Gregorio,

We really need to make certain that we are understanding this correctly. 
I BELIEVE this is what you now mean.

track 1: Signal A
track 2: Signal A + B
track 3: Signal A + B backwards
track 4: Signal B backwards


I do not understand how you can B forwards on track 2 and backwards on 
track 3.

I am assuming that you are playing this on a 4-track inline machine like 
a Teac 3340S

Let's look at
http://www.richardhess.com/tape/quarterinch_lrg.gif
which is approximately to scale.
(It is normally accessed from
    
http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/025-reel-tape/  
)

It could be a DIN tape with a narrow guard band, but I don't think that 
would explain everything.

I had been thinking all along it is what Mark D said...but even that 
does not make complete sense.

But here is an example of a two-track tape overwritten by a 
malfunctioning 1/4 track machine.

http://richardhess.com/notes/2009/09/02/dangers-of-old-tape-recorders-for-playback-using-the-elevator-head/

I really have to say if you're doing this type of work you need a method 
of magnetic tape development. Yes, it's pricey...but so is spending time 
guessing. I would not have figured out the above example nearly as fast 
without the developer and a calibrated loupe.

Cheers,

Richard


On 2012-02-28 10:28 AM, Gregorio Garcia Karman wrote:
> Hello Richard,
>
> you definitely spotted the problem at first glance. It should have been indeed 1, 2, 3, 4, in that order and I would say it is clear that it is a half-track tape. There is still the question of the extremely high crosstalk between channels which only occurs on two or three tapes out of the six hundred. I know it would be much easier but I can't develop the tape, so I have to go back to my original question. Which machine would record with such a narrow guard band, or otherwise what could be an alternative explanation?
>
> Huge thanks again
> G
>
> On 27.02.2012, at 15:19, Richard L. Hess wrote:
>
>> Gregorio,
>>
>> This is why I'm such a fanatic about developing tapes and looking at them. The fact that track 3 has B NOT backwards confuses me.
>>
>> Also, I'm surprised you are writing 1/3/2/4 because visually on the tape you'd see 1/2/3/4 and that helps understanding.
>>
>> You could use 1 + 4 to capture, but I'd rather fully understand why as the narrow tracks, especially at the edge, are not the most desirable unless that's all you have.
>>
>> With track 3 B NOT backwards, I'm at a loss to explain.
>>
>> http://richardhess.com/notes/category/audio/magnetic-tape-developing/
>>
>> Develop the tape and post a photo and link to it from the reply message to the list.
>>
>> Do not rule out misaligned heads. Also, some machines used 1/2 and 4/3 as stereo recording and they might have been UK machines instead of the more common US practice of 1/3  4/2 (in all instances L/R and SideA SideB).
>>
>> Cheers,
>>
>> Richard
>>
>> On 2012-02-27 5:39 AM, Gregorio Garcia Karman wrote:
>>> Dear List,
>>>
>>> looking forward to the beginning of a new digitization week: everything is going well in Cambridge thanks in great extent to the support of the members of the list. Huge thanks!
>>>
>>> Now, I have a small group of 1/4 inch tapes in the collection on which I am working (ca 1950s-70s, recorded mainly on Ferrographs) which seems to have a track format, which I haven't met before. On those tapes standard half-track and half-track butterfly Studer blocks consistently produce a dual mono signal with unacceptable crosstalk on both channels (bleeding of about -20 dB referring to the signal on the other channel).
>>>
>>> On the other hand, the output of a quarter-track headblock is as follows:
>>>
>>> track 1: Signal A
>>> track 3: Signal A + B
>>> track 2: Signal A + B backwards
>>> track 4: Signal B backwards
>>>
>>> It would seem that this very small group of tapes would have been recorded on a machine with a very narrow guard-band in comparison to the rest of the tapes I have. What is your opinion about transferring those tapes on a quarter track headblock and keeping tracks 1 and 4?
>>>
>>> I would also be curious about which machine could have had a track format that would agree with the former observations.
>>>
>>> Thanks for your comments!
>>>
>>> Gregorio Garcia Karman
>>> [log in to unmask]
>>>
>> -- 
>> Richard L. Hess                   email: [log in to unmask]
>> Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
>> http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.
> Gregorio Garcia Karman
> [log in to unmask]
>

-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.