FORR
"the ear does not detect even quite long saturations (I got only 1/1000 s as data)."
HYFRIER
"The ear DOES detect saturations quite easily"
I've tried to give a data which may be wrong and I would have like it to be corrected if needed. "Quite easily" refers to nothing, however it implies that the ear does not detect some saturations, at least.
~~~~~~~ Forr
§§§
"the ear does not detect even quite long saturations (I got only 1/1000 s as data)."
HYFRIER
"The ear DOES detect saturations quite easily"
I've tried to give a data which may be wrong and I would have like it to be corrected if needed. "Quite easily" refers to nothing, however it implies that the ear does not detect some saturations, at least.
~~~~~~~ Forr
§§§
Forr,
It is tiresome to have someone demand one "prove"every comment.
These results were "proven "EASILY"audible by controlled listening tests some 34 years ago AND a peak meter was used which could detect a 50 microseconds pulse and hold it for 10 seconds. These were also viewed on a log CRO.
Contrary to your view, extensive tests also proved NO instrument exists that produces extremely brief transient pulses. Typical rise times are 5 -12 msec. A normal peak meter is designed for 10 msec and is EASY to construct.
Table 1 shows the normal peak outputs from several popular types of studio microphones. All the readings are taken with the microphone operating into the primary of an unloaded transformer. Pickup distances are indicated for each instrument and were determined by normal studio practice. Table 2 is an abridgement of a similar study done by Fine Recording. Inc., several years ago. Details of this test setup are not available but the readings are probably taken without the 6dB pad commonly used on the U-47 microphone today. Some calculations based on the manufacturer's published sensitivity for these microphones indicates that acoustic sound-pressure levels in excess of 130-dB are common. While the latest console preamplifiers have less noise, less distortion, and more knobs than ever before, they are not designed to handle this kind of input level. In most commercially available preamplifiers, head room runs on the order of +20-dBm (1.0-dBm is 1 mw into 600 ohms), and gain is commonly set at 40-dB. With these basic parameters it is clear from the data shown in Tables 1 and 2 that severe overloads can occur on peaks from almost all instruments. For example, a U-87 microphone gives a peak output of -1 dBm from a large floor tom. Amplification by 40 dB in the microphone preamplifier results in an output swing of +39 dBm, or almost 20 dB above the overload point. Logically a peak of this magnitude should be severely distorted.
Table 1. Peak microphone output levels for percussive sounds. Microphone Voltage, Open Circuit, dB Ref. 0.775 V
Instrument Distance (in.) U-87 U-47 77-DX C-28 666
Bass drum (single head) 6 0 -6 -9 -15 -1
Large tom tom 12 -1 -6 -9 -10 -5
Small tom tom 12 -1 -5 -7 -9 -1
Piano (single note) 6 -25 -29 -38 -35 -32
Piano (chord) 6 -23 -27 -36 -33 -33
Orchestra bells 18 -16 -25 -33 -33 -30
Cow bell 12 -10 -12 -29 -19 -15
Loud yell 4 0 -11 --- -10 -10
The transistor characteristics which our subjects noted were the buzzing or white-noise sound and the lack of "punch." The buzz is of course directly related to the edge produced by overloading on transients. The guess that this is white noise is due to the fact that many of the edge harmonics like the seventh and ninth are not musically related to the fundamental. The ear hears these dissonant tones as a kind of noise accompanying every attack. The lack of punch is due to the strong third harmonic which is inaudibly "blanketing" the sound.
It is tiresome to have someone demand one "prove"every comment.
These results were "proven "EASILY"audible by controlled listening tests some 34 years ago AND a peak meter was used which could detect a 50 microseconds pulse and hold it for 10 seconds. These were also viewed on a log CRO.
Contrary to your view, extensive tests also proved NO instrument exists that produces extremely brief transient pulses. Typical rise times are 5 -12 msec. A normal peak meter is designed for 10 msec and is EASY to construct.
