Low-distortion Audio-range Oscillator

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gerhard

gerhard

Member
Joined 2005
hoffmann-hochfrequenz.de
Where do you buy the boxes? DK wants €70 or so for an empty one from Pomona. :eek:
Shocking. I need to build some RF filters.

BTW I delivered this week a 0.6 Kg parcel from our Saar state to Limoges, France,
traceable, to DHL (only abt. €17.50) and the lady said I was lucky that this worked at all.
Many packets, esp. to Asia would currently simply come back to .de .
Some countries would reject them.
And the prices were currently higher than normal.

Gerhard
 
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V

vicnic

Member
Joined 2004
HpW said:
As long you mask out the noise with a passive notch... for sure you will never ever see any noise bell around the fundamental! :D
Hp
Click to expand...
I know about the bell. I am using passive notches for to get lower as possible distortions at the measurement tool side, not for mask the bell.
If you are sure that the TL072 contribute significant noise, you can change it to another opamp. Then show us the difference please. Too many words. Where is the job?

Vic.
 
H

HpW

Member
Joined 2002
hpw-works.com
vicnic said:
I know about the bell. I am using passive notches for to get lower as possible distortions at the measurement tool side, not for mask the bell.
If you are sure that the TL072 contribute significant noise, you can change it to another opamp. Then show us the difference please. Too many words. Where is the job?

Vic.
Click to expand...

1. It is your product.

2. As soon I have a new LDO on my desk with 2 x OPA1656.

3. I do not have any OPA1656, nor would solder my existing any more!

4. I would measure as soon as possible

5. And provide to the corona world the results :D

Hp
 
V

vicnic

Member
Joined 2004
HpW said:
1. It is your product.
Hp
Click to expand...
Yes, and I previously wrote: "Probably you won't see the difference, if the TL072 will be changed." Maybe I am wrong in my experience in the past. Please show me that. Otherwise someone periodically write about the "noisy" TL072. The TL072 works in the AGC, not in the main signal phase. The contribution of the AGC is very small. Every cent counts in this concept.
 
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gerhard

gerhard

Member
Joined 2005
hoffmann-hochfrequenz.de
HpW said:
2. As soon I have a new LDO on my desk with 2 x OPA1656.

3. I do not have any OPA1656, nor would solder my existing any more!
Click to expand...

Now that you mention the OPA1656:

I happen to have its data sheet open in another window.
Is it unity gain stable?

Normally that is listed under key features, but the word "stable"
is so carefully avoided in the entire data sheet that it makes me nervous.
From the gain/phase plot it should be possible.

I just had a THS4022 ( > -9 or +10) that was completely stable
at +3.15 while the other half oscillated at 160 MHz with G= +11,
even when heavily overcompensated. Weird.
And that while giving an excellent phase margin in simulation.

cheers,
Gerhard
 
Edmond Stuart

Edmond Stuart

Member
Joined 2003
data-odyssey.nl
THD+N, an industry standard ?

This is what Bob Bauman (co-founder / chief hardware engineer at Lynx StudioTechnology, Inc.) told me once:
" .... the Ap does not measure THD alone. We have chosen to use the THD+N value (measured on the Ap) in our specifications because it’s an industry standard that allows customers to easily compare to other products and it is an excellent gauge of overall audio quality."

Cheers,
E.

(BTW, I disagree with above statement)
 
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