ocaukrell said:
Very cool. Poor_lackey just sent me a scan of the AEM6005 article. Looks really nice - lots of symmetry. I suspect sourcing the matched JFETs for the input (ECG/NTE461) may be problematic - I might try bunging a Vishay U404 in instead. Certainly it's not my intention to slavishly follow Tilbrook's design, but to fiddle at the edges somewhat.
hifryer said:
I'm not surprised it sounded bad, if it was oscillating. I know from experience that fast circuits can often be difficult to tame.
hifryer said:
I've gotta confess to being an engineer who ridicules tubes, and is guided by objective data, rather than feel-good garbage and marketing rubbish. I don't want my amp to sound warm, or rich, or anything of the sort. I want it to faithfully reproduce my music, and I know that the way to do that is to minimise distortion and noise.
Regards,
Suzy
suzyj said:
Yep,
that sounds like an engineer alright.
Just when i was getting ready to propose class A.
imo, everyone in the 80s spoke about how important layout design was, and all of the designs from then would have benefitted from a better board layout. I've assembled a few designs that are similar to the 5000, it would be interesting how much better you can make something like that.
Then move on.
Hi Suzy,
You touch on a very important point, something that is often overlooked. That the implementation of a design is just as important as the design itself. Your assement of the 5000 series amp is basically correct. The design is sound as shown on the schematic. The trouble with schematics is what they don't show. The interraction of various currents (particularly ground currents) and all the parasitic elements that make or break a design.
The phyiscal implementation of this design is where there are some problems. With a few modifications the amp sounds very good. I've had one running for many years and it is an excellent performer.
Having said that, I do run it as part of multi-amp active setup, so the performance of any one amplifier in the system is less critical than if it was being used full range. But I'm in no hurry to change the 5000 for something else.
The difference between a good design and a great design is attention to detail, understanding of all the parasitic elements and thorough evaluation. Schematics only tell half the story...
Cheers,
Ralph.
You touch on a very important point, something that is often overlooked. That the implementation of a design is just as important as the design itself. Your assement of the 5000 series amp is basically correct. The design is sound as shown on the schematic. The trouble with schematics is what they don't show. The interraction of various currents (particularly ground currents) and all the parasitic elements that make or break a design.
The phyiscal implementation of this design is where there are some problems. With a few modifications the amp sounds very good. I've had one running for many years and it is an excellent performer.
Having said that, I do run it as part of multi-amp active setup, so the performance of any one amplifier in the system is less critical than if it was being used full range. But I'm in no hurry to change the 5000 for something else.
The difference between a good design and a great design is attention to detail, understanding of all the parasitic elements and thorough evaluation. Schematics only tell half the story...
Cheers,
Ralph.
Dear Suzy,
You asked a question and I tried to help based on my experience in actually building, testing and listening to the amplifier.
I was also actually clever enough to not base my years of listening to it on its initial unstable state.
I haven't heard anyone suggest you should base any decisions on
" feel-good garbage and marketing rubbish" or want your amplifier to sound " warm, or rich, or anything of the sort".
What particular data are you planning to collect to prove your amplifier can "faithfully reproduce music" ????
The ETI5000 probably measures about 100 times below distortion thresholds that people have been able to demonstrate they can hear.
Perhaps you should research the numbers on all available designs and build the one with the best numbers. THD of 0.001% @ 1KHz into a resistor is achievable.
Perhaps you could use spectrum analysis and measure each individual harmonic but then you will need to decide if each of these will receive equal weight or is this more " feel-good garbage and marketing rubbish"????
Being a rigorous engineer can you devise a test that it will "faithfully reproduce music" without using music as the test???
Good luck.
cheers
You asked a question and I tried to help based on my experience in actually building, testing and listening to the amplifier.
I was also actually clever enough to not base my years of listening to it on its initial unstable state.
I haven't heard anyone suggest you should base any decisions on
" feel-good garbage and marketing rubbish" or want your amplifier to sound " warm, or rich, or anything of the sort".
