Pavel,
no skilled designers run power amplifeir front end diff amps with zero degeneration now days, so dont' try to make an argument for zero feedback or promote JFETS for the front end in this kind of way.
Its quite easy to get your second curve through degeneration - Marshal Leach showed us how to do it in 1977.
"
One possible approach (where GNFB ALWAYS makes problems):
PMA has attached this image:
Click the thumbnail to see the original image.
"
no skilled designers run power amplifeir front end diff amps with zero degeneration now days, so dont' try to make an argument for zero feedback or promote JFETS for the front end in this kind of way.
Its quite easy to get your second curve through degeneration - Marshal Leach showed us how to do it in 1977.
"
One possible approach (where GNFB ALWAYS makes problems):
PMA has attached this image:
Click the thumbnail to see the original image.
"
Do not be second guessing.
BJT opamps are still designed in this manner, and there are BIG problems with LM4562, e.g.
BJT opamps are still designed in this manner, and there are BIG problems with LM4562, e.g.
john curl said:
Thank you, John.
I'll draw both options and send it to you, to see if I got your idea right.
PMA said:
"Do not be second guessing."
Most decent BJT opamps recommended for audio use some sort of degeneration in the input stage.
The LM4562 limitations are in no way shape or form related GNFB (BTW, it uses degeneration in the input stage) but to common mode distortions, and some thermal induced distortions at high supply voltages. Both effects impact could be minimized in a competent design.
Over the last year, you failed to provide any shred of credible and reproducible evidence of any "BIG problems with LM4562". If you still think you have any, you may contact NatSemi, they are extremely sensitive to such feedback and a response is guaranteed. Otherwise, just blank statements about on a DIY forum are not worth the electrons required to post.
I know. While it is not possible to mind read, it is possible to notice trends like yours.Joshua_G said:
But I have been carefully wording my responses to allow you to claim that, rather than your continual deflection away from yourself and your words...
My point on idols was..I was not happy with syn08's use of the adulation term, as it made is appear that your primary motive here was to shake the pom poms as a cheerleader for JC, discounting the possibility that you bring something of merit to the table.
So I stated that all are guilty of idol worship to some degree, myself included. And if not that specifically, then respect.
While I certainly respect JC's accomplishments over the years, I certainly will not sit idly by while he promotes RRR as a magical thing happening to wires (as well as other interesting but inapplicable concdpts).. I do enjoy the circuits, however, and look forward to more discussion along those lines.
When you are ready to cut chips (build), perhaps you can post initial layouts for all to examine and critique..it may be a learning experience for all..
Cheers, John
You have to admit, however, that you do bring a lot of it on yourself.john curl said:
A shame, as I still believe you have a lot to give.
Cheers, John
jneutron said:
Quite obscure.
I could relate, should you state your point clearer.
As of bringing something of merit:
This thread is about better designing audio amplifiers. So far you brought here nothing related to that topic – you used this thread to expound a different topic.
jneutron said:
You can speak for yourself, you cannot speak for all people – you were not nominated.
jneutron said:
This thread isn't about cutting chips – it's about better designing audio amplifiers.
jneutron said:
This is in the eyes of the beholder.
jneutron said:
To my view, shame is when lesser people mock greatness.
How about, instead of shaming others – bring something of merit to this thread?
Then you should have asked for a clarification, rather than the statement you made.Joshua_G said:
No, better audio amplifiers are not just a schematic. Building it like a bowl of pasta will produce garbage. The layout is a critical aspect. Layout is what I speak of, and how to do it better.Joshua_G said:
As for bringing something not related to the topic? Do you believe RRR is related to the topic at hand?? I don't. But yet, you do not complain that it was off topic when JC started with it, eh?
Again with diversion...Joshua_G said:
Stay on topic.
You are kidding us, right?Joshua_G said:
You've never heard of "cutting chips"??? It means beginning the manufacture of hardware. That is why I put "build" in quotes right after the phrase, so you wouldn't embarrase yourself again.
Please, read slower. Thanks
Cheers, John
Agreed.Joshua_G said:
Again, I also agreeJoshua_G said:
Silly diversions again..Joshua_G said:
I say it is a shame that he brings disfavor to himself, you try to make it as though I am shaming him.
Classic diversion...
Merit, you mean like 20 year old circuits with obsolete parts? A good circuit should be updated as time goes on.
Any current work you care to share? This century perhaps?
Cheers, John
jneutron said:
Did you see the photos of the CTC Blowtorch published at the beginning of this thread?
If yes – what are you talking about?
If no – have a look and then come back.
Also, read this thread from the beginning and pay attention to what John Curl writes – you may learn a thing or two about building and layout.
jneutron said:
Only one who point finger at others brings shame to oneself.
Mocking at greatness is shame.
Back on topic please.
