John Curl's Blowtorch preamplifier part II - Page 327 - diyAudio
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Old 1st January 2010, 03:24 PM   #3261
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Default Jan Lohstroh

/OT on
Somewhere in this thread Jan Lohstroh came up, as the person who actually designed what later came tio be known as the 'Otala amp'. If you are interested in a bit of history, my interview with Jan Lohstroh is here:
http://www.audioamateurinc.com/digit.../pageflip.html
Starts on page 5.
/OT off

jd
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Old 1st January 2010, 05:03 PM   #3262
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John and others,

Someone actually walked into my office with the complete original Quantec service manual with all schematics and their tutorial on making noise measurements. I remember a few people were interested in this, unfortunately is is a bit of work to scan-in parts of it especially the foldout schematics. Is there still any interest?

Be warned the parts are mostly obsolete and I would not build all the discrete op-amps like they had to anyway.
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Old 1st January 2010, 05:06 PM   #3263
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Demian is your man, or Kirkwood Rough. They both own multiple Quantechs. They can and do repair them, as well.
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Old 1st January 2010, 05:22 PM   #3264
1audio is offline 1audio  United States
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I have the service manuals for most Quantech stuff. I think the tutorial would be of general interest since its still not well known here how to measure device noise.

What I'm looking for is the manual for the 315C (I have the 315B manual which has almost nothing in common with the c version) and drawings for the socket adaptors for the 5173. I have figured out, mostly, the adaptor wiring but I would like to see how they thought it should be done.

The later 5173 is mostly IC and only uses discrete devices where needed. The older units date from the late '60s when opamps would not have been adequate to the tasks.

I think a new design with a PC interface using a sound card could be very useful since Quantech is no more and there are no commercial equivalents I know of.
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Old 2nd January 2010, 07:20 PM   #3265
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John, what's the sudden silence concerning servos or are you easily distracted?
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Old 2nd January 2010, 11:20 PM   #3266
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Quote:
Originally Posted by Key View Post
Well give me a system and I will beat it. lol

With a hammer??

What do you mean exactly??

It would be more productive if you gave some examples of your work, or of the work of others that you believe is superior. Then it would be useful to state how or why whatever it is is actually superior, or SOTA.

Or else perhaps, you are just 14 years old and/or are used to going to various forums and banging your drum for fun? Or should I say, acting like a troll?

Dunno.

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Old 2nd January 2010, 11:22 PM   #3267
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Nah that's alright not worth the time.
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Old 2nd January 2010, 11:31 PM   #3268
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Quote:
Originally Posted by john curl View Post
I would like to again talk about servos, specifically the 2 servos in the JC-80 line amp stage. One servo is to reduce the DC outputs, (there are 2 outputs) as close to ground as possible. The other is to reduce the actual DC difference between the two outputs.
The servo at the bottom of the page looks at the 2 outputs and tries to minimize their difference by adding DC gain.
The servo at the top right compares both DC outputs to ground and tries to average the 2 outputs as close to ground as possible.
The combination of the 2 servos gives the circuit the ability to be direct coupled to a power amp and to change polarity by selecting one output or the other, without a pop when switching.
...ummm I would like to discuss this too... was the schematic of the JC-80 posted here.

Perhaps someone would post the link so that we can get back to this question??

Not sure what you mean, John, about that "adding DC gain" to minimize their difference. Might be clear looking at the skeezamatic??

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Old 2nd January 2010, 11:52 PM   #3269
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Quote:
Originally Posted by Key View Post
Nah that's alright not worth the time.
If it is not worth the time to substantiate your words, and it is not worth the time to be constructive:

Then please do not post in this thread any more?
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Old 3rd January 2010, 12:00 AM   #3270
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On second thought change my mind. Actually it is JC our subjectivist lord and savior who can't substantiate a single word in his claim about people with subpar systems not having valid opinions on hi resolution. He can't offer one tangible parameter that would make an expensive system better than a cheaper one except for the arbitrary price tag placed on these items. I'm afraid if you don't trust measurements then it is your side which hasn't a leg to stand on when claiming that one system is superior to the other.

If you want to come out and discredit people for the price they paid on there equipment then I think a perfectly fair counter argument is that these overly expensive systems simply do not benchmark as well as a great deal of there mid fi counter parts. They don't have half of the "synergy" because most of the time they are put together guided by superstitions and not any understanding of electronics.

Last edited by Key; 3rd January 2010 at 12:15 AM.
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