Dave Simpson
Plywood King
We were discussing amplifiers and speakers.
The difference between mainstream HIFI, budget seperates, midrange and high end?
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RobHolt
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That's hardly fair Dave.
A full and thorough explanation of all aspects of amplifier and speaker design would fill several books.
I'd be more than happy to provide details of several books from respected objectivist audio designers for you.
Might take you several weeks to even skim read but it will answer your question. Having done the reading, the forum would perhaps be a good place to pick over any questions or specific topics.
Doug Self's book on amplifier design would be a good place for you to start. This specifies the requirements for a 'competent' amplifier and then goes on to discuss them is detail.
RobHolt
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Who said all amplifiers sound the same?
You validate the assumption via controlled testing.
In other words, you take the Technics receiver mentioned above along with the Naim and you compare them - unsighted - driving speakers that induce neither voltage or current clipping.
If after repeated testing on a range of material and driving different speakers it proves impossible to identify a difference, you classify the amplfiers as nominally the same - not identical but close enough to be regarded as the same for their intended use. If you identify differences then go look at the measurements and you will find the answer. It is never due to the unexplained.
How do you establish a reference for 'competency'?
Well that is very easy for me but I suspect difficult for you
For me, a good Cambridge, Cyrus, Arcam, Quad, Nad, Pioneer, Marantz costing upwards at around £500-£1k all sound incredibly close in performance. Close enough and in fact good enough in performance for me to accept that as a solid standard. All have generally excellent lab performance short of clipping.
When I compare amplifiers to the likes of the above and hear a difference it is always due to known factors that can be measured.
High output impedance, *high THD, noise, poor PSU decoupling between stages, RF pickup, microphony (tubes), poor temperature stability (crossover distortion implications), crosstalk, frequency response, input stage clipping or distortion.
That will do for now
* The distortion spectrum within the THD is sometimes important.
However, if THD is very low, as is typical with modern SS amplifiers at <0.05% then quite frankly the distortion make-up becomes moot. However would I prefer 1% largely 2nd harmonic to 1% largely higher order - you bet.
Apologies for any dodgy spelling as I've just banged this out on some fartly little portable device.
Oh really, is that something new?
I love my little Viliv device, I'm using it now. I started ripping all my CDs two days ago to a portable 750GB drive connected to my router as you have done. iTunes ability to find artwork is not good though, I have about 20 CDs on there now and only 3 with the artwork! I did start at the old and obscure end of the collection though.
I also got the mobile internet via a sim card working. It does about 4Mb/s! Chufed
Dave Simpson
Plywood King
Thanks for the detailed reponse Rob. That's exactly what I'm looking for.
I appreciate the recommendation for Doug Self's books which you made several weeks ago in another thread. I'll be getting either Self on Audio or Audio Power Amplifier Design shortly.
Regarding blind tests on amplifiers, I've participated with many in the past and have always been able to identify differences unless there were problems found after the fact with testing setup (usually the gain set so low for both amps as to invoke the ear's lack of sensitivity at frequency extremes or rapid A/B switching with a box and a continuous stream of music instead of repeating a short passage.)
I'm relieved you are not of the opinion that all amplifiers sound the same. TBH, I was under the impression that was your belief and that's what provoked my first post on the matter. I'm glad you've set the record straight.
Regarding your opinion that most competent amplifiers have differences which are negligible or unimportant, I have no problem with that. We all have different values.
My opinion on the matter of how much we know about audio is only based on the results of years of listening. Bias, expectations, design quirks and interactions with other components is the sum total of my experience so far and regardless of what I may learn delving into the technical aspects down the road, I suspect what I've heard will remain what I hear in the future when the components are connected and used as intended in the real world. Time will tell of course.
best,
dave
I appreciate the recommendation for Doug Self's books which you made several weeks ago in another thread. I'll be getting either Self on Audio or Audio Power Amplifier Design shortly.
