John Curl's Blowtorch preamplifier part II - Page 3

john curl · 29th June 2009, 08:04 PM

Thanks Frank. Look at the graphs, carefully, everyone.
BV, I don't think you are looking deep enough, with enough experience, and with the right equipment. What I see is: Too many tones, it just takes 3 or so, to get a triple beat, not hard enough modulation, and poor resolution of the fine details, so important for basic research. I don't even have any idea what op amp you are testing.

syn08 · 29th June 2009, 08:14 PM

Quote:

Originally posted by john curl

I use a TEK 485, and a 7733 scope on my workbench, <snip>

Well John, your equipment is nothing to call home about. I have part of those dinosaurs and much more modern extra stuff, and I am a DIYer only. With what you have you can't evaluate a modern wideband opamp gain stage.

The only thing I am currently really missing is a curve tracer. I spotted a perfectly functional tek 476 in a local junk store and I'm still balking at pulling $500 for it.

john curl · 29th June 2009, 08:15 PM

Trust and experience with world class test equipment is a good way of knowing if it is working properly. If you can't tell, don't measure, and talk about it.

john curl · 29th June 2009, 08:20 PM

Yup, I'm John Curl, the junk test equipment collector, with a 350 MHz dual trace scope of impeccable credentials in front of me and a high speed storage 100 MHz scope to the left of me with a 100 Mega-ohm input probe. Just junk. Yesterday, I was offered a 475 scope for free, should I bother with it?

Netlist · 30th June 2009, 08:50 AM

The thread is clean from personal stuff, repeated posts, insults and everything else that is not helping the cause of audio.
Try not to get trapped again, instead be inventive and bring out some new ideas to discuss.
Think twice before pushing the ‘Post’ button.
Every post made that is not strictly technical will be deleted, no need to type it. A copy can be saved on your local hard drive in case it contains valuable technical information to repost. It is your responsibility.

Hugo

Joshua_G · 30th June 2009, 10:23 AM

Quote:

Originally posted by john curl
Everyone, and anyone who wants to know about the BLOWTORCH principles, limitations and costs, just look at the first 100 pages of the previous Blowtorch thread. Everything else, don't count on it, even though there are a few nuggets of wisdom, interspersed throughout.

I've learned a lot from the thread, even beyond the first 100 pages, however, selecting content is called for.

Trevor White · 30th June 2009, 10:43 AM

Quote:

Originally posted by john curl
Trevor, the 4558 is the IC that I have to listen through to compare SACD to DVD to CD. I can't afford an expensive player, because I don't design them.

That is no excuse to bag opamp technology just because you choose to be frugal with the source equipment that you buy which just happens to have low grade or common or garden variety components in it

regards
trev

PMA · 30th June 2009, 10:58 AM

This is pointless. You will easily find audible differences even between AD797 and OPA627, though you would measure 0.0002%.

PMA · 30th June 2009, 11:08 AM

Anyway, yesterday there was a request for PIM measurements. Images were displayed, so I would expect a comment.

syn08 · 30th June 2009, 11:08 AM

Quote:

Originally posted by PMA
This is pointless. You will easily find audible differences even between AD797 and OPA627, though you would measure 0.0002%.

Care to share a reference about such audible differences? Otherwise, the flag applies.

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29th June 2009, 08:04 PM	#21
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Thanks Frank. Look at the graphs, carefully, everyone. BV, I don't think you are looking deep enough, with enough experience, and with the right equipment. What I see is: Too many tones, it just takes 3 or so, to get a triple beat, not hard enough modulation, and poor resolution of the fine details, so important for basic research. I don't even have any idea what op amp you are testing.

29th June 2009, 08:15 PM	#23
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Trust and experience with world class test equipment is a good way of knowing if it is working properly. If you can't tell, don't measure, and talk about it.

29th June 2009, 08:20 PM	#24
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Yup, I'm John Curl, the junk test equipment collector, with a 350 MHz dual trace scope of impeccable credentials in front of me and a high speed storage 100 MHz scope to the left of me with a 100 Mega-ohm input probe. Just junk. Yesterday, I was offered a 475 scope for free, should I bother with it?

30th June 2009, 08:50 AM	#25
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	The thread is clean from personal stuff, repeated posts, insults and everything else that is not helping the cause of audio. Try not to get trapped again, instead be inventive and bring out some new ideas to discuss. Think twice before pushing the ‘Post’ button. Every post made that is not strictly technical will be deleted, no need to type it. A copy can be saved on your local hard drive in case it contains valuable technical information to repost. It is your responsibility. Hugo

30th June 2009, 10:58 AM	#28
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	This is pointless. You will easily find audible differences even between AD797 and OPA627, though you would measure 0.0002%.

30th June 2009, 11:08 AM	#29
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Anyway, yesterday there was a request for PIM measurements. Images were displayed, so I would expect a comment.