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Old 1st July 2013, 09:27 AM   #121
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I said to DF 96 there is is symmetry in a SE tube amp . It is that one device takes care of the amplification , energy symmetry if you like . I admitted I used curve cancellation between a pentode and semi triode to get what I would call a super triode . If you do that you must check it can be repeated . I prefer old fashioned biasing to help the outcomes . Add loop feedback if you like . Do listen if you do . Chooses speakers that suit it if hoping to use no loop feedback .

Looking at all other amplifiers I see class AB as the better alternative . It is probably true that push pull class A suffers in a similar way to class AB . I have seen arguments both ways about push pull and output transformers . Well argued that the magnetization never reaches zero which was considered a good thing . I have just this morning for the first time stated to question class A push pull transistor . Would it be better to be all NPN ? I think it would . Not least it overcomes many objections to that topology . All in all we might be fooling ourselves to think class A PP transistor is like class A PP tubes .


Class A PP transistor is probably inferior to class AB . I would love to say class B . It is very hard to make a hi fi class B ( exact B point is hard to set ) . The reason PP class A fails is that the power supply seldom is good enough . One good thing is it becomes obvious it fails . Class G seems a good idea . The Douglas Self class AC seems ideal ( G ) . I would suggest 5 watts in class A is plenty . That could be giving 20 watts into lower loads . My tests suggest that 5 watts is almost universal . Even for a night club . Simple over biased class AB is just fine . It avoids all the complexity . It keeps the power supply sensible . The input and VAS will happily do the same job as it does when class B . It will do it with greater ease and with nicer outcomes . Somehow this arrangement is seen as an advertising mans con trick by some . Pure stupidity to say that . Psycho-acoustics are more important than doctrine . When that loud what is the distortion we hear ? It is our own ears limiting ( mechanical ) . Over biased class B can even be done with a resistor if the heat sink is big enough ( replacing the usual Vbe bias regulator ) . Use a regulated supply to the VAS if so ( always do it is my advice even if bootstrapped collector load ) . Test into 1 R to be sure it is OK . I have tried it with MOS FET's . I suspect they suit AB better . Ron goes too high ?

Douglas Self has a patent on biasing the class B point to other than zero volts . This reminds me of how 741's were made to perform better . A simple constant current source to the output to make it into a form of class A by knocking out one internal output transistor . I never tried it with a power amps . It must work ?

We seldom see transistors in tube amps . When we do they are usually are FET's . Where possible J FET's . This is throwing away a good idea . As current amplifiers transistor can be as transparent as resistors ( more so than cheap metal films ) . They can mimic chokes . FET also . However the transistor may be ideal . I don't think you will see many as tubes are mostly a religion . Even if you don't use transistors in a tube amp use them to say how the amplifier might be better . If you buy an expensive choke on the strength of it that's OK . Also don't look at transistors that go to 6 MHz as having leprosy . In a zero loop feedback amp you will seldom ask for 50 kHz and the transistor will never have to switch . The transistor I have in mind costs $0.30 from ON semiconductors .

I will make a speculation about no loop feedback . Is it that it is better the speaker comes to a stop itself ? My speakers as I said previously crossover at 600 Hz using first order curves to both panels . Strikes me a SE tube amp can be engineered to exactly match that and have freedom form having to have a badly engineered transformer to get some bass ? The sub 600 Hz the job of an AB transistor amp in my case . No complex maths to do as the designer of the speakers did it for me . I put up a suggestion from Michael Gerzon in another thread that bass needs more separation than the mid-band for images to appear divorced from the speakers ( that is bass makes for better mid , real life also ) . This is why people think one sub-woofer will do . It won't . With my arrangement I could have that . My speakers already have a hole in the middle due to room available to use them . How curious to go further . I do have one listening position that works . A famous tube amp designer suggested we add resistors to our transistor amps to mimic how SE amps work . No one has every said it worked ? This surprises me . Critical damping may be the last undiscovered tweak ? Are we again talking religion ?

Early effect . It is often the unexpected problem with transistors . Darlington's especailly and I suspect cascodes . It is a colouration effect . Very pleasant and might be preferred . Most modern transistor cascodes dispense with a resistor between devices . 33R was typical in the old days . See if it helps .

Last edited by nigel pearson; 1st July 2013 at 09:32 AM.
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Old 1st July 2013, 09:38 AM   #122
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It seems remarkable that 100 years later, people are still talking about the tiniest differences between amplifier designs, and still debating about which nonlinearity sounds better than another. One might have imagined that the problem had been solved by now! In the old days a DIY-er could be the first in their street with a radio, TV or a stereo, but today's DIY-ers seem only happy when re-hashing the same valve circuits that their grandfathers built.

