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Old 3rd December 2012, 06:39 PM   #221
DF96 is offline DF96  England
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Quote:
Originally Posted by Charles
Now my question to the experts: What did I have to connect to my ADC's input in order to get really nasty alias-distortion ?
It does not require an expert to answer the question. If your website description of no filters is accurate, then (as I said in post 219) any signal with components above half the sample frequency will generate an alias. If this does not happen then you do have a filter.

The alias will be at a frequency of fsig - fs, and at about the same amplitude as the signal would have been were it not for aliasing. This means that aliasing is worse than the images produced by a filterless NOS DAC, as images are at high frequencies where audibility will be poor, while aliases are at lower frequencies.

At 96kHz sampling aliasing might not be too much of a problem as there won't be much music above 48kHz, but at 44.1 or 48kHz it will be unless the studio has poor bandwidth.

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PS: eager to hear your suggestions
Are you?

Last edited by DF96; 3rd December 2012 at 06:40 PM. Reason: comment on PS
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Old 3rd December 2012, 10:07 PM   #222
Charles is offline Charles  Germany
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Originally Posted by DF96 View Post
It does not require an expert to answer the question.
What does the fact that you didn't answer it tell us ?

But one point for action

Any others ?

Charles
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Old 3rd December 2012, 10:15 PM   #223
SY is offline SY  United States
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You may not like the answer, but it is the answer and a correct one. If you're unable to hear the aliased garbage from extended bandwidth signals, you should be able to find someone who can.
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Old 3rd December 2012, 10:20 PM   #224
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Originally Posted by Charles View Post
What does the fact that you didn't answer it tell us ?

But one point for action

Any others ?

Charles
you need an anti-aliasing filter otherwise your board is unusable. Any HF noise or signal content above fs/2 will be folded back into the normal audio spectrum.
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Old 3rd December 2012, 10:31 PM   #225
Charles is offline Charles  Germany
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Can I at least expect from you to read my question correctly ?

Here it is again:

What do I have to connect to my SAR ADC's input in order to get really nasty alias-distortion, even if I sample at 192kHz ?

Now don't hide in textbooks, come with your experience !

Okay, you probably cannot have the experience, then come with your engineering !!

Charles

Last edited by Charles; 3rd December 2012 at 10:33 PM.
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Old 3rd December 2012, 10:40 PM   #226
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Originally Posted by Charles View Post
Can I at least expect from you to read my question correctly ?

Here it is again:

What do I have to connect to my SAR ADC's input in order to get really nasty alias-distortion, even if I sample at 192kHz ?

Now don't hide in textbooks, come with your experience !

Okay, you probably cannot have the experience, then come with your engineering !!

Charles
it's a silly question because it depends on what you mean by nasty.

good engineering practice dictates that you can't assume the nature of the input signal to the adc and that any aliasing artefacts are not desirable.

Last edited by Trevor White; 3rd December 2012 at 10:53 PM.
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Old 3rd December 2012, 10:45 PM   #227
qusp is offline qusp  Australia
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right, so you made an ADC that is only able to sample at 192khz if you want to avoid aliasing being folded down into useful bandwidth?

well thats really useful.... but then you are stuck in a spot, since I presume you dont like resampling either?

just like the little player thats only ~16bit with the volume turned all the way up

the products are toys that you should have just kept as personal experiments

Last edited by qusp; 3rd December 2012 at 10:47 PM.
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Old 4th December 2012, 10:43 AM   #228
DF96 is offline DF96  England
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Quote:
Originally Posted by Charles
What does the fact that you didn't answer it tell us ?
That you did not ask the question you thought you were asking? I gave the correct answer to the question you wrote, but perhaps not the correct answer to the question you thought?

Or is this just a game of riddles to divert attention from your claim of an ADC which lacks, and does not need, anti-aliasing filters even when run at 44.1kHz? The statements on your website advertising this device appear to show a lack of understanding of how sampling works. This would be a concern to any potential customer who does understand sampling.

Please do not try to erect an artificial barrier between textbooks, engineering and experience. Everything we experience is done so in the context of our understanding, which may be true or false or a mixture. If your experience suggests that the Shannon sampling theorem is incorrect then either you deserve a Nobel Prize or the mental model by which you interpret your experience is incorrect and misleading you.
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Old 4th December 2012, 11:24 AM   #229
erin is offline erin  Australia
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Im not an expert in the field of anti aliasing filters, but I assume that to make an anti aliasing filter on the input of an ADC you would need either multiple op-amp filters to create a very sharp HF roll off at half or just below the sampling frequency, or a complex passive network to do the same job.

Many audiophiles seem to subscribe to the theory that less is more. The audio signal traveling through less components will result in a more pure sound. I personally find this to be the case - use what you need, not more than you need and also not less than you need.

Now, If this ADC has no anti aliasing filter, AND the user samples at say 88.2Khz, and say is archiving an LP record, then is the end user going to get any aliasing?

I suggest that they will not, because most LP's don't have audio above 40khz.

But, because the audio passed though less components before the AD conversion, there might be subjectively better sound from using this ADC. I think this is possible.

I also think that if making a live recording at 96khz or greater, that there would be little chance of aliasing occurring.

To me this sounds like a unique product, which when used in an educated way, by an educated person could result in better sound than a standard ADC with a brick wall filter.

Am I wrong about any of what I wrote above?
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Last edited by erin; 4th December 2012 at 11:39 AM.
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Old 4th December 2012, 11:43 AM   #230
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Originally Posted by erin View Post
Im not an expert in the field of anti aliasing filters, but I assume that to make an anti aliasing filter on the input of an ADC you would need either multiple op-amp filters to create a very sharp HF roll off at half or just below the sampling frequency, or a complex passive network to do the same job.

Most audiophiles seem to subscribe to the theory that less is more. The audio signal traveling through less components will result in a more pure sound. I personally find this to be the case - use what you need, not more than you need and also not less than you need.

Now, If this ADC has no anti aliasing filter, AND the user samples at say 88.2Khz, and say is archiving an LP record, then is the end user going to get any aliasing?

I suggest that they will not, because most LP's don't have audio above 40khz.

But, because the audio passed though less components before the AD conversion, there might be subjectively better sound from using this ADC. I think this is possible.

I also think that if making a live recording at 96khz or greater, that there would be little chance of aliasing occurring.

To me this sounds like a unique product, which when used in an educated way, by an educated person could result in better sound than a standard ADC with a brick wall filter.

Am I wrong about any of what I wrote above?
but you could be making the sound worse from aliasing artifacts and is an example of where less is worse !!

Higher sampling rates means the aliasing filters can be simpler but that doesn't mean they are not needed. Without aliasing filters any HF noise entering the signal chain can be folded back down into the audio band and corrupt the recording. It's just not done !!
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