What particular data are you planning to collect to prove your amplifier can "faithfully reproduce music" ????
The ETI5000 probably measures about 100 times below distortion thresholds that people have been able to demonstrate they can hear.
Perhaps you should research the numbers on all available designs and build the one with the best numbers. THD of 0.001% @ 1KHz into a resistor is achievable.
Perhaps you could use spectrum analysis and measure each individual harmonic but then you will need to decide if each of these will receive equal weight or is this more " feel-good garbage and marketing rubbish"????
Being a rigorous engineer can you devise a test that it will "faithfully reproduce music" without using music as the test???
Good luck.
cheers
suzyj said:
Thanks suzy,
it's more than sharp enough for my eyes at least!
I haven't got the time for now to study it closer but at a quick glance I'm with you, repacking it with some mothern transistors was my thought too, I don't really believe in the use of lowish hfe BF469/470 to such an extent as it's used in that schematic.
Never the less an interesting input/VAS topology, at least for the eyes and as a mind exercise!
Wellcome to the board BTW!
Cheers Michael
suzyj said:
Hi Suzy,
Good to see you here.
Those RS5 speakers you have can sound very good, in fact I have
a pair sittting in the next room and they were a reference for quite
a few years, albeit somewhat modded.
One thing about the RS5's is they can sound a bit lean and can lack
some timber if matched with the wrong source or amp. The emit
tweeters can also be very revealing and sound harsh with
some SS amps. On the plus side, when they are mated with the
right components they can sound awesome.
I have to agree with some of the views here that the numbers
will tell very little about the sound. I can vouch for this with a lot of
experience and not just in home reply but building front ends for
professional recording engineers doing live stereo to digital
recordings. Front ends (mic pre's) that used discrete zero feedback
circuitry sounded much more real than other designs with ultra
low distortion opamps... the engineers preferred the more lifelike
sound of the (slightly) worse measuring topology!
This has been discussed ad- nauseum here and a search will pull up
many of posts covering different views on this....plenty of heated
discussion too!
Back to the RS5's, I believe the AKSA kit amps from Hugh Dean
will be a very good match for them. In fact Hugh sent me up some
modules recently and I have been listening to them for a couple
of weeks. They are shockingly good for the price.
More importantly, they shouldl beautifully match the characteristics
of the RS5's.
If you would like to have a listen to the AKSA modules PM me, as
I am also in Sydney.
Cheers,
Terry
BF470/69 and Other Alternatives
Jaycar are still carrying old stock of these transistors (I picked up some early in the week).
But if you want better designs from magazines, check out Elektor Electronics. They have published many designs over the years. They published a high end design last year (but only 35W) which has a lot of attention paid to the various amplification stages. You can purchase pre made PCBs which are beautfully made. I am still running some amps from 82 that used the 135/50 MOSFET pair.
I have not been much of a fan of the Aus designs with EA being particularly dubious (prone to large scale IP theft).
Nigel
Jaycar are still carrying old stock of these transistors (I picked up some early in the week).
But if you want better designs from magazines, check out Elektor Electronics. They have published many designs over the years. They published a high end design last year (but only 35W) which has a lot of attention paid to the various amplification stages. You can purchase pre made PCBs which are beautfully made. I am still running some amps from 82 that used the 135/50 MOSFET pair.
I have not been much of a fan of the Aus designs with EA being particularly dubious (prone to large scale IP theft).
Nigel
I don't know about IP theft, but certainly the Australian magazine amps have all been designed with low measured distortion the principle concern.
This has resulted in very good specs but mediocre sound quality as auditioning did not appear to be part of the process.
I do not criticise them. They have only months to develop their circuits, their time and budget is very limited, and a large proportion of the effort is given over to the journalistic aspects. Given these considerations, it's commendable they do the job they do. There have been some seminal designs; the AEM6000 was a good sounding amp, for example.
Cheers,
Hugh
This has resulted in very good specs but mediocre sound quality as auditioning did not appear to be part of the process.
