‘Aphex exciter’ effect: the hidden “holy grail” of audiophilism?

[Philbo King]

Being around as an audio enthusiast for a while I noticed a few things.

1) Besides some general regulations on electronics and a company’s own definition of looks and quality, it does not seem that there are any regulations on what an amp should be or how it should measure etc.

2. Audiophiles like to mention that everything should be as 'direct' and flat as possible. Given that; an outsider would think.. “fine, an amp is an amp and now all equipment should sound the same”. But that is not what keeps the world going round. Amp X can sound like Amp Y with the bass dial 1 click ahead. Marketed by reviewers as ‘Amp X seems to be made for music genre x and y for genre y). As long as it is baked in, everything is fine.

3. Audiophiles seem to embrace the tube sound and like it when equipment stands out from the rest and has a bit of sparkle.

It was on this forum in another topic that I posted about that descriptions of measurements of the enhancer effect of class D Yamaha amps matches the description of the valve sound. That “sparkle in the midrange” and extra groove in the bass range. And Yamaha’s description came down to what is described in the link below.

Exciter (effect) - Wikipedia

en.m.wikipedia.org

• Making vocals sound more "breathy". This is why the original product was called an Aural Exciter
• Enhancing dull recordings, especially analog reel-to-reel tape recordings that have lost their "sparkle" due to repeated overdubs
• Restoring old recordings by simulating lost spectral content

And another source, a must-read in my opinion

Behind The Aphex Aural Exciter (Sound On Sound, Aug 1993)

Marvin Caesar: The Aphex Story

www.muzines.co.uk

I didn’t know tube amps were utilising a variation of this effect, but it seems it is what historically set the standard for ‘the valve sound’.

Now audiophiles seem to hate physical or digital switches due to the “everything should be direct” opinion.

But… when a variation of that same effect is ‘baked into’ the amp without emphasising it is; and if they don’t have to toggle a switch, that amp certainly seems to get an own identity and emotional value to audiophiles.

When I read descriptions of some vintage class A-B that “sound like valves” or have “a distinct sound” that are sought after, I now suggest the chances are high they utilise a variation of the Aphex exciter effect.

Bit like the metaphor of an illusionist telling how the trick works, versus a wonder healer that claims “this is magic”.

Disclaimer: This is to create a foundation to a myth of magic, not to trash the effect. I personally really like applied variations of this effect. My Yamaha Wxa50 has it and the vintage Sansui AU101 I bought recently might also have one (‘baked in’). I mainly bought the latter because it is a perfect design match to my Denton 85th loudspeakers. It is now in revision

Opinions? Or do you have gear utilising this effect in some way and do you like it or dislike it?

As I recall, this effect delayed bass slightly so the highs became clearer due to precedence effect. It was briefly popular in the 80s / 90s in recording studios. But like any effect, if used to excess it causes listening fatigue.

 

[voodooless]

an outsider would think.. “fine, an amp is an amp and now all equipment should sound the same”. But that is not what keeps the world going round.

So it’s all about the money then…

 

[AJM1981]

The holy grail reference was by the way a blink to the praise and market prices of historical amplifiers with their own "character in sound" as an amp should not add harmonic distortion in theory, but in reality spicing up things up is quite ok in my opinion.

So it’s all about the money then…

Obviously

Only difference is that the "hi-fi world" has loads of space for applying these marginal illusions and price tag value on emotional judgement.

When entering the reference monitor market, it is a different ball game. The fact that one can buy a monitor of a similar hi-fi loudspeaker (JBL for example) for 1/3rd or less of the price gives a hint. Also the reference monitor world is not written in stone but often it seems audiophiles confuse the "guidelines" of these two worlds.

 

[AdVis]

Ugh, I remember that abomination. It was touted as the best thing ever happening to studio's and IIRC you couldn't actually buy the unit, you had to rent it and it had a horrid price tag.

And of course some very nice albums were recorded using it in that time, which ruined them completely as there is no way to get rid of that over-bright raspy sound.

They did proudly list it on the album cover if it was used.

 

[AJM1981]

Ugh, I remember that abomination. It was touted as the best thing ever happening to studio's and IIRC you couldn't actually buy the unit, you had to rent it and it had a horrid price tag.

And of course some very nice albums were recorded using it in that time, which ruined them completely as there is no way to get rid of that over-bright raspy sound.

They did proudly list it on the album cover if it was used.

Interesting. I came across a couple of albums. With the disclaimer that applying an effect slightly on the hi-fi side to a degree that it is only barely noticeable is another thing compared to being able to go wild in turning knobs on a module.

For producers that time it sounds like "The best thing" before gated reverb : P

 

[dzerig]

Being around as an audio enthusiast for a while I noticed a few things.

1) Besides some general regulations on electronics and a company’s own definition of looks and quality, it does not seem that there are any regulations on what an amp should be or how it should measure etc.

The problem is there is only one definition for the performance of gear here: sinad. 123 sinads is better than 116 sinads yet most people reading the sinad information have zero idea how many sinads they can hear?

It's like saying to get to the moon we need 116 sinad, and saying a 123 sinad rocket is superior because it can go to mars. If we are going to the moon, why is more than 116 sinad better?

If the human limits of hearing is 116 sinad (at the theoretical level) why is 123 sinad 'better engineered" and not 'over engineered'?

