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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 29th March 2013, 04:09 PM   #37531
vacuphile is offline vacuphile  Netherlands
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I think the interview with Meitner is a fine example of Voodoo-electronics.
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Old 29th March 2013, 04:20 PM   #37532
qusp is offline qusp  Australia
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Originally Posted by vacuphile View Post
I think the interview with Meitner is a fine example of Voodoo-electronics.
my point exactly, thanks! it mystifies the technology by the use of buzzword loaded jargon

Last edited by qusp; 29th March 2013 at 04:23 PM.
 
Old 29th March 2013, 04:23 PM   #37533
1audio is offline 1audio  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by elektroj View Post
LOL! You guys don't even recognize when someone's making fun of you.

That spectragram that 1audio showed is meaningless! What about reducing the frequency span for a starters? i.e. zooming in on the center frequency..

For comparision - I just fed 9978 Hz sine to the analog input of an oldish "plain vanilla" Digidesign sound card residing in this same computer I'm typing this text on. The card itself is nothing fancy - 74HCU04 oscillator with off the shelf 48MHz crystal, residing in "harsh" enviroment and fed from the switched PSU.
Details on the settings are seen in the picture. I made the span as small as possible and activated 64 Bit analysis (see how "deep down" the analyzer can "look", if fed with the appropriate source + sufficiently low noise floor).

Do we see any sidebands? None! Nada! Zilch! It didn't matter in my case whether I used Hanning. Hamming, Triangular or Rectangular window.

What I am trying to say with all this - one has to have very low noise floor and/or very jittery clock feeding the A to D converter chip to see any sidebands by testing it with the signal fed to its input. If you see any that means the A to D converter is no good.

I'm affraid, it takes the specialized equipment ($$) to do any serious jitter measurements. I have a 43MS/s 25ps resolution analyzer here and even that is sometimes not "good enough".

Best,
First, the point was to see if the ADC was free enough of artifacts to see problems with the signal from the 48 KHz word clock. It is. And the system can show problems (see the Apogee plot I posted).

Your not looking in the right place using the analyzer you mentioned. You are looking at cycle to cycle jitter and won't see the audio frequency variations. Your measurement of a 9978 Hz signal did not indicate what the source is. If its a loopback no jitter will be visible. I checked several very high performance sources that I did not post and things like power supply modulations show just fine. Its the same process used by Stereophile which has several benefits. First its the audio output that matters. Second Stereophile has published a number of measurements to compare to.

Being able to look at the spectrum of a word clock directly is useful if only to see if there are real problems. Also, while having a clean word clock is important it doesn't tell you anything about the pll used in the DAC/ADC and what that adds. Eventually you must look at the audio outputs.

I have made really high resolution measurements and they do show issues occasionally. The QA400 is limited to 65K point resolution. My Praxis setup which is more costly (around $1200) can make up to 16 million point fft. It takes a while and you don't see much more. I have access to much more exotic equipment (e.g.: DSA8300 Sampling Oscilloscope | Tektronix ) but it still won't show these audio frequency problems and is a monumental PITA to use. I stopped looking at clock jitter directly since it was becoming fruitless.

If you are really obsessed with analyzing the clocks this is the go to instrument: http://www.symmetricom.com/products/...se-Test-Probe/ It was $5K when it was introduced, I don't know the current price.

.
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Old 29th March 2013, 04:24 PM   #37534
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by qusp View Post
my point exactly, thanks! it mystifies the technology by the use of buzzword loaded jargon
Sounds like Carver BTW I was glancing at the FIFO thread, good stuff!
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Old 29th March 2013, 04:54 PM   #37535
elektroj is offline elektroj  Europe
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<sigh>
 
Old 29th March 2013, 05:18 PM   #37536
qusp is offline qusp  Australia
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Originally Posted by scott wurcer View Post
Sounds like Carver BTW I was glancing at the FIFO thread, good stuff!
indeed it is not a unique methodology.

yep, Ians fifo is one of the most complete solutions ive come across here. its a pure brute force solution that does what its designed to do. it does turn a dac into something resembling mission control, but it gets results and with a refreshing highly engineered approach. it is missing something that goes bing, otherwise its audio geek heaven
 
