SS being fatiguing - yes they can be sometimes but so can a poor tube amp.
I was pleasantly surprised by the Pass Aleph series, they possess a somewhat tubey sound and are very pleasant over long periods of time.
I've got an Aleph 4 which brings out the best in SS and avoids the pitfalls of tubes.
SS will always have the higher power and better reliability. Running a high power tube amp will always eat tubes.
I was pleasantly surprised by the Pass Aleph series, they possess a somewhat tubey sound and are very pleasant over long periods of time.
I've got an Aleph 4 which brings out the best in SS and avoids the pitfalls of tubes.
SS will always have the higher power and better reliability. Running a high power tube amp will always eat tubes.
Well, I do take up electronics are a hobby. I have the experience and capability to build amps from ground scratch. It is good hobby and adventurous to build one. Not to mention I save money building on my own. This is like crossword puzzle for my retirement. But I have no intention to make it a live long hobby. Just want to build a good one........say two max. Just like I spent a year learning about guitar amps and I built two successfully. But I have no intention to build another one, it gets boring after two. So I have to be careful in choosing what to build. I am not going to start small and go up, never done that before and not about to start. My first complete guitar amp is a channel switching, high gain with power scaling already, never went through building a basic simple tweet type amp copy from schematic.
In my experience, clipping performance and characteristics are more related to circuits than devices.
With that in mind, there is no single inherent "harmonic distortion spectrum" a clipping tube or solid-state circuit will produce since the spectrum is largely circuit dependant. Don't believe it? Plug various different tube and SS circuits to oscilloscope and spectrum analyzer and I ensure you you will get widely varying results.
And if certain patterns or characteristics of distortion are design goals then they can be achieved with both tube and solid-state technology. This was discovered ages ago. Vice versa, circuit architectural choices can be equally employed to reduce distortion in most optimal way.
And what's a "natural" harmonic distortion spectrum? IMO, sounds more like a "buzzword" than anything that could be objectively quantified. IMO, all harmonics are "natural" or "unnatural" in some sense, and it largely depends on how you view things. In the end, it's all still nothing but distortion.
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I can tell you the sound of clipping of tubes is very different from SS regardless of circuit. In guitar amp, this is what we mostly work on......overdrive and clipping. BUT clipping is totally unacceptable in hifi arena, they all sounds bad.
One thing I notice in the pass, I used to have a SAE( Japanese made) amp, I notice if I cranked it loud, it did sound better, more solid. Even in guitar amp, seems like there is a certain power level of an amp that it sounds the best even though it's not clipping. It almost seem a little distortion make it sound better. To me, it seems like the high quality amps can sound good at low volume while the cheaper ones need to be cranked up higher to sound better.
One thing I notice in the pass, I used to have a SAE( Japanese made) amp, I notice if I cranked it loud, it did sound better, more solid. Even in guitar amp, seems like there is a certain power level of an amp that it sounds the best even though it's not clipping. It almost seem a little distortion make it sound better. To me, it seems like the high quality amps can sound good at low volume while the cheaper ones need to be cranked up higher to sound better.
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We agree on a lot of things, but I'd be amazed if I could hear a difference with adding more speaker cables. Speaker damping by the amps source impedance is limited by the DCR of a voice coil (usually around 6 ohms with a nominal 8 ohm driver), and the speaker cable is about 0.1ohm (10 ft. of 16AWG). The idea of cables acting as antennas and channeling Rf energy into the feedback input port of a power amp (which is tied to the output node) is possible, but seems unlikely to be a significant thing if the circuit design is good. This should be worse with tubes. Cheap parts are very often just as good as the expensive parts IMO, And not enough is said about the circuit design being a huge thing.
When I repair audio electronic devices, it's not that rare that I'll have to fix a design flaw, so the unit won't just blow up again after I've worked on it. And yes, I've yet to hear a transistor guitar amp that has nearly as good a distortion sound as a well designed tube amp. I've studied guitar amp distortion extensively, and built a bunch of amps to learn 1st hand from. One of my hobbies is blues guitar, where I want the perfect growl in my sound. It's all about distortion spectrum shape.