Regarding blind tests on amplifiers, I've participated with many in the past and have always been able to identify differences unless there were problems found after the fact with testing setup (usually the gain set so low for both amps as to invoke the ear's lack of sensitivity at frequency extremes or rapid A/B switching with a box and a continuous stream of music instead of repeating a short passage.)
I'm relieved you are not of the opinion that all amplifiers sound the same. TBH, I was under the impression that was your belief and that's what provoked my first post on the matter. I'm glad you've set the record straight.
Regarding your opinion that most competent amplifiers have differences which are negligible or unimportant, I have no problem with that. We all have different values.
My opinion on the matter of how much we know about audio is only based on the results of years of listening. Bias, expectations, design quirks and interactions with other components is the sum total of my experience so far and regardless of what I may learn delving into the technical aspects down the road, I suspect what I've heard will remain what I hear in the future when the components are connected and used as intended in the real world. Time will tell of course.
best,
dave
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RobHolt
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Oh really, is that something new?
I love my little Viliv device, I'm using it now. I started ripping all my CDs two days ago to a portable 750GB drive connected to my router as you have done. iTunes ability to find artwork is not good though, I have about 20 CDs on there now and only 3 with the artwork! I did start at the old and obscure end of the collection though.
I also got the mobile internet via a sim card working. It does about 4Mb/s! Chufed
No nothing new, just a really small notebook from the office that has a weeny little screen and keyboard.
I'd say iTunes finds about 80% of my artwork, but then you do listen to some strange music
If iTunes cannot locate the artwork just punch the album and artist into Amazon and you'll probably find it. Then just drag the album cover into iTunes and it will be stored.
I am seriously considering one 'gadget' though - a new Mac Mini and a nice big monitor to stand in place of my, ahem....legacy B77 right slap in the middle of the system.
So Mini/Monitor>Your Dac>Amp.
It can run as a self contained music server or headless via iTouch.
RobHolt
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Ah yes, people will attribute all sorts to others in order to make a point. I've never said that there are no audible differences between cables either, simply that all audible differences are due to understood and measurable factors. IMO most have close enough specs that the differences are inaudible but you can certainly find examples of cables that change the sound.
That is consistent with my views on most audio electronics - that we have reached the stage where kit is pretty much interchangeable with the difference being so small that they go unnoticed, but there must always be a basic level of competency. Analogue source components and speakers are a different kettle of fish with often huge differences and that is where I put my efforts these days. I think we pretty much 'sorted' amplifiers back in the late 70s and digital audio in the late 90s so long as you are avoiding kit on the lower rungs.
I have an old Kenwood amplifier (KA1200) that sounds pretty rough. Doesn't measure well though and I certainly wouldn't claim that it sounds the same as a good modern amp. However, I do know why and for me that is key.
Do read the Self books though Dave. Even if you end up rejecting his finding it still makes a thought provoking read.
regards,
I pretty quickly notice the difference between my valve amp and my old cyrus one, Rob, if I have to use it.
Well I don't think Rob was referring to valve components.
In this category there can be big differences especially amps.
Valve components are known to be musically colourful.
RobHolt
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I pretty quickly notice the difference between my valve amp and my old cyrus one, Rob, if I have to use it.
Then you make my point perfectly David, because I can assure you they'll measure very differently, unlike those examples in the list I posted yesterday.
RobHolt
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Well I don't think Rob was referring to valve components.
In this category there can be big differences especially amps.
Valve components are known to be musically colourful.
Agree entirely titian.
I'm not commenting on personal judgement either and perfectly understand why someone might prefer 'colourful'.
regards,
It's not just a matter of measurable parameters. It's under which conditions those parameters are measured.
A £200 amp may well measure identically to a £1000 amp under lab conditions if fed with a single frequency sine wave in to a purely resistive "ideal" load for example. However, there may well be measureable differences between various performance parameters between the two amps when fed with a more complex / demanding input signal. (even when short of clipping the input), in to "real world" loads as presented by a speaker/cable combination.