Where do you guys find the time to offer such sage wisdom to one another? A shame really, considering such sharp minds are being wasted on such trivial matters.
Is everyone having fun, yet?😀 Thanks Joshua_G for giving me a design challenge that I find interesting. Please send your drawings. Unfortunately, I still can't easily post drawings. I tried last night, but got error warnings.
Cal Weldon said:
Back on topic please.
Where do you guys find the time to offer such sage wisdom to one another? A shame really, considering such sharp minds are being wasted on such trivial matters.
I agree.
john curl said:
No, it's not fun with all that off topic arguing.
I think jneutron has a lot of knowledge that is interesting and maybe a lot of people could learn something, if they bothered read what he is writing. That said I don’t understand why he is discussing with somebody that seems don’t have even the slightest clue of what he is writing.
As I see it people should be more open minded and discuss different topics without arguing that they have the only correct answer to everything. It sometimes seems like this is a discussion between religious fanatics, all of them has the only and true solution to everything.
In the ThermalTrak thread we have a very interesting and good discussion and almost everybody (it is always some distortion) try to come with meaningful posts that is in topic and so far we don’t yell at each other even we different views on things ( It’s a lot of ways to Rome, not only one)
I know this is a thread about the JC Blowtorch, and that this post is off topic.
I don’t own a Blowtorch and I will probably never do, and yes I think it must be possible to make an even better product with modern components and new knowledge.
As I have stated earlier I have great respect in what JC has done and this is not meant to be a post for or against either JC or the Blowtorch.
Cheers
Stinius
🙂 🙂
Look, Jneutron has been picking at me for many years, even on other websites. I tried to make him a colleague, from the first, but I found that he ignored any book that I recommended, that he attacked colleagues of mine, such as Dr. Hawksford and Dr. VandenHul, without actually TRYING to emulate what they were contributing to audio theory, especially wires, and he never stops attacking me about my wire measurements, that I first made more than a decade ago.
Now, just for fun, last week, as my associate and I are finishing up a new phono preamp, I decided to see IF I could still measure wires with my test setup.
At first, I found much more residual distortion, even in my 'reference' cables, so I went on to clean all the external contacts, and exercise the pots and switches on my modified ST THD meter. Once I got the test working relatively OK, I tried different wires, once more. One $1000/meter coax cable that I tried, generated 8th harmonic. Why 8th harmonic at levels less than 50mV? When I replaced it with a VDH cable of the same length, the 8th harmonic went away. When I put back the expensive cable, it reappeared.
Now tell me this! How would 'grounding' or shielding make any difference in this measurement? Please remember, 2 coaxial cables both the same approximate length, and thickness. These two cables might NOT have exactly the same characteristic impedance although the VDH cable is rated at 75 ohms, but I have noted significant differences between other cables with this test, repeatedly over the years with the SAME characteristic impedance, so it does not seem to be the problem. Etc, etc. Over the years, I have to hear the same old criticisms, even if I am not bringing up the subject at the time. It does become tiresome.
Now, just for fun, last week, as my associate and I are finishing up a new phono preamp, I decided to see IF I could still measure wires with my test setup.
At first, I found much more residual distortion, even in my 'reference' cables, so I went on to clean all the external contacts, and exercise the pots and switches on my modified ST THD meter. Once I got the test working relatively OK, I tried different wires, once more. One $1000/meter coax cable that I tried, generated 8th harmonic. Why 8th harmonic at levels less than 50mV? When I replaced it with a VDH cable of the same length, the 8th harmonic went away. When I put back the expensive cable, it reappeared.
Now tell me this! How would 'grounding' or shielding make any difference in this measurement? Please remember, 2 coaxial cables both the same approximate length, and thickness. These two cables might NOT have exactly the same characteristic impedance although the VDH cable is rated at 75 ohms, but I have noted significant differences between other cables with this test, repeatedly over the years with the SAME characteristic impedance, so it does not seem to be the problem. Etc, etc. Over the years, I have to hear the same old criticisms, even if I am not bringing up the subject at the time. It does become tiresome.
john curl said:
John Curl.
Probably, if was some image, it may not be above 100kB in file size and must not be more than 1000x1000 pixels.
Use some image editor to reduce & compress and so make your attachment fit for internet publishing.
Also not all filetypes are allowed. If so, you have to convert to accepted filtype (indicated by 3 letter extension e.g .ps .jpg .zip)
If you have some extension that is not allowed, you can ZIP it.
This means you:
- Right Click on your file
- Find 'WinZip' in menu -> Add to to Zip file
- Try to attch your new filename.zip
I, too, would love to see you post some interesting 'drawings'.
Thank you 🙂
Lineup
john curl said:
John
This was very interesting reading, all of it.
But to one thing first: Did the 8th harmonic occur on the whole frequency spectre or was it for one fixed frequency?
Stinius
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