The real TAPE EMULATION circuit

In the last few month was thinking more and more about a project.

A tape recorder emulation circuit.

I thought about building a complete high quality tape recorder electronics with all the correct equalisation caracteristics of the recording and playback electronics.

One method would be to use a transformer as a record/playback head with the correct inductance/impedance like in a real recorder.
The other method would be to use two real heads, and to couple them magnetically.

Yesterday I read at Prosoundweb a report about the Rupert Neve's new Legendary Audio "Masterpiece" Analog Mastering System.
The guy who tested it said that the thing really does what it say.
http://recforums.prosoundweb.com/index.php/t/4767/0
Here is the complete unit:
http://www.legendaryaudio.com/index.htm
You can download the pdf from:
http://www.legendaryaudio.com/MasterpceBro.pdf
It is mentioned that the tape emulation unit use a real magnetical circuit, but do not give more details if it is a transformer or two heads.

This made me think that this is a viable thing and it would be intersting to do some experiments.
I'm mostly interested to build something similar because I would like to have it as an aditional option in the mastering process (and why not tracking)
I supose it is not a simple thing but it can be done. Also I think that because there is no tape involved, the premagnetisation electronics is not needed.

So my questions would be adressed to the tape recorder Gurus. What impedances/inductances are common for some of the high quality tape recorders. I remenber that I found on the net a table with lots of data for various heads, but now I don't know where it is.
Also at what level heads start to saturate?
What electronics do you recomend for this project. I was thinking about some old tube Studer electronics. Any sugestions? Any schematics?
Also, do you think it is possible to emulate the two head assembly with a transformer with the right magnetic material and the right impedances/inductances?
It would be necessary to have a small gap to emulate it as close as possible?

Lets do some brainstorming.

chrissugar

Chris, this is not another April Fool's Day one is it? It is after all Tax Day in the US....

:grin: :grin: :grin:
I have a feeling, that people will pay more attention from now on to my posts, because of that April Fool joke.
No Brad, this time is for real.

chrissugar

EDIT:maybe we should move this thread to the Drawing Board.

have you tried actually using analog tape? :twisted:

Pucho, please stop the jokes.
Not only used but actually built a complete one 15 years ago.

My idea is to emulate a device that have the positive aspect of the sound and the negative the weight, volume, tape, continous need to maintain it in perfect condition.
If 90% of the positive aspects of this device can be reproduced in a 2U rack it is a great achievement for me.
It is clear that there will be no tape saturation, but this is not the thing I'm after. I'm more for the glueing effect of the recorder.

chrissugar

the two head sounds like the the adapters that were/are sold for using a portable CD player in your car that had a cassette tape player.

There is a head mounted in the cassette tape housing that lines up with the playback head. The cassette tape holder head is driven by the headphone/line out of the cd player.

a broken cassette deck and an adapter.......................................

I've seen those adapters. I guess it'll be OK enough for cars, but for other applications, would it have a decent enough freq-range ? I don't know if there are any fundamental limitations lurking with such a setup.

It is clear that it works but I would avoid cassette recorder heads.
I would like to implement the tape equalisation for 15IPS and 30IPS like on the real tape machines, with tape machine electronics, so now I think the big question is what head/electronics or transformer/ electronics would be a good start.

chrissugar

I was thinking the cheap/free way would be a good way to learn and maybe it might have a "sound" that might be usefull.

I also wonder if the head in the cassette tape housing might have been designed to have some kind of eq for the playback, because it is driven by a "flat" headphone amp. This would be for the eq needed by the tape.

Sorry, may not have been paying enough attention, but I'm a bit at a loss what the principal difference of this all is compared to a 'normal TX'.

I'm not sure, that's why I asked.
It can be the ferite material used for the heads and/or the small gap through which is transmited the magnetic energy and who knows how many other factors.
Thoughts?

chrissugar

Thoughts?

Click to expand...

Dunno, but we might be on the wrong track...

I just feel that in that box there's simply a DSP inside - running a standalone version of

http://www.groupdiy.com/index.php?topic=3720

and

http://www.groupdiy.com/index.php?topic=5298

I don't know if you ever saw these or not, Chris. The first one is the bigger, better read.

I know those diode limiter variations. It is not what I want.
I want a real record/playback electronics with a real magnetic circuit in the midle. Almost a tape recorder but without the tape and the mechanics.

chrissugar

Well, one idea I had (I'm not the only one--it's come up a lot from many people) was to simply take a reel-to-reel deck, set up a tape loop, and run it through the record, playback, and erase heads in that order. You record to the record head, play back from the play head into your DAW, and then erase the loop to start over.

That sounds like an awful lot of trouble, though, if you ask me, and you end up needing to cannibalize a working tape deck anyway. The advantage is, you could build a bunch of channels up from several cheap two-channel decks.

I see what you're getting at, though. Basically, you want the record head and the playback head to be facing each other, with some kind of buffer in between?

What might that buffer be, I wonder...

In the scheme I described above, crosstalk between channels would be a major concern. The two heads facing each other would need to physically butt up against each other in order to minimize the crosstalk. One solution to this would be to use simple single-channel (mono) heads, and just set up several pairs for multiple channels. Are simple mono record or playback heads available these days?

It's also possible I might be way the hell off-track from what you're thinking.

Wow, three replies in a row. I'll try not to make a habit of this.

(there was a picture here)

The bottom part says "Mag. [as in 'magnetic'] on wheel" in case you were wondering. :wink:

Just a quick Post-It Note brainstorm...

EDIT: I'll just add more thoughts to this post.

One, I just realized that one would need an erase head in there somewhere. That's likely a given, though.

Two, you could vary the "tape speed" simply by speeding up or slowing down the wheel. Who knows? Maybe the 23" IPS setting would be the magical one. :grin:

I tried and used that method with the tape recorder as an insert unit.
My intention is to completely avoid it.
Also I'm not interested to take a Studer and modify it. I want this device to be small and convenient, without the used space, weight, mechanics, noise, power consumption etc.

There would be an aditional advantage with a unit like this. NO DELAY between the heads so it could be used as a realtime insert processor.

I think they should stay face to face (the heads) and probably in contact. Crosstalk is not a problem because that is also part of the sound of the tape recorder and the vinyl.

My only problem is if it can be done properly only with a pair of heads face to face or there is a transformer solution that can simulate what is happening in the two heads. Don't forget that the magnetic field is concentrated in a microscopic gap.

chrissugar

The idea with the disc is not bad but it has some disadvantages.

1-it is hard to make a disk that has the same magnetic properties like the tape.
2-there should be mechanical contact with the heads and that will distroy the head much faster then the tape.
3-it needs erase electronics
4-it needs mechanics
5-it will not work as a realtime processor

chrissugar

Well, at least I tried.

Okay, so we have two heads, play and record, sitting face to face...

I still think crosstalk would be an issue. Both heads will be rounded convex, right? Putting them face to face will place two convex surfaces up against each other, leaving lots of gap for magnetic fields to leak. When you're running actual tape, the tape surface is right up against the entirety of both heads.

Maybe one could fashion a "faceplate" to fit between the two. This place could have slots milled out of it to correspond to the track positions of each head. Make it out of hard iron and you might get some tape saturation effect, too. It might also depend on how many channels each head has. If we're only talking two, then it might be easier.

I'm no expert at any of this. I just like mental puzzles. :wink: