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Ethan Winer article in Sound on Sound Effects Pedals, Units & Accessories
Old 9th December 2009
  #91
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Quote:
Originally Posted by Ethan Winer View Post
It's easy to prove that tape "compression" is a simple transfer curve. Are you familiar with the concept of pre-distortion? This was used in MCI and Scully recorders, and possibly other brands, to reduce distortion. The idea is to add the opposite curve in the record electronics, to partially overdrive the peaks before they're recorded onto tape. The result is lower distortion, and the key is that the pre-distortion must accurately reverse what the tape does. I wrote an article for R-e/p Magazine years ago showing a circuit that does this based on two diodes and a variable resistor:

Pre-Distortion Techniques

--Ethan
Got lots of respect for you Ethan, but no, no, no - it's a hell of a lot more complex than that! :-(
Old 9th December 2009
  #92
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Originally Posted by Paul Frindle View Post
Got lots of respect for you Ethan, but no, no, no - it's a hell of a lot more complex than that! :-(
LOL, I'd love it if you'd elaborate.

Also, my concern is the top 90 percent which affects most of what is heard. Differences 20+ dB down are mostly irrelevant IMO due to masking.

I'm willing to do an experiment to compare the "saturation" of two diodes versus analog tape. Even something as simple as a 1 KHz sine wave can show the transfer curve of each accurately. But all I have here is a cheap cassette deck. If y'all would be satisfied with a cassette deck I'll do it. Otherwise, I need someone near me to volunteer a decent quality analog recorder.

I'd record a sine wave to the analog recorder in 1 dB steps from maybe -10 to the onset off gross clipping. Then I'd play that back and capture the result digitally, to see how the playback level changes. Then I'd do the same with a simple diode circuit.

Before I go to all this trouble I need to know if the results of this test will be acceptable as proof. If it's not acceptable, please describe a test you would be happy with, and that is also practical.

Anyone who says it's not possible to test this gets a Fail. heh

--Ethan
Old 9th December 2009
  #93
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I think a simple sine wave test is way too simplistic and will tell you nothing of how music will sound through the circuit. You would have to capture real music and then do an A/B comparison.
Old 9th December 2009
  #94
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^^ Okay, fine. You're in NYC? Do you have a capable tape recorder?

--Ethan
Old 9th December 2009
  #95
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Quote:
Originally Posted by johnnyc View Post
You would have to capture real music and then do an A/B comparison.
Also Johnny, just to clarify. You said you're a degreed EE, yes? Are you saying you believe there's no objective way to assess the accuracy of an emulation? How about a triangle wave? How about five sine waves at disparate frequencies?

--Ethan
Old 9th December 2009
  #96
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Quote:
Originally Posted by Ethan Winer View Post
^^ Okay, fine. You're in NYC? Do you have a capable tape recorder?

--Ethan
I'm in LA but don't have a tape deck, even my beloved cassette deck no longer works..

In my past experiences building guitar amps I could gets things looking good on the scope, 2 might look identical (distorted) at 1kHz but when you played an actual guitar through them they sounded completely different.

To really prove your point you would really need to satisfy all the audio parameters which is a lot of work, so at that point might as well just use audio as the test, more revealing and more enjoyable.
Old 9th December 2009
  #97
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^^^ Okay, I confused JohnnyC with JohnNYC. heh

So does everyone here agree that real music through a cassette deck is acceptable to compare with, for posting blind audition files here?

--Ethan
Old 9th December 2009
  #98
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Quote:
Originally Posted by Ethan Winer View Post
Also Johnny, just to clarify. You said you're a degreed EE, yes? Are you saying you believe there's no objective way to assess the accuracy of an emulation?
--Ethan
yes

there is an objective way but i think it's more through listening. everyone is so fond of double blind tests (i'm not personally but i can why people are) so that would be the best way.

get some music, record through analog and then through emulation circuit digitally and see if they sound the same
Old 9th December 2009
  #99
Old 9th December 2009
  #100
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Quote:
Originally Posted by johnnyc View Post
get some music, record through analog and then through emulation circuit digitally and see if they sound the same
Ok so now I'm quoting myself haha.

