Nelson Pass said:
Not entirely true i fear....distortion can sometimes 'sound good'....which is why it is deliberately introduced as an effect in guitar amps...ad nauseam.
Now...a 'High Fidelity' amplifier on the other hand, must of necessity, and by definition aspire to being 'transparent' and 'neutral'.....viz: possessing low distortion.
In other words, the passage of audio frequency stimuli must be accomplished without bending, or otherwise corrupting said signal......
There is no known audio impairment that cannot be detected by simple, and judiciously applied THD+noise....non whatsoever......
If one must have 'good sounding' distortion in ones amp.,, then such can be introduced at line-level....For obvious reasons, such a device can hardly be described as 'High Fidelity'...
Cui bono
To mikeks : Remember, that large listening benevolence to the distortion is mainly caused by special technical journal, which owners offten have trembling with fear, 'cos promotion is big bussines. Have anybody, like this testing editors, bigger possibility to know all sortiment on the market ? Have anybody bigger possibility, if they can or must, to make " brain washing " to listeners, which mostly belive him, 'cos they are experts ? When I see graph of distortion, which look like comb for mammoths, I know, that distortion will be horrible and immediately audible, but typical editor's words are in this case, that it is " very musical and transparent " and I can beat by my head to the wall
. All is very transparent - Cui bono ?
To mikeks : Remember, that large listening benevolence to the distortion is mainly caused by special technical journal, which owners offten have trembling with fear, 'cos promotion is big bussines. Have anybody, like this testing editors, bigger possibility to know all sortiment on the market ? Have anybody bigger possibility, if they can or must, to make " brain washing " to listeners, which mostly belive him, 'cos they are experts ? When I see graph of distortion, which look like comb for mammoths, I know, that distortion will be horrible and immediately audible, but typical editor's words are in this case, that it is " very musical and transparent " and I can beat by my head to the wall
. All is very transparent - Cui bono ? 
Nelson is right, there are MANY kinds of distortion. Do any of you skeptics know about FM distortion that caused by excessive negative feedback? I thought not.
Nelson, Charles, Dr. Candy and I are all experienced audio designers, BUT we have different approaches to the final goal.
If you want LOW distortion, buy Halcro. If you want medium distortion, buy Parasound. IF you want do kick back and relax to 'smooth' sound, buy from Charles or Nelson. They trade some harmonic distortion (AM) to entirely remove FM distortion. I compromise somewhere in between, because I have to meet THX specs.
Nelson, Charles, Dr. Candy and I are all experienced audio designers, BUT we have different approaches to the final goal.
If you want LOW distortion, buy Halcro. If you want medium distortion, buy Parasound. IF you want do kick back and relax to 'smooth' sound, buy from Charles or Nelson. They trade some harmonic distortion (AM) to entirely remove FM distortion. I compromise somewhere in between, because I have to meet THX specs.
john curl said:
There used to be an article on the EDN web site by Barrie Gilbert regarding slewing-induced distortion. The link I have seems to be dead though. If my memory serves me right, he showed mathematically that as slewing is approached, the phase of the output signal changes as the amplitude of the input signal changes. RF folks refer to this as AM to PM conversion. I assume this is the effect you're referring to?
Circuits without feedback are susceptible to this too. A common-emitter amp will have its collector-base capacitance modulated by the output voltage swing, causing some phase modulation as amplitude varies. Cascoding can fix this, but then again some people claim that cascodes "sound bad".
john curl said:
I am not averse to learning...perhaps John would like to demonstrate a circuit generating this FM distortion, and a repeatable procedure for measuring such...?!?
Moreover, John might like to demonstrate that this FM distortion may be present in obscene amounts, and still remain resolutely undetectable by THD+N...?
P.S:No need to go the halcro route.....less than 0.05% THD+N (ref:80KHz bandwidth), across the audio band....down to at least 4Ohms-preferably 2ohms, is more than acceptable....
OK........since you asked.....
Go look up the "differential phase and gain" specs of an op-map designed for video. That is what they are talking about.
To us old microwave telecom types, we called it AM-PM and AM-AM distortion.
IOW...........
AM-PM is how much the phase of the output shifts as the level is changed. Ideally, there is none, but..........if you measure a very high frequency signal.......while you run the level up all the way of a very low frequency tone........
There, that is how it is done.
Jocko
Go look up the "differential phase and gain" specs of an op-map designed for video. That is what they are talking about.
