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What I heard at the ARSC Conference demo some years ago was quite 
impressive.

joe salerno

Mike Gray wrote:
> What a simple and elegant idea - use the bias signal as a clock; 
> wow+flutter=jitter; heterodyne - same as recovering audio modulation 
> from an RF signal.  Congratulations to all involved.
> 
> One criticism I heard when I mentioned this technique to someone in the 
> restoration community - is the bias signal sufficiently stable to ensure 
> that the derived signal is accurate?
> 
> Just my 2 cents,
> 
> Mike Gray
> 
> 
> 
> David Glasser wrote:
>> I can answer some of the questions raised about Plangent, the need for 
>> specialized replay electronics and heads, and the machine at my 
>> company, Airshow:
>>
>> 1) The bias signal was never intended to be recoverable. That this is 
>> possible is a happy accident, but stock replay electronics and heads - 
>> by design - will not reproduce the bias signal.
>>
>> 2) The Plangent replay electronics and playback head have several 
>> features designed to make bias signal recovery possible - the head 
>> itself is a wide-bandwidth design and the first amplification stage is 
>> built into the headblock itself. The Plangent electronics are designed 
>> for wide-bandwidth, low noise reproduction, and they do not have a 
>> bias trap filter. The bias signal of most tape recorders is too high 
>> in frequency to be captured at 192kHz, but the Plangent electronics 
>> contain a very clever heterodyne mixer that will downconvert the bias 
>> signal, after its nominal frequency has been identified, to 24 or 
>> 48kHz which is easily captured by 96k or 192k conversion (and recorded 
>> to a separate digital track). A dedicated bias output feeds a PC-based 
>> spectrum analyzer used to identify the bias signal. An earlier 
>> incarnation of Plangent used a separate head to recover the bias. A 
>> separate head is no longer used. The electronics were designed by the 
>> late David Smith, and refined and hand-built by John Chester. We will 
>> post photos of the electronics, etc on the Airshow website soon.
>>
>> 3) Bias from a tape recorded on an ATR-100 is indeed not recoverable. 
>> ATR-100 tapes, however have other tell-tale signals that can be used 
>> as a reference. The ATR's logic circuits emit rf noise at several 
>> frequencies and tend to bleed into the record circuitry. For example, 
>> simply turning off the ATR's LED time display eliminates several noise 
>> spikes observable on our spectrum analyzer. (Consequently, we have 
>> installed an on/off switch on the display.)
>>
>> 4) While the transport of an ATR is not as gentle as a Studer A820, it 
>> can be safely used for all but the most fragile tapes. If we see 
>> enough of a demand for this service, we will add Plangent heads to our 
>> A820.
>>
>> 5) The Plangent processing is done at Jamie Howarth's lab in 
>> Massachusetts. We are only offering optimized transfers, and a conduit 
>> to Plangent's services.
>>
>> 6) As tape speed drifts, so to will the frequency of the recovered 
>> bias. For this reason, Plangent recommends that a reel be transferred 
>> song-by-song, and the bias frequency identified for each song. This 
>> obviously can increase the time and cost of the transfer.
>>
>> 7) All of this would be besides the point if it didn't sound good. The 
>> Plangent replay electronics are on a par with other high-end tape 
>> replay electronics like the Aria. I am naturally skeptical of digital 
>> signal processing, especially processing on the scale of the Plangent 
>> Process, but after hearing some of Jeffrey Norman's Plangent-processed 
>> Grateful Dead  masters, I am convinced that this is a major 
>> breakthrough in audio restoration technology.
>>
>> I've been involved in audio restoration for many years, but am new to 
>> the ARSCLIST, so I apologize if this post is inappropriate. We are 
>> very excited to be associated with Plangent, and I invite anyone who 
>> is interested in this technology to contact me directly, or contact 
>> Jamie at Plangent.
>>
>> David Glasser
>> Airshow Mastering
>> Boulder, CO
>>
>> www.airshowmastering.com
>> 303-247-9035
>>
>> On Apr 29, 2010, at 7:31 AM, Shai Drori wrote:
>>
>>> Hi Andrew
>>> I meant  that the recorded signal is so high that it is not present on
>>> tape, I think that is the magic of it. It still biases the heads but
>>> it's just too high for the tape itself. Don't forget that at 15ips
>>> you're describing a theoretical 56kHz at 1 7/8 ips. It's just not there.
>>> I love it. I like the way it sounds much better than the reocridngs I
>>> made on otari or Studer, dare I mention tascam. I can see the benefits
>>> of this system for film, but for nice audio tape in good condition, an
>>> ATR recording will be hard to lock to. Did they transfer any command
>>> recordings? I would love to hear the Borelo!!! What a recording (I know
>>> I will now ge tons of emails about my taste in music. In my defense, my
>>> wife would be on your side and add her thoghts about my clothes as 
>>> well).