Table 1 shows the normal peak outputs from several popular types of studio microphones. All the readings are taken with the microphone operating into the primary of an unloaded transformer. Pickup distances are indicated for each instrument and were determined by normal studio practice. Table 2 is an abridgement of a similar study done by Fine Recording. Inc., several years ago. Details of this test setup are not available but the readings are probably taken without the 6dB pad commonly used on the U-47 microphone today. Some calculations based on the manufacturer's published sensitivity for these microphones indicates that acoustic sound-pressure levels in excess of 130-dB are common. While the latest console preamplifiers have less noise, less distortion, and more knobs than ever before, they are not designed to handle this kind of input level. In most commercially available preamplifiers, head room runs on the order of +20-dBm (1.0-dBm is 1 mw into 600 ohms), and gain is commonly set at 40-dB. With these basic parameters it is clear from the data shown in Tables 1 and 2 that severe overloads can occur on peaks from almost all instruments. For example, a U-87 microphone gives a peak output of -1 dBm from a large floor tom. Amplification by 40 dB in the microphone preamplifier results in an output swing of +39 dBm, or almost 20 dB above the overload point. Logically a peak of this magnitude should be severely distorted.
Table 1. Peak microphone output levels for percussive sounds. Microphone Voltage, Open Circuit, dB Ref. 0.775 V
Instrument Distance (in.) U-87 U-47 77-DX C-28 666
Bass drum (single head) 6 0 -6 -9 -15 -1
Large tom tom 12 -1 -6 -9 -10 -5
Small tom tom 12 -1 -5 -7 -9 -1
Piano (single note) 6 -25 -29 -38 -35 -32
Piano (chord) 6 -23 -27 -36 -33 -33
Orchestra bells 18 -16 -25 -33 -33 -30
Cow bell 12 -10 -12 -29 -19 -15
Loud yell 4 0 -11 --- -10 -10
The transistor characteristics which our subjects noted were the buzzing or white-noise sound and the lack of "punch." The buzz is of course directly related to the edge produced by overloading on transients. The guess that this is white noise is due to the fact that many of the edge harmonics like the seventh and ninth are not musically related to the fundamental. The ear hears these dissonant tones as a kind of noise accompanying every attack. The lack of punch is due to the strong third harmonic which is inaudibly "blanketing" the sound.
Hyfrier,
"Typical rise times are 5 -12 msec."
My data indicate that the fastest recorded rise time of natural audio signals is about 12 micro seconds (a bandwidth about 30 kHz).
~~~~~~~~ Forr
§§§
"Typical rise times are 5 -12 msec."
My data indicate that the fastest recorded rise time of natural audio signals is about 12 micro seconds (a bandwidth about 30 kHz).
~~~~~~~~ Forr
§§§
Has anybody compared the AKSA to the UCD class-d amps, they also seem to have this best of the best reputation?
Leve
Leve
Hugh did that comparison....he told that AKSA eat the class D in the breakfast.
But also he told, in advance to that conclusion, that the UCD chip sounded wonderfull, that was very impressive.
24 hours listening, he discovered a lot of defects and he maid coments....but i do not remember where...i think was in his own forum, the Audio Circle.
regards,
Carlos
But also he told, in advance to that conclusion, that the UCD chip sounded wonderfull, that was very impressive.
24 hours listening, he discovered a lot of defects and he maid coments....but i do not remember where...i think was in his own forum, the Audio Circle.
regards,
Carlos
LBHajdu said:
Neither the AKSA nor the UcD are best of the best. They're both just very good designs, they differ in design philosophy and therefor sonics. I own an AKSA 55N+ and its a great little amp, I've also done a brief comparison to the UcD700AD, I'm hoping to have hands on experience with both in my own system this weekend if all goes well.
Hugh did that... he told that Aksa have eated the class D in the breakfast!
But also he told, in advance to that conclusion, that the UCD chip sounded wonderfull, that was very impressive.
24 hours listening, he discovered a lot of defects and he maid coments....but i do not remember where...i think was in his own forum, the Audio Circle.
regards,
Carlos
But also he told, in advance to that conclusion, that the UCD chip sounded wonderfull, that was very impressive.
24 hours listening, he discovered a lot of defects and he maid coments....but i do not remember where...i think was in his own forum, the Audio Circle.
regards,
Carlos
Carlos,
I think there's clearly a place for many amplifier designs on here, from the SKA to the ASKA and on through to Symasym, UcD etc.
Each has a sound of its own and a different perspective. Non are perfect, all have loyal followings and finally, the most important point is, they all eat similarly priced commercial designs for breakfast.
I think the reason why arguments start out on here is simply because we have no ability to properly convey what sound is, nobody can describe its presentation and impact as much as one can describe the taste of good food. Its a feeling much like love, pain, anger etc. and therefor is impossible to properly convey with words or anything else for that matter.
