Your 7725 is most likely working fine.
Take a read thru the ShibaSoku and 339a and oscillator discussions around here and you will find a lot of answers to your questions -- or, if not answers, some ideas will present themselves to you for further discussion.
-Thx-RNMarsh
Take a read thru the ShibaSoku and 339a and oscillator discussions around here and you will find a lot of answers to your questions -- or, if not answers, some ideas will present themselves to you for further discussion.
-Thx-RNMarsh
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the two channels (amongst other anomalies) did not agree exactly... fwiw.
I've read most of these threads, thanks.
A simple answer to my primary question would be useful, regardless of who or what it comes from. Would likely take a long time to come across the theory that amply explains if this would or would not work. (essentially "half" a notch).
_-_-
I've read most of these threads, thanks.
A simple answer to my primary question would be useful, regardless of who or what it comes from. Would likely take a long time to come across the theory that amply explains if this would or would not work. (essentially "half" a notch).
_-_-
Can you design something -- SIM or real - notch or HP filter and then see what results you get? However, I am pretty sure someone can tell you who have this combo. There are circuits used and published here on notch filters... Thats what i do... buy/build or modify the equipment and try it out and compare and test etc. Since I have aquired some excellent analyzers -- I have been able to compare the results against the QA400 and others to see which are more accurate and where/why etal. Now that I have some "standards' - such as the ShibaSoku 725D and the Audio Precision 2722, I am in a better position to tell whats what.
I havent tried to see how good the QA400 can be with a notch filter - as far as accuracy is concerned. But I have been given notch filters (and the B&K 1607 project) to try on it... just got side tracked. I used the notch filters for other purposes --- such as cancelling the 2H or 3h from the source generator to make it even better gen.
Another place to look is on the passive notch filter thread (B&K 1607) with or without active mod.
My goal was to see how close to the -160dB target I could come. So even -120 isnt of much use to me. So I havent tried to see what more the QA400 can do and do it accurately.
-Thx RNMarsh
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Of course I can simulate something, but it's not clear that this will tell me much about how it will behave in the real world hooked to a distortion analyzer. Which is partly why I asked.
We're almost entirely looking up in frequency...
Accuracy I suppose is important when you want to publish specs or compare things separated in time or space from each other. Relative accuracy is about all I need right now. Probably if I needed true accuracy, I'd ping someone like urself and spend a few bux on shipping and some beers, or something along those lines.
I am strapped for time - these posts here take a few minutes, not the hours it takes to do a real project of any sort - so I get to post and hope that I can pick up some things and plot my future exploits with better focus.
The Cyrill Bateman article (pdf) indicates that he required a 60dB notch at the time he did his oscillator work to get down to where he apparently was at -160dB (according to his displayed graphs). Although I seem to think he said that this actually got him to -130dB, no doubt I have to read that again as I have it somewhat confused now.
I will try to find the passive notch thread... part of my inquiry was because I have built passive HP with steep slopes and up to 60dB of stop band attenuation with a handful of parts. Doing the same tricks in active seems more daunting, re Kendall Castor-Perry's articles on the subject.
I missed him and a host of others, including SY at the just past AES 🙁
We're almost entirely looking up in frequency...
Accuracy I suppose is important when you want to publish specs or compare things separated in time or space from each other. Relative accuracy is about all I need right now. Probably if I needed true accuracy, I'd ping someone like urself and spend a few bux on shipping and some beers, or something along those lines.
I am strapped for time - these posts here take a few minutes, not the hours it takes to do a real project of any sort - so I get to post and hope that I can pick up some things and plot my future exploits with better focus.
The Cyrill Bateman article (pdf) indicates that he required a 60dB notch at the time he did his oscillator work to get down to where he apparently was at -160dB (according to his displayed graphs). Although I seem to think he said that this actually got him to -130dB, no doubt I have to read that again as I have it somewhat confused now.