To the guy who says distortion is distortion period, the way the ear distorts is perhaps a reference of what might sound natural. The ear is a single ended transducer. It seems likely to distort much like a single ended triode, where the harmonic distortion spectrum shape will be a relatively fast and even rolloff. the 2nd harmonic (which is the same note as the fundamental but an octave higher - and generally always sounds good) will be higher than the 3rd harmonic, and the higher order harmonics will taper off with a smooth curve. In many transistor amps, the 2nd harmonic is very low compared to the third. Even harmonics in general are way down compared to odd harmonics. So the feel of the sound may be less natural. Harmonic distortion spectrum shape is what gives each instrument its unique sound.
I did read that part about Bob Carver stating that putting a 1 ohm R in series with the output of a transistor amp gives you 80% of the tube sound. As usual there are other variables at play that could be significant. Such as how that 1 ohm resistor will help the amp circuit maintain a better phase margin - a reduction of the reactivity of the load as seen by the amp. This is why I always put a 100 - 200 ohm R at the output of every opamp circuit I build. But then years later Bob Carver piped up again and said, tube amps also sound better because of the speaker acting as a microphone, and channeling the room reflected sound back into the negative feedback input of the high feedback tube amp (since the neg FB port is tied to the output). Well... that could happen to some degree, but at audio frequencies the output impedance of a high feedback tube amp (25dB for ex.) is usually significantly less than an ohm, so the counter electromotive force generated by the speaker acting as a mic is largely shorted out. It reminds me of the concept that when you play a record, the physical energy created by the needle vibrating in the groove will cause the record to act like a very short term reverb chamber to a tiny yet maybe audible degree. The record is often only touching the turntable platter at the edges, so the record itself can vibrate. This and compression (always used in record making) could account for why many people think vinyl sounds better than digital. My point being that there are usually other variables at play in any audio research experiment. The trick is to know what they are and how they contribute. It seems to be a never ending scientific path. There's always more to learn.
I have no explanation, I can only report my experience. My speaker is JM Lab Focal floor speaker from the late 90s. That's all I can say. My wife that doesn't know anything about audiophile or electronics notice the difference too.
As an Engineer, I am very skeptical on all the snake oil. I was actually surprised about this too.But if you think about if the speaker dip down to 1 or 2 ohms at some frequency, a little bit of inductance or resistance of cable might make a difference. The bigger the cable, the lower the inductance as L is proportion to length/(cross sectional area). I don't know, I just use my ears as the judge. Maybe another pair of speaker won't make any difference.
In guitar amp, I can tell you changing the coupling cap from 1500p to 3000p change the sound, not just more base, actually change the sound. Change of resistance value change the sound tremendously. Audio is a different world that one cannot just go by theory. I am very into theory and derive all the equations and get into it very deep. But I learn after working on audio electronics, it really is an art.
As in the first post here, I already made the case that SS can achieve much lower distortion much easily. That's not even my question. My question is really how important is low distortion to the quality of the sound. That's ultimately is the only thing that matters.
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Low distortion is obviously what everyone should want in a hifi amp. There's the argument that a small amount of 2nd harmonic distortion will enhance music, if the same mechanism doesn't introduce too much IM. Although the 2nd sounds good, the IM won't, and will be particularly noticeable with choral music and piano music. From the 3rd harmonic on up, it's not probable that any of these harmonics will be pleasantly musically related to the fundamental (go play them on a piano like I did and see for yourself), so a fast rolloff of higher order harmonics is what the hard core audiophiles I know go after. So it's not just a question of how much distortion but also the spectrum shape.
The high feedback transistor amps all seem to have quite a bit of the higher order harmonic distortion products, while the tube amps usually have a significantly faster rolloff of them. Perfectly symetrical topologies look cool on paper, but cancel even order harmonics much more than the odds, creating a less natural sound.
