John Curl's Blowtorch preamplifier - Page 66

john curl · 14th March 2006, 07:08 AM

Folks, I'm for both theory and practice. It has been successful for me, over the years.
What are you two fighting about?

jacco vermeulen · 14th March 2006, 07:10 AM

Quote:

Originally posted by john curl
What are you two fighting about?

They're French.

Elso Kwak · 14th March 2006, 07:22 AM

Quote:

Originally posted by jacco vermeulen

They're French.

Does that xplain it Jacco? I think not!

jacco vermeulen · 14th March 2006, 07:54 AM

Je m'ens fou !
What's next, bashing the nicotine sasquatch ?

I prefer munching the crumbs Mr Curl leaves behind.

forr · 14th March 2006, 07:57 AM

JOHN CURL
---What are you two fighting about?---

I may have upset JBAudiophile in a previous thread, about a month ago. It was about the spectral content of harmonic distorsion.

JBAUDIOPHILE
---Zener diode can be done withn reverse polarized bipolar transistor.... Just have a look on this wonderful amp... Doidn't try this ? But what where some guys just doing excepting criticize others, eh Forrr ?---

Did I write anything against reverse biased bipolars used as zeners anywhere ? No. I am just supposed to have prejudices against. I saw Norman Thagart using them. In fact, I did not what to think about them until the most wellcome recent threads about constant current sources.

~~~~~~ Forr

§§§

john curl · 14th March 2006, 06:15 PM

For the record, reversed biased transistors have been used as 'zener' diodes since the first analog IC op amps were designed. It is a convenience, because additional processing steps do not have to be done, in order to create a 'zener' reference. This goes back about 40 years.
Now what we have established here, as far as I can tell, is that leds are probably the best way to reference a current source, unless you have a current limitiation, and this is where some special low voltage zeners, operating at 250 ua seem to be OK, except they will be fairly high impedance at their operating point, and therefore useless in our present current source examples.
I wish to point out that zeners are invariably rated at micovolts/ rt Hz, especially above 5V. To convert to rt/Hz, just divide Christer's measurements by 144, (I am guessing here, but that is the sq rt of 20KHz) Even 1uV/rt Hz is REALLY noisy. Most IC op amps work 100-1000 times quieter than this. My original Levinson JC-1, Sota headamp, and the Vendetta phono amp are rated at 0.4nV/rt Hz. This is 2500 times lower than a good zener. This is why I used a Norton equivalent of a zener instead. There I have a low Gm, low noise fet, like a J203, as the reference, with its noise attenuated by a large (100uf) cap to ground. It is true that there will still be some really low 1/f noise, but it works well in the audio range.

jean-paul · 14th March 2006, 06:37 PM

Jbaudiophile and Forr, please behave like grownup people and quit arguing. You can continue per PM if you both wish but don't bother other members with your quarreling.

I also suggest to read the stuff you're going to post before pushing that "submit reply" button. Gosh, I was thinking I was using Babelfish for a moment.

Justcallmedad · 14th March 2006, 06:59 PM

John, can you measure Leds noise with your Quan-Tech measurement set? I tried this w.e. but I was not able to get any decent results (LT 1028 10R-1k, 10 kHz bandwidth), however with zeners, even below 5 volts, I easily could, it was a very “messy” test rig (solderless testboard) and it’s why I didn’t report here the results with the impedance values.
Do you think it’s a good idea to use the current source available at the adjust pin of the LM317 as I thought in using it for an “elegant” and useful design in Post #649 (without C30 capacitor!).

... Jean Paul

.

forr · 14th March 2006, 07:18 PM

Hi JOHN CURL
Thanks for this documentation about reverse biased transistors. I believe that, when in series with a directly biased Si diode, or a transistor connected as a diode, they can make thermally stable references.

JEAN-PAUL
Sorry, I have been treated negatively twice in a first post, and even more in the following ones, that I could'nt stay without some replies (maybe crude, but polite) . I think any other DiyAudio "critic" mentionned would have react in a somewhat similar manner.

~~~~~ Forr

§§§

john curl · 15th March 2006, 12:13 AM

Richard, I could use the Quantech, but it would not be more accurate than Christer's set-up. It would give spot noise values at specific frequencies that might be helpful, but I doubt it.
Forr and jbaudiophile, let's not get off track, if possible. Actually, I like learning from Christer's measurements. He has been fairly thorough.

