Use of terms in audio fidelity discussions

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planet10 said:
Only at the grossest levels does THD correlate with perceived quality.
Let's assume there is some subjective experience which you can vary with a control knob from 0 to 10. 0 is 'nothing happens, no modification'; 10 is 'a lot happens'. Ask a thousand people to have the experience, while adjusting the knob to their preferred position. We are likely to find some clustering: some may prefer 0, some 1 or 2, others elsewhere. Some may like 3 or 4, but very few opt for bigger numbers than that.

Can we conclude that there is a very weak correlation between knob position and experience, so that knob position doesn't actually tell us much about the experience? Or should we conclude that people have different preferences, and the knob position is making a very real difference?

Now consider those who prefer 1 or 2. What if they declared forcefully that the reason they prefer this setting is because lower positions introduce a different unpleasant aspect to the experience? Even when shown that this is impossible, they persist in their belief that in order to achieve 0 (or thereabouts) it becomes necessary to spoil things in some unspecified and immeasurable way?

What if the knob adjusted spoons of sugar in a cup of coffee? Nobody seriously argues that absence of sugar somehow introduces alternative unpleasant tastes into coffee; they accept that sugar may mask tastes which are authentically coffee but some find unpleasant.

What if the knob adjusted THD on signal peaks? (and the distortion was mainly low-order)

For sugar we accept that all the knob does is vary sugar (and nothing else) to suit individual taste. Why do some find it so hard to accept the same concept for audio distortion? They declare that THD is poorly correlated with sound quality, when what they are really saying is that they prefer some THD.

Of course we could extend the experiment and ask people to estimate, unsighted, how much sugar has been added. Someone who claimed to have an excellent palate yet could only estimate sugar in coffee after counting the spoons would not be taken seriously; likewise those who refused to take part, saying that test stress affected their ability to taste sugar.
 
Hello i think i have found a way ...
I was listening to a very very good recording from this label ..

About Blue Coast Records | Blue Coast Records
i cannot say it is the ultimate sound for quality ... but OMG !
Then in the technical notes i read

.. Marenco chose 2” analog tape with Dolby SR as the multi-track format after comparisons with digital were made. Analog tape still cannot be surpassed for sonic response....

Well, i would study in depth the circuits schematics in that tape recorder, if only i knew which brand/model is.
Even through Utube the sound is moving ...

Looking For A Home - Blue Coast Collection - YouTube

I wonder if there is a site that sells service manuals ... I know that also lay-out and parts selection matter, but they could be a good start for sure.
Thanks and regards, gino
 
A part of the answer is that distortion, in audio, is a very complex behaviour, and a THD measurement grossly oversimplifies what could be going on, in a particular system. I had a fascinating time in my early years of exploring what the phenomenon of "convincing sound" was all about, when I used a very average boogie rock recording to assess other systems - to a man, they made a mess of the recording, confusing the sound elements sufficiently so that a typical response, by the other party, was "Why are you bothering listening to this 'bad' recording". If I answered, "Well, it's showing me how much distortion your system is adding to the playback - I've heard this being played without all that added confusion and messiness being in the sound" - then their reply would probably be "No, you're wrong - this system has very low measurable THD, your recording is poor, you need to listen to a good recording to hear how exceptional my system is!".

This difference in viewpoint is still very much part of the audio scene - and the debates continue ...
 
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Analogue tape cannot be surpassed for wow and flutter, noise, peak lopping and dropouts. And significant amounts of third-order distortion? Did I mention print-through? I guess a clever DSP person could simulate most of that digitally.

THD does simplify, granted, but nobody with any understanding would say anything different. Why do those who believe (wrongly) that THD tells us nothing keep (wrongly) accusing those who believe that THD tells us something of believing that THD tells us everything? Almost all mention of THD on this forum is initiated by those who choose to ignore it; haven't they ever wondered why the rest of us rarely mention it except in response to them?
 
Analogue tape cannot be surpassed for wow and flutter, noise, peak lopping and dropouts. And significant amounts of third-order distortion? Did I mention print-through? I guess a clever DSP person could simulate most of that digitally...

Hi what i meant is that i found a recording exceptionally transparent, clean, dimensional and so on made with a tape recorder automatically this implies that that recorder has very transparent electronics.
From this my interest to get/see schematics for instance of the preamp stages and so on ... to get hints.
But i do not know which recorder has been used ... :(
I believe also another thing ... that main damages can be done when the signal is low in level and strenght, like in a phono preamp for instance.
Then in a line stage and last in a power amp.
Given that i use only digital sources i think that the line preamp can make or break the sound more than the power amp.
I have found many decent power amps, less line preamps ... much less.
Maybe it is a matter of attenuator quality ? it could be.
Thanks and regards, gino
 
Studying a tape recorder preamp circuit may give you insight into low-level low-noise design with the complications of equalisation too. Useful for RIAA phono preamps. Less useful for line stages.