Just wanted to mention that to really PROVE this it would need to be evaluated under all conditions, signal levels, etc. Definitely not an easy task.
Old 9th December 2009
  #101
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Null test a loop back of actual music through both. Use about 4 minutes of material. eg. 30 seconds drums, 30 seconds full mix, 30 seconds vocals, 30 seconds another mix. Get it to null? Pass. No null? Fail.

Simple as that.
Old 9th December 2009
  #102
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Are we looking at comparing the transfer curves only?

We should carefully define what we are trying to prove or disprove as specifically as possible. If the item up for consideration is whether or not one can accurately "model" the transfer curve of a specific ATR/tape formulation/bias combo, then let's establish this right up front, as well as what will not be tested by this experiment.

I think that the question of emulating the transfer characteristics should come before any other tests.

-Ben B

Last edited by Ben B; 9th December 2009 at 09:49 PM.. Reason: for clarity
Old 9th December 2009
  #103
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Quote:
Originally Posted by mobius.media View Post
Null test a loop back of actual music through both. Use about 4 minutes of material. eg. 30 seconds drums, 30 seconds full mix, 30 seconds vocals, 30 seconds another mix. Get it to null? Pass. No null? Fail.
Actually, after seeing your mostly valid point, I can see that a blind listening test is best. I'm not interested in nulling, and I don't expect a perfect null anyway. But a perfect null is not important. What really matters is if you and other 'slutz can reliably identify real tape from tape-sim. Note that I'll use either Cakewalk's basic tape-sim, or possibly Magneto, as I see fit. This is a lot easier for me than wiring up an electronic circuit, and can still prove the basic point. Neither of those tape-sims are very sophisticated, so that will prove if a realistic tape-sim is really so complicated that it's highly CPU intensive. I'm not back-pedaling! Just trying to be practical.

If using a cassette deck is acceptable, I'll sample some tape hiss and add that to the sim version. That won't affect the basic character of the emulation, but will keep people from being able to identify the real tape by hiss alone. I may also measure the frequency response of the tape recorder and apply that using an EQ plug-in to the sim version. It depends on how much tonal flexibility the tape-sims offer.

So do we all agree that a cassette deck with decent quality metal tape is acceptable? I agree we need to test drums, and a mix, etc.

--Ethan
Old 9th December 2009
  #104
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Quote:
Originally Posted by Ethan Winer View Post
Actually, after seeing your mostly valid point, I can see that a blind listening test is best. I'm not interested in nulling, and I don't expect a perfect null anyway. But a perfect null is not important. What really matters is if you and other 'slutz can reliably identify real tape from tape-sim. Note that I'll use either Cakewalk's basic tape-sim, or possibly Magneto, as I see fit. This is a lot easier for me than wiring up an electronic circuit, and can still prove the basic point. Neither of those tape-sims are very sophisticated, so that will prove if a realistic tape-sim is really so complicated that it's highly CPU intensive. I'm not back-pedaling! Just trying to be practical.
Yes, you are backpedaling.

Whether people can identify by name one or the other is an entirely different question than whether they are truly indistinguishable (ie. nulled).

If you have forfeited your prior point, and want to switch to an ABX test, in order to do a proper ABX blind identification test, all listeners must first be provided with a non-blind opportunity to familiarize themselves with A and B.

In other words, you must post a clearly labelled example of what each process sounds like first, then post an unlabelled one and ask people to decide if they can still identify which is which.

But you won't want to do it this way either, will you?
Old 9th December 2009
  #105
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Quote:
Originally Posted by mobius.media View Post
Yes, you are backpedaling.
Okay, you send me a real tape recorder of high quality and I'll build the diodes circuit. heh

Quote:
Whether people can identify by name one or the other is an entirely different question than whether they are truly indistinguishable (ie. nulled).
Agreed, but the real issue is whether tape-sims can do the job. Everything else is just mental masturbation. And perhaps arguing just to be disagreeable, which I see a lot of in these type of threads.

Quote:
you must post a clearly labelled example of what each process sounds like first, then post an unlabelled one and ask people to decide if they can still identify which is which.
Not at all, though I agree it's a good idea to post the original Wave file as well as the real and tape-sim copies. Then people can hear how the sound was changed, to help them guess which is which.

So is a cassette deck acceptable or not?

