janneman said:
Excuse me?
This must have been one of very few moments of un-clarity in Doug's mind, if quoted correctly. Yes, if an amplifier boasts a meaningless damping factor of say 1000, it might then become 500.
But "appreciable power loss" into loads less than 4 ohms? Not in any practical application. Such a typical coil might consist of 15 turns of 1,2mm wire, 6mm diameter. The resistance of that would be about 5,5 milli-ohm. How low must the load go for that to cause appreciable loss?
G.Kleinschmidt said:Yeah, but just don't forget to burn them in by jump starting a few cars first. They won't sound right otherwise.
Okay, but isn't it possible that the cable could sound worse after burn-in?
Johan Potgieter said:
I think we all have to keep an open mind about effects that may occur that we cannot explain for some reason or other. However, the way I like to view it is in terms of the matter of degree that an asserted phenomenon departs from established science. The more it departs, the higher the bar for accepting the assertion without some reasonable evidence or further inquiry.
The real value lies in ultimately being able to connect the dots and establish some cause and effect. That's how we all learn and move forward.
That's why I can be such a pain in the but in asking for more information about thus and such. I don't care so much about the outcome as I do about understanding it better.
For all I care, coils may indeed detract from the sound, but I sure would like to try better to understand the circumstances under which they do, and what aspect of coils (linear effects versus nonlinear effects for starters) are at the root of those degradations.
Similarly, for all I care, many of us may have been using coils blindly by wrote over all these years when we didn't really need to. I think it is pretty fair to say that many decent amplifiers will do just fine 99% of the time without a coil, given what we know about reasonable combinations of speaker cables and speakers and possible mitigating effects.
Bob
Re: definition of 'rock solid'
A "Rock Solid" measurement method for the given application.
Cheers,
Glen
estuart said:Hi Bonsai, Glen and Mike,
Of course, I do know the meaning of 'rock solid'. The aim of my question was to let Glen explain how it can be that a rock solid measurement method is not appropriate for all kinds of amplifiers. Maybe we should call it a 'rock solid approximation'.
BTW Glen, how do you know that your method is reliable?
Probably, the only way to check this, is doing it my way.
Cheers.
A "Rock Solid" measurement method for the given application.
Cheers,
Glen
Bob Cordell said:
G'day Bob
I think one can say with a great deal of certainty that a coil, switched in and out of the circuit in an A-B test, will induce an audible effect, provided that the coil is large enough.
For one thing, there will be a reduction of amplitude at high frequencies. If the coil is made big enough, the loss of treble could easilly be percieved.
However, when one considers just how big an inductor would need to be to induce such an audible effect, a uH or two looks quite irrelevant - especially so when contrasted with other factors such as room accoustics and speaker positioning which can provide a drastically larger contribution.
Also, one cannot assume that just because an amplifier may not have an output coil, that it will not have an electrically equivalent output inductance.
Distortions caused by coil non-linearity would would show up on standard linearity measurements. Since we can easilly make amplifers with output coils that measure exceedingly well (Halco as an commercial example) in this department, it is obvious that this is almost a practical non-issue, provided that care is taken with the design, just as it has to be in many other aspects.
Cheers,
Glen
andy_c said:
Blasphemer! Burn!
Bob Cordell said:
Bob,
I would certainly agree with your whole post here although I am only quoting the above. Re that, yes. But I was thinking more of the times that I am asked to accept that 3 + 5 = 11, to again use a simple example. And this happens, and folks would get sour for my not at least "trying it". (I write for a local magazine and sometimes get flak of this kind.)
You wisely use the words "asserted phenomenon" and "established science". Exactly. And here folks must bear with me if I do not necessarily accept something that someone heard as asserted in the general sense - you know what I mean.
Also, yes again; there is such a lot of pious practices going on without any half-technical reason. In that sense one would certainly question also the insertion of output coils in some circuits - but that is not how you and I would design.
If questioning per se means that one is a pain in the butt, then I was paid to be one. I was a researcher, and us animals asked; to re-invent the wheel was asking to be fired.
Regards
It does, base 7.
Anyway, my questions earlier to John Curl were heading toward something that Mike said- take an amp that doesn't have an output coil, connect it to a highly capacitive load (like my ESLs), then add a 2uH coil and see if there's any audible difference. I have my own hypothesis about what the results will be...
mikelm said:
If you’re a bit of a masochistic type, and are prepared to read through this torturous thread in it’s entirety, you’d read that some of us have indeed done the subjective test.
