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Old 31st January 2012, 04:26 AM   #1611
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Quote:
Originally Posted by benb View Post
That's the first "single ended" amp I've seen with substantial crossover distortion!
Because it is exclusive design!
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Old 31st January 2012, 04:30 AM   #1612
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Quote:
Originally Posted by ThorstenL View Post
Hi,



What do you call this one?

Ultra Shockwave?

Mega Crusher?

Hyper Metal Screamer?

Massive Mega Muff Fuzz Face?
It depends on pot's position. Can be clean enough, if to properly balance the gain. Measure, adjust for minimum of distortions, and listen.
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Old 31st January 2012, 05:19 AM   #1613
anatech is offline anatech  Canada
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Hi a.wayne,
Quote:
1600+ post and no link to measurement vs sound quality , no ultimate amplfier..
?
Well, the perfect amplifier doesn't exist yet for one. Therefore, we all break down into groups according to what faults we can accept. Price is another differentiating factor, as well as the imaginative hype surrounding the more expensive pieces. How is a customer to know the difference between what is good, and what isn't.

I think the major problem here is that customers are not experts in sound reproduction for one. However, they want to be an expert in their own group. The media is willing to co-operate by making stuff up and passing on disinformation. The average person doesn't really stand a chance when you think of it.

If you wish to understand what factors are important, you will have to stop reading audio drivel and study some physics. That and a finely honed BS detector should steer you along the right path.

Why no figures of merit that apply to all amps? Because there are just so many places where bad designers go wrong, that's why. That and differences are often small and measurements easily invalidated if they are done improperly. Electronics dealing with signals in an exacting line of work in order to do it right. These people must invest in education, experience and the desire to get it right, rather than to build up their name and sell on the basis of magic parts and questionable circuit design.

You wouldn't ask non-professionals how to properly design a building (even a house), or how to operate on your body. Why do this when you are looking for high performance in a sound system. But that is pretty much what happens when the topic of audio comes up. That is why you will never get the answer you want until you can learn enough of the true science to be able to avoid being mislead. It's up to you to filter out the noise.

-Chris
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Old 31st January 2012, 06:17 AM   #1614
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Hi,

Quote:
Originally Posted by anatech View Post
You wouldn't ask non-professionals how to properly design a building (even a house), or how to operate on your body.
I would not ask most professionals either. Any number of collapsed buildings, building with just bad design etc. where designed by "professionals". And I am still drawing a (small) monthly pension because a "health professional" was grossly negligent, so that my ability to earn a living for insurance purposes, by the insurances own experts and doctors is 30% impaired.

I do a number of non-professionals who in any of these cases would have done a better job, if only because of their status they would have taken more care...

Just having professional status in a given field is no guarantee of competence just as the lack of such a status is not automatic proof of a lack of such competence.

Quote:
Originally Posted by anatech View Post
That is why you will never get the answer you want until you can learn enough of the true science to be able to avoid being mislead. It's up to you to filter out the noise.
The importance in this is the word "TRUE" before science. Much of what I have seen here presented as "scientific" in support of the objectivist position is merely a load of utter Hogwash. It is replete with circular reasoning, self referencing and just bad science.

Yet even many highly educated and experienced (not always in the field of sensory research) people are taken in by this precise hogwash.

Hence the need for an evidence basis in all of this, not for technocratic number worship or for a "it is good because we only listen and we like it", though that latter position possibly has a better claim on being evidence based than the first.

Ciao T
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Old 31st January 2012, 09:53 AM   #1615
godfrey is offline godfrey  South Africa
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Quote:
Originally Posted by tvrgeek View Post
I am having trouble visualizing the relationships between phase changes and the poles.
Poles and zeroes. A pole is where the frequency response curves downwards. A zero is where it curves upwards. You may want to look up "pole splitting" as well.
Quote:
Originally Posted by tvrgeek View Post
I have read the chapters, but I need some bench time to look and play with it.... I can't put a scope on a textbook.
Why not get a software simulator to play with. Mouse clicks are faster than solder joints and the components are free. Also, they include very nice virtual instruments that let you look at waveforms, bode plots, spectrums etc anywhere in the circuit. I use the free version of SIMetrix/SIMPLIS - very nice. A lot of folks here on the forum use LTSpice but IMHO it's user interface is an absolute nightmare. I was a little relieved recently to see in one of Bob Cordell's threads that LTSpice and SIMetrix can give almost identical results anyway.
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Old 31st January 2012, 10:34 AM   #1616
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Hi,

Quote:
Originally Posted by godfrey View Post
Why not get a software simulator to play with. Mouse clicks are faster than solder joints and the components are free.
I agree. I have been using sim's for ages (since the days of the original Electronic Workbench for DOS), they have been getting better and it is much faster to change a component in a simulator or try a new circuit topology to see if it can work at all...

Beware though, simulators do not account well for parasitics, the more "imperfect" a real component or layout is, the more the results will diverge. For example bipolar transistor models, while better than they used to be, still miss several areas of parasitics that are not modelled well, if at all...

So take the results of simulators "cum grano salis magnitudinem montis", especially in terms of THD, IMD and such.

I would never expect that something works in reality as well and precisely as the simulator predicts, the correlations become lower as complexity increases BTW, however it it does not work in a sim, looks like it will oscillate in a sim etc., it will usually not work in reality either.

Ciao T
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Old 31st January 2012, 10:43 AM   #1617
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Hi,

Quote:
Originally Posted by tvrgeek View Post
I am having trouble visualizing the relationships between phase changes and the poles.
In the analogue world all filters have frequency response changes AND phase changes unbreakably linked (we may call them infinite impulse response filters).

So a "pole" is a simple first order rolloff that will at it's -3dB frequency response change phase by 90 Degrees. Poles add up.

If we have for example two poles dominating a feedback loop (say a slow output stage and a fairly wide open loop band width (one might say insufficient compensation) there will be a frequency at which the phase shift of the feedback signal will reach 180 degrees, so it will become positive feedback, not negative. This is what makes oscillators.

For amplifiers this is often expressed as "phase margin", meaning how many degrees are there between the actual phase response of the amplifier and 180 degrees.

Ciao T
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Old 31st January 2012, 11:33 AM   #1618
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You mean 45 degrees, don't you T? For phase shift at -3dB amplitude.
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Old 31st January 2012, 12:36 PM   #1619
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Quote:
Originally Posted by ThorstenL View Post
Hi,



I agree. I have been using sim's for ages (since the days of the original Electronic Workbench for DOS), they have been getting better and it is much faster to change a component in a simulator or try a new circuit topology to see if it can work at all...

Beware though, simulators do not account well for parasitics, the more "imperfect" a real component or layout is, the more the results will diverge. For example bipolar transistor models, while better than they used to be, still miss several areas of parasitics that are not modelled well, if at all...

So take the results of simulators "cum grano salis magnitudinem montis", especially in terms of THD, IMD and such.

I would never expect that something works in reality as well and precisely as the simulator predicts, the correlations become lower as complexity increases BTW, however it it does not work in a sim, looks like it will oscillate in a sim etc., it will usually not work in reality either.

Ciao T
Hi Thorsten,

As I've no doubt you are already well aware, another area where overly simple circuit sims can give significantly misleading results is in modeling amplifier topologies which depend on device level complementary distortion cancellation to minimize open-loop THD. The results can look falsely great in the simulation because all same model transistors devices will all be identical in parameters, unlike with real world transistors.
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Last edited by Ken Newton; 31st January 2012 at 12:39 PM.
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Old 31st January 2012, 03:14 PM   #1620
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Ken, you are correct, but here I will surprise everyone by RECOMMENDING circuit emulation.
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