--Ethan
Old 9th December 2009
  #106
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Can I just jump in to say that (A) I'm really interested in hearing this and (B) why can't we just intellectualize what we hear and not make it any bigger than that. It's not a right or wrong issue. You understand the method of experimentation, you hear the results, you extrapolate your own conclusion.

Take a signal, even some recorded music - run it through a saturation plug, run it through tape, compare the two.

In fact I'd go as far as to say I'm not even interested in which one is really a plug and which is tape - I'm more interested in comparing the results to say "this one is doing this" while "this one is doing that."

Sometimes the process uncovers more than the solution. Just sayin.
Old 9th December 2009
  #107
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Quote:
Originally Posted by Ethan Winer View Post

Not at all, though I agree it's a good idea to post the original Wave file as well as the real and tape-sim copies. Then people can hear how the sound was changed, to help them guess which is which.

So is a cassette deck acceptable or not?

--Ethan
The objective as I see it is trying to prove that a tape-sim can perfectly recreate actual tape (in this case cassette), correct? With that being said, then guessing which is which will not prove the simulation to be accurate, only the null test will, or having them sound exactly the same.

This would still be a fun experiment, but if they sound different all it will show is one has a preferable (subjective) aesthetic to the other, which is cool too, but not the original premise of the discussion.
Old 9th December 2009
  #108
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Quote:
The real issue is whether tape-sims can do the job. Everything else is just mental masturbation. And perhaps arguing just to be disagreeable, which I see a lot of in these type of threads.
Yes, and I see most of that disagreeability from you. If your only point was that ITB processing and emulation can still roughly 'do the job', you should have stated it that way from the beginning. I doubt anyone would have very much disagreed.

The problem is your inclination to hyperbole and over-reaching claims about what is absolute, then further claims about 'only wanting to talk science' (despite prior claims not being remotely scientifically accurate).

Say what you mean. Say what is accurate. Don't just say things because they are big/sweeping/dramatic/controversial. End of disagreeability.
Old 9th December 2009
  #109
Quote:
Originally Posted by mobius.media View Post
Yes, and I see most of that disagreeability from you. If your only point was that ITB processing and emulation can still roughly 'do the job', you should have stated it that way from the beginning. I doubt anyone would have very much disagreed.

The problem is your inclination to hyperbole and over-reaching claims about what is absolute, then further claims about 'only wanting to talk science' (despite prior claims not being remotely scientifically accurate).

Say what you mean. Say what is accurate. Don't just say things because they are big/sweeping/dramatic/controversial. End of disagreeability.

what kind of test would you require...to resolve this.


cheers

Wiz
Old 9th December 2009
  #110
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madtheory's Avatar
I have a half track 15ips Revox PR99II with low mileage. I can't send it to you, but I could record test tones on it for the purpose of this experiment. Ampex 456.

Wouldn't it be more useful to record a slow sine sweep? Surely that would provide an accurate and useful transfer curve. I think it's a safe assumption that my M Audio converter is perfectly capable of reproducing a sine sweep accurately!

I have the Massey Tape sim also, so maybe I'll do my own comparisons and post them here. As Ethan points out, both recordings would have to hiss.

@mobius, I don't see how a null test is possible given the flutter of tape and the fact that accurate sync is impossible. Or are we calling it jitter? As for the phase issue, I think what Ethan was saying is that yes, there is a phase shift, but it's not audible because you don't have the original non phase shifted input signal to compare with. Is this right Ethan?

@Paul Frindle, can you post even a brief description of how complex it is?
Old 9th December 2009
  #111
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Quote:
Originally Posted by Wiz_Oz View Post
what kind of test would you require...to resolve this.

cheers

Wiz
It was stated by mobius earlier, post 101
Old 9th December 2009
  #112
Quote:
Originally Posted by johnnyc View Post
It was stated by mobius earlier, post 101

and so it is....


thanks for that...

fwiw


...i reckon null and blind test is the go...

cheers

Wiz
Old 9th December 2009
  #113
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Quote:
Originally Posted by Tomás Mulcahy View Post
Wouldn't it be more useful to record a slow sine sweep? Surely that would provide an accurate and useful transfer curve. I think it's a safe assumption that my M Audio converter is perfectly capable of reproducing a sine sweep accurately!