Although the measurements with a conventional sinewave, or 2 tone for IM says these amounts are very small, it's hard to say if they become significant when processing the complexity of actual music. Apparently it might, or many of us are fooling ourselves when we think tubes sound better before clipping sets in. But I've heard transistors sound so good I don't really care about the difference, if there is one.
The Linkwitz Orion speakers have about 6 opamps in the signal path of the active crossover and open baffle EQ, and the poweramps were Carver, which may be average quality, and they sounded stunningly good with very well recorded Orchestral music.
Personally I just don't have room for tube poweramps in my HiFi system. My main speakers are tri-amp'd. My center speaker is bi-amp'd, and there's one more poweramp for the side speakers up at the ceiling. Six stereo poweramps, and a rack full of everything else. If I had a wife, she would be very pissed.
The high feedback transistor amps all seem to have quite a bit of the higher order harmonic distortion products, while the tube amps usually have a significantly faster rolloff of them. Perfectly symetrical topologies look cool on paper, but cancel even order harmonics much more than the odds, creating a less natural sound.
Although the measurements with a conventional sinewave, or 2 tone for IM says these amounts are very small, it's hard to say if they become significant when processing the complexity of actual music. Apparently it might, or many of us are fooling ourselves when we think tubes sound better before clipping sets in. But I've heard transistors sound so good I don't really care about the difference, if there is one.
The Linkwitz Orion speakers have about 6 opamps in the signal path of the active crossover and open baffle EQ, and the poweramps were Carver, which may be average quality, and they sounded stunningly good with very well recorded Orchestral music.
Personally I just don't have room for tube poweramps in my HiFi system. My main speakers are tri-amp'd. My center speaker is bi-amp'd, and there's one more poweramp for the side speakers up at the ceiling. Six stereo poweramps, and a rack full of everything else. If I had a wife, she would be very pissed.
The last two days, I have been studying The SS power amp book by Bob Cordell. Also I just found out that they sell power amp chassis with heat sink on both sides build in for only about $120. This is the part that I afraid most......how to do the mechanical design of the chassis and heat sink to even make it look half way decent. The available chassis with heat sink solve all my concern and is cheap!!!
I finished about 200 pages of Cordell's book, it will be definitely cheaper and straight forward to build a SS power amp. I do have to layout the pcb which is not that bad at all. I did a lot of pcb designs in my career. I think I can get a run of pcb for less than $200, then buy double amount of power transistors to find the matching set.
Cordell laid out all the pros and cons on every stage in the amp, looks like it's not too bad design and build one. It's not like tube amps that you are really at the mercy of the OT and the tubes which is very expensive. I am not saying SS amp sounds better, I can say I listened to very good sounding SS power amp before. My speaker is not the best in the world, I really don't need an ultimate, end all power amp.
But I still have make up my mind. I just received the tube book by Morgan Jones, I might change my mind after read that. I just need to be well informed first.
I finished about 200 pages of Cordell's book, it will be definitely cheaper and straight forward to build a SS power amp. I do have to layout the pcb which is not that bad at all. I did a lot of pcb designs in my career. I think I can get a run of pcb for less than $200, then buy double amount of power transistors to find the matching set.
Cordell laid out all the pros and cons on every stage in the amp, looks like it's not too bad design and build one. It's not like tube amps that you are really at the mercy of the OT and the tubes which is very expensive. I am not saying SS amp sounds better, I can say I listened to very good sounding SS power amp before. My speaker is not the best in the world, I really don't need an ultimate, end all power amp.
But I still have make up my mind. I just received the tube book by Morgan Jones, I might change my mind after read that. I just need to be well informed first.
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Reading books about amplifiers
Alan, I am yet to find the book about amplifier design that is pragmatic about what is and is not audible, and humble about the folly of using sighted listening tests to determine audible improvements or distortions. Therefore, such books tend to either covertly or overtly give the impression that all kinds of circuit details are significant (i.e. audible, because what other basis for significance holds water?). In the end, they are paeans to the author's mastery of his domain, where said domain is error minimisation (SS amp) or refinement of principles drawn from gross assumptions about what sounds better (valve amp), but never are the authors driven exclusively by solid research on what is audible and therefore what is the design direction that is inaudibly erroneous into any load, at a range of power levels that the end user or his advisor can choose based on need, and that is cheapest and most reliable.
