Hi All,

The "Look Ahead" system was (is) not only used in the disc mastering 
process involving audio tape but in the process of making a sound 
negative for film release prints as well (also a dying technology).

The Nakamichi dragon, AFIK, does not use a look ahead tape head but a 
separate channel that is part of the play head. The fact that Richard 
Hess noted about one revolution for the auto-azimuth circuit to react is 
disconcerting.Even though, by design, the Dragon is chasing azimuth, I 
thought it would be faster than that.

Cheers!

Corey

Corey Bailey Audio Engineering
www.baileyzone.net

On 5/8/2019 2:45 AM, Tim Gillett wrote:
> Thanks Richard, that sounds like a practical use of the tools available.
>
> Thinking more conceptually about Stuart's point about a repetitively 
> skewing azimuth and the potential   hysteresis problem, I recalled 
> today the old system used in disc cutting where a "look ahead" tape 
> head would read the volume levels of the master tape before the actual 
> repro head received the same signal. It gave the disc cutter lathe's 
> lead screw servo time to widen or narrow the groove spacing dependent 
> on track volume.
>
> A similar system might be used for tracking faster and repetitive 
> azimuth changes in a tape.  A "look ahead"  head gathers information 
> about the azimuth skew. The information - after processing - controls 
> the  azimuth settings of a Nak Dragon style downstream read head.
> Since we're only interested in playback, not record, the "look ahead" 
> head could fit in the space previously occupied by the record head or 
> even the erase head. Just a thought.
>
> Cheers,
> Tim
>
> ----- Original Message ----- From: "Richard L. Hess" 
> <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, May 08, 2019 6:58 AM
> Subject: Re: [ARSCLIST] Tascam 122n MK models
>
>
>> Hi, Tim,
>>
>> You approached Stuart's challenge from a different direction. I can 
>> tell you that I've received tapes that "pin" the Dragon's auto 
>> azimuth capability. If it's a Dragon-worthy tape, I'll readjust the 
>> mechanical azimuth to get some range on the motor-driven azimuth, and 
>> then put it back. If it's not a Dragon-worthy tape, I'll put it in an 
>> MR-1.
>>
>> Cheers,
>>
>> Richard
>>
>> On 2019-05-07 6:13 p.m., Tim Gillett wrote:
>>> Hi Stuart ,
>>>
>>> I've serviced a Dragon but not to test the limits of its azimuth 
>>> correction system. I guess we're talking about severe azimuth 
>>> changes, beyond what the Nak was designed to deal with. Law 
>>> enforcement people must have had to deal with such recordings as 
>>> court evidence and who knows what they may have come up with. I've 
>>> read of the JBR company and a modified microcassette player they 
>>> pitched to forensic people. I think it had a play head split into 
>>> something like 12 tracks.
>>>
>>> Cheers,
>>> Tim
>>>
>>> ----- Original Message ----- From: "ROBINSON Stuart" 
>>> <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Tuesday, May 07, 2019 6:19 PM
>>> Subject: Re: [ARSCLIST] Tascam 122n MK models
>>>
>>>
>>>> I have never used a Dragon, but what I wonder when I think about is 
>>>> how long it takes to respond to azimuth changes? Does it for 
>>>> example respond fast enough to react to tapes that have 
>>>> country-laning issues? I have had cassettes where record issues 
>>>> have meant an almost constantly shifting azimuth and I wonder 
>>>> whether the system can correct for this or if it will end up in 
>>>> hysteresis always trying to seek the ideal point.
>>>>
>>>> Stuart Robinson,
>>>> Audio-Visual Archival Technician,
>>>> School of Scottish Studies Archives,
>>>> The University of Edinburgh
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Association for Recorded Sound Discussion List 
>>>> [mailto:[log in to unmask]] On Behalf Of Tim Gillett
>>>> Sent: 07 May 2019 04:03
>>>> To: [log in to unmask]
>>>> Subject: Re: [ARSCLIST] Tascam 122n MK models
>>>>
>>>> Hi Corey,
>>>>
>>>> On a dual capstan deck, the reason it's better for azimuth 
>>>> stability is its uniform back tension. In a standard single capstan 
>>>> deck, back tension from the supply reel tends to increase as the 
>>>> tape plays from start to finish.
>>>> Changing back tension can change azimuth. An interesting 
>>>> complication in our situation is that the deck which originally 
>>>> recorded the cassette we are now playing, may not have been dual 
>>>> capstan, meaning its recorded azimuth may well change from start to 
>>>> end of tape side.
>>>>
>>>> I was in a team digitising thousands of Oral History cassettes 