At the same time, progress in DSP continues, and the advent of the active speaker means that amplifiers barely break into a sweat - with myriad benefits for sound quality, and allowing the designer to simply plug amp modules in like Lego - anything else is self-indulgence!

Companies like Meridian are forging the way, but the DIY-er could actually be right at the cutting edge with the field still wide open as regards methods of measurement, crossover settings, room correction. They could spend all their time considering the sonic compatibility between drivers, the finer points of directionality, or even the aesthetics of the cabinet without the massive overhead of worrying about phase shift, efficiency, 'padding' and so on - the active DSP can just soak these minor complications up.

Welcome to the 21st century!!
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Old 1st July 2013, 10:19 AM   #123
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Originally Posted by nigel pearson View Post
Psycho-acoustics are more important than doctrine . When that loud what is the distortion we hear ? It is our own ears limiting ( mechanical ) .
Well, I have heard bad loud, and I have heard good loud. Bad loud is most PAs, which at the extremes are like a combination of a dentist drill and jackhammer, attempting to make that particular moment in time as unpleasant as it possibly can be, . Good loud is the real thing, like being 10 feet away from a big band in full cry, without some miserable PA mangling it to FUBAR. Both are deafening, both will set your ears ringing - one is a torture, the other is a pure delight - some part of your being has no trouble differentiating the qualities of what's being heard even under those 'extreme' conditions, .
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Old 1st July 2013, 10:27 AM   #124
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@ CopperTop. Room correction is clearly bettered by not interacting with the room in a way that needs to be corrected. It's the only means that truly works. It's things like this, baffling and amps that deliver simple goodness which are at the business end of keeping it good.
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Old 1st July 2013, 10:32 AM   #125
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My main point is class AB is very good . All other classes work very hard to have true advantages over it . Most fail . The amateur with the help of Douglas Self can become a reasonable expert . If they are curious they can go beyond it . It is almost like Douglas makes it so we all could enter Formula 1 and win . That would be like going back to the time of James Hunt . Safety I fell is not all about money however some of it was . James Hunt's day was not safe . In hi fi we can still be Colin Chapman and do " what if " designs . I watched the F1 race yesterday . As an engineer both mechanical and electrical I couldn't wait to getting back to reading the forums . Out of respect to my day of rest I waited until today .

Class D is money wins F1 . Someone simplifying it would change that . Buying a Hypex Module seems all wrong to me .

In F1 I would introduce a new class winner . Money verses outcome class . Force India might be leading that one .

DSP Is great when in the digital domain already . Hopefully the system is great in the non digital domain also . DSP sometimes re-clocks and improves . My friends who use it professionally say it is a requirement to get it to work using a variety of makes of digital device . Musicians buy tools to do their work , they have no idea of compatibility issues . The sound engineer does that job . It should be better than if no DSP was used even when no apparent processing is required .


The strangest thing with an Arcam DAC . With CD doubtful it was my cup of tea . With you-tube I thought it is time I had something like this . Weird .

Last edited by nigel pearson; 1st July 2013 at 10:38 AM.
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Old 1st July 2013, 10:45 AM   #126
AllenB is offline AllenB  Australia
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Originally Posted by ontoaba View Post
I know some harash sound created by bjt outputs are warm and with this harash tonal character, bjt output amps could not sounded like tubes.
I prefer BJTs to FETs. Even using the 162 (and their complementary part whatever it's called), I tried the N and P channels in single ended form and AB but I couldn't live with them.

There aren't many BJTs I'd call better than good but I once had a few of those Toshibas which were. Some small signal transistors are surprising as outputs.
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Old 1st July 2013, 10:50 AM   #127
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@ CopperTop. Room correction is clearly bettered by not interacting with the room in a way that needs to be corrected. It's the only means that truly works. It's things like this, baffling and amps that deliver simple goodness which are at the business end of keeping it good.
I put this on another thread . This guy was the number one expert on room effects . He should have been my friend if I had tried harder , he taught me a lot . His patents are the basis of many modern devices . Surprising in video also . The rules for data compression are similar . I am not sure to what extent things we use are Gerzon . The maths mostly . Others may well do it differently now and better ? He did the foundations . Bob Stewart of Meridian is holder of these patents I beleive ?

http://www.audiosignal.co.uk/Resourc...uffling_A4.pdf

Michael showed why EQ devices sound different . Not because of the most obvious reasons . At first analogue EQ .

http://www.audiosignal.co.uk/Resourc...isation_A4.pdf

Last edited by nigel pearson; 1st July 2013 at 10:53 AM.
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Old 1st July 2013, 01:52 PM   #128
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Originally Posted by nigel pearson View Post


I would suggest 5 watts in class A is plenty . That could be giving 20 watts into lower loads . My tests suggest that 5 watts is almost universal . Even for a night club .