The important questions in today's world of amps, to the impartial end user, are [1] exactly what speakers will it drive (efficiency, load impedance vagaries), [2] what input voltage will it see and what impedance will its upstream component need to see, and [3] what is the listening environment in terms of room size and reverberation and peak SPL levels at which listening positions. Therefore what power levels into what loads will avoid clipping.
If the end user is impartial to amp type, I suspect that the right answers at the moment are: for modest drive requirements, a chip amp; for high drive requirements, a class D amp unless the load is difficult at high frequencies, in which case a beefy SS amp.
As you can see, I am saying that the amplifier decision needs to be reassessed for every application and environment. If the application is undemanding and cost is not a driving factor, the end user can choose from a number of technologies based on non-sonic criteria.
What happens in practice of course is quite different. The end user conducts 'listening tests' under sighted conditions, doesn't understand that such testing conditions allow conscious and unconscious biases to dominate the actual sound waves, and thinks he hears better and worse sounding amps because he 'trusts his ears'. Then he chooses on that basis (and often becomes quite religious about amps). And you know what? That's the right thing to do - for oneself. Because in the real world he will be listening to his hifi in sighted conditions, so the above-mentionsed biases will be operating and he will be 'hearing' the attributes that he thinks are in the sound waves: he cannot turn it off by conscious effort, so he needs to build it in to his decision process. The 'dangerous' bit is when he advises others about what amps sound better, not realising that the biases that are 'fooling' him are not about sound waves and only applicable to himself.
So in the end, the real outcome of reading books about amps, is that you are modifying your existing 'bias settings' into a new 'bias setting' that will colour your perceptions during listening. And all beyond your conscious control. How ironic, given that the paradigm and motive for reading them in the first place is that the knowledge gained will allow you to make more informed decisions. How very ironic.
Alan, I am yet to find the book about amplifier design that is pragmatic about what is and is not audible, and humble about the folly of using sighted listening tests to determine audible improvements or distortions. Therefore, such books tend to either covertly or overtly give the impression that all kinds of circuit details are significant (i.e. audible, because what other basis for significance holds water?). In the end, they are paeans to the author's mastery of his domain, where said domain is error minimisation (SS amp) or refinement of principles drawn from gross assumptions about what sounds better (valve amp), but never are the authors driven exclusively by solid research on what is audible and therefore what is the design direction that is inaudibly erroneous into any load, at a range of power levels that the end user or his advisor can choose based on need, and that is cheapest and most reliable.
The important questions in today's world of amps, to the impartial end user, are [1] exactly what speakers will it drive (efficiency, load impedance vagaries), [2] what input voltage will it see and what impedance will its upstream component need to see, and [3] what is the listening environment in terms of room size and reverberation and peak SPL levels at which listening positions. Therefore what power levels into what loads will avoid clipping.
If the end user is impartial to amp type, I suspect that the right answers at the moment are: for modest drive requirements, a chip amp; for high drive requirements, a class D amp unless the load is difficult at high frequencies, in which case a beefy SS amp.
As you can see, I am saying that the amplifier decision needs to be reassessed for every application and environment. If the application is undemanding and cost is not a driving factor, the end user can choose from a number of technologies based on non-sonic criteria.
What happens in practice of course is quite different. The end user conducts 'listening tests' under sighted conditions, doesn't understand that such testing conditions allow conscious and unconscious biases to dominate the actual sound waves, and thinks he hears better and worse sounding amps because he 'trusts his ears'. Then he chooses on that basis (and often becomes quite religious about amps). And you know what? That's the right thing to do - for oneself. Because in the real world he will be listening to his hifi in sighted conditions, so the above-mentionsed biases will be operating and he will be 'hearing' the attributes that he thinks are in the sound waves: he cannot turn it off by conscious effort, so he needs to build it in to his decision process. The 'dangerous' bit is when he advises others about what amps sound better, not realising that the biases that are 'fooling' him are not about sound waves and only applicable to himself.