I do not criticise them. They have only months to develop their circuits, their time and budget is very limited, and a large proportion of the effort is given over to the journalistic aspects. Given these considerations, it's commendable they do the job they do. There have been some seminal designs; the AEM6000 was a good sounding amp, for example.
Cheers,
Hugh
EA IP Theft
During the 80s a number of articles appeared to be straight lifts from an English magazine that was trying to establish a local presence at the time. A story I heard was that the local magazine threatened advertisers with a boycott if they advertised in the English magazine, thus killing it's chances of success here.
ETI and AEM always seemed to be quite original. In fact ETI started a UK version as I recall.
During the 80s a number of articles appeared to be straight lifts from an English magazine that was trying to establish a local presence at the time. A story I heard was that the local magazine threatened advertisers with a boycott if they advertised in the English magazine, thus killing it's chances of success here.
ETI and AEM always seemed to be quite original. In fact ETI started a UK version as I recall.
AKSA said:
Hi Hugh,
Yes, it can be somewhat frustrating to find out after a lot of hard
earned experience that most of these kit amps are basically a
starting point.
However they have been the path to higher knowledge for many
who cut their teeth on these designs and then went on to
investigate many other posibilities.
That can't be a bad thing
Cheers
Terry
Terry, Hugh,
To me there seems to be some sort of religous / political problem in audio engineering.
The othodox meter readers in one camp extreme and the subjectivist lunatic fringe / marketing charletans in the other.
We have had a stalemate for so long now most everything actually worth disscussing is forbidden in polite company!!
Loners make progress but get little group leverage. Seems to me the first step is acceptance and acknowledgement of how little we do know and the identification of areas where we think it might be possible to make progress.
In many areas a schematic or traditional measurements have little relevance. e.g. Given two well designed, high power, low distortion, low noise amplifiers - are they identical in fullfilling your needs?
The ONLY way to find out is to LISTEN to them.
e.g. Both are monoblock pairs BUT e.g. we hear large differences in imaging. One pair has a more defined broader and deeper rear stage. The other seems to make the speakers disappear more. One presents the image in a slightly different plane to the other.
WHY? What to measure? Dynamic phase diffferences?? Tolerance of actual parts outside the feedback loop??
Not easy!!!!
BUT my point is, no amount of denying these differences are possible is going to make us believe they are not there!!!
No amount of reducing harmonic distortion and noise still further and further is going to shed any light!!
Some people are doing interesting work in these areas but now dont talk about it as it has become close to "pearls before swine"!
How do we get back on track ? How do we avoid the rubbish and not get shouted down by College level arguments from those who actually believe SPICE is real.
How do we elevate the discussion????
and yes Terry, why do many of the very best condensor mics still use tube head amps??? and in an area where noise is critical??
HEADROOM!!??? or more... ??
cheers
To me there seems to be some sort of religous / political problem in audio engineering.
The othodox meter readers in one camp extreme and the subjectivist lunatic fringe / marketing charletans in the other.
We have had a stalemate for so long now most everything actually worth disscussing is forbidden in polite company!!
Loners make progress but get little group leverage. Seems to me the first step is acceptance and acknowledgement of how little we do know and the identification of areas where we think it might be possible to make progress.
In many areas a schematic or traditional measurements have little relevance. e.g. Given two well designed, high power, low distortion, low noise amplifiers - are they identical in fullfilling your needs?
The ONLY way to find out is to LISTEN to them.
e.g. Both are monoblock pairs BUT e.g. we hear large differences in imaging. One pair has a more defined broader and deeper rear stage. The other seems to make the speakers disappear more. One presents the image in a slightly different plane to the other.
WHY? What to measure? Dynamic phase diffferences?? Tolerance of actual parts outside the feedback loop??
Not easy!!!!
BUT my point is, no amount of denying these differences are possible is going to make us believe they are not there!!!
No amount of reducing harmonic distortion and noise still further and further is going to shed any light!!
Some people are doing interesting work in these areas but now dont talk about it as it has become close to "pearls before swine"!