We all interprete things differently and have different tastes, so what do we do? We degenerate things down into something we do understand and that's numbers, schematics, components, layouts etc. The thing is all those things are a means to an end and non describe the sound or presentation. I personally find it hilarious when folks comment on a design and have never heard it. No matter how great someone may think they are, I'm sorry but nobody can 'hear' an amplifier through technical analysis.
If we sat the all the big DIY amps in one room and listened to them. I'll bet the atmostphere would be much calmer more polite and actually tell folks something. I'd imagine there'd be a few shocks too when the preferences in amplifier were compared to the specs, topology or whatever other technical aspect you care to mention.
Bottom line is too many ego's spoil the soup.
I think there's clearly a place for many amplifier designs on here, from the SKA to the ASKA and on through to Symasym, UcD etc.
Each has a sound of its own and a different perspective. Non are perfect, all have loyal followings and finally, the most important point is, they all eat similarly priced commercial designs for breakfast.
I think the reason why arguments start out on here is simply because we have no ability to properly convey what sound is, nobody can describe its presentation and impact as much as one can describe the taste of good food. Its a feeling much like love, pain, anger etc. and therefor is impossible to properly convey with words or anything else for that matter.
We all interprete things differently and have different tastes, so what do we do? We degenerate things down into something we do understand and that's numbers, schematics, components, layouts etc. The thing is all those things are a means to an end and non describe the sound or presentation. I personally find it hilarious when folks comment on a design and have never heard it. No matter how great someone may think they are, I'm sorry but nobody can 'hear' an amplifier through technical analysis.
If we sat the all the big DIY amps in one room and listened to them. I'll bet the atmostphere would be much calmer more polite and actually tell folks something. I'd imagine there'd be a few shocks too when the preferences in amplifier were compared to the specs, topology or whatever other technical aspect you care to mention.
Bottom line is too many ego's spoil the soup.
pulses, slew rate & dynamic range
Some claim we can detect presence of signals up to 40KHz if loud enough.
Simple math tells us if DVD audio can reproduce 40KHZ and IF the signal is a sine wave then min rise time is about 6 microseconds.
Even if we need to swing 120V then the max slew rate requirement is only 20V/microsecond. Easily handled by most decent amps.
The speed thing is not the issue, it is the required voltage swing for peaks.
Say for example we need 17W RMS for avg levels of 95db at listening position (Talking Heads; peak/avg ratio 40:1) then we will need about 700W peak capability for some music.
Obviously this is where a 700W amp will sound different to a 55W amp!!
It is the peak to avg ratio which requires high voltage swing NOT RMS heat capability.
The other problem is; is this what we really want???? We probably need a compressor for casual listening!!! ;-( Otherwise we may be straining to hear quiet passages only to get blasted by loud ones. This already happens on many classical recordings with perhaps only a 50db dynamic range! We end up riding the vol control!!
I find the soft clipping of tubes a nice natural compressor!! ;-)
( A very important advantage as we know our amps will often be clipping if we listen loud!! )
cheers
Some claim we can detect presence of signals up to 40KHz if loud enough.
Simple math tells us if DVD audio can reproduce 40KHZ and IF the signal is a sine wave then min rise time is about 6 microseconds.
Even if we need to swing 120V then the max slew rate requirement is only 20V/microsecond. Easily handled by most decent amps.
The speed thing is not the issue, it is the required voltage swing for peaks.
Say for example we need 17W RMS for avg levels of 95db at listening position (Talking Heads; peak/avg ratio 40:1) then we will need about 700W peak capability for some music.
Obviously this is where a 700W amp will sound different to a 55W amp!!
It is the peak to avg ratio which requires high voltage swing NOT RMS heat capability.
The other problem is; is this what we really want???? We probably need a compressor for casual listening!!! ;-( Otherwise we may be straining to hear quiet passages only to get blasted by loud ones. This already happens on many classical recordings with perhaps only a 50db dynamic range! We end up riding the vol control!!
I find the soft clipping of tubes a nice natural compressor!! ;-)
( A very important advantage as we know our amps will often be clipping if we listen loud!! )
cheers
Perceptible THD
Those with open minds may find these results of controlled listening tests interesting:
Minimum Perceived THD (%) by 5 different Audiophile Groups
Small Ensembles with Pianos & or lyric voices 1.1, 1.5, 1.3, 2.5, 2.2
Small Ensembles without Pianos & or lyric voices 3, 2.3, 2.5, 5.2, 3
Big EnsemblesWith Choir & or Organ 0.6, 1, 1, 2.2, 2.5
Generally as distortion decreased an increase on detail, transient response and image to detriment of a loss in body and warmth was perceived.