Some line stages damage the sound simply because they are unnecessary, so they require a mixture of amplification and attenuation - always a good way to insert extra noise. Others do it because they were designed (deliberately or accidentally) to be mild FX boxes. A line stage is about the easiest part of the audio chain to design as it has about the easiest job: mid-level signals, so not much to worry about with noise or distortion. Given that, it may be surprising how often it is got wrong.
 
Studying a tape recorder preamp circuit may give you insight into low-level low-noise design with the complications of equalisation too. Useful for RIAA phono preamps.
Less useful for line stages.
Some line stages damage the sound simply because they are unnecessary, so they require a mixture of amplification and attenuation - always a good way to insert extra noise. Others do it because they were designed (deliberately or accidentally) to be mild FX boxes. A line stage is about the easiest part of the audio chain to design as it has about the easiest job: mid-level signals, so not much to worry about with noise or distortion.
Given that, it may be surprising how often it is got wrong

Thanks again and yes ... this is exactly my feeling.
So in the end it is not easy to do it right. :rolleyes:
You want an evidence ? just have a look ad the Blowtorch 3D.
If the task were easy line preamps would not provoke all this interest ;)
Thanks again and best regards, gino
 
If the task were easy line preamps would not provoke all this interest
I am unsure if you are being ironic here.

As a general rule, the issues which certain people get all excited about are the simpler issues (which they still get wrong). I assume this is because they have no comprehension at all of the more difficult issues. So people get excited about cables and line stages when they should be getting excited about phono preamps and power amplifiers and loudspeakers. I guess swapping one bad line stage for another is somehow more 'audiophile' than tweaking a tone control knob.
 
I am unsure if you are being ironic here.

Hi, ironic ? I am serious. The Blowtorch 3d is going to be a guinness 3d
I think that the subject is extremely interesting, as it really is.
And it is about a line preamp (maybe also phono ?)

As a general rule, the issues which certain people get all excited about are the simpler issues (which they still get wrong). I assume this is because they have no comprehension at all of the more difficult issues. So people get excited about cables and line stages when they should be getting excited about phono preamps and power amplifiers and loudspeakers.
I guess swapping one bad line stage for another is somehow more 'audiophile' than tweaking a tone control knob

I can tell you that with a friend we tried his CJ against my old Bryston in his chain.
The resulting sound was extremely different ... almost night and day.
I am more than sure that a Blowtorch would have made the same system fly.
For me the line preamp is like a corner stone.
Than speakers impact power amp selection of course ... especially difficult ones.
But the preamp for me is THE PIECE.
Now if i could find a poor guy Blowtorch (i know it is not possible anyway)
I should try using better pots for start.
Thanks and regards, gino

P.S. non LP here ... i am too lazy for them ... only files ripped from cds (that i own of course )
 
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Analogue tape cannot be surpassed for wow and flutter, noise, peak lopping and dropouts. And significant amounts of third-order distortion? Did I mention print-through? I guess a clever DSP person could simulate most of that digitally.

You can actually buy analog-tape plug-in apps for digital audio workstations. The plug-in cleverly emulates all the issues of a tape machine to give the sound that 'tape sound'.

Its a whole market out there: you can buy tube-mike plugins, guitar-amp plugins, tube compression plugins, EMT plate reverb plugins, you name it.

Jan
 
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I'm sure you will forgive me if I give such claims the credence they deserve. To achieve a true "night and day" difference requires that at least one of the systems is faulty, incompetent or has a somewhat uneven frequency response.

Ok i have exaggerated.
But really the tube preamp was more rounded and warm ... more musical ? less precise also but nicer with voices.
The solid state preamp instead had a much much solid bass and seemed more extended in the highs, unfortunately with a midrange flatter
All considered i preferred the solid state preamp (the circuit can be found in the bryston web site, a discrete op-amp per channel)
So not actually night and day but very different also for a not trained ear.
Kind regards, gino
 
The point being, that subjectively the differences were "major" - at a technical, normal measurements level they would have been very similar - but the remanent, audible, distortion spectra were completely different, and this is what one's hearing picks up on - it ignores all those nice technical "accomplishments", but zooms in to where there is an irritating artifact, annoying the bejeezus out of you!

Something like driving a Ferrari - are you impressed by the smooth power, the thrilling throb of the exhaust? No, there's a rattle in the dash, every time the engine is in a certain rev range - and this sound fills your aural universe! Somehow, this fact is not enhancing the enjoyment of your "toy" ... :D
 
I've been researching, designing and building audio preamps, poweramps, processors and speaker systems since the 1960's. I've worked in Engineering at Dolby Labs and Tektronix. I'm semi-retired now, but still too active as an audio engineering hobbyist.