I will try to find the passive notch thread... part of my inquiry was because I have built passive HP with steep slopes and up to 60dB of stop band attenuation with a handful of parts. Doing the same tricks in active seems more daunting, re Kendall Castor-Perry's articles on the subject.
I missed him and a host of others, including SY at the just past AES 🙁
The Radiometer CLT1 uses a passive low pass filter on the source and a passive high pass filter on the receive side. Its good for as much as -170 dB third harmonic. I posted the circuit for one of the filters some time ago. Continuous tuning is not possible but I don't think necessary either.
I managed to get two of them so I can test 4 terminal devices like pots. Too much hassel to use normally.
I don't think DIY of the filters is easy. The ferrite cores are as big as grapefruit. However I think combining the concept with a soundcard makes a lot of sense.
I managed to get two of them so I can test 4 terminal devices like pots. Too much hassel to use normally.
I don't think DIY of the filters is easy. The ferrite cores are as big as grapefruit. However I think combining the concept with a soundcard makes a lot of sense.
Found on page Chinese QuantAsylum the DataSheet and Manual QA400.
In Chinese of course!
http://www.quantasylum.net/fp8400-p-30.html?cPath=4
http://www.quantasylum.net/download/FP8400彩页.pdf
http://www.quantasylum.net/download/FP8400_Users_Manual.pdf
Will we have this literature translated into English language?
Another interesting fact is that in China, the QA400 is presented with another model and another brand.
http://www.fpinstrument.com/Product/
In Chinese of course!
http://www.quantasylum.net/fp8400-p-30.html?cPath=4
http://www.quantasylum.net/download/FP8400彩页.pdf
http://www.quantasylum.net/download/FP8400_Users_Manual.pdf
Will we have this literature translated into English language?
Another interesting fact is that in China, the QA400 is presented with another model and another brand.
http://www.fpinstrument.com/Product/
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the manual comes with the download of the software...
... seems pretty clear that there are some people in Washington state who have set up shop and are selling the product under the QA name to English, non-asian markets, different front panel. The product is made in China, sold in china under the FPInstrument name.
Who is doing the actual development? Your guess is as good as mine.
_-_-
... seems pretty clear that there are some people in Washington state who have set up shop and are selling the product under the QA name to English, non-asian markets, different front panel. The product is made in China, sold in china under the FPInstrument name.
Who is doing the actual development? Your guess is as good as mine.
_-_-
I believe the development is happenig here. Matt is clearly on top of it. The primary market is China production lines. We are just fortunate to have access.
Demian --- Out of Poland looks interesting for your work with customers --- Same name FPInstruments.
-RM
-RM
Hmmm... strange idea just passed before me.
I am pretty sure the 7725 has a back panel "analog" out - the residuals.
Think I will try to pass that into the front end of the QA and see what it says...
...assuming the tree I am planning to drop that is within 2 feet of the lab falls in the intended direction and not the wrong way, smashing everything! Have no fear, we are "experienced".
I am pretty sure the 7725 has a back panel "analog" out - the residuals.
Think I will try to pass that into the front end of the QA and see what it says...
...assuming the tree I am planning to drop that is within 2 feet of the lab falls in the intended direction and not the wrong way, smashing everything! Have no fear, we are "experienced".
40-60dB will do.... you will need to measure the attenuation at 2 x fundamental freq and use for correction of measured 2H value.
-RNM
I received the VP-7721-22 manuals -on loan to copy - and they are designed, made and serviced/calibration by Matsushita Communication Ind - Electronic Measurement Div. Yokohama, Japan. [045-93201231]
No wonder the Panasonic guys had nothing to tell us/give us. Even the Panasonic manuals are copy-right by Matsushita. Got to go to Matsushita and/or their rep to get your info.
Thx-RNMarsh
No wonder the Panasonic guys had nothing to tell us/give us. Even the Panasonic manuals are copy-right by Matsushita. Got to go to Matsushita and/or their rep to get your info.