14th March 2006, 07:54 AM	#654
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	Je m'ens fou ! What's next, bashing the nicotine sasquatch ? I prefer munching the crumbs Mr Curl leaves behind. __________________ Looks like Sponge Bob has killed another thread.

14th March 2006, 06:37 PM	#657
jean-paul diyAudio Moderator Emeritus Join Date: Sep 2002 Location: The Netherlands	Jbaudiophile and Forr, please behave like grownup people and quit arguing. You can continue per PM if you both wish but don't bother other members with your quarreling. I also suggest to read the stuff you're going to post before pushing that "submit reply" button. Gosh, I was thinking I was using Babelfish for a moment. __________________ It's only audio

14th March 2006, 06:59 PM	#658
Justcallmedad diyAudio Member Join Date: Jun 2004 Location: Paris	John, can you measure Leds noise with your Quan-Tech measurement set? I tried this w.e. but I was not able to get any decent results (LT 1028 10R-1k, 10 kHz bandwidth), however with zeners, even below 5 volts, I easily could, it was a very “messy” test rig (solderless testboard) and it’s why I didn’t report here the results with the impedance values. Do you think it’s a good idea to use the current source available at the adjust pin of the LM317 as I thought in using it for an “elegant” and useful design in Post #649 (without C30 capacitor!). ... Jean Paul . __________________ Richard Perez

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14th March 2006, 07:08 AM	#651
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Folks, I'm for both theory and practice. It has been successful for me, over the years. What are you two fighting about?

14th March 2006, 07:57 AM	#655
forr diyAudio Member Join Date: Dec 2004 Location: Next door	JOHN CURL ---What are you two fighting about?--- I may have upset JBAudiophile in a previous thread, about a month ago. It was about the spectral content of harmonic distorsion. JBAUDIOPHILE ---Zener diode can be done withn reverse polarized bipolar transistor.... Just have a look on this wonderful amp... Doidn't try this ? But what where some guys just doing excepting criticize others, eh Forrr ?--- Did I write anything against reverse biased bipolars used as zeners anywhere ? No. I am just supposed to have prejudices against. I saw Norman Thagart using them. In fact, I did not what to think about them until the most wellcome recent threads about constant current sources. ~~~~~~ Forr §§§

14th March 2006, 06:15 PM	#656
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	For the record, reversed biased transistors have been used as 'zener' diodes since the first analog IC op amps were designed. It is a convenience, because additional processing steps do not have to be done, in order to create a 'zener' reference. This goes back about 40 years. Now what we have established here, as far as I can tell, is that leds are probably the best way to reference a current source, unless you have a current limitiation, and this is where some special low voltage zeners, operating at 250 ua seem to be OK, except they will be fairly high impedance at their operating point, and therefore useless in our present current source examples. I wish to point out that zeners are invariably rated at micovolts/ rt Hz, especially above 5V. To convert to rt/Hz, just divide Christer's measurements by 144, (I am guessing here, but that is the sq rt of 20KHz) Even 1uV/rt Hz is REALLY noisy. Most IC op amps work 100-1000 times quieter than this. My original Levinson JC-1, Sota headamp, and the Vendetta phono amp are rated at 0.4nV/rt Hz. This is 2500 times lower than a good zener. This is why I used a Norton equivalent of a zener instead. There I have a low Gm, low noise fet, like a J203, as the reference, with its noise attenuated by a large (100uf) cap to ground. It is true that there will still be some really low 1/f noise, but it works well in the audio range.

14th March 2006, 07:18 PM	#659
forr diyAudio Member Join Date: Dec 2004 Location: Next door	Hi JOHN CURL Thanks for this documentation about reverse biased transistors. I believe that, when in series with a directly biased Si diode, or a transistor connected as a diode, they can make thermally stable references. JEAN-PAUL Sorry, I have been treated negatively twice in a first post, and even more in the following ones, that I could'nt stay without some replies (maybe crude, but polite) . I think any other DiyAudio "critic" mentionned would have react in a somewhat similar manner. ~~~~~ Forr §§§

15th March 2006, 12:13 AM	#660
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Richard, I could use the Quantech, but it would not be more accurate than Christer's set-up. It would give spot noise values at specific frequencies that might be helpful, but I doubt it. Forr and jbaudiophile, let's not get off track, if possible. Actually, I like learning from Christer's measurements. He has been fairly thorough.

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