[sdiy] "Digital vs analog waveforms" [was: Ways for innovation]

[nvawter]

holy cow, that's awesome :)

It's begging to be exploited!  I wonder what it would be like to make 
lo-fi bias signals?  Low-frequency?  non-sinusoidal?  wow and flutter in 
the bias signal?



On 2016-01-28 10:38, Sarah Thompson wrote:
> It seems to me that nobody ever really acknowledges that analog tape
> actually also samples the recorded signal in time, though doesn't
> quantize in level. The bias signal, usually a sine wave at 50 - 100KHz
> or so, is added to preemphasized version of the audio as it is fed to
> the record head. This overcomes the large amount of hysteresis in the
> magnetic materials in the tape by rapidly flipping between linear(ish)
> regions. This overcomes the coercivity of the iron oxide, but has the
> side effect that the audio is only really recorded during the peaks of
> the bias signal. Though not identical to digital sampling, this does
> still cause very similar aliasing issues, so the signal path still
> needs antialiasing filters, even though they are typically not thought
> of as such.
> 
> This is also why higher bias frequencies often sound better, though
> were harder to achieve due to the relatively high voltages needed.
> 
> Sarah
> 
> Sent from my iPad
> 
>> On Jan 27, 2016, at 6:16 AM, Tom Wiltshire <tom at electricdruid.net> 
>> wrote:
>> 
>> I expect he's just saying that he likes a nice clean 16-bit/44.1KHz CD 
>> over a noisy old cassette tape. Hard not to agree, really. Especially 
>> once the tape's been in the back of a cupboard unloved for a few years 
>> and has print-through to boot. That's "degradation of stated media", I 
>> suppose.
>> 
>> Still, even offered a brand new consumer cassette or a CD, you'd still 
>> choose the CD, wouldn't you? There's no comparison in terms of S/N or 
>> distortion, not to mention wow and flutter.
>> 
>>> On 27 Jan 2016, at 11:17, Chris Juried <cjuried at yahoo.com> wrote:
>>> 
>>> Hi Aaron,
>>> 
>>> Are your preferences based on degradation of stated media and/or 
>>> accurate reproduction of the original waveform?
>>> 
>>> Sincerely,
>>> 
>>> Chris Juried
>>> Audio Engineering Society (AES) Member
>>> InfoComm-Recognized AV Technologist
>>> http://www.JuriedEngineering.com (Juried Engineering, LLC.)
>>> http://www.TubeEquipment.com (Tube Equipment Corporation)
>>> http://www.HistoryOfRecording.com (History of Recording)
>>> 
>>> This e-mail, and any attachments thereto, is intended only for use by 
>>> the addressee(s) named herein and may contain legally privileged 
>>> and/or confidential information. If you are not the intended 
>>> recipient of this e-mail, you are hereby notified that any 
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>>> 
>>> 
>>> From: "Lanterman, Aaron" <lanterma at ece.gatech.edu>
>>> To: synth-diy List <synth-diy at dropmix.xs4all.nl>
>>> Sent: Sunday, January 24, 2016 4:38 PM
>>> Subject: [sdiy] "Digital vs analog waveforms" [was: Ways for 
>>> innovation]
>>> 
>>>> On Jan 22, 2016, at 10:27 AM, spivkurl at wearerecords.com wrote:
>>>> 
>>>> they express their unfounded claims about how a digital waveform is 
>>>> that same or "higher resolution" (uh I hate that) than an analog 
>>>> waveform…
>>> 
>>> I must once again remind cite the Nyquist-Shannon sampling theorem:
>>> 
>>> https://en.wikipedia.org/wiki/Nyquist–Shannon_sampling_theorem
>>> 
>>> When you’re listening to a “digital waveform,” by that point it’s 
>>> been converted back to analog. Analog and digital transmission and 
>>> storage formats have different strengths and weaknesses. Analog 
>>> formats tend to degrade gracefully; digital formats have a sharp 
>>> degradation curve, in which they’re perfect until they’re garbage (as 
>>> I’ve learned going through archiving some old DAT tapes). Digital 
>>> waveforms are converted to “analog” for transmission — the cable your 
>>> internet service uses doesn’t know anything about “bits,” but the 
>>> circuits encoding and decoding those bits do.
>>> 
>>> I’ll take a “digital waveform” off of high-rate AAC file or a CD over 
>>> an analog waveform off my old consumer cassette tapes.
>>> 
>>> - Aaron
>>> 
>>> 
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