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Old 20th February 2006, 12:55 PM   #21
Bobken is offline Bobken  United Kingdom
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Hi Eva,

I am glad to hear that you tried this out for yourself.

Far too much I read on the Internet is posted merely based on hearsay, or there is no 'reference' shown to indicate how the results have been arrived at.

The only difference between your trials on output inductors, and mine on Zobel networks, seems to be that although we both measured the results (or attempted to, in my case, but found no measurable differences, as I said!), you don't make any mention of what the effect (if any) was on the sound, whereas I did.

I cannot help wondering, when anyone asks about which of two choices is likely to give "the best most natural sound" as happened here, which style of reply would be the most useful to him

However, it may be that you know fab better than I do, and that really he meant "which would measure the best", in which case I have completely wasted a lot of my time!

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Old 21st February 2006, 01:55 AM   #22
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Folks,

I have the gnawing feeling that we may be getting a little ahead of ourselves here.

Fab's original question was simply whether any 1 of the 2 displays on his scope was better than the other. Defining "better", I took it that he was concerned about amplifier stability under various conditions, as oscillatory effects were clearly way above the audio spectrum. Sonic effects came up only in post #5, and then not what they are, but rather whether there would be any - there is a difference! We did all appear to concentrate on the stability effects, not sonics.

Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation by stating that the only way to be sure about "such choices" as Fab had to make was to actually listen to the results. My perception of "the choices he had to make" was that it was all about supersonic to r.f. effects which could possibly cause instability and the ill consequences thereof, not how it might sound.

And in this region, with respect to whoever says what, one can only have success by measuring or analysing on a computer programme, as there is nothing to hear (as we all seem to agree) unless the circuits under discussion (series choke and Zobel) were extending into the audio spectrum, where they were never supposed to be working in the first place. In the case of an amplifier so poorly designed that this was required, essential attention has to be devoted elsewhere, e.g. the compensation as Bobken suggested. In this respect I am also confused as to the audible difference between components, employed as said in circuits that should not have effect in the audio spectrum in the first place.

I do not wish to enter a fray about the significance of the often touted listening tests, except to cite an example from a very well known audio magazine: Years ago some 6 internationally known critics were asked to make a short-list of the best amplifiers (amongst other components) in their view, as well as their personal choice. The personal best for some were not even on the list of others. And these were seasoned critics! For whose taste must I now design?

Design of several of the best-known amplifiers were completed before a single listening test was conducted. If the right things are measured correctly, it will sound right to most people (also said by both Douglas Self and JLH, not to mention Baxandall, Williamson and Walker - if a Hall-of-Fame is of any significance). Meaningful listening tests are a science in themselves to be of any statistical value, as illustrated by tests conducted a.o. in the Scandenavian countries, notably under Prof. Bengt Sorenson, to mention but one specialist. To each his own, but a wealth of documented test results has made it abundantly clear that there exists such diversion in listening test results as to be of limited value to a designer.

But I am a little off-thread - only the door was opened.

Best regards.
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Old 21st February 2006, 09:56 AM   #23
Bobken is offline Bobken  United Kingdom
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Hi Johan,

Sorry if I appear to cross swords with you here but I take strong exception to your comment :

"Bobken, I think that in your post #8 you may have inadvertently brought sonics into the equation" etc.

Johan, before I even saw this thead or posted any comments at all, the originator clearly stated the following in his (subsequent) post # 5.

"My question is then: what is the best way to get the best *more natural sound* into the speaker and desensibilising the amp circuit to load impedance". This is recounted word-for-word, and this was what I replied to.

Goodness only knows how anyone in their right mind can suggest that *I* "brought sonics into the equation" as you have just done, if this query from the thread's originator is read properly!

As the question of *best... sound* came first in this particular query, I simply dealt with that particular issue first in my subsequent reply.

I then went on to comment on some other issues including those relating to the stability of amps.

Similarly, although this is presumably not directed at me here, I don't know how you can also say in direct relation to the issue of sonics in post #5 :

"... and then not what they are, but rather whether there would be any - there is a difference!"

There is absolutely *nothing* in that post #5 you refer to which supports these comments of yours, whatsoever.
Please take the trouble to read that post again before any further 'misquotes' or misleading comments on your part relating to the substance of any previous posts.

My quote above, taken verbatim from post #5 makes it abundantly clear that the originator assumes there could be some sonic effects, or why would he start this question "what is the best way to get the best more natural sound"?

My comments may also be a little off thread, too, but they relate factually to what has been posted here, and not to any mis-readings nor erroneous assumptions, or whatever.
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Old 22nd February 2006, 04:04 AM   #24
fab is offline fab  Canada
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ok, I will try to write faster because I lost again (many times now) my reply because of time expiration !!! moderator please do something...

Thanks to all your comments. It seems that, based on some comments, both waveforms are acceptable...but the one with inductor is more safe to use?

My understanding is that the good electrical characteristics are the same goal as the good sound unless the characteristics are not the ones to look for. So the "best sound" or "best electrical characteristics" are the same since we all want good sound, right?