How do we get back on track ? How do we avoid the rubbish and not get shouted down by College level arguments from those who actually believe SPICE is real.
How do we elevate the discussion????
and yes Terry, why do many of the very best condensor mics still use tube head amps??? and in an area where noise is critical??
HEADROOM!!??? or more... ??
cheers
hifryer said:
Hi Hifryer,
You get right to the nub of what I see as the problems with audio.
I'm lucky enough to work in science. For my day-job, I design fairly esoteric RF and microwave kit. At the moment I'm doing RF-CMOS design - trying to design radio-astronomy receivers with commercial CMOS processes (rather than the more normal GaAs or InP processes), so that we can take advantage of the huge progress that CMOS has made in terms of ft, integration levels, and cost.
In my design work, I follow a scientific method. I make a hypothesis, construct an experiment to test that hypothesis, analyse the results, and then go back and do it all again. That leads to insight into the way things work, and is a tried and proven method, going back to the likes of Plato.
However, as an outside observer to audio design, I see a lot of statements of faith, subjective assessment, terminology that obfuscates, rather than informing, and hype. Refering to poorly defined concepts, like "presence", and "MOSFET mist" only lead me to believe that the speaker isn't confident about what they're saying, and is trying to weave a web to conceal their lack of knowledge.
However, terms like intermodulation distortion, harmonic distortion, noise figure, slew rate, etc all have a well defined basis in physcal principles.
So I think that if you can define "presence" and "MOSFET mist" in terms of basic physical principles, then the engineers (me included) will listen and take note.
Cheers,
Suzy
I must be one of the few that sit in the middle.
I have heard some cables (interconnects) that do sound better than standard no name ones.
Although I believe that in MOST audio systems replacing the front end parts can result in sonic benifits, I firmly believe that the speakers are, and will be for some time, the single biggest weak link in any system.
Lets say you have a $300 amp, and $300 speakers, increase that figure for an upgrade. (1000 amp, 1000 speakers)
Which do you think would give the greater improvement ?
Lets try with a bit more.
1,000 amp / 10,000 amp
1,000 spk / 10,000spk
Every time, my moneys on the speakers.
I have heard some cables (interconnects) that do sound better than standard no name ones.
Although I believe that in MOST audio systems replacing the front end parts can result in sonic benifits, I firmly believe that the speakers are, and will be for some time, the single biggest weak link in any system.
Lets say you have a $300 amp, and $300 speakers, increase that figure for an upgrade. (1000 amp, 1000 speakers)
Which do you think would give the greater improvement ?
Lets try with a bit more.
1,000 amp / 10,000 amp
1,000 spk / 10,000spk
Every time, my moneys on the speakers.
Suzy,
I didn't use terms like "MOSFET mist" or "presence" but having listened to many amplifiers I have little problem understanding what is meant!! A racing driver might use equivalent terms in regard to the "feel" of the steering. It has a real physical cause but might be eventually traced to baffles in the fuel tank rather than more and more refinement of damper settings!!! But the model didnt include this!!
Suzy, paradoxically, you get right to the nub of what I see as the problems with audio!!!
I have no doubt you are a highly accomplished, learned and talented engineer. Much of this will be a great advantage to you as you now delve into audio engineering.
However forgive me for being so rude as to tell you you are extremely naive when it comes to what it takes to reproduce music for a satisfying emotional response. Beyond the very basics it has surprisingly little to do with levels of noise and harmonic distortion.
It is a psycho-acoustic phenomenon. It is all about perception. We know very little about the functioning of the ear / brain WRT music.
I dont doubt that all follows the laws of physics and there are many measurements, if we knew what they were, that would be helpful.
But you need to learn very early that there is little accepted correlation between simple conventional measurements like THD and the actual perceived quality of first rank equipment. Most all of which measures more than acceptably. An amplifier with 0.005% THD @ 1KHz will not necessarily sound better than one with 0.1% and often will sound a lot worse.
Im sorry, but only when you learn this will you progress! Our ears are not a microwave receiver and I suspect the issues ( not necessarily the engineering) in audio are more complex and ambiguous.
