not sure that I "get it".
 

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To me, you've perhaps described a set up using active crossovers (even though I don't see those mentioned specifically above) for each driver instead of a passive network vs. what I'd consider to be an "active speaker" aka "powered speaker", but it's greatly appreciated that you clarified what you meant.

Having used 'active spkrs' for 30 years ... a "set up using active (ie. line level) crossovers" is indeed what I call an 'active spkr'. And the fundamental basis of an 'active spkr' ... is that there is no passive XO components between an amp channel and the driver it's powering.

From my limited time playing in the hobby and seeing advertisements, I've seen a number of "Active Speakers" (some advertised as monitors) that use passive XOs. They simply have an amplifier per channel (possibly 1 per driver, but not always that I can tell). They seem to vary quite a bit, but what does seem to be relatively consistent is that they have the amplifier 'in the same box' as the drivers. When I looked for any definitive information... as usual, I came up with nada.

Indeed, marketing has subsumed - bcoz it's sexy - my definition of an active spkr into other situations. I don't call a spkr which has:
* a power cord
* and a mono amplifier channel
* with a passive XO feeding more than one driver

... an "active spkr" - I call it a powered spkr!
 
Indeed, marketing has subsumed - bcoz it's sexy - my definition of an active spkr into other situations. I don't call a spkr which has:
* a power cord
* and a mono amplifier channel
* with a passive XO feeding more than one driver

... an "active spkr" - I call it a powered spkr!
That's the PITA. Lots and lots and lots of other people call those exact type of products / designs "active speakers".

No one is or isn't "correct about it".

I really like the addition of "line level" into your personal definition. Makes perfect sense.
 
Sure. What dac do you use for that? Is it USB, AES, SPDIF, TOSLINK, something else? How many channels? What is the best stereo dac you have access to?
I use a Hypex active plate amp with digital input. Or the digital input of KH120ii (in my office). Interface RME UFX or Babyface.
Works very well and clean and avoids additional conversions.

@gabdx You can do your recording, level EXACTLY the same level and do a null test (= invert one of the recordings and listen to what is left - this is the difference between the items). When there is 0 difference ... you have to search elsewhere for the difference.
 
It may be useful to think of THD as being like the TOTAL in this sign:
View attachment 1437597

Hey, Cuyama, we've been there quite a few times... on the road from the 5 ( And the Oil Highway ) to the 101 and Santa Maria above Santa Barbara... a nice drive...

Distortion wise... it might be interesting to compare a '73 Marantz with a 77 Sansui. In those few ensuing years, the Japanese went from addressing THD to IM and slew rate.

The older amplifiers sound bass heavy and dark... the latter amplifiers sound much lighter and dynamic.

To me ears, the amps with lower IM and higher slew rates sound a lot more realistic.

So there.. Both amps have low enough THD, yet they sound completely different.
 
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Having used 'active spkrs' for 30 years ... a "set up using active (ie. line level) crossovers" is indeed what I call an 'active spkr'. And the fundamental basis of an 'active spkr' ... is that there is no passive XO components between an amp channel and the driver it's powering.



Indeed, marketing has subsumed - bcoz it's sexy - my definition of an active spkr into other situations. I don't call a spkr which has:
* a power cord
* and a mono amplifier channel
* with a passive XO feeding more than one driver

... an "active spkr" - I call it a powered spkr!

Then you got hybrids.... where one speaker has the power cord, a crossover and a built in STEREO amp that feeds its partner... a "passive" speaker.

Throw in a bluetooth or WiFi receiver and now you got a streaming active passive speaker system.

How do you measure and publish THD for such?
 
All this stuff about THD. I have seen amplifiers that measure superbly for THD. But there is no guarantee they can properly reproduce a sound stage. I know of one (which I believe has internal SMPS) that measure great in terms of THD but collapses the sound stage pretty completely (probably due to correlated noise that doesn't show up well on an FFT). Another amplifier measures even better for THD, really superb, the sound stage is lopsided. That type of thing can happen where there are layout issues that cause asymmetrical crosstalk. The problems make both of those amplifiers useless for me.
That's why I pointed out that we can listen to the soundstage, but not measure it.
 
One of the reasons mentioned is crosstalk between channels.
But, we need to create a really bad design to crosstalk to be audible on top of the normal signal.
Even for integrated same chip dual channel amps such as class-D TPA3255 - I saw crosstalk measurements going from -80dB (1kHz) to -60dB (20kHz).

Let's say we are listening at 1W in each channel and they crosstalk at -70dB,
Would this small level affect image sound?
 
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Hmm..

Take two such amps that image differently.... ( keep the speakers and FE the same )... perhaps use a pair of calibrated headphones.. mount them on a head ( binaural configuration ) ? Use a known physical device configuration -say at the plane of the tweeters.

Start with a pulse signal, moving it from left to right. Measure the impulse, frequency and so on.

That could be a start.

Obviously, the speakers would have to be a known quantity, hopefully very linear in the midrange.