To us old microwave telecom types, we called it AM-PM and AM-AM distortion.
IOW...........
AM-PM is how much the phase of the output shifts as the level is changed. Ideally, there is none, but..........if you measure a very high frequency signal.......while you run the level up all the way of a very low frequency tone........
There, that is how it is done.
Jocko
Picasso (after whom I model myself when possible) did not
often paint photographic images, and his work was often
derided as something "any school child" could paint. This of
course was not true, and additionally Picasso had wonderful
proficiency at accurate representational images. Every once
in a while he would embed one in a painting just to annoy the
critics.
The Old Farts designer club to which John Curl refers, has many
members who are equally adept at designing for a lot of
different characteristics. What you see from them is what they
choose to do, not what they are constrained to do.
Upupa Epops seems hell-bent on "objectivism" which I have no
problem with, having spent some years there myself with good
success, but he does not seem to allow much room for an
alternative viewpoint.
I like building and appreciate all sorts of things, including my
Behringer 24/96 and my stock car radio. I publish zen amps
and the like not because they are the world's greatest amps
but because they are very accessible to DIYers in terms of
understanding fundamentals, and it's fun to see how much
mileage you can get out of a transistor or two.
Chip amps will certainly teach you how to build a power supply
and basic layout, but they don't lend themselves to a deeper
understanding of the interior of the black boxes, and that's
why I don't involve myself publicly with them. (That may change -
we are currently playing with shootouts between several chip
amps).
So, Artist Formely Known as Mikek, if you think .05% thd
constitutes really low distortion, we are talking the same
language. I don't like 5%, and I'm not really impressed by
.000005%. Been there already.
often paint photographic images, and his work was often
derided as something "any school child" could paint. This of
course was not true, and additionally Picasso had wonderful
proficiency at accurate representational images. Every once
in a while he would embed one in a painting just to annoy the
critics.
The Old Farts designer club to which John Curl refers, has many
members who are equally adept at designing for a lot of
different characteristics. What you see from them is what they
choose to do, not what they are constrained to do.
Upupa Epops seems hell-bent on "objectivism" which I have no
problem with, having spent some years there myself with good
success, but he does not seem to allow much room for an
alternative viewpoint.
I like building and appreciate all sorts of things, including my
Behringer 24/96 and my stock car radio. I publish zen amps
and the like not because they are the world's greatest amps
but because they are very accessible to DIYers in terms of
understanding fundamentals, and it's fun to see how much
mileage you can get out of a transistor or two.
Chip amps will certainly teach you how to build a power supply
and basic layout, but they don't lend themselves to a deeper
understanding of the interior of the black boxes, and that's
why I don't involve myself publicly with them. (That may change -
we are currently playing with shootouts between several chip
amps).
So, Artist Formely Known as Mikek, if you think .05% thd
constitutes really low distortion, we are talking the same
language. I don't like 5%, and I'm not really impressed by
.000005%. Been there already.
john curl said:
I am not averse to learning...perhaps John would like to demonstrate a circuit generating this FM distortion, and a repeatable procedure for measuring such...?!?
Moreover, John might like to demonstrate that this FM distortion may be present in obscene amounts, and still remain resolutely undetectable by THD+N...?
P.S:No need to go the halcro route.....less than 0.05% THD+N (ref:80KHz bandwidth), across the audio band....down to at least 4Ohms-preferably 2ohms, is more than acceptable....
Oh....and what precisely does FM stand for in this context Mr. Curl??
I think anyone wanting to develop some kind of feel for this
sort of phenomena would want to get a copy of James
Gleick's "Chaos, the Making of a New Science" for a really
good read. It has an excellent "hand waving" sort of
explanation of the strange behaviour of which non-linear
dynamic systems are capable, and how feedback exacerbates this.
exacerbate:/ Vocabulary word for the day. Has nothing to do
with sex......generally.
sort of phenomena would want to get a copy of James
Gleick's "Chaos, the Making of a New Science" for a really
good read. It has an excellent "hand waving" sort of
explanation of the strange behaviour of which non-linear
dynamic systems are capable, and how feedback exacerbates this.
exacerbate:/ Vocabulary word for the day. Has nothing to do
with sex......generally.
Some people say that an amp itself is a main source of a different kind of distortion. For example: Halcro has got dedicated cables which fulfills manufacturer demands. I suppose, that a huge and complicated Halcro's PSU is the first potential danger for the quality of its sound. What about of a plugged CD?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.