John Curl's Blowtorch preamplifier part II - Page 408

Joachim Gerhard · 9th April 2010, 09:26 PM

Beyschlag makes excellent resistors and i will call them on monday to add some clarity to this confusion. Nothing can substitude audition so this game " who makes the best sound" is still a matter of practical experience and will power and dedication to details.
When a component is successfull on the marketplace everybody will say:
OHH yes, this sounds good because they use the XYZ. resistor capacitor etc.
But comming up with your own solution and choice is much more difficult.
There is no recipy for success and what works on one ocation may not work under different circumstances. One last thought: a component that sounds superiour is most of the time not the component that sells well. Quality is only for the choosen few and nothing has changes since the midlle ages in that regard.

john curl · 10th April 2010, 12:45 AM

When are you coming to Berkeley, again, Joachim?

3GGG · 10th April 2010, 01:30 AM

Without the time to read over 2000 pages is this preamp available to buy as a kit or PCB?

iko · 10th April 2010, 01:49 AM

No, this is a commercial design of John Curl. I've read hundreds of pages of this thread and of part one of this thread. Some people came up with some similar designs, from hints that John Curl gave them. Some members of this forum think that this design is obsolete and doesn't hold water (see syn08), others think that this is something special. It's best to make up your own mind, however painful that may end up being. Good luck!

john curl · 10th April 2010, 02:32 AM

Nothing for free, except info.

simon7000 · 10th April 2010, 04:27 PM

Two more areas of concern:

How does distortion add?

Is there really DC on the AC power lines?

PMA · 10th April 2010, 04:34 PM

Quote:

Originally Posted by simon7000

Is there really DC on the AC power lines?

How easy to answer. Evening shot of my power line (with 1:2 divider):

simon7000 · 10th April 2010, 04:41 PM

Quote:

Originally Posted by PMA

How easy to answer. Evening shot of my power line (with 1:2 divider):

Okay ruin my fun.

Next question does using a DPDT switch to change the AC power connection every time a piece of gear is turned on have an effect that is clearly heard?

1audio · 10th April 2010, 06:49 PM

Probably the loud snap as the supplies jump up and down will be audible by most people. If you are referring to the difference in leakage and RFI that may also be audible. There are several related issues so simply flipping the ac line external or at the entrance of the box isn't enough. You need to model the leakages and the RFI paths to optimize the power. Good isolation transformers usually help (bad ones are just annoying and usually buzz).

DC does appear on the power line, usually from a nonlinear rectified load (a light bulb with a diode in series to dim it for example). This causes residual magnetizing currents in transformers etc. making them buzz and have higher harmonic distortion.

Distortion doesn't simply add OR subtract. (Some people have proposed measuring the residual THD of an analyzer and removing that from the measured distortion to arrive at real distortion- it doesn't work.) At low levels the phase and amplitudes of harmonics and add or even cancel, usually only at the specific measurement conditions. Never so nice for music.

john curl · 10th April 2010, 07:06 PM

Demian, I don't think that many understand that power transformers that are balanced, on paper, are NOT balanced relative to their leakage relative to each primary input. Flip the switch or reverse the cord, and good things can happen.

10th April 2010, 06:49 PM	#4079
1audio diyAudio Member Join Date: Mar 2004 Location: SF Bay Area Blog Entries: 2	Probably the loud snap as the supplies jump up and down will be audible by most people. If you are referring to the difference in leakage and RFI that may also be audible. There are several related issues so simply flipping the ac line external or at the entrance of the box isn't enough. You need to model the leakages and the RFI paths to optimize the power. Good isolation transformers usually help (bad ones are just annoying and usually buzz). DC does appear on the power line, usually from a nonlinear rectified load (a light bulb with a diode in series to dim it for example). This causes residual magnetizing currents in transformers etc. making them buzz and have higher harmonic distortion. Distortion doesn't simply add OR subtract. (Some people have proposed measuring the residual THD of an analyzer and removing that from the measured distortion to arrive at real distortion- it doesn't work.) At low levels the phase and amplitudes of harmonics and add or even cancel, usually only at the specific measurement conditions. Never so nice for music. __________________ Demian Martin Product Design Services

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9th April 2010, 09:26 PM	#4071
Joachim Gerhard diyAudio Member Join Date: Mar 2009	Beyschlag makes excellent resistors and i will call them on monday to add some clarity to this confusion. Nothing can substitude audition so this game " who makes the best sound" is still a matter of practical experience and will power and dedication to details. When a component is successfull on the marketplace everybody will say: OHH yes, this sounds good because they use the XYZ. resistor capacitor etc. But comming up with your own solution and choice is much more difficult. There is no recipy for success and what works on one ocation may not work under different circumstances. One last thought: a component that sounds superiour is most of the time not the component that sells well. Quality is only for the choosen few and nothing has changes since the midlle ages in that regard.

10th April 2010, 12:45 AM	#4072
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	When are you coming to Berkeley, again, Joachim?

10th April 2010, 01:30 AM	#4073
3GGG diyAudio Member Join Date: Mar 2010	Without the time to read over 2000 pages is this preamp available to buy as a kit or PCB?

10th April 2010, 01:49 AM	#4074
iko diyAudio Moderator Join Date: May 2008 Location: Toronto	No, this is a commercial design of John Curl. I've read hundreds of pages of this thread and of part one of this thread. Some people came up with some similar designs, from hints that John Curl gave them. Some members of this forum think that this design is obsolete and doesn't hold water (see syn08), others think that this is something special. It's best to make up your own mind, however painful that may end up being. Good luck!

10th April 2010, 02:32 AM	#4075
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Nothing for free, except info.

10th April 2010, 04:27 PM	#4076
simon7000 diyAudio Member Join Date: Nov 2008 Location: Oakmont PA	Two more areas of concern: How does distortion add? Is there really DC on the AC power lines?

10th April 2010, 07:06 PM	#4080
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Demian, I don't think that many understand that power transformers that are balanced, on paper, are NOT balanced relative to their leakage relative to each primary input. Flip the switch or reverse the cord, and good things can happen.