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Old 23rd February 2013, 07:59 AM   #1771
RNMarsh is offline RNMarsh  United States
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And here's the HP 339A at 1Khz when the QA400 was working --> (top or 0 is -80dB) Monitor output with Viktors generator as a source.

Viktor_339A.jpg
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Old 23rd February 2013, 11:08 AM   #1772
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RNM -- make sure to test with the OPA2604 -- this opamp can run "hot" (+/-24V) and will drive 600 ohm loads.

Have you seen Bob Pease's ap note 1671 "Gain and Linearity Testing for Precision Operational Amplifiers"
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Old 23rd February 2013, 05:21 PM   #1773
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jackinnj View Post
RNM -- make sure to test with the OPA2604 -- this opamp can run "hot" (+/-24V) and will drive 600 ohm loads.


OK. I'll get a few of them and see how they do.


Have you seen Bob Pease's ap note 1671 "Gain and Linearity Testing for Precision Operational Amplifiers"
Dont remember title ... I'll take look. Thx-RNMarsh
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Old 24th February 2013, 08:11 PM   #1774
mkc is offline mkc  Denmark
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Hi Richard,

work has been a Bi... the last few months. Not to complaint. I have work.

It is my intention to open a QA400 thread. I have only had time to hook up my QA400 in loop back mode. I'm pretty sure there is a SW bug in the generator SW.

However, do you know what killed your, if that is what happened?

Btw, I loved your Audio Amatuer articles. In the late 80's I thought I had invented the intput stage you used and the folded cascode, which I later discovered I had not :-)

Best regards,
Mogens
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Old 24th February 2013, 09:56 PM   #1775
1audio is offline 1audio  United States
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Please let us know when you open the thread on the QA400. I have just tried the latest beta software and it seems to work pretty well. I have had a few lockups mostly related to USB. All of the features seem to work. My particular QA400 seems to have something odd on its input Z, it measures 10K, not 100K and that caused some confusion when I was calibrating it.

Attached is a preliminary schematic for an interface to make the QA400 compatible with higher level signals etc. in expresspcb. The layout should be done the beginning of the week. Not shown are the cables needed to interface, I'll draw those up this week as well.
Attached Files
File Type: zip QA400 interface 3.zip (61.4 KB, 41 views)
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Old 24th February 2013, 10:54 PM   #1776
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by mkc View Post
Hi Richard,

work has been a Bi... the last few months. Not to complaint. I have work.

It is my intention to open a QA400 thread. I have only had time to hook up my QA400 in loop back mode. I'm pretty sure there is a SW bug in the generator SW.

However, do you know what killed your, if that is what happened?

Btw, I loved your Audio Amatuer articles. In the late 80's I thought I had invented the intput stage you used and the folded cascode, which I later discovered I had not :-)

Best regards,
Mogens
I think it was when i unplugged the usb at some important time for the QA400. Its been very quirky ever since. I cant get it to display data. and it indicates drop outs frequently. It says the usb is connected. Wont cal - though there is output. Messed up for sure.
The SW could be a bit smoother in operation. But the manual is pretty complete.

Having said that, I dont want to give the impression it is a bad product and I do have the old favorite emu0204 and arta software as back up. The QA400 measures at least 6dB better and the integration is very convenient for me. So, I went ahead and ordered one. The first one was a demo/eval unit that I didnt pay for.

Glad you liked the articles... I had the drive to work, play, build, test and write back then. Now I have more free time and might get to put down some more info once again.

Thx-RNMarsh

Last edited by RNMarsh; 24th February 2013 at 11:02 PM.
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Old 26th February 2013, 12:32 AM   #1777
davada is offline davada  Canada
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Quote:
Originally Posted by RNMarsh View Post
I think it was when i unplugged the usb at some important time for the QA400. Its been very quirky ever since. I cant get it to display data. and it indicates drop outs frequently. It says the usb is connected. Wont cal - though there is output. Messed up for sure.
The SW could be a bit smoother in operation. But the manual is pretty complete.

