[ProAudio] HX Pro was :FeralA - Recordings released encoded with Dolby A

[Alan Garren]

thanks, as John says, makes sense to me.

Cheers

Alan

On 2/11/2020 11:32 AM, Bill Whitlock wrote:
> Since it keeps the total bias fluxivity more constant, the physical 
> location where it no longer switches the remanent magnetic field on 
> the tape (the recording zone) should remain more stable, not less. In 
> non-HX recording, the location will move in response to high levels at 
> high audio frequencies.
>
> Bill Whitlock
>
>
> -----Original Message-----
> From: Alan Garren via ProAudio <proaudio at bach.pgm.com>
> To: Bill Whitlock <engineer_bill at verizon.net>; proaudio 
> <proaudio at bach.pgm.com>
> Sent: Tue, Feb 11, 2020 11:13 am
> Subject: Re: [ProAudio] HX Pro was :FeralA - Recordings released 
> encoded with Dolby A
>
> yes, I was casting about in my head for the appropriate work to call 
> HX, process seemed most likely.
> the point is that, as you point out, it modulates the bias, which 
> should then change the location of the trailing edge? What affect does 
> this have on the bias signal on the tape for John and Jaime to process?
> Cheers
> Alan
>
> On 2/11/2020 11:03 AM, Bill Whitlock wrote:
> I'd hesitate to call HX Pro a "process".  All HX Pro does is to 
> account for the fact that HF program material tends to "bias" itself 
> and that this HF program content, when combined with fixed ultrasonic 
> bias results in significant self-erasure and loss of HF MOL (maximum 
> HF level residual on the tape).  So HX Pro simply modulates the 
> ultrasonic bias so that the combined effect of program HF bias plus 
> ultrasonic bias remains constant.  Depending on tape and speed, it can 
> improve HF "headroom" or maximum HF audio output level by up to 6 or 8 
> dB.  It doesn't change frequency response of the record/play process - 
> except at levels where MOL/saturation is an issue. I guess it 
> technically is a "process" but it's record side only, no "decoding" 
> needed.
>
> Hope that made sense. Lots of folks actually believe(d) that HX Pro 
> was another noise reduction system. It's not of course, it's simply a 
> way to get the most out of a given tape at high audio frequencies. Not 
> so much an issue at 15 IPS, but really a big deal at 1-7/8 IPS - where 
> it can make ordinary iron oxide tape perform like chrome.
>
> Bill Whitlock
>
>
>
> -----Original Message-----
> From: Alan Garren via ProAudio <proaudio at bach.pgm.com> 
> <mailto:proaudio at bach.pgm.com>
> To: John Chester <jkc at jkc-lab.com> <mailto:jkc at jkc-lab.com>; proaudio 
> <proaudio at bach.pgm.com> <mailto:proaudio at bach.pgm.com>
> Sent: Tue, Feb 11, 2020 10:42 am
> Subject: [ProAudio] HX Pro was :FeralA - Recordings released encoded 
> with Dolby A
>
> On 2/11/2020 10:12 AM, John Chester via ProAudio wrote:
> > Why does perfect azimuth adjustment usually not produce minimum
> > interchannel time difference?  The most obvious answer is gap scatter
> > in the record head, but there are others.  Record EQ may not be
> > precisely matched, and bias setting may be different. Recording occurs
> > at a point slightly past the trailing edge of the record head gap, and
> > that distance varies as bias level changes.
>
>
> This causes me to wonder if you have had to try this on an HX processed
> tape. I am only aware of one pro deck with HX Pro, the studer A820, and
> most people leave it turned off anyway. But it is there on some later
> models. (possibly on the A827 as well, can't remember)
>
> Seems like a horror story for your process, chasing a HF modulated bias
> level.
>
>
> Cheers
>
> Alan
>
>
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