I have the Massey Tape sim also, so maybe I'll do my own comparisons and post them here. As Ethan points out, both recordings would have to hiss.

@Paul Frindle, can you post even a brief description of how complex it is?
A sine sweep is a start but will not tell you anything about the interaction among different frequencies, the transient response, dynamic range, etc.

I would love to hear tape vs sim files

Not speaking for Paul, but in general any non-linear simulation/model is inherently difficult and complex, even a simple transistor circuit. You can approximate things but it is unreasonable to take those approximations as being a perfect representation.
Old 9th December 2009
  #114
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Quote:
Originally Posted by Wiz_Oz View Post
what kind of test would you require...to resolve this.
In all honesty, I consider it resolved already. The subject of tape vs sim is interesting, but it's not at all why I felt compelled to post here (or in the other threads) in the first place.
Old 9th December 2009
  #115
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Quote:
Originally Posted by Ethan Winer View Post
Yes, you can hear phase shift while the amount of shift is changing
This is exactly what jitter is!!!!

Sorry we've been debating on 2 different thread so I kind of forgot where this one started and had to re-read some earlier posts

I propose we just start 2 new threads
1) Tape vs Tape-Sim - for people with access to both post the files and we can debate the differences
2) Audibility of Jitter - would be nice to do a bunch of loopbacks with various converters and see how different brands change internal vs external clocks
Old 10th December 2009
  #116
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Quote:
Originally Posted by johnnyc View Post
how different brands change internal vs external clocks
Not many...
Old 10th December 2009
  #117
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Quote:
Originally Posted by johnnyc View Post
The objective as I see it is trying to prove that a tape-sim can perfectly recreate actual tape
Quote:
Originally Posted by mobius.media View Post
If your only point was that ITB processing and emulation can still roughly 'do the job', you should have stated it that way from the beginning. I doubt anyone would have very much disagreed.
LOL, Mobius, that is exactly what I said at the beginning! The first time I mentioned tape-sims in this thread was in Post #20 where I wrote:

Quote:
Originally Posted by Ethan Winer View Post
it's important to keep the big picture in mind. There are lots of ways to get an effect, and they don't have to sound identical to be successful.
I never said tape-sims are identical to tape! It was you (and a few others) who disagreed just to disagree. Things went downhill quickly from there.

--Ethan
Old 10th December 2009
  #118
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Quote:
Originally Posted by johnnyc View Post
This is exactly what jitter is!!!!
Except that jitter is never audible, where varying phase shift from 0 through 1200 degrees is audible. heh

Quote:
Sorry we've been debating on 2 different thread so I kind of forgot where this one started and had to re-read some earlier posts
I do that all the time myself.

--Ethan
Old 10th December 2009
  #119
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Quote:
Originally Posted by Ethan Winer View Post
LOL, Mobius, that is exactly what I said at the beginning! The first time I mentioned tape-sims in this thread was in Post #20 where I wrote:
And that is fine.

Quote:
Originally Posted by Ethan Winer
I never said tape-sims are identical to tape! It was you (and a few others) who disagreed just to disagree. Things went downhill quickly from there.
Except:

Quote:
Originally Posted by Ethan Winer
I never talk about the artistic aspect of this stuff because that's entirely subjective. But when people say "plug-ins cannot do the same thing as tape" that is entirely objective and easy to prove or disprove. What tape does is easily quantified, and not complicated. It can be easily simulated with a plug-in, or a pair of diodes as shown in the article I linked above.
If you had said it can be "partially simulated" or "partially approximated", that would have been different. Why say "easily simulated" is you can't actually do it or haven't already proven it is possible? Just to be misleading and inflammatory?

Even Paul Frindle had post in disagreement. I guess he was just being disagreeable as well.

Also, again, the first sentence of that quote is false. You very often talk about your artistic preferences, as do we all. I don't know why you always feel the need to insist otherwise.
Old 10th December 2009
  #120
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IMHO Ethan's words mostly add to the education gearslutz should provide for the hungry. But the fact that a number of people disagree with him comes mostly from theory vs. experience. Not every theory takes every contributing factor into account, so some theories fall short. Maybe you side with the theory .. maybe you notice/hear things NOT in line with the theory... here we are.
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