M8 Cross Field Head Design, is this HiFi?

[stephe]

Picked up a Akai M8 I plan to restore that touts having "cross field heads". Looks like this is just for recording and am curious how well this works. TIA

 

[mediatechnology]

I had a GX-360D and it worked and sounded quite good. The cross field head is for bias only instead of combined record and bias current in a single record head.

 

[StevenOH]

Good description of this trick is in these magazines:

https://www.worldradiohistory.com/Archive-All-Audio/Archive-Audio/60s/Audio-1969-01.pdf -page 23
https://www.worldradiohistory.com/A...ive-Studio-Sound/60s/Studio-Sound-1969-01.pdf -page 22
Seems to be the same article...

Attach is from the German mag. Funkschau 1965 #7.

 

[stephe]

Very interesting. So possibly recording at 3.75ips could sound closer to a 7.5ips recording with this technique?

 

[stocktrader200]

Tape recording is dead now. The VCR Helical spinning head was the best advanvce. Now even the hard disk is on its last legs.

 

[stephe]

People say vinyl records are dead, tubes are dead and everyone is streaming a DAC through a class D amp...

I'm listening to tapes on a GX4000D R2R though a 300B tube amp and they sound fantastic to me 🙂

I am curious why you even read an analog source thread if you think this tech is "dead"?

 

[woodturner-fran]

@stephe please post your progress here. I have one of these, mint cosmetic condition, all original valves, but it needs a complete overhaul. I'd be very interested in how you get on and what you think of it.

I only have a handful of tapes so it has always been on the backburner.....

 

[stephe]

I plan on doing a whole video series on it!

 

[StevenOH]

Cross-field is a great Akai invention, and was patented all over the world.
It prevents erasing effect on the audio signal on the tape when it leaves
the narrow gap and the audio field of the head, but still in the much wider
HF bias field. This erasing effect not only significantly reduces the amplitude
of the short wavelength / high freq. signals (depending on the tape speed),
but also creates a lot of distortions for the signals on the tape.
The Cross-Field is devised to narrow the HF bias field at the recording gap to
the same width as the audio signal field.

https://reel-reel.com/tape-recorder/akai-m8/

Manuals are here:

https://www.hifiengine.com/manual_library/akai/m-8.shtml
https://www.audioservicemanuals.com/a/akai/akai-m/82485-akai-m-8-owners-manual
https://www.manualslib.com/manual/3343946/Akai-M8.html -sm
https://elektrotanya.com/akai_m-8_stereo_tape_recorder.pdf/download.html -sm

 

[stephe]

So it appears if you don't currently have an active account at hifi engine, there is no option to create a new account? weird... Otherwise, thanks for the links!

 

[analogadikt]

Thanks Stephe for this topic. I have two of these and want to make a properly working one out of them. Shall follow your progress.

Regards,

 

[msdin]

Tandberg first introduced the cross-field head in their TB-6X tape recorder in the 1960s

 

[StevenOH]

I was intrigued with the issue of priority in this technology, and did some research into this.
Apparently, Tandberg did their first X-F model TB-6X in 1966:

https://tandberg.datagutten.net/tandberg_Story.html

The next thread had plenty of discussion of this issue, and the last post explained,
that Tandberg didn't patent anything:
https://www.tapeheads.net/threads/what-is-the-story-behind-cross-field-record-heads.37999/page-3
-there you will find an adjustment procedure.

Akai had filed plenty of X-F patents, with the first one being in 1962, in the GB, being Norway "backyard".
Akai cross-field GB920690A -1963:
https://worldwide.espacenet.com/patent/search/family/009699880/publication/GB920690A?q=pn=GB920690A

And many more after this, for example in 1965:
https://worldwide.espacenet.com/patent/search?q=nftxt = "Akai" AND pd = "1965"