First of all, I would take what Stereophile says with a BIG grain of salt (don't believe it - their top priority is making the advertisers happy - like with most publications). Here in Portland Oregon USA I'm involved with an audiophile club, "The Oregon Triode Society", where some of the members worry endlessly about too many parts in the signal path, how the molecules line up in wire metal, many feel that tubes are a must, etc. etc. One member has his/her (not sure which) transformers special made with pure silver wire... I could go on...

Tubes can seem to sound better when they generate a significant 2nd harmonic (which they often do, largely because of loose tolerances and lower negative feedback). The second harmonic distortion product is the same as the incoming note but an octave higher. Most other distortion products sound bad to most people (heavy metal guitarists excluded). The more complex the music, the less desirable the 2nd harmonic distortion product (it necessarily comes with higher I.M. distortion which generates sum and difference frequencies - good for electric guitar distortion, bad everywhere else).

Op-amps can sound bad if the peripheral circuitry operates them on the verge of oscillation (poor phase margin). The Linkwitz Orion Speaker system sounds extremely good to my ear, and yet it has at least a half dozen op-amps (OPA2134) in the signal path, along with many passive components. It's a tri-amp'd open baffle speaker system, with additional opamp stages for substantial active EQ and even time shifting (delay on the tweeter for better impulse response or lobing situation - not likely an audible improvement but it's there to make the purists happy). And then there's the poweramps which are all solidstate.

One guy in our club swears he can hear the difference between various high end capacitors and even resistors (I can't except for noise in resistors), and transformers (several of us couldn't). People roll tubes and op-amps trying to find the best sounding one... It's my opinion that it's usually more about the peripheral circuitry.

Advice: Don't be afraid of opamps, use 1% metal film resistors where you can (especially in front end circuitry where the signal level is low), use cheap polypropylene film caps (Solen for ex.), use gold alloy plated connectors and switches if you can, but mostly learn what you can about how to set up an op-amp such that it has a good phase margin, and you'll be fine.

My own stereo system has many dozens of op-amps and sounds as good as any system I've ever heard to my ear. My system is triamp'd, there's heavy active EQ for the open-baffle speakers, I have a four section Baxandall tone control circuit, and probably every recording I've ever played has gone through a similar number of op-amps in the recording/mixing process.

I've come to know "purists" as poorly educated well meaning people. They believe too much of what they hear in the grape vine, so to speak. Don't worry about speaker wire either. Buy 16 AWG AC line cord at any hardware store. Bump it up a guage if the wires are more than 20 feet long or you lose a few watts of power on the wire (not likely audible). The connectors could be a weak link, but not likely the wire. If the design of a preamp is really bad, there could be a difference in interconnect cables - a high capacitance cable could cause an op-amp to ring or oscillate spuriously.

Phase Margin Advice: Op-amps are designed to expect to see zero ohms for AC from about 1HZ to well into the megahertz range, when looking at the power supply, so put 0.1uF caps within an inch of each opamp across the supplies. I usually put amybe 100uF across the powersupplies on each board too, just to be sure (long power supply wires can be significant inductors at very high frequencies). Also, put a 100 - 200 ohm resistor in series with the output of the opamp circuit (outside of the negative feedback path) so any capacitance that the opamp sees in the load will have much less effect on the phase margin. Most opamps have a better phase margin when there's a cap across the feedback resistor that limits the bandwidth (to 100kHZ or whatever). I always put a passive Rf filter at the input of my circuits, so I don't ask the opamp to do something it can't do well. These days with so many sources being digital, there's a pretty good chance that some Rf "digital noise" will come in from the source material. Almost nobody does this but it makes good sense to me (a 1K resistor in series at the circuit input, and then a 1nF cap to ground, forms a 160kHZ low pass Rf filter, for example).

The audio field has become more predatory and misguided over the years in my opinion. Be careful what you believe. Most of what I hear is wrong. $500 speaker wire is ridiculous, and there's even a person I know of that sells speaker wires for as much as $14000 for two 20 foot lengths...

Linkwitz and Zaph have websites that I'd recommend learning from. Also my website: http://www.spiritone.com/~rob_369/
Remember, every mistake is a valuable learning experience. Good Luck.
 
