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Old 22nd April 2007, 12:03 PM   #11
AKSA is offline AKSA  Australia
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Glen,

It's a shame you are so idle this evening - the results have been less than edifying!

Y'know, I've been designing amps with no CRO, no distortion analysers, no oscillators and no meters of any kind for decades. It's difficult work, but I always rely on my very large bio-engineered ear which hangs just above my workbench. It delivers flawless judgements every time, though communicating with it is tricky!

It must be very difficult launching an entirely justified crusade against novices. They are so crass, uneducated and, well, subjective. Hell, they don't even know Ohms' and Kirschoff's laws!!

Have a great week, Glen, and keep those great designs coming! In all those 44 transistors for 12W, how did you possibly leave out the base stoppers?

Hugh
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Old 22nd April 2007, 12:16 PM   #12
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Quote:
Originally posted by AKSA
Colin,

you have discovered something which would have evaded you if you had studied PSpice and striven to reduce distortion. I think this happens because we are listening to music, not test tones.

Cheers,

Hugh
I completely agree with you Hugh!

Quote:
Originally posted by AKSA
Glen,

I've been designing amps with no CRO, no distortion analysers, no oscillators and no meters of any kind for decades. Hugh
Hats Off to Hugh!
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Old 22nd April 2007, 12:56 PM   #13
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Just as speaker design cannot be done without instruments amplifier design cannot be done without same
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Old 22nd April 2007, 01:26 PM   #14
AKSA is offline AKSA  Australia
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Certainly Consort,

I was joking , don't take me too seriously (that goes for you, too, Glen!!) - of course I have all the usual instruments....

I find the CRO in particular indispensable, and I'm constantly measuring to get the DC and AC conditions right. I assess linearity from triangle waveforms at very high frequency, and carefully examine phase shift with X-Y CRO traces. These aspects are fundamental. There is no magic, but there remain the subjective aspects intrinsic when listening to music. This is how many people assess amps, after all.

Then I move into issues of fine dimensioning, component choice, layout, etc.

Hugh
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Old 22nd April 2007, 04:24 PM   #15
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If I understand correctly, we have folks with special gifts ploughing through the night, getting to their perfect designs (screw Self et al) by correcting matters they are not sure of, addressing things not understood because they have not been discovered yet .... Where they do encounter an obstacle now and then by stumbling over it in the dark, it is glibly dismissed by the obvious logic that it is - wel - a stumbling block in their chosen path.

Arrival at Nirvana would seem not to actually be by benefit of superior hearing, but by the substancially greater benefit of superior intuition (which is also naturally not completely understood - must retain a sprinkling of mystery!)

By the way, we are listening to test tones. A whole (usually) harmonius lot of them. It is called music. For better testing we just make sure that things are OK one note at a time, before we let Beethoven throw the whole lot together.

In all this honesty, I must own up to one of my more irritating shortcomings. I hate sarcasm, especially when protected by a barn-back-door of: "Oh, I was only joking!"

Also just for the record, I have been using a cascode Vas plus a little more since 13 years ago - nothing fresh - but for slightly more tangible reasons. I have not quite gone through the quoted articles; hope to find some measurements at the end. Another one of my faults: I am a sceptic. I need to be shown that at least the basics are in order before I can consider the magic.
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Old 22nd April 2007, 04:46 PM   #16
mikeks is offline mikeks  United Kingdom
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Quote:
Originally posted by Johan Potgieter
If I understand correctly, we have folks with special gifts ploughing through the night, getting to their perfect designs (screw Self et al) by correcting matters they are not sure of, addressing things not understood because they have not been discovered yet .... Where they do encounter an obstacle now and then by stumbling over it in the dark, it is glibly dismissed by the obvious logic that it is - wel - a stumbling block in their chosen path.

Arrival at Nirvana would seem not to actually be by benefit of superior hearing, but by the substancially greater benefit of superior intuition (which is also naturally not completely understood - must retain a sprinkling of mystery!)
Thanks for this most excellent description of subjectivism (AKA John Curl et al)

Cheers!
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Old 22nd April 2007, 10:23 PM   #17
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Default I enjoy Doug Selfs work immensely.

