MikeB said:[snip]Or again thin ice ?
Mike
No Mike, you sum it up quite nicely. You seem to support my view in the If You Know What You Are Doing, FB Is Your Friend department.
. But that also goes for a NonFB design. If you don't know what you are doing, it will sound pretty bad as well.Jan Didden
Well said Mike. I agree with all your points, and would add that lag compensation/phase lead can also affect bass performance.
Both our amps use very high feedback factors. Done right, it seems to sound damn good, doesn't it?
David, people are misled by your marvellous Indonesian humility and good manners. But they see that you learn incredibly quickly and are an impressive intellect....... Kanwar sees this clearly, it appears!
Cheers,
Hugh
Both our amps use very high feedback factors. Done right, it seems to sound damn good, doesn't it?
David, people are misled by your marvellous Indonesian humility and good manners. But they see that you learn incredibly quickly and are an impressive intellect....... Kanwar sees this clearly, it appears!
Cheers,
Hugh
Hi, Mike,
Very nice points I can see that "free from oscilating" is not enough, more to do for the benefit of the sonics.
Is the openloop curvature should be as flat as possible, or there existed somekind of "open loop curvature" that sounds nice (curve for OL bandwith, analogy like Fletcher-Munson for our ear)?
But at least Mike has give a clue of "what to do" with feedback design.
Very nice points
I can see that "free from oscilating" is not enough, more to do for the benefit of the sonics.Is the openloop curvature should be as flat as possible, or there existed somekind of "open loop curvature" that sounds nice (curve for OL bandwith, analogy like Fletcher-Munson for our ear)?
That's right
But at least Mike has give a clue of "what to do" with feedback design.Janneman, AKSA, Kanwar, I'm just learningI know, I think he just wants to put us in a black box with no windows
lumanauw said:
That's right
Clue to no-feedback desin:
1. Linear VAS with flat fr. res. 20kH.
2. Hot follower of any kind.
3. Forget all Mike's points.
4. Don't forget connect speakers.
5. Push the Power-ON button.
6. Don't forget
AKSA said:
Hi Hugh, i thought of lag compensation/phase lead beeing part of proper feedbackcompensation, a very difficult task...
Yes, done right, high feedback amps are excellent !
lumanauw said:Hi, Mike,
Very nice points
Is the openloop curvature should be as flat as possible, or there existed somekind of "open loop curvature" that sounds nice (curve for OL bandwith, analogy like Fletcher-Munson for our ear)?
I prefer to keep "everything" flat, colorizing should not be done by the amp... Local feedbacks will keep it flat anyway...
Rozak, with no feedback amps my points are quite pointless...
Mike
Greetings from Norfolk
I am still following the discussion with great interest, and have come to the conclusion that the no feedback designs are created by some who are highly competent electronics designers, but lack the tools or tenacity to carry out a full theoretical cirtcuit analysis - i.e. purely mathematical analysis of the amplifier's response with feedback - this may well not be possible in some cases, but in most it would be very arduous and time consuming.
This is NOT to decry their efforts and designs, but just the case that they are not my cup of tea.
I have also noted a lack of response to my third point in my post #24 dated 02-06-2006 - I repeat it below for your comment.
3. Whilst I agree that a frequency response to somewhat above the normal audio range (20 kHz) to maintain phase is a good idea, I cannot accept that a response to greater than (say) 200 kHz is necessary.
I cannot think of any source of audio which will produce frequencies of much more than 20 kHz.
As most audio is, today, taken from CDs, the limit of frequency from these cannot be more than 22 kHz for a mono recording (if such exists today) as the sampling frequency is 44 kHz.
Vinyl records will be limited to around 20 kHz due to many factors – ‘needle’ response, cartridge inductance, input cct. shaping, etc.
This leaves magnetic media, and the response from this will be inherently limited by the design of the replay head. Similarly the mini disk.
Radio signals are limited in their frequency range by the transmission requirements – not to occupy too much radio spectrum space.
Also, all commercial media will tend to be audio spectrum limited by the manufacturer or recording studio, as appropriate.
If there is a source of audio which extends beyound the 20 KHz frequency I would be interested to hear of it.
Good listening
Richard
I am still following the discussion with great interest, and have come to the conclusion that the no feedback designs are created by some who are highly competent electronics designers, but lack the tools or tenacity to carry out a full theoretical cirtcuit analysis - i.e. purely mathematical analysis of the amplifier's response with feedback - this may well not be possible in some cases, but in most it would be very arduous and time consuming.
This is NOT to decry their efforts and designs, but just the case that they are not my cup of tea.
I have also noted a lack of response to my third point in my post #24 dated 02-06-2006 - I repeat it below for your comment.
3. Whilst I agree that a frequency response to somewhat above the normal audio range (20 kHz) to maintain phase is a good idea, I cannot accept that a response to greater than (say) 200 kHz is necessary.