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The point being, that subjectively the differences were "major" - at a technical, normal measurements level they would have been very similar - but the remanent, audible, distortion spectra were completely different, and this is what one's hearing picks up on - it ignores all those nice technical "accomplishments", but zooms in to where there is an irritating artifact, annoying the bejeezus out of you!
Something like driving a Ferrari - are you impressed by the smooth power, the thrilling throb of the exhaust? No, there's a rattle in the dash, every time the engine is in a certain rev range - and this sound fills your aural universe! Somehow, this fact is not enhancing the enjoyment of your "toy" ... :D

Hi and i understand your points.
Still we were two and also my friend, the owner of the system and of the CJ preamp, agreed that there was a "noticeable" difference in sound.
As my preamp was much cheaper i tended to compliment his preamp as more musical.
But he was perplexed by hearing so better bass from the solid state unit, as i was also.
So if this "brick" could only have the midrange of his i would be done.
The sound was quite flat, lean and a little hard with digital.
Maybe i sound try a tube buffer at the output ? :D
Thanks again and kind regards, gino
 
I've been researching, designing and building audio preamps, poweramps, processors and speaker systems since the 1960's. I've worked in Engineering at Dolby Labs and Tektronix.
I'm semi-retired now, but still too active as an audio engineering hobbyist.
....
Also my website: Bob's Website
Remember, every mistake is a valuable learning experience. Good Luck.

Hello, thanks a lot for the very valuable advice.
Please give me some more time to study your very interesting pages.
By the way i have a question.
Lately i listened to recordings take from analog master tapes.
I was amazed about their quality ... very very nice, very realistic sound.
Then i looked at some schematics and i noticed that many of TOTL reel recorders have/had transformer coupled outputs.
So my interest for signal coupling transformer has increased a lot.
May i ask you where did you purchase the ones used in your creations ?
I have something in mind.
Thanks a lot again.
Kind regards, gino
 
ginetto61 said:
Ok i have exaggerated.
But really the tube preamp was more rounded and warm ... more musical ? less precise also but nicer with voices.
The problem with exaggeration is that it can quickly turn into male bragging, which then confuses people who aren't very bright and they begin to believe the hype.
"More rounded and warm" may be code for 'added 2nd-order distortion, and an early HF rolloff'.

The solid state preamp instead had a much much solid bass and seemed more extended in the highs, unfortunately with a midrange flatter
You may be describing a flat frequency response, which should be true of any line stage in the absence of tone controls. I am becoming increasingly convinced that audiophiles actually do like/want tone controls, but they don't want tone control knobs so they achieve the same effect through 'equipment rolling'. Sadly, this only works with very expensive but poorly engineered equipment (or 'ear-tuned' equpment), as everything else has a flat frequency response.

Post 34 contains much wisdom. My only objection is when it uses "purists" to describe the misguided. Surely a purist is someone who intelligently strives for excellence, not someone who believes fairy stories?
 
The problem with exaggeration is that it can quickly turn into male bragging, which then confuses people who aren't very bright and they begin to believe the hype.
"More rounded and warm" may be code for 'added 2nd-order distortion, and an early HF rolloff'

Hi and yes this is what i thought myself as well.
But the sound with the tube pre seemed also more detached from the speakers, filling the space around them better.
The solid state sound was clearly cleaner and stronger.

You may be describing a flat frequency response, which should be true of any line stage in the absence of tone controls. I am becoming increasingly convinced that audiophiles actually do like/want tone controls, but they don't want tone control knobs so they achieve the same effect through 'equipment rolling'. Sadly, this only works with very expensive but poorly engineered equipment (or 'ear-tuned' equpment), as everything else has a flat frequency response

I am completely against tone controls
I have even bypassed the balance control
The SS preamp is a low distortion discrete op-amp concept
And i see than many line drivers are similar.


Post 34 contains much wisdom. My only objection is when it uses "purists" to describe the misguided. Surely a purist is someone who intelligently strives for excellence, not someone who believes fairy stories?

I agree. On the purist i think that a purist has also very stronge basic beliefs
It is not my case at all ... always struggling between rational and irrational.
One case ? signal coupling transformers
I am sure they distort some signals and limit bandwidth, surely more than a cap for instance. :eek:
And still i see a huge number of experienced sound engineers loving unconditionally Neve consoles, full of them. :rolleyes:

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Where is the truth ? :confused::mad:
Thanks again and kind regards, gino
 
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It's not too hard to find, gino - most audio reproduction to some degree adds a certain level of unpleasant distortion, for various reasons - the type of 'sound' that immediately identifies the source as not being the real thing. And it has proven very elusive to measure this, to be able to pinpint the artifacts ... so, has largely been ignored by the audio industry; some solutions, like the Neve, are used to "nicefy" the sound, to try and counteract the seemingly inevitable degradation ...

But that's not the only way - if sufficient care and effort is put into optimising the reproduction chain, rather than just flavouring it with another, added, distortion mechanism - like a valve buffer - then highly respectable reproduction can be achieved. Unfortunately, this technique is not available as an easy, off the shelf, simple band aid solution - and therefore is rarely encountered in action ...
 
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