BTW My life's work was in a field of engineering. "many of my best friends" are engineers and many of those knowledgeable in audio have little trouble with my viewpoint. Especially the concert goers and music lovers among them!
Experiencing is believing. It is a very personal and experiential art.
cheers
I didn't use terms like "MOSFET mist" or "presence" but having listened to many amplifiers I have little problem understanding what is meant!! A racing driver might use equivalent terms in regard to the "feel" of the steering. It has a real physical cause but might be eventually traced to baffles in the fuel tank rather than more and more refinement of damper settings!!! But the model didnt include this!!
Suzy, paradoxically, you get right to the nub of what I see as the problems with audio!!!
I have no doubt you are a highly accomplished, learned and talented engineer. Much of this will be a great advantage to you as you now delve into audio engineering.
However forgive me for being so rude as to tell you you are extremely naive when it comes to what it takes to reproduce music for a satisfying emotional response. Beyond the very basics it has surprisingly little to do with levels of noise and harmonic distortion.
It is a psycho-acoustic phenomenon. It is all about perception. We know very little about the functioning of the ear / brain WRT music.
I dont doubt that all follows the laws of physics and there are many measurements, if we knew what they were, that would be helpful.
But you need to learn very early that there is little accepted correlation between simple conventional measurements like THD and the actual perceived quality of first rank equipment. Most all of which measures more than acceptably. An amplifier with 0.005% THD @ 1KHz will not necessarily sound better than one with 0.1% and often will sound a lot worse.
Im sorry, but only when you learn this will you progress! Our ears are not a microwave receiver and I suspect the issues ( not necessarily the engineering) in audio are more complex and ambiguous.
BTW My life's work was in a field of engineering. "many of my best friends" are engineers and many of those knowledgeable in audio have little trouble with my viewpoint. Especially the concert goers and music lovers among them!
Experiencing is believing. It is a very personal and experiential art.
cheers
The problem, Suzy, is that engineers often talk exclusively in these numerical and measureable terms which are essentially meaningless to audiophiles. It is just the language of an arcane science, which by nature is exclusive. But is it really productive to dismiss someone's view because they do not understand a second order differential equation?
Yet, people who love their music and listen very intently to what they hear from a recorded music system may have no other way to express what they hear than the very despised terms you identify.
OK, so there's a standoff of epic and historical proportion. Who is right?
The engineer is right because scientific method is espoused and only those things 'with a proper basis in physics' are discussed and used for design purposes. Good logical stuff.
But the music lover is also right because these subjective terms best describe what is happening to his/her beloved music. Music is, after all, a subjective communication.
Hmmm, still no conclusion here.......
So, if we are to decide anything at all, what about the economics? As an engineer you must work to a budget, and cooperate with management, marketing and advertising departments as to what is required, how it's to be sold, what sort of BOM must be dictated.
Then you will know that no consumer product - and an audio amplifier is certainly a consumer product, arguably different to your astrophysics equipment - is sold solely on an engineering level.
Sales are made on two levels; the intellectual, rational basis, and the subjective, 'feel good' basis. Both levels are involved to close the sale. Often the clincher is whether the buyer likes the seller. Not very scientific at all........
You communicate your feelings well for the touchy feely comments of non-engineers and impassioned audiophiles. But surely there are things in your life where subjective issues rule? And do they not cost money, just like audio equipment?
I rest my case....... ignore the subjective and marketing aspects at your peril. Fall too willingly into one camp, and lose entirely the perspective of the other which is equally valid. Music is about emotion, and a good system should be able to convey that emotion. This is utterly unmeasureable, but instantly recognisable by the human organism.
Cheers,
Hugh
Yet, people who love their music and listen very intently to what they hear from a recorded music system may have no other way to express what they hear than the very despised terms you identify.
OK, so there's a standoff of epic and historical proportion. Who is right?
The engineer is right because scientific method is espoused and only those things 'with a proper basis in physics' are discussed and used for design purposes. Good logical stuff.
