OK, so your trace of the unattenuated output of the Hiface and mine look the same. Now, what is the problem in your setup whereby the attenuators are not delivering an exact scaled-down version of that waveform?
Yeah, fine, where's 100pF gonna come from? You'll never get 100pF as strays, 2 or 3 maybe, at most 10 and that's unlikely. 10nH of inductance. Like I told TNT; be realistic. You're just stretching things beyond the feasible because the idea that somebody might see off the top of their head that using a DMM is perfectly adequate freaks you out. I didn't come down with the last shower of rain you know. I been doin' this **** for years.
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I don't understand this, could You explain, please?
DO You really think that adjusting the variable gain (by 3 times) of the very same oscilloscope channel (> 500MHz in that shot)
will change the response with any important amount? (I did not see any change while doing that, as one should not, on a TEK scope)
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Sy, I can not follow You here.
I had attenuated the signal with pretty good attenuators.
Then re-amplified with a pretty high bandwith amplifier.
The results visible in the shots fit ~perfectly, what regards the edges.
Where is it that I am lost?
I had attenuated the signal with pretty good attenuators.
Then re-amplified with a pretty high bandwith amplifier.
The results visible in the shots fit ~perfectly, what regards the edges.
Where is it that I am lost?
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Since it's been in my lab all weekend, I'll not try to guess. ESP isn't my strong point.
It's not where you get lost, it's where you stopped.
If an ideal attenuator has a scalar transfer function (e.g., 0.5 for a 6 dB attenuator), the output waveform will look identical to the input waveform. Now you could deliberately manipulate the length of cable used in the measurement and its termination to cause an antiphase reflection and partially null some of the lower level higher frequency mixture riding on the top, but not only is that a poor solution, it's a solution to a problem that doesn't appear to be a problem.No, Sy, I don't see any problems with that method of mine, sorry. After scaling down and going back with much higher bandwith than the signal has, one should simply get back the original waveshape.
Edit: now I see your edited text.
Please, do not accuse me with anything of falsification, in that test I did not do anything else that had been documented, (inserting an attenuator) and I had even described earlier why it is happening.
Your objections are not valid, sorry.
Edit: now I see your edited text.
Please, do not accuse me with anything of falsification, in that test I did not do anything else that had been documented, (inserting an attenuator) and I had even described earlier why it is happening.
Your objections are not valid, sorry.
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Then why are these "reflections" not present with a cheap Chinese unit measured exactly the same way (except for plugs/jacks)? Is it a black hole? And why are the relative size of these "reflections" identical in my measurement with and without the attenuator on the Hiface, as would be expected from proper cable and termination?
Of course, from the important standpoint of what analog signal emerges from all of this, none of these issues seem to matter.
Of course, from the important standpoint of what analog signal emerges from all of this, none of these issues seem to matter.
This is the unit I used for a low-rent comparison:
USB Port Mini Converter SPDIF Coaxial Output DAC - eBay (item 250637376165 end time Nov-18-10 04:21:10 PST)
USB Port Mini Converter SPDIF Coaxial Output DAC - eBay (item 250637376165 end time Nov-18-10 04:21:10 PST)
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