Thread: Best Pure Musical Amplifiers (power not important)

Originally Posted by a.wayne

Not exactly , classical requires more class A or lose the Timbre , body and nuance on instruments at low levels , very critical in catching the micro /macro details of a symphony, much different from low crest factor rock which really sounds more realistic and best on class B drive ..!

So whats really critical Is amp selected transition point from class A to class B , hence why its necessary to match Speaker sensitivity, db required and load to amplifier bias operation ..


Regards

This statement is false in several ways. First, what you are talking about is the need for low level detail, which is common to all genres, even death metal. Second, the class of operation has nothing to do with that. Distortion does. The 'transition point' is unimportant, unless you have a class AB amplifier that is poorly designed. But you can have a class D amplifier do just as well, since they can be very good at low level detail, equal to or better than the best class A amplifiers (and take this from someone who has been designing and building class A amplifiers for the last 50 years). A class D amplifier doesn't have that transition thing to which you refer.

The speaker sensitivity has nothing to do with the

load to amplifier bias operation

At. All.

The loudspeaker impedance can affect the operating point of the amplifier though. Generally the lower the impedance, the more the amplifier will tend more towards AB operation. If the amplifier is tube and uses an output transformer, and if the transformer is properly loaded then the impedance will not affect this since the required load on the tubes will be satisfied. But in OTLs and solid state A/AB amplifiers the impedance can affect the class of operation. The sensitivity has nothing to do with it.

Originally Posted by Mikado463

Class B amps, so I was lead to believe were primarily used for PA systems ? I know of no credible 'musical' amp that operates as such. Most Class A/B amps operate with an amount of initial bias into Class A before operating in A/B. Perhaps that is what you were trying to convey ?

The Wiggins Circlotron amplifiers made by ElectroVoice back the late 1950s were class B and intended for home hifi use, not PA. Normally class B introduces distortion at the signal crossing around the zero point since the magnetic field in the output transformer collapses. This made class B impractical for home use. The Wiggins Circlotron got around this problem because the output transformer does not have B+ imposed upon it so the magnetic field never collapses. As a result it was low distortion operating class B. It used a pair of 6V6 power tubes and made 25 Watts at full output! I suspect the reason it wasn't more popular is not because of its sound but because to execute a Circlotron you need two floating power supplies for the output section, so a pair of rectifier tubes and electrolytic filter caps that are insulated from the user. The extra expensive of this offset the cost of just adding an extra set of power tubes to get the same power in AB mode so the idea died.

The Circlotron resurfaced a few years later; for example we've been using it since the inception of the company. But so far its not been used again for class B although it could...

Originally Posted by 4N6

Ralph,

Thank you for all the wisdom. It seems there are others that talk a good game, yet are simply know-it-all, opinionated idiots.

BTW, I remember first hearing your amplifiers when I was a student at U of M in the late 80's and early 90's at a stereo shop on Snelling Ave. I can't remember the name of the shop, but your amps with some Spica speakers were terrific.

That was House of High Fidelity.

Originally Posted by Mikado463

All well and good 70 years ago, but I stand by my comment of not knowing of any credible Class B amps being produced for hi-fidelity music use today.

The qualifier you added here is certainly true! But there's no reason it could not be done again. The EV amplifier isn't bad.

Originally Posted by a.wayne

So class of operation has nothing to do with distortion , cant tell if you are playing or just intellectually dishonest, before peddling high feedback class D , your feedback mantra's were historical , now pedaling ClassD and you are all over the place with your faux science , no more anti feedback chat, still obvious you dont know nor understand the difference between speaker sensitivity and efficiency, you used to get that mixed up too...


I guess HIgh Feedback Class D is now where it's at Ralph, maybe with Spica's ......


can you Post up some actual bench numbers Ralph, to help educate the rest of us



Regards

I was anti-feedback because I knew that the amount needed was more than could be applied to any circuit I knew of, tube or solid state. I've been of the opinion for a long time that rising distortion with frequency is a Bad Thing and the only way to achieve that if the circuit lacks the Gain Bandwidth Product is to not use feedback. That includes all tube amplifiers and nearly all solid state amps made. The devices needed didn't even exist until sometime in the 1990s.

Norman Crowhurst wrote about the problems of higher ordered harmonics and IM introduced by feedback 60 years ago. But I realized that there was a way to get more feedback (self-oscillating class D), and also to get around the problem Crowhurst wrote about. So I am consistent with my prior position and that is why you've seen my comments about feedback change in the last 5 years.

Yes, distortion and class of operation have little or nothing to do with each other. Class A has traditionally been used to put the output device(s) in its(their) most linear region in an effort to reduce distortion. But other design criteria can easily overshadow the good class A might bring to the table, like distortion caused by poorly applied negative feedback, blocking distortion caused by driver circuit problems and so on. A properly designed class AB amplifier can easily have less distortion and be more musical than a class A amplifier on this account. Its the other things in the circuit that will determine if that is true or not.

There's no 'faux science' here; if you want to know more, Bruno Putzeys has written an excellent paper on the subject of feedback and Gain Bandwidth Product:

https://linearaudio.net/sites/linear.../volume1bp.pdf

Of course you can discount me all you like but you're putting yourself in a bad position going after him; his paper has the math/education about which you're asking.

Your statement about my understanding of sensitivity vs efficiency is false. If you doubt that, the likelihood is very high that you misunderstood one of my prior posts.

You are correct about high feedback and class D- that is where its at. IME its a mistake to think that because you've heard some, you've heard them all.