Coding Transformers

swurveman
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Coding Transformers Apr 27, 2016 7:48:51 GMT -6

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Post by swurveman on Apr 27, 2016 7:48:51 GMT -6

Can somebody explain how plugin coders can code a plugin that claims it provides the sound of a preamp's transformer? It just seems like the way the transformer behaves depends on the type of source it is presented with - soprano voice, bass, acoustic guitar etc. etc. So, I don't see how a code could imitate how a plugin could behave like the real thing with all the tones, notes, chords and textures it is presented with.

The cynic in me thinks it's an EQ being called a preamp. So, I'm asking because I don't want to be closed minded on these things. We don't discuss coding a lot here, but understanding at least some of it could help determine what is possible and what is not in the plugin world.

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svart
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Coding Transformers Apr 27, 2016 8:23:36 GMT -6

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Post by svart on Apr 27, 2016 8:23:36 GMT -6

I don't know how they do it, as I'm sure there are proprietary ways that each company does it, but I know how i'd do it.

I'd devise a battery of tests that encompass most of the normal working modes of the transformer/preamp and extract the difference of the input signal and the output signal.

The difference signal is the change that the UUT (unit under test) does to the input signal.

I'd do these:

High power signal (distortion/compression)
Low power signal (noise)
DC offset (asymmetrical clipping, flux saturation, etc)
Complex signal (Modulated tones, white/brown/pink/random noise)
Simple signal (Sine, sweep)
Impulse signal (transient, step response)
Forward tilt
Reverse tilt
IP2/IP3 (non-linearities and multiple tone mixing)
Phase/group delay

And more.

All these things characterized and then combined will likely give you a good approximation of how a complex system reacts to any given input signal and should allow a good imitation.

These are smart folks doing this, and there is some extremely complex design theory behind some of these things. It's not as simple as one might think.

Last Edit: Apr 27, 2016 8:24:43 GMT -6 by svart

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javamad
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Coding Transformers Apr 27, 2016 9:09:35 GMT -6 swurveman likes this

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Post by javamad on Apr 27, 2016 9:09:35 GMT -6

Hi,

I'm a programmer so I can speak to the coding aspect of it with a reasonable amount of certainty. That said I have made no plugins.

The procedure in my mind would be as follows.
1. Identify the device to be simulated
2. Identify the sample set of input signals you wish to simulate (more samples = more realism)
3. Set up your digital analytics at the input and output of the device to be simulated (setting up analytics at different stages withing the device would make the simulation more accurate and the calculation of the algorythms easier.)
4. Run each sample signal through and take your input and output readings, at each setting on the device ... so a *lot* of data to be collected.
5. Once you have the data, you can then analyse and discover the algorithms of what is changing in the signal with each component you have isolated in the device.

Once you have the algorithms you can then apply those changes to any new input signal and it should "sound like" you just ran it through the sample device. If you have done enough component analysis you can now create a user interface with knobs and buttons and apply the algorithms depending on the settings the user has adjusted to.
Note: the 'changes' in sound in digital audio are represented by changing some numbers within the limits of the sampling frequency the plugin is working at.

Now you know why its so expensive to develop these plugins. It would in fact be much cheaper to create a plugin to do random alterations to the signal .... but who on earth would buy that when we all want SSL Channel strips on our laptops!

Last Edit: Apr 27, 2016 9:13:46 GMT -6 by javamad

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swurveman
RGO Senior Member

Posts: 2,506

Coding Transformers Apr 27, 2016 9:11:59 GMT -6

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Post by swurveman on Apr 27, 2016 9:11:59 GMT -6

Apr 27, 2016 8:23:36 GMT -6 svart said:

I don't know how they do it, as I'm sure there are proprietary ways that each company does it, but I know how i'd do it.

I'd devise a battery of tests that encompass most of the normal working modes of the transformer/preamp and extract the difference of the input signal and the output signal.

The difference signal is the change that the UUT (unit under test) does to the input signal.

I'd do these:

High power signal (distortion/compression)
Low power signal (noise)
DC offset (asymmetrical clipping, flux saturation, etc)
Complex signal (Modulated tones, white/brown/pink/random noise)
Simple signal (Sine, sweep)
Impulse signal (transient, step response)
Forward tilt
Reverse tilt
IP2/IP3 (non-linearities and multiple tone mixing)
Phase/group delay

And more.

All these things characterized and then combined will likely give you a good approximation of how a complex system reacts to any given input signal and should allow a good imitation.

These are smart folks doing this, and there is some extremely complex design theory behind some of these things. It's not as simple as one might think.

Thanks for your explanation svart.

Would you recommend a good book for laymen as a start to understanding audio electronics?

Frank Johnson- Songwriter/Musician/Engineer
www.facebook.com/Songflowerrecording/

NoFilterChuck
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Coding Transformers Apr 27, 2016 10:02:54 GMT -6 swurveman likes this

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Post by NoFilterChuck on Apr 27, 2016 10:02:54 GMT -6

dspguide.com/

they use lots of FFTs and Convolution to apply a frequency curve to an input signal along with tailored noise.

www.uaudio.com/blog/cat/ask-the-doctors if you really want to nerd out and learn how UAD does it. Specifically: www.uaudio.com/blog/circuit-emulation-software/

Last Edit: Apr 27, 2016 10:03:47 GMT -6 by NoFilterChuck

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schmalzy Senior Member Posts: 580	Coding Transformers Apr 27, 2016 13:46:25 GMT -6 Quote Select Post Deselect Post Link to Post Back to Top Post by schmalzy on Apr 27, 2016 13:46:25 GMT -6 Maybe someone could contact the Kush Audio guys to see what they can tell us. They just released the Omega Transformer Plugins. I'm sure there's a little there they could reveal without giving away the farm.

mrholmes
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Coding Transformers Apr 27, 2016 18:54:54 GMT -6

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Post by mrholmes on Apr 27, 2016 18:54:54 GMT -6

To me the question is not how they do it, the question is how they work in a mix.
And to my surprise I use very often the UAD 1176s with compression set off to just get the in and output transformer mojo.

Its not exactly the same as with real ones but it sounds great too.

IMO it still makes sense to have access to some real transformer mojo.
Such as my WA 76 or my 1073 pre.

Post by swurveman on Apr 27, 2016 7:48:51 GMT -6

Post by svart on Apr 27, 2016 8:23:36 GMT -6

Post by javamad on Apr 27, 2016 9:09:35 GMT -6

Post by swurveman on Apr 27, 2016 9:11:59 GMT -6

Post by NoFilterChuck on Apr 27, 2016 10:02:54 GMT -6

Post by schmalzy on Apr 27, 2016 13:46:25 GMT -6

Post by mrholmes on Apr 27, 2016 18:54:54 GMT -6