I agree Thorsten, but some statistics I picked from I don't remember where any more indicated that most of spent most of our time at or below the level of 1 Watt into 8 Ohms when listening to music at home. While I find this a little too generalized for comfort, even doubling that number still means we need more power for transients only.
And making a class AB amp work in pure class A up to say 2...3 Watts is no big brainer, it doesn't require extensive knowledge of rocket science.
Ultimately, that's the rationale used by most tube audio gear manufacturers peddling 10 Watts or so SET power amplifiers. While some of them may indeed sound sweet, to me, the reproduction of transients never really sounds as convincing as with a higher powered transistor amp. And I do have exceptionally easy to drive speakers, with a nice sensitivity of 92 dB/2,83V/1m.
Hi,
At some frequencies signals below nominal 0dB SPL are audible.
The -20dB SPL (0dB SPL simply means not audible, it is not absolute zero) makes sure we stay away from this. Maybe -10dB SPL would suffice, I like to work with round numbers.
Ciao T
At some frequencies signals below nominal 0dB SPL are audible.
The -20dB SPL (0dB SPL simply means not audible, it is not absolute zero) makes sure we stay away from this. Maybe -10dB SPL would suffice, I like to work with round numbers.
Ciao T
Hi,
More bias, shaping distortion away from high orders etc. are all strategies we may employ to minimise audibility of the distortion, if we somehow cannot maintain the "all distortion below -20dB SPL" dictum.
Your speakers are not suited to any SE Amplifiers, exepting MAYBE the biggest of the class, that is dual 211 or dual 845 beasties. A single 300B will not stand a chance operating sensibly into something like.
My current speakers are broadly similar, but any less than 30 - 40 Watt Tube Power is hopeless.
So the problems you are having are not the SE Amplifiers themselves, but using them with inapproriate speakers.
Buy a Laborghini. Attach a one ton trailer. Then try to get decent acceleration, like 0 - 60MPH in under 5 seconds and fail.
Who do you blame?
The designer of the Lambo for making a car that cannot pull 1 Ton Trailers to 60MPh in 5 seconds, or the ejit that tried to pull a 1 Ton trailer with a Lambo?
Ciao T
More bias, shaping distortion away from high orders etc. are all strategies we may employ to minimise audibility of the distortion, if we somehow cannot maintain the "all distortion below -20dB SPL" dictum.
Your speakers are not suited to any SE Amplifiers, exepting MAYBE the biggest of the class, that is dual 211 or dual 845 beasties. A single 300B will not stand a chance operating sensibly into something like.
My current speakers are broadly similar, but any less than 30 - 40 Watt Tube Power is hopeless.
So the problems you are having are not the SE Amplifiers themselves, but using them with inapproriate speakers.
Buy a Laborghini. Attach a one ton trailer. Then try to get decent acceleration, like 0 - 60MPH in under 5 seconds and fail.
Who do you blame?
The designer of the Lambo for making a car that cannot pull 1 Ton Trailers to 60MPh in 5 seconds, or the ejit that tried to pull a 1 Ton trailer with a Lambo?
Ciao T
Thorsten, just two short notes:
1. My speakers were tried with smaller powered amps, however, as far as I can recall, all of them used two tubes in the output per channel, and
2. I don't really care because I do not like the sound of tube audio. They don't sound right to me, no matter what anyone says, however, I am obviously just one guy and my motto is live and let live. I don't like it, but I don't knock it.
So, as you can see, I do not have any problems driving my speakers since I am a 100% solid state man. Home audio ranges from 50 to 180 W/8 Ohms in Three Easy Steps, and even the smallest of the lot, H/K 6550, rated at 50/70W into 8/4 Ohms, is exceptionally load tolerant. In addition to which the speaker itself has a nominal impedance of 8 Ohms, minimum of 6.5 Ohms, and the worst phase shift is -25 degrees, which makes it an EXCEPTIONALLY easy load to drive.
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Completely agreed.
It's just that my own taste runs into the bipolar group, as MOSFETs don't do it for me either. Although I am always open to new experiences. You never know, and I have had a few surprises in my time, and in both directions.