>>> Shai
>>>
>>> On 4/29/2010 1:52 PM, Andrew Hamilton wrote:
>>>> Dear Shai,
>>>>      As I wrote in your quoted response, below, there are other
>>>> signals besides bias that the PP can lock to.   They mention "logic
>>>> control" signals.   I suspect there are other ghosts they could bust.
>>>>      The ATR is only bias-free while reproducing.   But when
>>>> recording, it should be present, at 432 kHz - almost as high as the
>>>> Dave Hill Aria bias.  Even if you recorded at 30 ips and then, on
>>>> playback, select 3.75 ips and then also  vari-speed the oscillator to
>>>> 50% of that, the 432 kHz bias signal would still be at 27 kHz.  Did
>>>> you remember to digitize at 2x F/s?  Otherwise, it would have been
>>>> filtered out by the ADC.
>>>>
>>>> Please audition the samples on the PP website.  They made a believer
>>>> out of me.   There's a Waves plugin to inject wow and flutter into a
>>>> digital recording.   The PP would not be able to undo this since it is
>>>> simulated and does not contain a veiled clock.
>>>>
>>>>
>>>>
>>>>
>>>> Andrew
>>>>
>>>>
>>>>
>>>>
>>>> On Apr 29, 2010, at 5:53 AM, Shai Drori wrote:
>>>>
>>>>> I can see that working with 160 or even 200 (you can hear it if you
>>>>> slow down the tape enough), but the ATR is bias free, at least on
>>>>> tapes I made so far. The system is interesting though. How does it
>>>>> monitor to see that the original bias did not drift while recording?
>>>>> This would make you track the wrong frequency..
>>>>> Shai
>>>>>
>>>>> On 4/29/2010 10:24 AM, Andrew Hamilton wrote:
>>>>>> There are other forensic time stamp signals besides bias which would
>>>>>> allow for an ATR-100-recorded tape to be de-fluttered by the PP
>>>>>> DSP.   However, even though a tape may be played back by the Airshow
>>>>>> ATR-100, it's entirely possible that the tape was recorded elsewhere
>>>>>> by a different machine (having a much lower bias f).  I believe that
>>>>>> Airshow are offering this service with PP for already-existing
>>>>>> analog tapes, rather than for creative layback transfers.
>>>>>>
>>>>>> David Glasser is chief engineer at Airshow and he has mastered a
>>>>>> huge amount of audiophile CDs, DVDs, and SACDs.   Great ear; great
>>>>>> rooms; great gear.
>>>>>>
>>>>>>  From the PP website:
>>>>>>
>>>>>> "software algorithm, developed with researchers at Cambridge
>>>>>> University in England, which identifies a steady-state ultrasonic
>>>>>> reference tone (such as tape bias or logic control) embedded within
>>>>>> the original analog signal and then performs continuous
>>>>>> high-resolution pitch correction in order to keep the reference tone
>>>>>> at a fixed frequency..."
>>>>>>
>>>>>>
>>>>>>
>>>>>> Andrew
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Apr 29, 2010, at 4:15 AM, Shai Drori wrote:
>>>>>>
>>>>>>> My experience with the ATR is just the opposite. I have tested
>>>>>>> various transport and some tapes were handled only by the ATR. Does
>>>>>>> the system figure out bias frequency automatically. What does it do
>>>>>>> with tapes recorded on the atr where the frequency is so high it
>>>>>>> doesn't show up on playback (400kHz+)?
>>>>>>> Shai
>>>>>>>
>>>>>>> On 4/29/2010 8:54 AM, Paul G Turney wrote:
>>>>>>>> Well they only use ATR 102 machines which are notoriously rough
>>>>>>>> tape handlers....
>>>>>>>>
>>>>>>>> They use software to track and maintain a bias frequency so that
>>>>>>>> any speed anomolies are and wow and flutter are reduced by
>>>>>>>> maintaining perfect pitch with this tone.
>>>>>>>> Not worked with Airshow mastering.
>>>>>>>>
>>>>>>>> It appears to be a monopoly on the software so Airshow would be
>>>>>>>> subbing the work out to PP.
>>>>>>>>
>>>>>>>> PT
>>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: Chandra Lynn [mailto:[log in to unmask]]
>>>>>>>> Sent: Thursday, April 29, 2010 02:12 AM
>>>>>>>> To: [log in to unmask]
>>>>>>>> Subject: [ARSCLIST] Airshow Mastering&  Plangent Processes
>>>>>>>>
>>>>>>>> I noticed some earlier postings about Plangent Processes. It
>>>>>>>> eliminates wow,flutter and speed aberrations from analog masters.
>>>>>>>> They are now working withAirshow Mastering to offer optimized tape
>>>>>>>> transfers. The announcement is onAirshow¹s site at
>>>>>>>> http://www.airshowmastering.com/plangent.htmlHave any of you
>>>>>>>> worked with Airshow or Plangent? If so, what has been 
>>>>>>>> yourexperience?
>>>>>>>>
>>>>>>>>
>>>>>>
>>>>
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