John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Jump to Latest
#11,621
jneutron said:
My belief is that is it a direct result of the public's lack of desire in the sciences. As such, it is engineers, physicists, scientists..all of em.

It was noted here in the US, that for the general public to understand a scientific article, the article had to be written at a 12 year old's level.

Try as I may via the tours I give, I've not been able to dispute that assertion.

It makes me unhappy.

Cheers, John
Click to expand...

What's the worry ?

Ray Kurzweil, "China is committed to building 50 MITs, as they put it. That’s not an exaggeration. They’re creating scores of world-class technology universities."

:-/


.
 
#11,623
#11,624
simon7000 said:
GRRR! WOW! UNEXPECTED!

I just did another check on my transformer that is connected to an AC line with a DC offset of .88 volts measured by the circuit shown earlier. I used one meter on the input and another on the output. Same meters for all of the measurements.

As you can see there was some jiggle in the AC Mains so looking at the in to out ratio shows A STEADY LOSS OF OUTPUT! I would have expected an offset in the hysteresis loop but not a shift! This is a small signal transformer rated for 48 VCT out at 125ma. It is loaded by a pair of 1K resistors to the center tap. So it is a bit hotter due to the lack of load.


Input Out Ratio Ratio Diff % Out Drop
125.2 60 0.479233227 0 0
125.5 60 0.478087649 0.001145577 0.239043825
126.6 60.5 0.477883096 0.00135013 0.281727225
125.6 60 0.477707006 0.00152622 0.318471338
123.9 59.1 0.476997579 0.002235648 0.466505246
125.2 59.6 0.476038339 0.003194888 0.666666667


Again not the expected result! The transformer is actually becoming less efficient!


J.N. Do I need to explain this more clearly for the crowd here? 🙂


Note the table does not save column spacing when it goes from preparing to posting! Sorry!
Click to expand...


Please do learn to truncate data to meaningful resolution for readability.

3 significant digits is fine, and trival to do in a spreadsheet.

Cliff
 
#11,625
cliffforrest said:
Please do learn to truncate data to meaningful resolution for readability.

3 significant digits is fine, and trival to do in a spreadsheet.

Cliff
Click to expand...

Last time I rounded to significant digits there were lots of complaints and confusion, so the intelligent folks in the know will just have to suffer. I figure they will get the meaning.

But just for you.

% Loss
0.0
.24
.28
.32
.47
.67
 
#11,626
Ultra low noise amp E.H.Nordholt

Nice to see this amp here. Mr. Nordhold asked me to build it at that time.
I also remember we made a special (big)transistor in the IC foundry of Delft University with a lot of bjt's in parallel to get a very low Rb.
At the end of the project a complete amplifier on a chip was made for Ortofon to put in a MC head.
But never came in production....
 
Last edited:
#11,629
loek said:
Nice to see this amp here. Mr. Nordhold asked me to build it at that time.
I also remember we made a special (big)transistor in the IC foundry of Delft University with a lot of bjt's in parallel to get a very low Rb.
At the end of the project a complete amplifier on a chip was made for Ortofon to put in a MC head.
But never came in production....
Click to expand...

I might have the only two left in the world, any bids? (just joking)😀
 
#11,630
simon7000 said:
GRRR! WOW! UNEXPECTED!

I just did another check on my transformer that is connected to an AC line with a DC offset of .88 volts measured by the circuit shown earlier. I used one meter on the input and another on the output. Same meters for all of the measurements.

As you can see there was some jiggle in the AC Mains so looking at the in to out ratio shows A STEADY LOSS OF OUTPUT! I would have expected an offset in the hysteresis loop but not a shift! This is a small signal transformer rated for 48 VCT out at 125ma. It is loaded by a pair of 1K resistors to the center tap. So it is a bit hotter due to the lack of load.
Click to expand...

How well does the output loss correlate with winding temperature?
 
#11,632
jneutron said:
Yah..they were...till they ran outta concrete..

Hey look, they dinna even know what rma flux was, even though I recall seeing a home depot there...least, I think it was a home depot..😱

Cheers, John
Click to expand...

From same interview... "By the 2020s we will be placing millions or billions of nanobotsblood cell-size devices inside our bloodstream to travel into our brains and interact with our neurons. "

Mr. Kurzweil is prone to hubris.
 
#11,634
johnferrier said:
Linear Audio, Volume 1

Look forward to the articles Scott and Ed !


.
Click to expand...

Jan has once again produced a great edition of Linear Audio marked by many talented contributors.

There is also an article in there on negative feedback by Bruno Putzeys. I'm sure John will love it. It is titled "The F-word - or, why there is no such thing as too much feedback". It will be interesting to see what he has to say, but I'm sure in any case it will be controversial.

Cheers,
Bob
 
#11,639
Excuse the interruption for a minor detour back to engineering students (and may I add that its possible there is no "problem" just differences, maybe thats a good thing) I thought you may enjoy skimming this short thread:

Class AB Amplifier - New to the analog world

Not sure I got the above link to work (a younger person would have) but its from the solid state forum.

I found it refreshing and optimistic (maybe his professor knows more, at least about motivating, than his students understand).

p.s. I really enjoyed your recent discussion of eddy current noise, at least the 1% I understood.

Thanks
-Antonio
 
Status
Not open for further replies.
Top Bottom