DIY tape rec/repro heads

[Steerpike]

Has anyone made (from scratch) their own record &/or reproduce heads for a tape recorder? Full-track or half-track ¼" or ½" possibly, since I think cassette widths and tolerances are just too tiny. Still, there are people who build their own phono cartridges!

[gain-wire]

OHHH MY GOD

what are the odds of someone wanting to do the same as me? And tell me, it isn't for cassette decks right...

It's for a multitrack recorder isn't it? That's one of my current projects.

Come one, tell me, tell me the answer, you may be a .. what you got planned here, I want in!

In any case to answer to your question, I have not tried nut am considering making an 8 track head out of individual heads from a VCR rotary drum. Although they might be too small. Poor bass response. I was thinking I'll make the laminations myself. For example: take an iron dowel, 3/8" diameter, and cut "slices" out of it. Then wind the coil with thin 38 gauge magnet wire on the back of each lamination. I wish I had a scanner to better illustrate what I mean. The laminations would be held in place with a central shaft, made of a nonconductive material, then the hole thing would be placed inside...

I' m saying too much!

anyway, if you're interested send me a message.

O.

[Steerpike]

Originally Posted by gain-wire

It's for a multitrack recorder isn't it?

Nice idea, but no, I wasn't going to be that ambitious. Yet.
I want ¼-inch ½-track 2-channel heads for my Ampex 351, which at the moment is full-track mono. I do have two amplifier boxes.

In any case to answer to your question, I have not tried but am considering making an 8 track head out of individual heads from a VCR rotary drum. Although they might be too small. Poor bass response.

The track width is VERY tiny on VHS or Beta heads. And I think because they are designed for MHz response, they have very few turns in the winding which would - as you say - make them horrible at bass or even any audio frequencies. What tape width are you going for ?

At one time I did fantasize about buying a ½-inch 8-track head (as used in some Teac & Fostex low budget machines) and putting it into a VHS transport in place of the head drum - to make an 8-track-analogue-VHS recorder.

I was thinking I'll make the laminations myself.

Interesting idea, though lots of work - sliing a dowel. And do dowels have 'nice' magnetic properties? I had in mind using a stack of transformer core laminations: bolt them together ridgily, then grind them to the required shape.

The really hard part would be to make the azimuthal angle of the two (or more in your case) heads exactly the same.

There is probably a valid reason why R-2-R prof heads are so expensive. But if you've seen photographs (can't recall where on the www they are) of the setup for making early reVox heads, it looked slightly DIY, and those heads were not junk.)

[Geek]

I rewound a cassette erase head once
(potting compound fell out like sand, leaving a nice "play piece" )

That's when I discovered there was such a thing as #50 AWG and at the time, could be bought locally

Cheers!

[gain-wire]

What?! A VCR recorder? I thought about that too! Holy cow, it's like we think the same things... I still might go forward with that project,once I finish this one. Actually I powered up the motors yesterday for the first time like, ten years, and man they were noisy. I'm hoping I can simply clean the brushes or maybe it was because I didn't have enough capacitance in my DC circuit (270uF).

Anyway, an AMPEX 351 eh? Why don't you just get some heads for it? If you look on gearslutz, there's a member who has some Ampex parts for sale. quarter-inch half track shouldn't be that hard to get, right?

And yes you are right, those VCR heads would be inefficient at audio frequencies but at least they are already built. Meaning the hard part is done.

GEEK, 50AWG? what is that like 0.0005 inch diameter? I thought it stopped at around 43AWG.

[Geek]

Originally Posted by gain-wire

GEEK, 50AWG? what is that like 0.0005 inch diameter? I thought it stopped at around 43AWG.

Nope! Smallest commercially produced is #56.
(whaddya think is in SMD inductors?)

I used 42AWG on it though, but they had #50 in stock.

Cheers!

[gain-wire]

amazing... #56 is 0.00049inch. It's not even one thou. That's much smaller than a thin hair! I had no idea they could make it that small. Mind you when I think about those SMD inductors, and bonding wires in Integrated circuits, then yeah, I guess those are good reasons.

Now I realize that the problem in making my own core laminations (I don't even know why they are called laminations, it's just one piece of metal per head track right?) is that to slice the metal out of a thin sheet, you get burrs, and you can't cleanly file them out, so you wreck the edges where it's supposed to be perfectly square. And they didn'T have laser cutting in the seventies, so how did they make them?

Unless, you file, then you sandpaper, then you go down to like 1000 grit emery paper... Sounds like tedious work just thinking about it.

Here's a link for those interested in wire guages : [/URL]http://www.litz-wire.com/wirediminsions.html[/URL]

[gain-wire]

sorry gauge
http://www.litz-wire.com/wirediminsions.html

finally!

[kevinkr]

Originally Posted by Steerpike

Nice idea, but no, I wasn't going to be that ambitious. Yet.
I want ¼-inch ½-track 2-channel heads for my Ampex 351, which at the moment is full-track mono. I do have two amplifier boxes.



<snip>

There is probably a valid reason why R-2-R prof heads are so expensive. But if you've seen photographs (can't recall where on the www they are) of the setup for making early reVox heads, it looked slightly DIY, and those heads were not junk.)

I'm not quite sure I would totally agree with the last assertion based on bad experience with same. They worked, but not that well, and were not durable. The QC on the cylindrical epoxy encapsulated heads was variable - see my old G36 thread for an absolutely egregious example. (I'll be getting a few more G36 shortly and may have more to share at that point.)

I've had some problems with early stereo ReVox playback heads, and the cylindrical heads in particular wore out comparatively quickly.

I think very rapid head wear may be a problem anyone attempting to make their own heads might face - the soft iron used in the early ReVox heads wore out very quickly. I am not sure that the more advanced metallurgy used in more recent tape heads could be replicated in any diy scenario.

The gaps in a playback head are typically on the order of a couple of thousands of an inch, beyond that the playback frequency response starts to fall. The gap width must be smaller than the wavelength of the highest frequency to be reproduced - by some amount I haven't the time to work out at this moment. The gap width is not constant, the farther you are from the head surface the wider the gap - this is of course the wear out mechanism in all heads and the design is dictated by magnetic efficiency considerations

A recording head might be the place to start, its coarser gap might make success more likely.

It's an interesting project and if you can find the right materials and can machine them with sufficient precision you might have some chance of success. I think winding the coils is the easiest part although this is not trivial either. The problems are probably surmountable with patience and experimentation, but the right materials are a must.

[Steve Dunlap]

http://en.wikipedia.org/wiki/Tape_head