Low-distortion Audio-range Oscillator - Page 78 - diyAudio
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Old 23rd October 2012, 12:17 AM   #771
klewis is offline klewis  United States
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Quote:
Originally Posted by WSJ View Post
Thanks for the offer to post your adjustment proceedure. I'm ordering two boards form Frex today.
A couple of notes on parts, I found Farnell Uk carries polystyrene caps in tighter tolerances. So the 10,000pF, 2.2nF and 47pF all came from there. The other polystyrene caps I ordered tripple the quantity from mouser and hand selected with a LC meter. But you might just want to order all at 1% tolerance from Farnell.

Ken
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Old 23rd October 2012, 02:58 AM   #772
klewis is offline klewis  United States
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More testing of the AN67 tonight - I zoomed in a bit more on the target harmonic frequencies. Other than 2nd H all were burried in the noise floor of the signal analyzer. The frequency rose slightly through the test proceedure from 10,032 to 10,036. It was a bit higher yesterday, and maybe a bit warmer in my test room.

Oh and the test frequency is now the reading taken from the hp8903a via HPIB.

Ken
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Old 23rd October 2012, 03:54 AM   #773
WSJ is offline WSJ  United States
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Thank you for the info about the caps. I'm looking forward to the post about your adjustment procedure.
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Old 23rd October 2012, 04:32 AM   #774
1audio is offline 1audio  United States
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Default KH4400 Measurements

This is more of a demo of too much resolution. It the KH4400 adjusted per spec. but only modified with the injection locking scheme I mentioned. I locked it to the Boonton's PLL stabilized 1 KHz output. I'm injecting 1V at 1 KHz but I could see no difference in distortion with and without.

The measurement is a 16,000,000 point fft at 192KHz/24 bit (with the AK5394a demo board for capture) If it was not locked I could not get the measurement, the frequency would drift too much for this in the 20 minutes or so it took to make the measurement. I will do another pass with a different windowing function. The Key differences I see is the shape at the base of the measurement with different windows.

I don't think 16M points offers much beyond 512K unless you need to see something at the noise floor.
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Old 23rd October 2012, 04:40 AM   #775
1audio is offline 1audio  United States
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And this is the same as previous except at 10 KHz.
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Old 23rd October 2012, 01:41 PM   #776
RNMarsh is offline RNMarsh  United States
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With the proper algor., an DAC could make the basis of a super low distortion sine wave generator of any freq or multi-tone for IM. ??

Last edited by RNMarsh; 23rd October 2012 at 01:52 PM.
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Old 23rd October 2012, 02:10 PM   #777
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With the proper algor., an DAC could make the basis of a super low distortion sine wave generator of any freq or multi-tone for IM. ??
Don Lancaster's "Magic Sine Waves"?
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Old 23rd October 2012, 02:50 PM   #778
RNMarsh is offline RNMarsh  United States
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Default DAC based low thd oscillator.

Quote:
Originally Posted by jackinnj View Post
Don Lancaster's "Magic Sine Waves"?
Yes, possibly. Or a really good 24 bit could do really well with a tracking filter. Or, 1 bit. It would have the advantage of any freq and fast freq changes and multiple tones. --RNM
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Old 23rd October 2012, 03:10 PM   #779
1audio is offline 1audio  United States
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A DAC as a source for ultra low distortion will be elusive still. Several limitations make it hard to do. First the max sample rate (192 KHz in practice) second the linearity is not that good, well below the performance of these oscillators, with only the ES9012 coming close, and finally keeping the digital junk away from the analog output (plus isolation issues) is a very difficult thing to do.

I think for now analog source and digital capture(enhanced with analog front end magic) is as good as is possible.
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Old 23rd October 2012, 07:02 PM   #780
davada is offline davada  Canada
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A DAC as a source for ultra low distortion will be elusive still. Several limitations make it hard to do. First the max sample rate (192 KHz in practice)
Why are we limited to this? There are a lot of industrial DAC's available.
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