I like some others feel that maybe he might not be into music as much as measurements, however as I dont know him personally I may be wrong. I read his workings as fast as I can find them and many others, I consider myself a sponge for information, I enjoy this hobby without ego or a mission to try to change conventional thinking. I have ploughed through the web in search of material that I can learn from, ploughed these forums, reading threads and each ones take on various issues concerning amplifier design and it would take years to work on them all with my limited knowledge as compared to many others here but fortunately sometimes what I do lack in knowledge it has been gained by careful study of datasheets. As I do not have access to measurement tools beyond a DMM, nor the extra financial abilities to do so at this time my tools are my ears and by economics have to be. I do not laugh at these tools of measurement, I know they are valuable but not free ). As of lately obviously my big path of self discovery has been with the second stage VAS in which I know I could have used only lead compensation and put a big zero in the high frequencies at output but this I found to sound worse in control than too much lag. I of course found mixed lead and lag to sound better, but to the extent of which ratio to use seemed elusive for a cohesive balance until recently. Maybe I am delusional to think that this makes for better music, but may as well be delusional and have some good music to get lost in at the same time..


As always objective explanations are more than welcome.

Thanks All.
Colin
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Old 22nd April 2007, 10:53 PM   #18
phn is offline phn  Sweden
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Quote:
Originally posted by mikeks


Thanks for this most excellent description of subjectivism (AKA John Curl et al)

Cheers!
A reply worthy an objectivist (AKA the Pope et al).
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Old 23rd April 2007, 01:08 AM   #19
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Hi Colin,

Firstly, my summation was as general as I could keep it without being personal, although such sentiments unfortunately are caused by responses of individuals. It was thus not aimed at you specific - you also did not say that you saw it as such, but just to keep the air clear.

Regarding Doug Self, I was using him as collective of all engineers (apology Doug), definitely including myself! (.... but his excellent article "Science vs. subjectivism" sprang to mind.) Your impression and that of others of him might have arisen because his contributions were almost entirely technical - that is what he is. You could say exactly that of myself plus a host of other technical writers, but that cannot mean that we do not also enjoy music. I have also never met him, but I believe he plays an instrument. I know his qualifications include M.Sc Engineering (electronics) and MA (psychology), which certainly do not indicate a limited interest.

Back to subject, I agree entirely with your feelings about compensation. Mixed lag and lead are usually superior to just lag; in fact the prominent C.dom (over b-c of the VAS), can cause serious TIM at h.f. if too big, as it sometimes is to get stability, and from there on round the whole circuit, ending up as design that could be improved. I again refer to a very informative article on this by Dr John Ellis (EW March 2003). He sometimes posts here. Also here (to get back to my previous irritation) no amount of thumb-sucking and intuition will get this exactly right; certainly not listening. Phase and loop gain investigation are mandatory. (It must not only "sound right", it must be right with sufficient margin to accomodate component spreads. How do you listen for that?) Unfortunately this makes life difficult for those without the means - but then such capabilities are becoming more and more available as PC add-ons, for the benefit of all. (Imagine how we toiled 30 years ago, drawing point-by-point graphs, etc! )

Regards.
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Old 23rd April 2007, 02:50 AM   #20
GK is offline GK  Australia
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Quote:
Originally posted by AKSA
Glen,

It's a shame you are so idle this evening - the results have been less than edifying!

Y'know, I've been designing amps with no CRO, no distortion analysers, no oscillators and no meters of any kind for decades. It's difficult work, but I always rely on my very large bio-engineered ear which hangs just above my workbench. It delivers flawless judgements every time, though communicating with it is tricky!

It must be very difficult launching an entirely justified crusade against novices. They are so crass, uneducated and, well, subjective. Hell, they don't even know Ohms' and Kirschoff's laws!!

Have a great week, Glen, and keep those great designs coming! In all those 44 transistors for 12W, how did you possibly leave out the base stoppers?

Hugh

Hugh, this is just another typical dim and evasive retort from you, which contains nothing of substance and addresses none of the points raised.
Your comments on a “crusade against novices” are patently obtuse. There is absolutely nothing wrong with being a novice, and if there is anything at all in my posts of late that has been crusader-like, it is against the likes of self-fancying audio messiahs like you who stupidly encourage novices to fiddle with important aspects of their amplifiers that they lack the expertise and equipment to do properly. This is likely to lead to more grief than joy and is downright irresponsible and objectionable on your part.
As for your comments on my 12W amplifier design, they’re just as dim as the rest of your comments.
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