>>>> mostly recorded on simple single capstan cassette decks. We used 
>>>> Tascam Mk III playback machines which, like Naks have a constant 
>>>> back tension, but controlled electronically, not by dual capstan. 
>>>> Often the azimuth alignment would slowly drift from start to end of 
>>>> the tape side, seemingly always in the same direction. If we'd used 
>>>> Naks I suspect the result would have been similar.
>>>>
>>>> Ideally, such tapes would be played in a similar deck with similar 
>>>> back tension changes! Or on a model such as a Dragon, but I wonder 
>>>> how many of us have access to one of those?
>>>>
>>>> The other thing is that it's the constant back tension which 
>>>> *allows* removal or lifting of the pressure pad. This means that 
>>>> many otherwise fine dual capstan cassette decks would potentially 
>>>> benefit from the adding of a pressure pad lifter, as per the Naks. 
>>>> I've modded a few such dual capstan decks (Pioneer, Tandberg, Sony) 
>>>> with a custom made pressure pad lifter with good results. It's not 
>>>> always appreciated that the absence of the pressure pad greatly 
>>>> improves head life, which is one of the main reasons I like Naks 
>>>> myself.
>>>>
>>>> The Tascam 122 MkIII retains the pressure pad but it mostly works 
>>>> againt the record head, not the play, but has a role to play in 
>>>> maintaining the back tension across the play head downstream of it. 
>>>> The pressure pad on the record head causes quite a bad wear groove  
>>>> after not too long a time, but in even the worst wear cases I've 
>>>> never seen a play head - sitting right next to the record head- 
>>>> worn nearly as badly or unsalvageable.( The Tascam
>>>> 122 head is a beautiful piece of engineering IMO, which unusually 
>>>> allows full adjustment of the record head independently of the play 
>>>> head. They're not locked together). In my view the 122 record/play 
>>>> head assembly should be replaced not when straight line playback 
>>>> performance suffers, but earlier when the record head becomes 
>>>> grooved due to the wear from the pressure pad..
>>>> This is especially so when azimuth is routinely adjusted and the 
>>>> tape is forced to distort inside the "tramline track" of the worn 
>>>> record head as the head twists with azimuth adjustments. Of course 
>>>> this applies to any tape head in any machine.
>>>>
>>>> I noticed on a head from a later model Nak deck, relief slots were 
>>>> factory cut into the head faces. A nice feature, especially in a 
>>>> transfer situation where azimuth is regularly being adjusted.
>>>>
>>>> Tim Gillett
>>>>
>>>> Perth,
>>>> Western Australia
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Corey Bailey" <[log in to unmask]>
>>>> To: <[log in to unmask]>
>>>> Sent: Monday, May 06, 2019 11:06 AM
>>>> Subject: Re: [ARSCLIST] Tascam 122n MK models
>>>>
>>>>
>>>>> Hi John,
>>>>>
>>>>> I prefer cassette decks with a dual capstan mechanism for 
>>>>> playback. The
>>>>> reason is that cassettes, particularly old ones, tend to skew and 
>>>>> a dual
>>>>> capstan deck will hold azimuth better throughout the length to the 
>>>>> tape.
>>>>> Some Nakamichi's also have the added feature of a pressure pad 
>>>>> lifter. If
>>>>> you are going to consider a NAK, be sure and buy one that was 
>>>>> built post
>>>>> 1982. Dual capstan decks are expensive, even used which, I think, 
>>>>> is the
>>>>> only way you will find one. The Tascam that you mention is current 
>>>>> but a
>>>>> good used dual capstan machine will out perform it, hands down.
>>>>>
>>>>> My $0.02
>>>>>
>>>>> Corey
>>>>>
>>>>> Corey Bailey Audio Engineering
>>>>> www.baileyzone.net
>>>>>
>>>>> On 5/5/2019 7:19 AM, John Schroth wrote:
>>>>>> Hoping to get some input from everyone.
>>>>>>
>>>>>> I'd like to add a Tascam 122 cassette deck to our inventory. I've 
>>>>>> been
>>>>>> studying up on the different models, reading conflicting reports. 
>>>>>> Does
>>>>>> anyone have recommendations on which of the models they prefer - the
>>>>>> original 122, MK-II or MK-III?
>>>>>>
>>>>>> Thanks in advance for any input.
>>>>>>
>>>>>> Kind Regards,
>>>>>>
>>>>>> John Schroth
>>>>>>
>>>>
>>>>
>>>> ---
>>>> This email has been checked for viruses by Avast antivirus software.
>>>> https://www.avast.com/antivirus
>>>> The University of Edinburgh is a charitable body, registered in 
>>>> Scotland, with registration number SC005336.
>>>>
>>>
>>
>> -- 
>> Richard L. Hess                   email: [log in to unmask]
>> Aurora, Ontario, Canada                             647 479 2800
>> http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.