I cannot think of any source of audio which will produce frequencies of much more than 20 kHz.
As most audio is, today, taken from CDs, the limit of frequency from these cannot be more than 22 kHz for a mono recording (if such exists today) as the sampling frequency is 44 kHz.
Vinyl records will be limited to around 20 kHz due to many factors – ‘needle’ response, cartridge inductance, input cct. shaping, etc.
This leaves magnetic media, and the response from this will be inherently limited by the design of the replay head. Similarly the mini disk.
Radio signals are limited in their frequency range by the transmission requirements – not to occupy too much radio spectrum space.
Also, all commercial media will tend to be audio spectrum limited by the manufacturer or recording studio, as appropriate.
If there is a source of audio which extends beyound the 20 KHz frequency I would be interested to hear of it.
Good listening
Richard
Originally posted by lineup
I agree to this.
Natural sounds with very fast rise and slope, like a 10 kHz squarewave
does not exist.
Very sharp transients, like when hitting a bottle of glass with a metal stick
still have not at all character close to squarewave rise.
Of what I have read in internet, the air acts as a lowpass filter
and so air has difficulties to act in a very fast rise transient way.
Now, recordings can of course use synthetical sound transients and even high freq squarewaves.
But I do not think loudspeakers and air can reproduce them.
If my amplifiers have an upper freq response of 100 kHz
I do not worry at all.
Well, you maybe did not read my post.
So here it is again.
I am not surprised the other guys here,
some of them who likes to build (only in theoretical advanced reasoning of course
) amplifiers with bandwith of 700kHz, 1 MHz and even 2 MHz, with complicated nested whateverdo not want to read my opinion.
The funny thing is,
when these guys actually build something,
they are ( or have to be ) more down to earth regarding frequency response.
Gandalph said:
Hmm, Vinyl, SACD, DVD-Audio...
For Vinyl: http://www.diyaudio.com/forums/showthread.php?postid=702600#post702600
Mike
I gues that we should not be focusing too much on 20KHz or whatever, during the feedback debate.
The school of thought is that Feedback designs turn nasty when the feedback loop is too slow, and efferctively offers no feedback, when the transient signal is Very Fast, ie has a Very fast Slew Rate ( not necessarily HF )
Slew rate is the Rate of Change of Volts per microsecond.
A loud Kick drum due to its Much higher Voltage swing will be more demanding of slew rate than the zero crossing slew rate of a 20 KHz signal, because in music, the amount of 20KHz energy is just tooo small. ( rarely more than a few watts of 20KHz bursts are ever fed to a tweeter, ... Except when the power amp splutters or clips )
The school of thought is that Feedback designs turn nasty when the feedback loop is too slow, and efferctively offers no feedback, when the transient signal is Very Fast, ie has a Very fast Slew Rate ( not necessarily HF )
Slew rate is the Rate of Change of Volts per microsecond.
A loud Kick drum due to its Much higher Voltage swing will be more demanding of slew rate than the zero crossing slew rate of a 20 KHz signal, because in music, the amount of 20KHz energy is just tooo small. ( rarely more than a few watts of 20KHz bursts are ever fed to a tweeter, ... Except when the power amp splutters or clips )
I agree.
However, I guess that any objective reasoning will accept an amp that has an Open Loop Bandwidth ( before Feedback) of 20 KHz. That would be 'blamless' in regards to poor sound due to feedback.
Not that this is easy to achieve in practice...
Beyond this bench-mark, a DC to X-Rays freq response would have little audible merit ?
It's difficult to make a cct that performs exactly like calculations. Many parameters are different than databook, tolerances in component parts, parasitic capacitance or inductance of PCB tracks changes quite some important poles/zeros, they has big influence of the final result, including whether the final is stable or not (in case of feedback amp). The lack of measurement equipment for these adds another problem. Myself tends to solve problems more with try&error with real cct in workdesk.
You will not hear music above 20khz, but you can hear the impact. I suspected that good designs not only focussing below 20khz, they also consider what happened above Mhz also.
You cannot hear 25Mhz, right?
But try this : over-ride your original music with 25Mhz sinusoidal, not necessarily big amplitude (0.2V is enough), and then hear what happens
Hi, Mike,
How do you know that ? Yes, the result is the sound is more "sparkling", trebles are heard more clear, details are more revealing. Ordinary man (who don't know what happens) even said it is better sounding
They said that the sound result is "faster". TIM is heard as a fast sound impression?
I'll never forget what PRR said. He said a slight TIM is OK. But too much you will have trebles splish-splashing everywhere.
How do you know that ? Yes, the result is the sound is more "sparkling", trebles are heard more clear, details are more revealing. Ordinary man (who don't know what happens) even said it is better sounding
They said that the sound result is "faster". TIM is heard as a fast sound impression?
I'll never forget what PRR said. He said a slight TIM is OK. But too much you will have trebles splish-splashing everywhere.
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