Minimum distortion ( below their perception ) was perceived as excessive sound depersonalization by 3 of the 5 groups.
These psychoacoustic effects reveal there is much more to good sound than chasing numbers and that very low levels of THD may be pointlless at best and can create a negative with many listeners.
cheers
Those with open minds may find these results of controlled listening tests interesting:
Minimum Perceived THD (%) by 5 different Audiophile Groups
Small Ensembles with Pianos & or lyric voices 1.1, 1.5, 1.3, 2.5, 2.2
Small Ensembles without Pianos & or lyric voices 3, 2.3, 2.5, 5.2, 3
Big EnsemblesWith Choir & or Organ 0.6, 1, 1, 2.2, 2.5
Generally as distortion decreased an increase on detail, transient response and image to detriment of a loss in body and warmth was perceived.
Minimum distortion ( below their perception ) was perceived as excessive sound depersonalization by 3 of the 5 groups.
These psychoacoustic effects reveal there is much more to good sound than chasing numbers and that very low levels of THD may be pointlless at best and can create a negative with many listeners.
cheers
I want to find this SKA amplifier, i could not find it...can you inform please?
Yes, Shin Obiwan..... i like your ideas, to show more units here...i do not know exactly if this will broke some forum rules...i really do not know.
I am a free and flexible guy related those things...in my mind, every suggested amplifier can be posted inside XXX thread....every YYY or ZZZ amplifier...for comparison purposes or for some suggested option...i have no problems....i really will apreciate to watch the other options.
But sometimes there are forum friends and moderators that enter to say:
Topic!!!
Topic?
So..... i do know exactly what they think about..... but it seems people do not like orange mixed with beans....i think this is delicious.... Feijoada, a brazilian food...use black beans, pig meat, highly condimented and spiced, and we use to eat with oranges...so...those things depends on culture, tastes, point of views, forum rules and moderators decisions.
regards,
Carlos
Yes, Shin Obiwan..... i like your ideas, to show more units here...i do not know exactly if this will broke some forum rules...i really do not know.
I am a free and flexible guy related those things...in my mind, every suggested amplifier can be posted inside XXX thread....every YYY or ZZZ amplifier...for comparison purposes or for some suggested option...i have no problems....i really will apreciate to watch the other options.
But sometimes there are forum friends and moderators that enter to say:
Topic!!!
Topic?
So..... i do know exactly what they think about..... but it seems people do not like orange mixed with beans....i think this is delicious.... Feijoada, a brazilian food...use black beans, pig meat, highly condimented and spiced, and we use to eat with oranges...so...those things depends on culture, tastes, point of views, forum rules and moderators decisions.
regards,
Carlos
Re: pulses, slew rate & dynamic range
I find you are right, hifryer
Interesting with all them dynamic peaks coming from a microphone.
In another thread a guy wanted an amplifier of 250 Watts
to be able to produce +30dB peaks
Is this realistic?
In my mind it is not.
Not to reproduce 97% of all CD-recordings.
When mastering a CD you are left with 2 choices.
- Use the recording as is, uncompressed and set average level as low as needed to get all the peaks.
- Compress or even cut very high peaks and get a higher average level
As far as I know from reading hifi magazines
it is not unusal to see CD-records with abrupt cut of peaks
-30dB gives average level of CD = 0.06 Vrms
Allowing +20dB peaks gives CD with 0.2 Vrms recording level.
Most CD are mastered having 0.5-0.7 Vrms, -12dB -10dB
hifryer said:
I find you are right, hifryer
Interesting with all them dynamic peaks coming from a microphone.
In another thread a guy wanted an amplifier of 250 Watts
to be able to produce +30dB peaks
Is this realistic?
In my mind it is not.
Not to reproduce 97% of all CD-recordings.
When mastering a CD you are left with 2 choices.
- Use the recording as is, uncompressed and set average level as low as needed to get all the peaks.
- Compress or even cut very high peaks and get a higher average level
As far as I know from reading hifi magazines
it is not unusal to see CD-records with abrupt cut of peaks
-30dB gives average level of CD = 0.06 Vrms
Allowing +20dB peaks gives CD with 0.2 Vrms recording level.
Most CD are mastered having 0.5-0.7 Vrms, -12dB -10dB
FORR
"My data indicate that the fastest recorded rise time of natural audio signals is about 12 micro seconds (a bandwidth about 30 kHz)."
