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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 10th October 2013, 04:01 AM   #43981
elektroj is offline elektroj  Europe
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Originally Posted by SY View Post
...Modern designers with the goals of performance and reliability would (and do) make use of technology that wasn't available then, ...
... and still manage to miss the target despite (or because) the use of it.
 
Old 10th October 2013, 05:17 AM   #43982
a.wayne is offline a.wayne  United States
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Originally Posted by davym View Post
That said I still find it of interest, insulting the guy helps who exactly?
You must be new here , the insults havent yet started .....

Scott , Sy and John have a special , err , relationship! Sy 's the enforcer of tides and greetings to all things presented by John for boutique application and try as they might , John's monologue will continue with no IC in sight , to Scott's chagrin ...

Seen ....

PS: Sy maybe steaming over the A21's, err long story .....

Last edited by a.wayne; 10th October 2013 at 05:19 AM.
 
Old 10th October 2013, 05:39 AM   #43983
ezavalla is offline ezavalla  Argentina
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Originally Posted by fas42 View Post
therefore, more 'intelligent' ways of measuring need to be devised ...
If you try to measure the "subjective performance", you will surely fail. In your posts, you always explain what you feel with your tests, however.. you never quantify your "measurements". But it isn't the real problem...the trouble with your comments is that you are taking yourself as the "reference line" for all measurements, but you are unable to see that everything that you consider marvelous, can probably be taken as garbage by another one.
So... what's the truly "subjective reference line"???
The answer is: there isn't such thing as "truly reference line" when we talk about "subjective measurements". However, engineers need to design a loudspeaker or an amplifier or whatever, in order to allow all the people to listen to the music.
What can be done about it? It is quite simple: measure THD, measure the radiation beam, measure the reflection time, etc. You need to MEASURE everything that can be used as a quantification factor
So... "subjective measurements" are crap.. at least from an engineer point of view, unless he is trying to modify the acoustic behaviour from a room (they are crap anyway, but at least can be taken into account with a grain of salt).
 
Old 10th October 2013, 07:08 AM   #43984
RNMarsh is offline RNMarsh  United States
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Geeez... checking in to see if anything has changed .... nope

Zzzzzz.
 
Old 10th October 2013, 07:45 AM   #43985
fas42 is offline fas42  Australia
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Originally Posted by ezavalla View Post
So... what's the truly "subjective reference line"???
The answer is: there isn't such thing as "truly reference line" when we talk about "subjective measurements". However, engineers need to design a loudspeaker or an amplifier or whatever, in order to allow all the people to listen to the music.
What can be done about it? It is quite simple: measure THD, measure the radiation beam, measure the reflection time, etc. You need to MEASURE everything that can be used as a quantification factor
So... "subjective measurements" are crap.. at least from an engineer point of view, unless he is trying to modify the acoustic behaviour from a room (they are crap anyway, but at least can be taken into account with a grain of salt).
I appreciate your points, and agree it's very hard ... THD, or just straight distortion, for me at least, is the most important indicator, and that's what I focus on. Since this results from the sum total of all the elements in the system working the only truly valid way of verifying performance is to 'measure' what's emerging from the speakers, and compare that against what was recorded, the source waveform.

That of course has huge challenges, and currently no mechanism or software processing is going to have a chance of unraveling meaningful differences - items like Diffmaker are still far too primitive ...

But, I hope to work towards resolving that situation: acquire a far better recording setup, particularly one that handle high SPLs without overloading, so that the direct driver output can be captured with minimal reflected energy intruding; then calibrate the loop; and finally do some waveform processing and start to digest what the differences can tell me.

So far my admittedly very primitive recordings of what my gear does tells me that my ears aren't lying, the system produces the results that my brain thinks it is - therefore I'm motivated to go the next step ...
 
Old 10th October 2013, 08:06 AM   #43986
RayCtech is offline RayCtech
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Originally Posted by SY View Post
Depends on what you want to learn. This thread mostly deals with circuit design from 30-40 years ago and the application to fashion audio. Modern designers with the goals of performance and reliability would (and do) make use of technology that wasn't available then, but there's lot of other threads about that. Take your choice.
SY - Please prove that there have been any improvements in SQ in the products of what you call "Modern designers" when compared to the 30 - 40 years old designs.

I think you know that you cannot....
 
Old 10th October 2013, 08:07 AM   #43987
john curl is offline john curl  United States
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Now where were we? If we would want to make this particular example, we would have to look on the design sheet for the 2SK147 and pick some numbers off the graph.
First, to get 13 ma on the input stage, you would need approximately a 17ma Idss. You can do your own calculation of this.
To understand the effective gain, you have the equation 300/5+1/Gm
In this example, that is 300/5+18 or 300/23 or a gain of 13.
The noise ideally would be 2/3 (1/Gm) +5 or 17 ohms. It will be slightly worse than this because no jfet is perfect, and without 1/f noise.
Now, this is not an IDEAL circuit, because it is NOT push pull, and it will have LOTS of 2'nd harmonic distortion. Also, you have to hand pick the current source load to match what you want the second stage current to be.
A better solution is to make a COMPLEMENTARY gain stage just like the first one, but with complementary parts, remove the current source, and let the two complementary gain stages drive each other. Then you get a voltage gain of about 26 , 3dB lower noise, AND much less THD, especially if you convert the 5 ohm resistor to a 10 ohm, 10 turn wirewound pot that can be carefully adjusted. Now the noise will be equivalent to about 9 ohms which is about 0.4nV/rt Hz. (ideally) QED (This is not a perfect circuit, and please correct me if I made any mistakes) '-) The REAL circuit has a bit more to it.)
Attached Images
File Type: jpg 2SK147.jpg (586.4 KB, 254 views)
File Type: jpg ddd.jpg (200.2 KB, 249 views)
File Type: jpg scp1 simplified.jpg (198.9 KB, 256 views)
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Old 10th October 2013, 10:27 AM   #43988
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by RayCtech View Post
SY - Please prove that there have been any improvements in SQ in the products of what you call "Modern designers" when compared to the 30 - 40 years old designs.
There haven't been. Boxes of gain could and were made to be sonically transparent decades ago- it's a solved problem. The issue these days in fashion audio is differentiation of parity product (from a pure ears-only POV). From a measurement POV, one can now make quieter and lower distortion electronics using fewer parts, which won't sound any different than other, older boxes of gain, but are simpler and less expensive to design and build.

Of course, many designers in fashion audio are still making effects boxes, and there are hobbyists who like to spend time rationalizing that, but that's a different story.
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Old 10th October 2013, 12:12 PM   #43989
RayCtech is offline RayCtech
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Originally Posted by SY View Post
There haven't been. Boxes of gain could and were made to be sonically transparent decades ago- it's a solved problem. The issue these days in fashion audio is differentiation of parity product (from a pure ears-only POV). From a measurement POV, one can now make quieter and lower distortion electronics using fewer parts, which won't sound any different than other, older boxes of gain, but are simpler and less expensive to design and build.

Of course, many designers in fashion audio are still making effects boxes, and there are hobbyists who like to spend time rationalizing that, but that's a different story.
As expected: Absolutely no evidence, and even additional fogging..
Please prove the last statements and document the evidence.
 
Old 10th October 2013, 12:15 PM   #43990
SY is offline SY  United States
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John Curl's Blowtorch preamplifier part II
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Originally Posted by RayCtech View Post
As expected: Absolutely no evidence, and even additional fogging..
Since this has been cited, oh, about a thousand times, I don't see how the 1001st time is going to slow down the march of ignorance.

For a quintessential and extreme example of effects boxes, see Wavac.
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