John Curl's Blowtorch preamplifier part III

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That's fascinating.... Big difference! Thanks....

When the threshold curves for noise are plotted they are pretty different than the Fletcher Munson curves - we are more sensitive perceptually to noise by > 12dB @ -4KH
Another reason is that we are listening to differences in noise holistically, not trying to pick out specifics like we do with music replay
 
@billshurv,

They don't use 'crap' was my point.<snip>

Ok, that clears my confusion. :)

Btw, the line about "one want's to have an argument and his handle is not ...." that was an example of british humor, wasn't it?

@ Evenharmonics,

What you accused me of claiming (by not quoting) didn't take place outside of your own mind. Go back and reread post #21590.

Hm, so it was another Evenharmonics who wrote #21417 , really ?

Evidence is still missing.
 
Hm, so it was another Evenharmonics who wrote #21417 , really ?

Evidence is still missing.
Of course you would say so because you are in denial for the sake of your audio business.
I build my own amps so I'm not familiar with high quality commercial amplifiers for reference.
You mean you've never used store bought amplification device ever?
 
Class AB is basically class A at more or less normal listening level. But with CFP especially, over bias can be as bad as under bias. Depends on topology and transistor type.

That's a very very definite maybe, depending on too many variables. Remember that the definition of where B ends and AB starts is completely arbitrary. The lm3886 and TDA739x are both considered AB as are some way-past-Oliver-criteria amps. Broad swaths are not the best idea.

As far as "over biasing" a cfp, depends on ones goal.
 
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Attached is a standard speech intelligibility test file.

You will need a pencil and paper when you listen to this. There are 50 test words. Just write down what you hear. After a few folks confirm they have done this I will show the word list.

BTY spelling does not count. So if the test word is "Jerk" and you spell it Jyrk" that counts as right. If you think it is "Zerk" that is wrong.

You can use headphones or near field loudspeakers and try out your hearing abilities or your actual sound system and include room effects.

I tried this earlier and played it just once via laptop speakers (Dell Vostro at lowish volume)

View attachment 764127
One listen/write, one listen back with one correction ?.


Dan.

Dans results are in his .txt file.

My differences to those of Dan's are here.

Code:
STAID/STEAD
ELK/ELEC
WEEN/WEAN
FEW/VIEW
SCUFF/SCOFF
OUGHT/ART
MADE/MAID
VAT/BAT
GEM/JEM
OWE/OH
 
I guess that’s somewhere in the middle. :confused:
As I don't know any class B on the hifi market ;-), I had instantly read AB, in the original johnego message.
On my side, I would better class the class D in the same range than Class A, as crossover distortion is what's make the difference between A & AB.
Btw: About details, I found, listening to Bruno Hypex amps and some others that they were over simplifying the message. Easy listening, good separation, something lost in the very low levels that makes the music a little, how to say, sterile ?

But I do not exclude the hypothesis that it is the absence of distortions to which the class AB accustomed us.
Reason why some had the idea of those Class A-D amps ? (Never listened to them)

Anyway, as I think switching frequency too close to the upper frequency of the audio range in class D amps, and dislike the output filter, what about Class G ou or H ?

Someone made a listening test of some good ones if exists?
 
I can not hear differences in files presented here and I don’t comment on perception issues.
But these two files is an exception, I clearly hear differences.
I couldn’t imagine that the kind of distortion shown in the 1kHz screenshot can have such pronounced effect (aural and on FFT) on the 1kHz to 1.3khz noise.
Thanks Pavel for the info and test file.

George

That's fascinating.... Big difference! Thanks....

Thank you both. The distortion used is interesting because it affects just low level signals, which I was not able to do before. It may represent a very bad class B transistor amplifier of early seventies. Now, it depends on music we listen to.

If this distortion is applied to a rock music (I tried well recorded Godwhacker by Steely Dan in 96/24), it is almost impossible to tell that the distortion was added. If I added the same distortion to Beethoven's No. 9 symphony Movement No. 1, the distortion is immediately audible in the low level passage just after the beginning. Interesting. Thinking about preparing files, but I am not sure if it is not a wasting of time.
 
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@billshurv,


Ok, that clears my confusion. :)

Btw, the line about "one want's to have an argument and his handle is not ...." that was an example of british humor, wasn't it?

.


Mainly, but there are people on this thread who are completely closed to learning or accepting another viewpoint. Which is a shame because, noisy though the signal is, there is good stuff to be learned here :)
 
Thank you both. The distortion used is interesting because it affects just low level signals, which I was not able to do before. It may represent a very bad class B transistor amplifier of early seventies. Now, it depends on music we listen to.
That's interesting, Pavel - thank you! Can you say more about these distortions & how they were created - might help others experiment too?

If this distortion is applied to a rock music (I tried well recorded Godwhacker by Steely Dan in 96/24), it is almost impossible to tell that the distortion was added. If I added the same distortion to Beethoven's No. 9 symphony Movement No. 1, the distortion is immediately audible in the low level passage just after the beginning. Interesting. Thinking about preparing files, but I am not sure if it is not a wasting of time.
Yes, interesting - I don't believe it would be a waste of time
 
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