Thx-RNMarsh
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Matsushita is Panasonic's parent holding company. Panasonic is a brand. Its a maze that will lead back to the same place.
Tie a rope onto the tree and put a bit tension in the right direction. Wouldn't want to destroy your lab. Hee hee.
Matsushita is the company. Panasonic is the brand name.
I knew that. Should have thought of it sooner.
Oh. I see Demian already pointed that out.
Matsushita in North America deals with Panasonic consumer products. I don't think they have a market for test equipment here. Never did.
Find out if there is a Matsushita industrial sales rep for North America.
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I already said that long ago... Just reaffirming it with the original docs.
It 'should' lead anyone with these products to the source of the material needed... whether they cooperate is another matter.
-RNM
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What is really needed is some astute person *in* Japan, who speaks Japanese, and who is willing to try to help out. Undoubtedly, these units and their manuals exist, it's just a matter of being able to "schmooze" the right person(s).
Panasonic announced that they were ceasing "support" of this measurement stuff as of summer 2010, iirc, or maybe it was 2011. Suddenly, or not so suddenly "Levear" shows it, and guess what company holds a major stake in Levear??
Panasonic announced that they were ceasing "support" of this measurement stuff as of summer 2010, iirc, or maybe it was 2011. Suddenly, or not so suddenly "Levear" shows it, and guess what company holds a major stake in Levear??
BTW -- what is it from these products you/others are interested in knowing from the manuals?
Some notes on the literature cover for the VP-7722A says -- at one time repair could be had by: WHA Electronics in Fishers, IN.
Maybe they will get/give copy or info [317-596-8600] ?
-RNM
Some notes on the literature cover for the VP-7722A says -- at one time repair could be had by: WHA Electronics in Fishers, IN.
Maybe they will get/give copy or info [317-596-8600] ?
-RNM
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Anybody looked at the QA400 output in continuous wave mode? I just looked at it with a Boonton 1130 and it seems that the frequency (nominally 1kHz) varies from something like 950Hz to 1150Hz second by second. The output signal has so much noise that the THD is shown as about -65dB and on the scope the residue shows only noise, no recognisable waveform.
I did a sanity check with my function generator set to 1kHz which varies about 0.01Hz max, and the residue shows a nice 2nd harmonic at around -62dB.
I am beginning to think that this QA400 is maybe a bit too 'special'.
Jan
I did a sanity check with my function generator set to 1kHz which varies about 0.01Hz max, and the residue shows a nice 2nd harmonic at around -62dB.
I am beginning to think that this QA400 is maybe a bit too 'special'.
Jan
I just sort of confirmed your measurements. The frequency issue comes from the noise in the signal. On my counter the frequency is sable to 5-6 digits. On the Boonton its not- but it gets better when you engage the filters.
I measure -69 dB THD+N on the QA400 with the Boonton (Loopback gets -96 dB and much more stable frequency display). The noise you see is one of the big questions of digital audio. Is it significant, and how does it sound? It doesn't show on the loopback in the QA400 the same way. The averaging etc. in the QA400 seems to remove it.
I'm sure there is more to this than we see here.
Below is a quick snapshot showing the residual noise spectrum of the QA400 source vs. the Shibasoku AR590 at the same source level, measured at the output of the Boonton 1121. There is a significant difference in noise.
I measure -69 dB THD+N on the QA400 with the Boonton (Loopback gets -96 dB and much more stable frequency display). The noise you see is one of the big questions of digital audio. Is it significant, and how does it sound? It doesn't show on the loopback in the QA400 the same way. The averaging etc. in the QA400 seems to remove it.
I'm sure there is more to this than we see here.
Below is a quick snapshot showing the residual noise spectrum of the QA400 source vs. the Shibasoku AR590 at the same source level, measured at the output of the Boonton 1121. There is a significant difference in noise.