Simply, what do YOU do for your own diy amp?
Is the RC load test significant? or is there another test.
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Old 22nd February 2006, 08:16 AM   #25
Eva is offline Eva  Spain
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The one with inductor will almost always look this way despite of the load. The other without inductor is load dependent.
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Old 22nd February 2006, 01:33 PM   #26
Bobken is offline Bobken  United Kingdom
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Hi fab,

Based on JLH's comments (and he should know), you are unlikely to *hear* any differences with these two square-waveforms, as I already posted. However, I have not carried out this particular direct listening comparison, myself, using similar waveforms.

Generally, good "electrical characteristics" as you put it should sound better, but as I have also tried to point out, this is not the whole story as far as the best sound goes. Using a *correctly designed and damped* output inductor should give you a better phase-margin of stability, and as this should not adversely affect the sonics, it would seem "safer" as you say.

I have found it best for 'sonics' to use the intended speakers and cables in any trials/tests wherever you can, and you could end up with a slightly different result using alternative speaker/cable combinations, as their complex impedances will vary somewhat.

It is more important to achieve the best stability (clean square-waves) before adding the output inductors, in my experience, by adjustments to any compensation caps etc. Adding the inductor will usually 'upset' the waveforms to some degree, as I have found and several notable commentators have also explained, but this should not be harmful to the sound.

One of the advantages which the DIYer has which is absent for manufacturers or designers (which JLH first drew my attention to)is that we only need to optimise the amp's stability for our own 'known' loads, whereas the others need to take into account a multitude of different set-ups which users might choose to use.

I have commented quite a lot recently in connection with one of "my own DIY amps" in posts #10, #13, #20, and #21 (stability issues are discussed here) in the "JLH Mosfet Amp - Modifying it" thread, and in posts #21, #24, #30, and #32 in the thread "Fuses Impacts on sonics of a supply" if, as you appear to be, you are seriously interested in some listening trials/conclusions/developments etc.

Hugh Dean of Axa Amplifiers has also written about 'voicing' amplifiers recently in another thread, but regrettably Eva has attempted (with her usual destructive and derisory comments) to destroy any credibillty here.

Actually, "good sound" is not well-defined and different listeners will not always agree on what is good or not. However, my own approach has been to get as close as I can to the real experience, and hence use live concerts as a yardstick here.

I am lucky in having several simple-miked recordings of an artist (male vocalist) whose concerts I have been attending for nearly 30 years, so I know quite well how he sounds in real life. The male voice covers a surprising amount of the audio spectrum, and these recordings are a great help in making decisions over various choices relating to the naturalness/expressiveness and the fine details to be heard in this voice.
It helps that these concerts were all in a very small and intimate venue, so it is not too dissimilar from my own listening environment.

Regards,
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Old 22nd February 2006, 10:04 PM   #27
Fanuc is offline Fanuc  United Kingdom
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Hello Bobken,

Any chance of getting your email address? Regarding the JLH designs etc

Best Regards
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Old 22nd February 2006, 10:56 PM   #28
Eva is offline Eva  Spain
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Bobken:

I'm not destructive, I'm just scientific. This implies that I don't follow that obsolete middle-age thinking scheme in which statements have to be blindly taken as axioms or rejected depending on how famous was who is claimed to be the author.

I don't design my circuits following what is written on The Sacred Stone Tablets
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Old 23rd February 2006, 12:04 AM   #29
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Here's an output coil as a source of inspiration!

Cheers Michael

Click the image to open in full size.
Link to a Halcro dm38 pic on Stereophile's homepage..
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Old 23rd February 2006, 10:28 AM   #30
Bobken is offline Bobken  United Kingdom
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Hi Eva,

Whether it is intended or not (and I happen to think it is) you are extremely destructive in the manner in which you join in on many posts on this Forum. Other posters have mentioned this to you before, and as they have suggested, it seems like all you are interested in is to show-off your self-declared superiority, rather than to carefully explain something to an enquirer.

We all know you are quite clever, but when you 'sweep all before you' in such a derisory manner, implying that everyone else is an idiot, or whatever, and doesn't know anything about audio electronics, this is not very encouraging to others.

You don't know *everything* quite yet, as your open disagreements over some of what I have said make apparent to me. I have not posted anything which I have not actually experienced myself through very many years of audio involvement, except where I make it clear by saying that this comes from someone else, and I have or have not (yet!) verified it myself.

There are times when I have also honestly said I am not absolutely certain why something I have discovered is the way it is, but since I know for myself that these are facts (whether I fully understand it, or like it, or not, and quite franky I don't care if you do or don't either) I would be an idiot to ignore them.

You appeared to cause a great deal of ill-feeling in several other posts I have seen recently, and I simply don't know why this should be necessary. You frequently jump in with a few scathing remarks, often not well-explained, and I don't know how you can be so arrogant and ignore the comments of many other posters when you do this. Their points can be valid too!

40 years ago, I felt similarly to yourself in that measurements showed everything related to audio, and that technical excellence was what was *entirely* responsible for good sound.

Since then, I learned the error of my ways.

If you wish to bury your head in the sand and ignore this, I don't mind one little bit, but kindly don't keep on destroying the attempts of others, some of whom do know a thing or two, and who are genuinely trying to share a few significant matters with other people who are not so bigoted as you clearly are.

Regards,
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