When that loud what is the distortion we hear ? It is our own ears limiting ( mechanical ) .




I will make a speculation about no loop feedback . Is it that it is better the speaker comes to a stop itself ? My speakers as I said previously crossover at 600 Hz using first order curves to both panels . Strikes me a SE tube amp can be engineered to exactly match that and have freedom form having to have a badly engineered transformer to get some bass ? The sub 600 Hz the job of an AB transistor amp in my case . No complex maths to do as the designer of the speakers did it for me .

I put up a suggestion from Michael Gerzon in another thread that bass needs more separation than the mid-band for images to appear divorced from the speakers ( that is bass makes for better mid , real life also ) . This is why people think one sub-woofer will do . It won't . With my arrangement I could have that . My speakers already have a hole in the middle due to room available to use them . How curious to go further . I do have one listening position that works .

A famous tube amp designer suggested we add resistors to our transistor amps to mimic how SE amps work . No one has every said it worked ? This surprises me . Critical damping may be the last undiscovered tweak ?
Nigel;

What tests do you use that suggest 5 watts is enough for nightclub?

What is distortion spectrum of speakers used in your testing?

What is SPL? What is distortion spectrum at 85dB, 95dB, and 105dB?


What kind of IMD with transients?


Dominant imaging cues occur >500Hz.

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DSP Is great when in the digital domain already .
What's up with this statement? No microphones are digital. Do you listen to exclusively tape and vinyl solely produced by analog systems? DSP is OK if somebody else does the ADC?
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Old 1st July 2013, 05:54 PM   #129
Pano is offline Pano  United States
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Welcome to the 21st century!!
Where sounds, ears, music and the laws of physics have now changed?
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Old 1st July 2013, 05:55 PM   #130
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This 5 watt thing came by accident . A friend found that nearly ever situation he could find 5 watts at lets say no more than 5 metres could be served by 5 watts . The reason perhaps is rather simple . Magnet circuits usually saturate at much the same level whatever else is different . The choice of the designer is what efficiency they want . Lets go buy a 50 Tesla magnet is less than possible as an upgrade . The 5 watts is helpful . I am convinced it is of real relevance . The first 1 watt not really , the first 5 watts perhaps .

5 watts at 105 db /watt/metre when 5 watts is loud . You easily might have 4 speakers in a club . There will then be 300 to 1000 of very OK watts on top of that . The real " oh my goodness this is hi fi although PA " will still be 5 watts . The tingle in the spine might be a slow dance and Randy Crawford at typical 5 watts .

It seems to me ( and the freind ) that speakers scale down as they move into houses and it is still 5 watts .

I had an experience with some Western Electric cinema speakers of frightening efficiency . Some 2A3's were hooked up ( 3 watts ) . It was OK in a crude sort of way and loud ( very ) . What should I expect from 1940's technology ? Then a 300 watt modern amp . Wow they were good . Still think it was the 5 watts that mattered . I have to say they were better with the modern amp. Much more control . My simple point was that 5 watts in class A in over-biased AB would be enough . Probably if going 300 watts class G/H would be better ( A + C ) . If 50 to 100 watts I say try it . You can for some minutes on most amps try it . Try Saxophone solos like the one inside Duke Ellington's Black Beauty ( modern recording ) . It is the hoot of the Sax which punches the chest . It needs only that 5 watts . Sure the transients will be much above 5 watts . LP's of Frank Sinatra need it . Reissues don't have it very often . Buddy Holly also .

The 600 Hz is a bit unfortunate on my speakers . However as I said the speaker designer sorted that out to my satisfaction . What a free lunch that I don't have to reinvent the wheel , what I need is done already . Not least someone is asking me to tune some 211's and I so want to have the pleasure of nearly owning some . I need to listen as I usually do to know what I am doing is OK . PSU alone is a challenge .

Interesting what you say about microphones . Friends between them have nearly every nice microphone you can name . They buy pairs and lend them to each other . My challenge was if using 2 x 2N4403 and 741 plus CCS to negaive rail would the microphone shine through ? The belief is it would . I think I will force that we try it . It is the ultimate source of sound argument . These mics get used at a local church as one lady loves to hear how her voice can sound when a decent mic . The mixer is as cheap as money can buy .

DSP . If I made you misunderstand it was this I wanted to say . If a signal is already in the digital domain it seems daft not to use DSP . If it is analogue as a microphone or LP the system should be good without DSP as a point of reference . No reason to say not to use DSP even so . Then the system is fly by wire or conventional by choice . Alas aircraft are not and that seems too good to be true , I fear flying . When asked why I say because I understand how it works .
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