Won't that throw up more mist? Or at least make things etwas feucht? (apologies Dennis!)
Sure, no problemo, just subscribe to Italy's "Suono" magazine, they have had it for over 20 years now.
And it can show up things. They once had a test of power amps, like 14-15 years ago. In it they had offerings from Harman/Kardon, Sony, Nakamichi and, to the point, Musical Fidelity. Well, H/Ks was absolutely clean up until about +1 dB, Sony's was good to 0 dB, Nakamichi's started to deteriorate at about +1.2 dB, while the Musical Fidelity's, the small model touted as Class A (which it really wasn't, it ran in class A until about 14 of its nominal 30 W/8 Ohms or so, so it was really a High Bias product), was a mess all around. The thing was running wild from about -5 dB upwards.
What about the low frequency cut-off, and what value it needs to be?
I run into this one with FM tuners, where you need flatness to at least 3Hz on the detector out composite signal to get full stereo separation from the MPX decoder.
Also, though you can have a system where individual components have decent low frequency cut-off, when you put all the components in series, you create a bunch of serial low low pass filters. Then that "system" has a total low pass characteristic that's the sum of the components, (and cables used). This can be different for everyone, depending on how things "match". And this does not even yet include the speakers, but then yes, they have their own low pass cutoff.
And what is the music requirement for low frequency cutoff? Don't think about sine waves, think about transients. What is the relationship between the width of a transient and frequency content?
And when you roll off the low end, what does that do to the phase response, and can anyone hear the phase of, say, an 80Hz signal's harmonics?
I ask because I've read that many designer's feel there is a "sweet spot" for low end roll-off that "sounds good".
I run into this one with FM tuners, where you need flatness to at least 3Hz on the detector out composite signal to get full stereo separation from the MPX decoder.
Also, though you can have a system where individual components have decent low frequency cut-off, when you put all the components in series, you create a bunch of serial low low pass filters. Then that "system" has a total low pass characteristic that's the sum of the components, (and cables used). This can be different for everyone, depending on how things "match". And this does not even yet include the speakers, but then yes, they have their own low pass cutoff.
And what is the music requirement for low frequency cutoff? Don't think about sine waves, think about transients. What is the relationship between the width of a transient and frequency content?
And when you roll off the low end, what does that do to the phase response, and can anyone hear the phase of, say, an 80Hz signal's harmonics?
I ask because I've read that many designer's feel there is a "sweet spot" for low end roll-off that "sounds good".
Roughly, the wider the 'transient', the lower the lowest frequency content. For a single unrepeated transient the frequency content goes down to DC, but that does not necessarily mean that the audio system has to go down to DC. We perceive very low air frequency air movements as a draught rather than sound.
You are right to say that LF cutoffs accumulate. Cables don't have an LF cutoff; they go down to DC. Rolling off the LF is necessary with any realistic speakers. My guess is that, apart from the special case of stereo decoders, the main need is to maintain channel balance on LF phase rather than worrying too much about the actual value. Having said that, you can reckon that there is a significant phase change up to about a decade in frequency either side of the -3dB point.
The 20Hz LF cutoff often quoted is not too daft, when you realise that the lowest note in music is 17Hz (?) and many speakers rolloff quickly below about 40-60Hz. Then there is the need to balance LF and HF cutoff, so the product of the two is in the right region. There was a thread about this last year.
AudioGraph Power Cube - Stand Alone System
I brought this up with Floyd Toole a couple of days ago (having asked Martin Zanfino, now with Infinite Algorithms and formerly VP Engineering with Harman Kardon, what was that 2-d representation of a 3-d plot with different loads that showed how close to perfect voltage sources power amps were?), and he dug a bit and found the audiograph site. I love their water-cooled model
Marty remarked that when h/k started to characterize their and others' amps using their own version of the power cube, audiophiles remarked that it was one of the first measurements that seemed to correlate with perceived sound quality. The h/k amps were designed by Ritchie Miller, who according to Marty is still active although formally retired, and they emphasized high current capability as well as wide bandwidth.
Brad
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