In the same way for example two cables may well measure identically with respect to frequency response under certain conditions but may well have differing effects on the overall performance of a "system" when the electrical characteristics of the specific input/output circuits they are connected to are taken in to consideration.
My only point being, to determine the "affects" of any particular part of a system you need to consider all of the variables. This is as true for a "Hi-Fi" system as it is for any other electrical (or otherwise) system.
A £200 amp may well measure identically to a £1000 amp under lab conditions if fed with a single frequency sine wave in to a purely resistive "ideal" load for example. However, there may well be measureable differences between various performance parameters between the two amps when fed with a more complex / demanding input signal. (even when short of clipping the input), in to "real world" loads as presented by a speaker/cable combination.
In the same way for example two cables may well measure identically with respect to frequency response under certain conditions but may well have differing effects on the overall performance of a "system" when the electrical characteristics of the specific input/output circuits they are connected to are taken in to consideration.
My only point being, to determine the "affects" of any particular part of a system you need to consider all of the variables. This is as true for a "Hi-Fi" system as it is for any other electrical (or otherwise) system.
Dave Simpson
Plywood King
I'm not aware of anyone who doesn't believe measurements are important including those who believe many components and cables sound different from each other (the magic circle folks?) I simply find them meaningless for telling me what a component actually sounds like other than obvious quirks with wild swings in FR perhaps. They're more useful to me as an end user for determining compatibility.
Any magic circle friends disagree?
Any magic circle friends disagree?
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RobHolt
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You don't need wild swings to change the sound.
just 0.5db change is perfectly audible, not if it's a narrow peak but certainly it can change tonal balance if wider.
For example, a Naim power amplifier has 0.3 ohms output impedance while a Cambridge 840 has 0.05 ohms. Drive a low impedance speaker system using a fairly typical passive crossover and you will easily see broad 0.25-1.0db FR changes.
Those are audible.
Where it gets interesting is when you increase the output impedance of the 840 and finds that it starts sounding like the Naim
So you can swap one expensive box for another or you pop to your local electronics store and send $1 on a pair of resistors.
Dave Simpson
Plywood King
That actually answers my first question on how you can modify one amp to sound like another;-)
cheers,
dave
cheers,
dave
Well it goes part of the way towards an answer. From an engineering point of view it's not just resistance that would matter but other things such as bandwidth product, slew rates, distortions etc.
The impact of such things on our perception of the sound aren't fully understood however. For example. How would you measure transparency?? is it purely a function of resolution and therefore noise floor? or are other factors at play? It is known that a little bit of noise actually improves the human ears ability to resolve smaller levels for example. In fact it's a technique that is used in CD production/playback.
The real problem however is that our hearing, (as with all our other senses), is relativistic. Our senses are only able to measure relative changes, not absolute ones. We know something is hot, only because it is "hotter" than what we are currently percieving for example. One reason that people from other climes complain about the weather, it's called aclimatisation. In terms of vision, one person may have the colour saturation of their TV higher than another person and they may percieve the other persons TV to be lacking colour, even if measureably it can be seen to be more accurate, again aclimatisation.
For our hearing similar things happen. Take a perfectly flat frequency response. If you give that response a broad 1db suck out through the midrange, it may well be percieved as being very similar (if not identical) to givng the treble a broad 1db lift. Our ears/brain are incapable of knowing the actual levels, all we percieve is that the treble is around 1db higher than the midrange. How that translates to the consciously percieved sound quality of the system depends on the individual and their frames of reference.
There are many more examples of how sound is percieved in a relative way. It is this relativistic nature which to an extent leads to the "black art" in amplifier design for example. We can make the measurements, and then the adjustements, but how they translate to percieved sound quality is to a great extent only broadly understood.
However, that is not to say that we don't understand what the changes/measurements tell us about the accuracy of the system.
Edited to add - this forum has an annoyingly short session time out. In the time it took me to write the response above I had been logged out !!
