Exciters

[Spogg]

Hi Flowstoners!

I've been reading about exciters and I fancy having a go at making one.
I've read about the techniques and there appear to be various approaches, so I wondered if anyone had an opinion as to the "best" technique...

Cheers

Spogg

[RJHollins]

Hi Spogg

Not sure of 'the best' ... back in the daze, it was the APHEX AURUAL EXCITER.

During the '80s this was core to the, now classic, funk rhythm guitars ... STRAT>Aphex>1176

[martinvicanek]

Can't wait to see what you come up with, Spogg. My own attempts at this were not at all successful. I suppose the secret is in the delicate parameter tuning.

[RJHollins]

Trying to jog the memory back to 30+ years ago ...

I seem to recall analysis conversation that look to explain WHAT/HOW the APHEX Exciter worked.

One of the key points: The use of the 'exciter' did NOT raise the signal level. Therein was possible clues.

When one of the Techs pulled it up on the bench, he noted the waveform viewed on the scope. As the 'excite' level was raised, he noted that the high frequency did not go up in gain, but rather: The 'width' of the waveform was expanded [not the correct tech term].

Recalling ... it was his opinion that the observed Hi-FREQ enhancement was attributed to the extension [in time] that the hi-freqs were being presented. [almost in the way a 'digital delay' can extend a sound].

I confess ... this was quite some time ago. In fact ... in those daze, the APHEX AURAL EXCITER was not a commercial product for purchase. It was RENTED by the processing minute. It was years later when a commercial, rack mount unit was found in most every studio.

Spogg ... don't know if any of this is useful in any way. There have been several products released since [BBE Sonic Enhancer, etc], but the APHEX started it all. [as I look over and see a Nile Rodgers CD on the shelf]

[Spogg]

First off, many thanks to Martin and RJ for joining in!

@Martin: You've worried me mate! If you had not much success then what hope is there for me? Any chance you could tell me what you tried or even upload your attempts? Also, how did you assess the results?

Having spent some hours researching this topic the principle seems to resolve into the following procedure:

- Tune a variable static (unmodulated) HPF to target the range to be enhanced. This will be between 3-8 kHz typically
- Pass the HPF output through a non-linear transfer function (maybe tanh(x) ). This creates new and hopefully even-order harmonics.
- Mix this "distorted" signal back in with the incoming dry signal in an amount to suit the source material. Very easy to overdo this they say.

There are variations on this theme and they seem to all be in the harmonic distortion channel. For example you can compress the HPF output to get a more consistent drive into the non-linear stage. You can delay the dry signal slightly to bring the distorted signal timing forward, thus creating, supposedly, a more forward vocal in the mix. There is much talk of frequency-based phase shifting but this is generally thought to be manufacturer's hype since filters will do this anyway.

So, in conclusion, the 3 main controls for this process would be Tuning, "Drive" and Mix (like on the Aphex) with any others supplementing the detail of the effect.

The other method I came across:
- Tune a HPF filter (again)
- apply dynamic processing to it, typically compression
- mix it back in with the dry

This method doesn't create any new harmonics of course, so it can only modify the spectral balance of what's already there.

@RJ: I was interested by the engineer noting a widening of the waveform. This would probably be the case if the source was a sine wave going into the Aphex since the added harmonics would tend to alter the shape of the wave (assuming everything was in phase).

Flowstone provides a wonderful playground to experiment with these ideas without the risk of severe soldering iron burns, so I will do this of course and maybe make a Quilcom which gives what seems to me the best outcome.

What fun!

Cheers

Spogg

[martinvicanek]

@Martin: You've worried me mate! If you had not much success then what hope is there for me?

Ah, come on, you are being too modest. More than once have you demonstrated your creative ideas and put them into practice. That's why I am so keen to see what you accomplish next.

Any chance you could tell me what you tried or even upload your attempts? Also, how did you assess the results?

Nah, nothing serious or systematic. Certainly nothing that I kept, given that it just sounded distorted, not at all "exciting".