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Old 1st May 2012, 09:53 PM   #4941
dvv is offline dvv  Serbia
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Quote:
Originally Posted by FrankWW View Post
no. he didn't.

he had chinese maps from venice, i believe.

lots of folk knew what was 'over there'
I don't see how knowing that China is there makes the world round?
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Old 1st May 2012, 10:01 PM   #4942
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DVV, my great grandfather came from your general area, long ago, and apparently he migrated to the USA, partially because the area would be taken over by a different group every couple of years, and they would burn all the textbooks!
Still, I am amazed that you knew about Daugherty and Greiner, 1966. I puzzled over it, for some years. Matti's 1970 paper was published. Still, I stayed an 'op amp' kind of guy, but after 1971, it seemed worthwhile to try Matti's ideas, and I have never looked back.

Last edited by john curl; 1st May 2012 at 10:24 PM.
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Old 1st May 2012, 10:04 PM   #4943
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by dvv View Post
Very possibly, SY.

I'm 59 years old, and in my schooling, went through, in proper sequence, Yugoslav, Turkish, Pakistani, Yugoslav, British and Yugoslav educational systems. I have lived (lived = 1 year or longer), beside naturally my own country, then Yugoslavia, now Serbia, in Turkey, Britain and Egypt.
Well 1 yr in the British education system, during that era is equivalent to 10 yrs in the "US" educational system.. Subtract points for Pakistan ...

Last edited by a.wayne; 1st May 2012 at 10:08 PM.
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Old 1st May 2012, 10:06 PM   #4944
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Of course, there was the small paper in back of the RDH, in later years. Qualitative, but not quantitative. We all knew that amplifiers would 'run out of steam' either with rise-time or higher distortion with higher frequency drive.
However, it was the OP-AMP model that gave slew rate a definitive presence.
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Old 1st May 2012, 10:09 PM   #4945
DF96 is offline DF96  England
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Why are we talking about 'belief' in relation to how feedback amplifiers work? I am baffled by this sort of talk. Can we each independently decide which facts of mathematics and circuit theory we choose to believe? The impact on perceived sound quality may be a matter of belief, but the effect on the amplifier in-out function is a matter of fact.
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Old 1st May 2012, 10:25 PM   #4946
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DF96, what I think is important, is what works!
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Old 1st May 2012, 10:47 PM   #4947
DF96 is offline DF96  England
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Quote:
Originally Posted by john curl
what I think is important, is what works!
If you are selling stuff, maybe. For those of us who do audio as a hobby why it works may be important too - it certainly is for me.
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Old 1st May 2012, 11:40 PM   #4948
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Default Williamson

[IMG]Click the image to open in full size.[/IMG]

I remember hearing my first Williamson amp and being taken aback by it's transistor like sound . Dry , fast and crystal clear . I have heard very poor ones also where someone used surplus store transformers etc . We built one with Sowter transformers which worked well ( 10 sections not 14 ) . .

The remarks here stand out in my head . I found also but not in this text him saying not to adapt the circuit because a type of distortion not yet named was heard .

I think the lad was 19 when he designed this . I know all the arguments about Williamson , however it is the landmark our industry was built upon . He went on to build robotic machines for car factories and died young I beleive ( 66 ? ) . It is rumored he designed the Quad 11 and ESL 57 .
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Old 1st May 2012, 11:43 PM   #4949
a.wayne is offline a.wayne  United States
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Quad ..... Interesting ....
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Old 2nd May 2012, 12:17 AM   #4950
tvrgeek is offline tvrgeek  United States
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[QUOTE=dvv;3007267]Commercial product designers are, unfortunately, bossed by their sales people and are pushed to produce great specs rather than great sound. One of the things they are forced to do is to use a lot of overall NFB.

This yields better classic THD figures, however, since it also implies greater open loop gain, this also means a more narrow open loop power bandwidth. This in turn tends to produce more HF distortion open loop, and hot ding, you CAN hear it.

For around 30 years, we have accepted the axiom that an amplifier should have an open loop bandwidth of no less than 20 kHz, yet you will find in many commercial offerings an open loop bandwidth of 4 kHz and such like. But whack it with a lot of global NFB, and you get classic THD figures like 0.01% or less.....]


Yes, with the help of fine folks in this thread I agree with all said. If Creative/e-mu can figure out why their drivers keep crashing my PC, I can get back to it. I am half way through a couple of speaker builds and my voicing sessions are being interrupted by bad software. I am really hoping that proper notch filters at the driver breakup points will be the correct fix, allowing better overall quality amps.

Anyway, I have a very generic little amp ( e-bay special) that is going to be easier to modify than the Hafler was, so I am fully game to try a lot more with it. The biggest advantage is it is not made of unobtanium, but cheap Chinese counterfeits. I'll post the corrected schematic in a bit with some of my ideas. It starts off very "Self-ish" as do most amps.

Basic question: Is it better to adjust the output idle current so the two halves match, or to set so the signal clips symmetrically? I found I could not do both on the Hafler at the same time.
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