Low-distortion Audio-range Oscillator - Page 92 - diyAudio
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Old 29th November 2012, 02:54 AM   #911
davada is offline davada  Canada
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Default 339a Disto

While I've got this apart.

Any Ideas?
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Old 29th November 2012, 03:03 AM   #912
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
Could it be the same phenomena that affects the AGC in the oscillator? Ripple etc. on the amplitude/phase controls?

I'll have a look and post some data.

Cheers,
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Old 29th November 2012, 03:17 AM   #913
davada is offline davada  Canada
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Default TP1 and TP2 error signals

This is TP1 and TP2 error signals off the phase and level detectors.
This is what is sent to the LDR's
Attached Images
File Type: png TP1 error signal.PNG (64.3 KB, 160 views)
File Type: png TP2 error signal.PNG (65.2 KB, 157 views)
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Old 29th November 2012, 03:30 AM   #914
Frex is offline Frex  France
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Hello davada,

Could you say what FFT software do you use for your screenshot ?
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Frex
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Old 29th November 2012, 03:51 AM   #915
davada is offline davada  Canada
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Quote:
Originally Posted by Frex View Post
Hello davada,

Could you say what FFT software do you use for your screenshot ?
Regards.
Frex
Hi Flex,

I don't know that I can at this time because I'm involved with the beta test program for the hardware and software. That's why I obscured the name. Its not ready for release but I will ask if I can share what it is.

It is very near an EMU0204 and ARTA in performance.

Cheers,

David.
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Old 29th November 2012, 03:57 AM   #916
Frex is offline Frex  France
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Ok, thank you!
I follow from many years all of available FFT softwares, and i didn't recognized the screenshot .. I will be interesting to know if it's a new software if it's a commercial product (or not?).
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Frex
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Old 29th November 2012, 04:17 AM   #917
davada is offline davada  Canada
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Quote:
Originally Posted by Frex View Post
Ok, thank you!
I follow from many years all of available FFT softwares, and i didn't recognized the screenshot .. I will be interesting to know if it's a new software if it's a commercial product (or not?).
Regards.

Frex
It is geared to be a commercial product but priced in the same range as an EMU0204 and a licensed copy of ARTA. I think it will be tailored for audio and production line testing.

Cheers,

David.
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Old 29th November 2012, 04:24 AM   #918
davada is offline davada  Canada
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Quote:
Originally Posted by Frex View Post
Ok, thank you!
I follow from many years all of available FFT softwares, and i didn't recognized the screenshot .. I will be interesting to know if it's a new software if it's a commercial product (or not?).
Regards.

Frex
This is the control panel.
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File Type: png Panel.PNG (395.3 KB, 156 views)
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Old 29th November 2012, 05:08 AM   #919
1audio is offline 1audio  United States
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Quote:
Originally Posted by davada View Post
This is TP1 and TP2 error signals off the phase and level detectors.
This is what is sent to the LDR's
It seems unlikely that those signals could be causing the distortion in the output. But their presence at all suggests the distortion is hiding under some rock nearby. It could be as simple as the harmonics from the level detector getting back in via a shared ground. Not an issue if you stop at -80 dB. Big issue if you are going for below -100 dB.

I would next try making the integrating caps on the level detectors larger and see if the harmonics increase or decrease. Those are the obvious nonlinear stage and driving them harder will show if they are coupling into the rest of the circuit.

The other candidate would be the LDR's themselves. Reading this thread DIYHiFi.org • View topic - LDR as a volume control suggests the LDR's in the 339 would be in the 2% THD generation. The Silonex parts would be substantially better. Looking at Nelson Pass's measurements you should keep the voltage across the LDR's below .2V or less. If they are the cause then a 20 dB improvement would be immediately visible. Perhaps you can look differentially across the LDR's in the 339?
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Old 29th November 2012, 09:11 AM   #920
coluke is offline coluke  Italy
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Quote:
Originally Posted by davada View Post
This is the control panel.
Wow - recognized it! Seen a few demo videos a couple of days ago, and discovered myself wondering about release date. It looks great (particularly the H/W), and seems very promising indeed (although I'd add a few more FFT windows...) - need another beta tester?

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