I started building amplifiers as a teenager with National Semiconductor’s LM380 audio amplifier IC, after which I progressed to discrete single rail designs with BD681/BD682 outputs, single transistor input stages, bootstrapped VAS and capacitively coupled speaker outputs – not "HiFi" by any stretch of the imagination.
I’ve played with fancy caps, big coils and no coils, heavy speaker wire and thin speaker wire and many other things. The only way things such as these can cause sonic degradation is if they are implemented completely incompetently.
I can’t hear a reduction in THD from 0.005 % to 0.001% by substituting in electrolytic input coupling capacitor with some fancy capacitor. I can’t hear the added +/-0.3dB or so of amplitude ripple over the entire audio frequency spectrum contributed by an inductor of a uH or two connected in series with my speakers. I can’t hear supersonic ringing that occurs on transients at the series resonate frequency of the inductor and a highly capacitive load.
None of this is mysterious – there are solid scientific facts which dictate why I can’t hear such things. My hearing is not defective – it is just not super-human.
I generally don’t argue on grounds of subjective evaluation though, because it is entirely pointless – there will always be at least one nincompoop who resolutely insists that he can hear even the slightest audio imperfection and declare himself the winner on grounds of having superior hearing abilities.
That is why I stick to the technical side of the debate.
Hi Glen,
sorry to say - I might well be the nincompoop that you refer to.
I dislike the sound of most resistors in the signal path.
I recently changed an electrolytic for a film cap and for me it was MUCH better
then when I DC coupled it was another improvement.
leads sound different even when the basic LCR model has them fine up into the mega hertz region
I have absolutely no technical explanation how it is I can hear this.
I just accept that I do not fully understand any of this stuff
On the subject of a coil on the o/p - I will try it this w/e and report it here ( for what is it worth ) I know in advance whatever I say some will believe me and others will not - It's a funny old world
cheers
mike
sorry to say - I might well be the nincompoop that you refer to.
I dislike the sound of most resistors in the signal path.
I recently changed an electrolytic for a film cap and for me it was MUCH better
then when I DC coupled it was another improvement.
leads sound different even when the basic LCR model has them fine up into the mega hertz region
I have absolutely no technical explanation how it is I can hear this.
I just accept that I do not fully understand any of this stuff
On the subject of a coil on the o/p - I will try it this w/e and report it here ( for what is it worth ) I know in advance whatever I say some will believe me and others will not - It's a funny old world
cheers
mike
Wow Glen, the LM380 oscillator! Those who were able to make it stable and convince it to be an amplifier, went on to more sophisticated things. The rest, well...
This thread is the worst. I started out doing experiments with different output networks. One thing led to another, and I just now pulled every component out of one PCB of an amp, and rebuilt it from the ground up, no pun intended. Tomorrow I'll do the other channel. I doubt there'll be any real audible difference, but the knowledge that I've upgraded all the parts and forced the measurements down further should be worth something mentally.
This thread is the worst. I started out doing experiments with different output networks. One thing led to another, and I just now pulled every component out of one PCB of an amp, and rebuilt it from the ground up, no pun intended. Tomorrow I'll do the other channel. I doubt there'll be any real audible difference, but the knowledge that I've upgraded all the parts and forced the measurements down further should be worth something mentally.
Conrad Hoffman said:
Well, I don't make amplifiers with the LM380 anymore, but I have to say, I never really had much of a problem making them work without oscillating. They did require a little care though. Big electrolytic bypass caps in parallel with a 100nF green cap or two, an RC Zobel directly on the output and the input leads located well away from the output leads generally did it.
I agree that there is something satisfying about getting the best measured performance out of an amplifier design – it’s a technical challenge and is fun. However, some things still need to be kept in perspective.
Cheers,
Glen
john curl said:
John, you're right. I shouldn't trust my own eyes either. In fact, I should actually let others think for me - especially others like you. Baaahhhhh.
No, wait, a reality check....I don't design for audiophiles, and I don't care what they may think about my ears. I think I would be a fool if I did.
Sorry, but I have to go away now to burn in my speaker cables. My amp has been running for 3768 hours now and it is almost ready for a listening test.
Cheers,
Glen
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