Low-distortion Audio-range Oscillator

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#5,863
vicnic said:
Some freshly measured data of the capacitors distortions. Three or more pcs of the each type was measured in this schematic:
http://content6-foto.inbox.lv/albums/e/elterra/CapsC/CapsMeas.jpg

1) Kemet 1206 200V 0.01uF COG – 3 pcs measured
2) TDK 1206 630V 0.01uF COG – 6 pcs measured
3) Xicon 50V 0.01uF polystyrene – 10 pcs measured
4) Wima FKP2 100V 0.01uF – 6 pcs measured
5) Wima FKP2 63V 0.022uF– 5 pcs measured
6) Wima FKP2 100V 0.022uF– 5 pcs measured
7) LCR Components 63V 0.022uF polystyrene -5 pcs measured
Click to expand...

I wonder if you (or anyone else) has looked at Panasonic PPS SMDs ?
https://industrial.panasonic.com/ww/products-ec/smd-film-capacitor/smd-film-capacitor/echu/index


Patrick
 
#5,867
RNMarsh said:
Did you notice that the X10 extra range (-110dB) is only for the meter and not the monitor output? The monitor output remains at -100dB.

??


THx-RNMarsh
Click to expand...

On the 725C this is true. I don't remember on 725D because I don't use it. At these very low levels the noise makes the meter dance around in the x10 mode and 110dB range.

I believe the x10 is intended for analysis mode. other wise it is very difficult to read low level THD.
It is kin to a scope magnifier.

The 110dB is a range on the 725D. The X10 is for analysis mode.
If you were in the 110dB range and thought it is x10 the is would explain the extra 10dB I see in your measurement.

In analysis mode and in the 110dB range the x10 would give you 120dB of meter range, it's a meter magnifier.
 
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#5,871
davada said:
On the 725C this is true. I don't remember on 725D because I don't use it. At these very low levels the noise makes the meter dance around in the x10 mode and 110dB range.

In analysis mode and in the 110dB range the x10 would give you 120dB of meter range, it's a meter magnifier.
Click to expand...


The 725D analyzer monitor output is -100dB max even if the X10 meter magnifier is On.

So what you see is what you get with -100dB at zero ref level on QA401 display.

Today the 2H and 3H are different by a few dB... maybe room temp change?

I let it cook again and see the harmonics. The 2H is higher, and my question is can the 2H be trimmed to lowest level internally?

I havent checked but is there a dB diff when using the QA401's balanced input with unbal source..... 1/2 the diff input ??


THx-Richard
 
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#5,872
RNMarsh said:
The 725D analyzer monitor output is -100dB max even if the X10 meter magnifier is On.

So what you see is what you get with -100dB at zero ref level on QA401 display.

Today the 2H and 3H are different by a few dB... maybe room temp change?

I let it cook again and see the harmonics. The 2H is higher, and my question is can the 2H be trimmed to lowest level internally?

I havent checked but is there a dB diff when using the QA401's balanced input with unbal source..... 1/2 the diff input ??


THx-Richard
Click to expand...

Richard in normal mode there is no x10. This function is only active when the analyzer is set for analysis mode. THD measurement only.

When the analyzer is in normal mode and the range is set for 100dB then the monitor output is 100dB and when the analyzer is in normal mode and the range is set for 110dB then the monitor output is 110dB.

You are correct that the Analysis Gain +10dB setting only effects the meter. But you are not measuring in this mode.

Please set the range to the 100dB, (0.001),(10uV) in normal mode with analysis mode turned off, monitor from the "Normal" monitor output and repeat the measurement.
 
#5,874
RNMarsh said:
This is what I always do and results are from this exact same setup that you describe. we are saying same things.


-RNM
Click to expand...

Okay. But you brought up the x10 gain so wasn't sure.

If you can't measure lower then this is the residual of the analyzer you have there.

The gen measures the same on both the 725C and 725D I have here. Both agree.
The 725D at some frequencies measures lower but we are talking just a few dB not 10dB.
The two analyzers and even the 339A all agree with gens that have inherently greater distortion like the 339A gen.

I don't know why you can't get the same measurement. But I'm not there and can't see how you're setup. You did however get much better results a few years ago when you had my prototype there. Both prototype and your gen measure the same and yours a bit better at some frequencies. So this leaves me scratching my head wondering what's going on and you said yourself that you're not getting the low measurements that others here do.

So we need to get to the bottom of this.
 
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