ShinOBIWAN
"Where does your data come from?
Links?"
I think they come from Burdick at Benchmark
http://www.benchmarkmedia.com/
However it's easy to understand. Microphones are better than the ear but are nevertheless bandwidth limited. And there must be very low energy content in most natural ultra-sound "sounds" which are not anymore sounds if we consider sound as what is audible by humans.
~~~~~~ Forr
§§§
"My data indicate that the fastest recorded rise time of natural audio signals is about 12 micro seconds (a bandwidth about 30 kHz)."
ShinOBIWAN
"Where does your data come from?
Links?"
I think they come from Burdick at Benchmark
http://www.benchmarkmedia.com/
However it's easy to understand. Microphones are better than the ear but are nevertheless bandwidth limited. And there must be very low energy content in most natural ultra-sound "sounds" which are not anymore sounds if we consider sound as what is audible by humans.
~~~~~~ Forr
§§§
HIFRYER
" Perceptible THD
Those with open minds may find these results of controlled listening tests interesting [...]"
Contrarily as you may think, I prefectly agree, I think exactly that since twenty years : moderate distorsion levels (even a slight noise) are prefered to no distorsion at all and this is the main story about the differences between amps.
Where I am more puzzled than ever is : why leave the power amplifier to control this distorsion in an imperfect manner ? It will be much better to do it with dedicated electronics where it could be adjusted at will between even and odd order components and leave the classical low distorsion figure to the amps.
~~~~~~~ Forr
§§§
" Perceptible THD
Those with open minds may find these results of controlled listening tests interesting [...]"
Contrarily as you may think, I prefectly agree, I think exactly that since twenty years : moderate distorsion levels (even a slight noise) are prefered to no distorsion at all and this is the main story about the differences between amps.
Where I am more puzzled than ever is : why leave the power amplifier to control this distorsion in an imperfect manner ? It will be much better to do it with dedicated electronics where it could be adjusted at will between even and odd order components and leave the classical low distorsion figure to the amps.
~~~~~~~ Forr
§§§
Lineup
I agree many recordings are severely compressed as most listen in automobiles. But my example is a real one measured off a pop CD.
Forr
I agree. But this is not currently available. Maybe when everything is digital in the whole signal path ( soon) we will buy software with various controls and effects. 1,000W will be commonplace and sound good.
In the meantime, I had the thought ( not original) of adding a pot to an SRPP preamp stage so as to vary distortion by varying the plate load. Could dial in the sound you like ;-)
But the problem is it seems more complex than that in that you don't seem to be able to "cure" an over-clinical SS power amp by adding an over-tubey pre-amp!
cheers
I agree many recordings are severely compressed as most listen in automobiles. But my example is a real one measured off a pop CD.
Forr
I agree. But this is not currently available. Maybe when everything is digital in the whole signal path ( soon) we will buy software with various controls and effects. 1,000W will be commonplace and sound good.
In the meantime, I had the thought ( not original) of adding a pot to an SRPP preamp stage so as to vary distortion by varying the plate load. Could dial in the sound you like ;-)
But the problem is it seems more complex than that in that you don't seem to be able to "cure" an over-clinical SS power amp by adding an over-tubey pre-amp!
cheers
Sound shaper
Hey guys,
It just ocurred to me; there could be a great project in this!
Can anyone dream up a relatively simple way of creating two controls which can independently add say 0 - 2% of 2nd and 3rd harmonics?
Being digitally challenged ( studied, passed and forgotten!) , I'd prefer an analogue solution.
The problem with the SRPP idea is that as the distortion level changes the mix changes also. Maybe could sound reasonably effective though?
cheers
Hey guys,
It just ocurred to me; there could be a great project in this!
Can anyone dream up a relatively simple way of creating two controls which can independently add say 0 - 2% of 2nd and 3rd harmonics?
Being digitally challenged ( studied, passed and forgotten!) , I'd prefer an analogue solution.
The problem with the SRPP idea is that as the distortion level changes the mix changes also. Maybe could sound reasonably effective though?
cheers
hifryer said:
How many pop CD with average sound level at 63 mV rms (-30dB) can we find?
I can promise I have no such disc.
Even a level at 200 mV rms (-20dB) would be rare, I am most sure.
When using very low recorded average level,
we will run into several problems that are worse
than loss of a few peaks in music.
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