Distortion: Acquired Taste or .......

Ethan Winer said:

About 30 years ago a company called Aphex came up with a distortion box for mix engineers. They called it the Aural Exciter, and its release was intentionally shrouded in mystery by Aphex. They wouldn't even sell the box. You had to rent it, and pay a per-minute license fee based on the length of the recordings it was used on! The first few years they even lied about what it does and how it works. They have since come clean, perhaps after someone else pulled back the curtain.

--Ethan

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I was going to mention the Aural Exciter, but I'm glad you did. We worked with those in broadcasting. So many pop/rock/top 40 stations use them ahead of their Optimod 8100As and 8400s to add that extra crispiness that makes the FM signal stand out on the dial. Well, at least until every OTHER top 40 station added one to their chain.

The tube vs. transistor debate becomes a non-sequitur when operating within the design limits. The simple rule is not to overdrive an amplifier. Tubes have a great function inside of a Marshall 100 guitar amp, since that's where the unique property of the way a tube saturates and interacts with the output transformer and feedback/back EMF from the loudspeaker all comes into play.

Way back in the '60s, I experimented with getting rid of the output transformer on amplifiers. A good ultralinear audio transformer was something only the well-heeled could afford. So I knew I had to find a way to drive a speaker directly without a transformer. Using low impedance triodes (6AS7s) in a push-pull/parallel configuration, and with a split rail solid state power supply for a low source impedance, I came up with a configuration that would provide about a 16-ohm output. I didn't have the money for more 6AS7s, and if I did, I feel confident I could have gotten it down to 8 or even 4 ohms for better damping. The amp was essentially flat from 10Hz to 250KHz and could pass a clean square wave from my Precision signal generator.

I found my old file drawer with the 'ancient' schematics and here's the driver and output stage config. I don't know what happened to the previous stages.. I think I had a 6SN7 phase inverter and a 6SL7 preamp stage on another sheet that seems to be lost...



This amp was a lot of fun and I had it driving my 18" McMurdo Silver electro dynamic speaker and a Bozak tweeter array and it was the cat's meow back in those days.

Great points Mark.

Mark (Basspig) Weiss said:

Many years ago, I recall reading about some testing where it was found that a little bit of noise added to a recording caused a controlled listener group to vote that they perceived more high frequency content in the music on that noise-added recording than on the same recording without the noise.

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Not unrelated, I believe that the added noise of analog tape is responsible for people thinking that analog is somehow "wider" than digital. If you think about it, the noise on the left and right channels is different, in stereo, and sounds wide all by itself. This is simple to prove by playing stereo pink noise and switching playback between stereo and mono. One sounds very wide, the other sounds mono. So adding stereo noise, even if fairly soft, adds an artifical dimension of width.

Sometimes the choice between a live orchestra and a recording results in the listeners preferring the recording over the real thing, because the real thing is relatively dry and neutral in comparison, whereas the recording might have added HF emphasis making it sound more 'airy'.

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I generally prefer a good classical recording to a live concert. There are very few seats in even a great auditorium that have the clarity and presence you get with good microphone placement. Not to mention the lack of distracting coughs and clothes rustling in non-live orchestra recordings.

One of my favorite tricks is me making an O.R.T.F stereo pair recording of me playing my violin

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I did something similar last year, with mixed results: Recorded Realism

--Ethan

Mark (Basspig) Weiss said:

Many years ago, I recall reading about some testing where it was found that a little bit of noise added to a recording caused a controlled listener group to vote that they perceived more high frequency content in the music on that noise-added recording than on the same recording without the noise.

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That is definitely true. We can show that with pictures. Here is a version of it I created for another discussion. The left image is the same as the right but with Gaussian noise added to it. Notice how the left image is sharper (look a the arm for example). Again, the only difference between the two halves is extra noise added to the left side:



Reason is pretty simple. Noise has high frequency content by definition (it is a broad spectrum of frequencies mixed together). So if you go from a situation where is not any/enough high frequencies to one where the noise is placed there, the subjectively, you will feel that the image/music all of a sudden has restored energy there. The above trick is used when an image is too of a low resolution for the level of enlargement. A bit of noise makes it appear to have higher resolution than it really has.

Aural Exciter.....excuse me while I throw up. I had a Numark DJ Mixer in the 90s that came with it. It was a quick way to clear the dance floor I tell ya.

Tomelex, what speakers do you use with your SET amps? I too like SET amps. I've had the same amp play with medium sensitivity speakers and good high sensitivity speakers. Funny thing is the stereotype about SET amps being slow and rolled off at the extremes applies to use with mid sensitivity speakers but with speakers with high sensitivity and impedance curves that are fairly flat, SETs (actually my WE 300Bs in particular) display no such rolling off or lack of kick.

I'm thinking the distortion might be more a function of the amp losing control of the drivers rather than being the amps own distortion.

Yes, that's supposed to be ground there, Tom. I often didn't draw it, as these were personal schematics to help me have a quick hard copy of what was going on in my head, so the details were often left out.


Amir, those two images look the same in terms of sharpness, to me. But I'm a cinematographer and do a lot of work with images and video signals, so my eye is trained to discriminate between noise, false contouring and real detail. The modulation transfer function is a valueable thing to understand, as it frees the mind and the eye to see deeper into reality. But then, I am the Keeper of the Purple Twilight.

I like popcorn with salt, if salt shadows the plain popcorn taste, so be it!

flez007 said:

I like popcorn with salt, if salt shadows the plain popcorn taste, so be it!

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To strain this metaphor to the next degree, that's not the issue. The issue is that if you build the salt into your pan, you get just as much salt in your cobbler as you do in your pop corn, exactly the same "color" in your balanced recordings as you get in your warm ones.

P

Agreed Phelonious... it all falls into personal preferences.