So in the end, the real outcome of reading books about amps, is that you are modifying your existing 'bias settings' into a new 'bias setting' that will colour your perceptions during listening. And all beyond your conscious control. How ironic, given that the paradigm and motive for reading them in the first place is that the knowledge gained will allow you to make more informed decisions. How very ironic.
Well, we're back to the original post again!!!! That's what I find audio electronics so frustrating, electronics theory and knowledge help a lot less than people think. This is even worst in guitar amps where the most important thing is not even knowledge, it's the ear. I am doing it for my own amp here, I don't think I will enjoy designing music electronics as knowledge doesn't matter as long as you know the basics. That's the reason after I completed two guitar amps that I am very happy with, I am moving on, it's no fun anymore.
I can't really agree with this.
Listening is important but it isn't the only skill required in building or modifying amplifiers. If you can't identify what you hear (in terms of objective electrical behavior), or have no clue what or how to modify things to make the circuit respond closer to your individual tastes then what good are your great "ears" for?
No. It's not that simple. In practice, almost all amplifiers are driven into clipping. Therefore what the amp does during clipping has some importance. An experienced amplifier designer always checks the clipping behaviour.
If you doubt it, play music, at a comfortable volume through a solid state amplifier that is the best available to you, while watching the output on an oscilloscope. You'll see flat-topping occaisonally on peaks. Certainly not all the time, but it does occur. That is the nature of music.
Noted Australian engineer Neville Thiele wrote a most interesting paper on this back in the 1960's.
Back then, loudspeakers with ceramic magnets and good bass response had become available to manufacturers at low cost (eg Rola C8MX twin cone). That and a growing awareness of "hi-fi" triggered the inclusion, in top of the range stereos and TV audio of:-
1) Larger cathode bypass capacitors;
2) Better output transformers using the then new low cost grain oriiented silicon steel, improving both bass and trebble range
3) More negative feedback, enabled by the better output transformers
4) Coupling capacitors considerably increased in size, to take them out of influence with the higher neg feedback wrt pahse shift.
These systems checked out very good on test, wide range response, low THD. But the public didn't always like them.
Neville Theile investigated why. What he found was that music peaks in the positive direction drove the amp output tubes into grid cut-off. Grid cutoff charges the coupling capacitors so the grid becomes more negative. Just after the music peak the tube is now overbiased and cutting off on negative peaks until the coupling capacitor re-equalises its charge.
So, instead of the amp just clipping on the music peak for maybe a millisecond or two, following the peak it flat-topped for a few tens of milliseconds on relatively low levels well within the amp power rating.
It happens that the ear has difficultly in detecting the odd bit of clipping lasting only a few milliseconds. Some people cannot detect it at all. But clipping lasting for tens of milliseconds sounds bad to everyone.
In Mr Theile's paper, he has an amusing anecdote at the end. He said that whenever a prototype new model was demostrated to factory management (elderly accountant generic business types), they often seemed bemused and unaware of improvements in the sound quality. But when he demostrated the effect of halving the coupling capacitor capacitance on clipping behavior, in an amp specially rigged for the purpose, their eyes lit up and they put on broad smiles!
The solution is simple: Use the minimum size coupling cap to feed the output stage to meet the low frequency response spec, plus use DC coupling in low level stages if inside the feedback loop, and use a really good output transformer so you don't have instability with neg feedback.
As solid state amps are generally DC coupled, they don't suffer from coupling capacitor blocking, but there are other mechanisms in solid state amps that can make clipping behaviour bad. For instance, as I learnt the hard way in my first SS amplifier design (1967), resistors in series with emitters (to improve linearity and dampen Early effect) makes it possible for the previous stage to drive the collector-base junction into forward bias - so during clipping the output phase is momentarily inverted. Now, on music that does sound truely AWFUL! And the amp may have vanishing small THD on test.
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