Having said that, I dont want to give the impression it is a bad product and I do have the old favorite emu0204 and arta software as back up. The QA400 measures at least 6dB better and the integration is very convenient for me. So, I went ahead and ordered one. The first one was a demo/eval unit that I didnt pay for.

Glad you liked the articles... I had the drive to work, play, build, test and write back then. Now I have more free time and might get to put down some more info once again.

Thx-RNMarsh
What your describing is a USB problem. Either a problem with the USB port on you comp or a USB driver problem. You can down load USB drivers from cypress semiconductor. Look for CYUSB.SYS. There is also a forum on Cypress's website discussing driver problems and resolutions. Remove all old QuantAsylum usb drivers before installing new.

Cheers,
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Old 28th February 2013, 06:06 PM   #1778
RNMarsh is offline RNMarsh  United States
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I am still working on the "USB" problem. Meanwhile, I got a loan of a ShibaSoku AG16B oscillator from Demian when in San Fransisco yesterday. On the newest ShibaSoku analyzer, I measured the THD+N on second (at 1v rms out into high Z) as .00007% for 2H and .000025% for 3H. Using an HP3580A swept analog filter, the noise floor from the analyzer output and the HP is about -140. The harmonics are at that floor..... a 9H showed up at -143.
When I can average out the noise with the QA400 FFT, I can get a more accurate finding on the Harmonics but this is much better than the KH4400A. Or, the HP339A. A KH4402B is coming up next but this ShibaSoku combo is what I need to reach my goal of -140dB THD+N (withOut FFT).

Thx-RNMarsh
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Old 28th February 2013, 06:44 PM   #1779
1audio is offline 1audio  United States
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The Shibasoku oscillators are so much better than the KH4400 I first thought something was broken when measuring them with the 725. I don't think you will get to the AG16 performance with something conventional. I have another older version of the oscillator with identical performance. At this level its time to move on and just use the stuff.

I'm almost done with the QA400 interface. I'm getting it checked and will send out for boards by the weekend I hope. The next challenge is to make a lockable oscillator and matched notch filter to get close to this level of performance with a QA400.
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Old 28th February 2013, 08:15 PM   #1780
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Quote:
Originally Posted by RNMarsh View Post
I am still working on the "USB" problem. Meanwhile, I got a loan of a ShibaSoku AG16B oscillator from Demian when in San Fransisco yesterday. On the newest ShibaSoku analyzer, I measured the THD+N on second (at 1v rms out into high Z) as .00007% for 2H and .000025% for 3H. Using an HP3580A swept analog filter, the noise floor from the analyzer output and the HP is about -140. The harmonics are at that floor..... a 9H showed up at -143.
When I can average out the noise with the QA400 FFT, I can get a more accurate finding on the Harmonics but this is much better than the KH4400A. Or, the HP339A. A KH4402B is coming up next but this ShibaSoku combo is what I need to reach my goal of -140dB THD+N (withOut FFT).

Thx-RNMarsh
Hi Richard,

I have been following this thread, and it is a great one. It looks like some great oscillators, and ways to measure their very low distortion, have been described.

It looks like most of the work has been done at 1kHz, which is entirely appropriate. However, very low frequencies and high frequencies are where it is much more difficult to get very low distortion. As we all know, at low frequencies like 20 Hz we have the problem of AGC ripple if we are to have reasonable settling times. At high frequencies we have more operational-amplifier-related problems like THD etc.

Do you have some data on this oscillator's THD and settling performance at 20Hz?

Similarly, do you have some distortion measurements for high frequencies? I realize that with analyzers like the 3580A and even really good sound cards we may only be able to see spectra out to about 50kHz. So can you tell us about 2nd and 3rd harmonic distortion with a fundamental of, say, 15 or 16kHz?

Cheers,
Bob
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