Tape machine 'mojo'

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untune

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I've been bouncing an idea around in my head for a few weeks, something to potentially work on in a few months time. I have a bunch of Ampex line input/output transformers set aside and I've been thinking about what to do with them. Originally I was going to use them for passive duty, adding a bit of flavour to various sources, balancing unbalanced signals and whatnot. I'm curious, however, if there's any viability in creating a stripped down version of the record/repro electronics from the original tape machine (minus the tape, of course) and making a mojo/saturation device of sorts. Perhaps a 4 into 1 mixer.

It's purely an idea at this stage, I'm just wondering if it might be worth the time investment. Choosing a single tape speed and EQ (let's say, 15ips NAB) would (presumably?) negate the need for some calibration parts of the circuit, and I'd guess that without tape the bias electronics would be unnecessary. Perhaps something like diode based saturation or another transformer in the middle, in lieu of tape. Essentially it would go [input transformer > record pre-emphasis amp > (potential saturation circuit/ interstage transformer) > repro de-emphasis amp > output transformer]. Keeping some (relative) authenticity to the sound of the original design... There are multiple 39v rails though and I don't know if it'd be that simple to start chopping things out.

The transformers themselves have nice qualities when pushed in the right way, they could just do with some controllable gain in the right places. What do people think?

Cheers
 

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gyraf

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I don't think it would be all that simple

..without the tape itself, I think you are left with a very-very-small residue of what the signal path originally sounded like.

Perhaps it would help to add a VERY crappy stepdown transformer based on some VERY non-ideal core (large hysteresis)..

or do it like the plugins: emphasis-clipping-deemphasis - for the kinda nonlinear clipping that we perceive as tapis'h

/Jakob E.
 

untune

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I don't think it would be all that simple

..without the tape itself, I think you are left with a very-very-small residue of what the signal path originally sounded like.

Perhaps it would help to add a VERY crappy stepdown transformer based on some VERY non-ideal core (large hysteresis)..

or do it like the plugins: emphasis-clipping-deemphasis - for the kinda nonlinear clipping that we perceive as tapis'h

/Jakob E.
Thanks Jakob, yeah I agree—I doubt you'd get close to that particular type of saturation with no tape involved, but I was thinking more like you've suggested there, the crappy stepdown transformer or the emphasis-clip-deemphasis. Just curious if it'd have an interesting effect on the sound. Apparently the Neve tape sims used inductively coupled coils to replicate the tape heads but that's over my head :LOL:

Cheers
 

untune

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....smoke screen aside, "inductively coupled coils" is a transformer - no more, no less :)
Which is what I thought when I read it, and was the idea I originally had—but I thought nah, surely there must be something else going on :LOL: perhaps experimenting with a small step down transformer and a diode ladder might be a good place to start!
 

JohnRoberts

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The attraction about using tape paths when recording was to introduce some natural compression when driving tape paths into saturation (popular on drum tracks).

[edit- to be clear it is the magnetic tape that is saturating /edit]

It seems in theory some real time path with tape in the middle might work as an effect, but printing to tape involves strong magnetic fields that would interfere with any real time loop reading signal from the same tape. Perhaps there is some way to parse out the tape saturation from closely placed read and write heads with tape in the middle.... nah

JR
 

abbey road d enfer

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The tape "mojo" is the result of several effects, of which magnetic saturation is certainly the dominant one, but also the way bias modifies it, self-erase effects and time modulation due to transport.
It is probably possible to simulate the former with a xfmr using a tape oxide core, but the rest is within the domain of non-minimum phase effects. It would need serious research IMO.
 

JohnRoberts

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The tape "mojo" is the result of several effects, of which magnetic saturation is certainly the dominant one, but also the way bias modifies it, self-erase effects and time modulation due to transport.
It is probably possible to simulate the former with a xfmr using a tape oxide core, but the rest is within the domain of non-minimum phase effects. It would need serious research IMO.
I don't want to encourage this, but could one just wad up a bunch of old magnetic tape and stick it inside a transformer in place of an iron core?

Asking for a friend.... :cool:

JR
 

abbey road d enfer

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I don't want to encourage this, but could one just wad up a bunch of old magnetic tape and stick it inside a transformer in place of an iron core?
As you know, that would make a very inefficient xfmr, but after all, the tape recording process is also very inefficient. I believe that would be a good direction for capturing the magnetic saturation effect, but not the rest of the artifacts.
 

gyraf

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soo... who'll be brave enough to wind a small toroid transformer on a core of spooled up 1/4" tape

..asking for a friend..