Old 29th March 2013, 05:30 PM   #37537
john curl is offline john curl  United States
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Sorry Jacco, if I appeared to 'diss' you, by using your input to respond to something that even I hate in the hi end audio industry.
One of my 'disappointments' in high end audio is NOT that something costs a lot, because some assembly techniques and materials really DO cost a lot to use and process.
What 'bugs' me are the designs that make a really fancy case and then just put IC's or something even more 'crude' inside, and they jack the price way up high.
This makes for embarrassing examples that the rest of us have to contend with, from the comments of our online critics and others who are skeptical of the audio industry.
The first time that I saw this was in the late 1970's, when a French audio company put forth a preamp with a fancy name, a control stick, like on a plane, for a volume control, AND when you looked inside, you found only very dated IC's and cheap parts. YET, the cost of the preamp was significantly more than previous examples in the marketplace.
A few years later, I just about laughed, out loud, when Matti Otala's Citation power amp built by HK, came out at $5,000 dollars and the only fancy add on was a gold plated circuit board. This was another extreme mark-up example.
My last example, but not the least, was another HK product that took another company's internal circuit board and re-packaged it at several times the price of the original unit.
Hi End design doesn't necessarily come cheap. There is the inefficiency of small product runs, the extra cost of labor to get the 'fit and finish' right, etc. BUT that does not excuse where the actual circuitry is relatively cheap, YET the final product price is enormous. I agree with everyone here that there are examples of this in hi end audio, BUT not usually, just sometimes.
Other times, products like Nelson Pass, Charles Hansen, and I make are highly regarded, and IF EXPENSIVE, have the obvious reason for the added expense obvious when you look inside. It is NOT that everything has to be expensive, but IF it is expensive, then let it be because we went 'all out' to produce the best product possible, and our approach took us in a particular direction.
For example, do you realize the Nelson, Charles and I use the SAME jfets in our better designs? Why, when they are now so hard to obtain? It is because they work better than anything else, and if this increases the price, so be it.
It may well be that IC's if properly applied, can 'fool' most of the people all the time, and be perfectly adequate for 90% of the listening public in virtually every case, but there will be exceptions and they tend to be our customers, if they can afford it.
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Old 29th March 2013, 05:31 PM   #37538
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by qusp View Post
He is playing up the difficulties and expense to design things properly to avoid the jitter etc. when it can be eliminated completely with a module bought here on the forum for $250 + 2 clocks and works with i2s or spdif sources alike, with any dac with i2s input, producing the same very high quality regardless of the source.

he speaks of cutting edge things that may be possible in the future that are pretty much already being done here by hobbiests without the polish and aircraft grade alloy chassis.
qusp
When I am defending or bushing a person I do it in an obvious way. In that article, it was only the technical issues and ideas that I noted. Only!
And that article was on a commercial (promotion) magazine. Meitner has published on jitter also in AES (I don’t have access there): "Time Distortions Within Digital Audio Equipment Due to Integrated Circuit Logic Induced Modulation Products", Ed Meitner and Robert Gendron, presented at the 91st AES Convention, New York, October 1991, Preprint 3105
Me, just as you, haven’t paid attention to the date. The article writes: Published: Mar 1, 1993. Ed saw it.
That a diy module can solve the issue is very encouraging.

George
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Last edited by gpapag; 29th March 2013 at 05:44 PM.
 
Old 29th March 2013, 05:42 PM   #37539
simon7000 is offline simon7000  United States
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The analyzer is now $10,000! Pat has one and this is his answer attached.

ES
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File Type: png es12 ad.png (77.3 KB, 163 views)
 
Old 29th March 2013, 05:48 PM   #37540
gpapag is offline gpapag  Greece
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by BV View Post
DIY way.. Vertical axis is relative level of unwanted "artifacts" in Dunn (J-test) spectra..
BV thanks for the chart.

Quote:
Originally Posted by elektroj View Post
George, take a look at this approach:
DAC Overview
Best,
Elektroj
Piece of cake. But what is the physical quantity that this methodology show?

Quote:
Originally Posted by 1audio View Post
Someone here mentioned it and I took the bait. It turns out to be more involved than it might seem. I posted my incomplete notes here on using a tuner: http://www.diyaudio.com/forums/blogs...-analysis.html
Thank you Demian. Iíll look into it.

George
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