But the music lover is also right because these subjective terms best describe what is happening to his/her beloved music. Music is, after all, a subjective communication.
Hmmm, still no conclusion here.......
So, if we are to decide anything at all, what about the economics? As an engineer you must work to a budget, and cooperate with management, marketing and advertising departments as to what is required, how it's to be sold, what sort of BOM must be dictated.
Then you will know that no consumer product - and an audio amplifier is certainly a consumer product, arguably different to your astrophysics equipment - is sold solely on an engineering level.
Sales are made on two levels; the intellectual, rational basis, and the subjective, 'feel good' basis. Both levels are involved to close the sale. Often the clincher is whether the buyer likes the seller. Not very scientific at all........
You communicate your feelings well for the touchy feely comments of non-engineers and impassioned audiophiles. But surely there are things in your life where subjective issues rule? And do they not cost money, just like audio equipment?
I rest my case....... ignore the subjective and marketing aspects at your peril. Fall too willingly into one camp, and lose entirely the perspective of the other which is equally valid. Music is about emotion, and a good system should be able to convey that emotion. This is utterly unmeasureable, but instantly recognisable by the human organism.
Cheers,
Hugh
suzyj said:
Hi Suzy,
I must admit I have thought about this reply for quite some time.
At first, because you are so scientifically minded, I thought of an in
depth explanation of the complete recording process.
From venue/studio to type of micing / placement, mic selection, mic
pre type, console, recording media (dig or tape), effects used,
compression, EQ, monitoring amp / speakers. Mastering process,
effects, compression, types of converters used, amps speakers, final
WR reduction / SR reduction to 16/44.1 for CD release. There's
probably hours of typing required and that would only scratch the
surface.
Audio is a well defined science and I believe it is helpful to
understand the *whole* process at every step of the chain. To
understand how we actually hear things, what affects our
perception before one can even think about drawing
water tight conclusions as to why different parts of the chain
sound as they do.
Perhaps an easier approach is to 'backward engineer' the whole
scenario. Find the solution and then think about what the problem
is.
I suggest sourcing or building 2 amps as follows:
a) The lowest THD, most linear amp you can muster based purely on
known and measured criteria. You should be able to easily acheive
very low 0.00x% THD numbers close to full power.
b) An existing amp that is known to 'sound excellent' based purely
on listening tests and popular opinion. My recommendation here
are obviously AKSA and a quick search in DIYA will find much
support from -people who have owned and heard them- .
Listen to the two amps for a week or two. Be totally unbiased.
Have a think about which one you want to live with. Which one
sounds like music in your room, which one doesn't. Which one
makes you sing along to it and which one makes you wan't to turn it
off?
This experiment could pose many questions to you as it has for
many of us.
I, and plenty of others, can design an amp that gets around 0.001%
or less THD at close to full power right up to 20kHz.
But there's not much point in buying or building an amp that you
don't want to listen to.
Cheers,
Terry
Maybe what's needed is a dictionary, so that engineers can understand audiophile-speak, and audiophiles can understand engineering jargon.
Here's some (slightly tongue in cheek) definitions I've just chucked together over lunch:
Warm: Excessive second order distortion.
Tinny: Excessive third order distortion.
Fatiguing: Excessive fourth (and above?) order distortion, or intermods.
Transparent: Low THD and IMD.
Good imaging: High slew rate - low IMD.
Noisy: Well here's one we can all agree on
Muddy: Poor high frequency response, poor slew rate, excessive IMD.
Any other thoughts?
Cheers,
Suzy
Here's some (slightly tongue in cheek) definitions I've just chucked together over lunch:
Warm: Excessive second order distortion.
Tinny: Excessive third order distortion.
Fatiguing: Excessive fourth (and above?) order distortion, or intermods.
Transparent: Low THD and IMD.
Good imaging: High slew rate - low IMD.
Noisy: Well here's one we can all agree on
Muddy: Poor high frequency response, poor slew rate, excessive IMD.
Any other thoughts?
Cheers,
Suzy
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