/Jakob E.
 

JAY X

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¡Interesting subject!... ¿How did it Rupert Neve in the portico series?

Jay x
 

Tubetec

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It sounds a bit preposterous to me to try and make a transformer core out of magnetic tape and I suspect it was with a heavy dose of irony John made the suggestion in the first place :p

In normal studio usage the tape flies past the heads at 15 or 30 ips , momentary overloads / tape saturation dont hang around in the vicinity of the heads , so probably recover time is quite fast . I did read something about using two tape heads ,face to face ,one to drive the signal into, one to pick it up again , might work to add some degree of colour , but hardly likely to give the balistics(if thats the right term ) of tape moving past heads . The rotating drum principle like used in a Binson echo might be one way of doing it without the usual wear , pops and clicks of tape loop echos , but your still dealing with motors and speed controlers and mechanicals.

Probably a lot simpler to get as good a 1/4 inch 3 head machine as you can within your budget and inconjunction with a DAW record both the direct(non tape) sound and the off tape (repro) signal and later re-align the time difference introduced by the tape path , now you can add in the desired amount of tape sound in parralel with your clean signal . Same idea Permo suggested in the G36 thread.

I suppose the million dollar question to those who rubbish anything other than 'doing the very best we can' with modern sound/electronics techniques is , what are your favourite sounding albums ?
 

Ricardus

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It sounds a bit preposterous to me to try and make a transformer core out of magnetic tape and I suspect it was with a heavy dose of irony John made the suggestion in the first place
I didn't think he was saying the tape itself, but the iron the tape is coated with. Is there no way to build a core out of that?
 

Tubetec

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Hi Ric ,
I guess you could find a solid iron oxide core material with similar properties to magnetic tape but I dont think sonically its ever going to have the same spongey quality as tape on the fly .

Im not going to bother re-tweeting Johns post #8 , but I guess he did qualify his remark by saying he wouldnt be encouraging it to begin with , caveat lector ?:unsure:
 

ccaudle

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simulate the former with a xfmr using a tape oxide core
o_O
So would that be considered a ferrite core transformer? ;)

Actually now that I looked it up barium ferrite is used to make ferrite magnets, and is used for some high coercivity tape formulations.
Probably data tape, I don't remember hearing about barium being used for audio tapes like cobalt and chromium were.
Not sure where you will be able to get a torroid or pot core of FeO or CrO2, that doesn't seem like an off the shelf item. Probably winding a transformer on a barium ferrite permanent magnet isn't quite what was suggested (although I guess you could put it in an oven and cook it at the curie temperature if you wanted to get back to just a barium ferrite torroid).

This is definitely one of those ideas that could be crazy or could be genius, and you have to test it to tell which it is. Whoever tries it first needs to report back and tell us which it is.
 

Tubetec

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Even back in the days of cassette tape , despite a gain in terms of s/n and a little bit extra HF extension ,chrome or metal never distorted quite as gracefully as ferric (iron) based formulations . The other thing was chrome and metal tapes are far more abrasive and caused more wear on the heads . At higher tape speeds typically found in studio gear the size of the particles in ferric didnt impose the same limitations on Hf response that they do at lower IPS' .
 

JohnRoberts

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Anybody who has listened to a single word I ever wrote, would know I don't believe in making distortion on purpose.

I throw this magnetic tape core idea out to the universe to chew on, then spit out.

Of course it wouldn't be a 1:1 mimic of tape saturation. Anyone seriously pursuing that would use DSP... but you have to admit a magnetic tape transformer core would be sexy and sell.

JR
 

Tubetec

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Whats your favourite sounding album John ? would you have tried and to tell the Beatles or Creedence to turn their amps down because they were producing too much THD ? :D
 

abbey road d enfer

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o_O
So would that be considered a ferrite core transformer? ;)
Ferrite and tape coating formulation are very different, in the sense the latter has high remanence, when the latter has very little.
In order to approximate the transfer of tape, one would use ultrasonic bias.
I guess you could put it in an oven and cook it at the curie temperature if you wanted to get back to just a barium ferrite torroid).
You would still get a core that has a too wide magnetizing curve for use as a xfmr.
 

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