Low-distortion Audio-range Oscillator

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.. and for comparison the RTX6001 generator tested under the exact same conditions. H2: -131dB and H3: -130dB
Note the valley in the noise floor created by the notch filter.
 

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The 2nd is -134.9dBFS or -154.9dBV.
The notch attenuation is 9.4 dB so the 2nd is actually 'only' -145.5dBV.
The fundamental is 14.6dBV and the difference thus 160.1dBV.

The REW software is not as flexible as your AP and as long as I cannot tell the software that the RTX is amplifying the signal by 20dB, I prefer to use dBFS and clearly state what the full scale is.
 
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> delayed by that f*cking Corona virus ...

Some people risking their lives to get your PCB done !!


P.

I realize that, and I don't blame the people for the delay etc. I am sure it must be a hard time for them, and to be honest they did their best to get the boards out asap.

BTW discovered some nice Neutrik XLRs. They consist of an inner part that you put on the PCB and an outer part that you mount on a panel. That way you can take out the board & connectors without having to dismantle the box! A plug-in plug, so to say.

All fits in a 1590BS Hammond diecast box.

Jan
 

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AX tech editor
Joined 2002
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Just now I have tested my new 40dB preamp (discrete, jfet input).
The chain : Viktor1k_2Vrms -> passive_notch1k -> preamp40dB -> X-Fi_HD
The result is slightly better than the OPA827 based post-notch solution.
In any case, H2/H3 is under -150dB.

View attachment 820381

View attachment 820382

Very nice! Is that 40dB preamp in the open?

Jan
 
AX tech editor
Joined 2002
Paid Member
Just now I have tested my new 40dB preamp (discrete, jfet input).
The chain : Viktor1k_2Vrms -> passive_notch1k -> preamp40dB -> X-Fi_HD
The result is slightly better than the OPA827 based post-notch solution.
In any case, H2/H3 is under -150dB.

View attachment 820381

View attachment 820382

Should it not be '+6-9'? The fundamental is +6dBV so that adds to the distortion distance between fundamental and distortion in dBV. The 2nd is attenuated by 9dB (I guess) so that subtracts. Not a big change though.

I also looked at your sim of this. I see that the OL gain at 20k is ~90dB. With a 40dB CL gain, and -150dB distortion at 20k, that means the OL distortion is about -100dB at 20k. That is unbelieveable!

Jan

Jan
 
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