 

[Anton S]

It's a studio effect and anything goes in the creative process.

...

The implication here being that the creative process ends - or should end - at this point? That playback should be a passive experience confined to reproducing as faithfully as possible exactly what's been recorded onto the commercial product? Hogwash!

 

[MaxwellsEq]

Having worked (as an EE) on a lot of pre-digital studio enhancement kit, the issue was that they all added noise and had imperfect transfer functions even when effects were set to zero. The more effects, the more the impact. Of course this may still have been lower than tape noise, but in those days, we couldn't see noise spectra, so it's quite likely the noise was additive, not masked.

 

[Jaxjax]

 

[phoenixdogfan]

View attachment 357981
source: https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1977-12.pdf pg. 99 of the magazine

Full disclosure: I do like the way this album sounds -- but it's got an undeniable late-70s/southern California sheen to it.

EDIT: Dang, that was a stupid review!
Carmelita is one of my favorite-est Warren Zevon songs of all of his oeuvre -- and I'd consider myself a significant fan, even at this late date.

Utter idiocy. Everybody knows about the Pioneer Chicken Shack even if you've never lived in LA. And that album holds your attention because it's sung by Linda Ronstadt at her artistic peak ('nuff ced) not because of the crap in the production chain.

 

[mhardy6647]

Utter idiocy. Everybody knows about the Pioneer Chicken Shack even if you've never lived in LA. And that album holds your attention because it's sung by Linda Ronstadt at her artistic peak ('nuff ced) not because of the crap in the production chain.

Told ya!
Yes, I remember Pioneer Chicken even in northern CA when we lived there -- and, yes, it's a very, very good pop record, Aphex notwithstanding. Sold a zillion copies. Mrs. H & I both have copies on LP from way back when -- and there's not a lot of overlap in our record collections.

 

[AJM1981]

My 70s Sansui Au101 solid state also seems to have some of the “up-spicing”. Lots of emphasis on the “byproducts” of instruments and vocals (air flow, timbre, scratches etc) that “sweet” sound that was projected on valves as well. Not too surprising as it was produced shortly Sansui’s valve amps.

This is all kind of sketchy in quotes, but I remember a quote about filmsound (paraphrased) that sound is tailored to not be realistic but to amplify its realism. I get the idea that this on another level is also kind of going on and what the Yamaha Wxa50 does with its digital enhancer switch.

Another quote recently is that “valve amps these days don’t really sound like valve amps anymore”.

If it is really true that to a margin the exciter effect is somehow applied. Then I wonder what made that shift happen from applying a sense of extra realism on one side to “as it is recorded” on the other one. As a signature sound might have nothing to do with the kind of amp in the first place (an integrated amp and a class D can sound like a valve amp).

Was it a user-opinion shift? (Everything should be flat, no aides etc) or was it that the exciter effect would be reserved for top-end lines only in order to not only create a difference in the amount of bells and whistles in switches, but rather to mark a line of audible difference between models.

A weird but probably useful parallel as a metaphor I would like to make is with photography. That Adobe RGB always seemed to make colours more pronounced, maybe even a bit eye candy to a minor margin, while some might argue that a “flat” color scheme is more appropriate.

Perhaps above applies more to the saturation, but an enhancement of “structure” seems quite applicable to what the exciter effect does.

Interesting phenomena none the less..

 

[Smaestro]

So now you've got me wondering how this effect compares to the rich buttery sound of a single-ended transformer coupled amplifier using a direct-heated power triode for output.

The difference between an Exciter and all Exciter VST plugins is that they inject harmonics independent of volume. It was pointed out to me in another thread that there are volume dependent harmonic injector VST's out there, but I haven't found one yet.

Let me clear this up a bit.

Exciters
Many exciter plugins work on level peaks. It's simply called saturation. Excitation is nothing more than subtle saturation, usually applied on the upper mids and highs. (But can also be done on bass).

As Level dependent saturation is the behavior of any piece of equipment reaching the end of its headroom. Tubes amp smoothly approach that 'break up' in a more pleasing way than solid state gear. Therefore any tube simulator will do level dependent excitation.

Edit: Btw this does not mean that all tube Hi-Fi amps will add saturation. If designed that peak levels never reach the headroom limit, no added harmonics will be added.

There are millions of VST's. Two free ones to try:

Softube Saturation Knob

Saturation Knob

Free VST analog distortion plugin. Fattens up drums and bass, adds harmonics and shimmer to vocals. Add grit and get your best mix with a single knob.

www.softube.com

Very simple, just one amount knob, and a type switch to select between for full bandwidth saturation, or only on the low, or only on the high frequencies.

VOS ThrillseekerXTC

ThrillseekerXTC mkII released

ThrillseekerXTC – bringing mojo back ThrillseekerXTC mkII is a psychoacoustic audio exciter based on a parallel dynamic equalizer circuit. It takes our hearing sensitivity into account especi…

varietyofsound.wordpress.com

The mojo and drive section specifically are an exciter. The Low, Mid and Air sections are an EQ with additional saturation as well, so you have multiple ways of adding harmonics.

Transformers.
Level dependent saturation is something different than transformer saturation. The main difference is that a transformer takes time to saturate, so it's not level, but the integral of level and time that decides wether a transformer will saturate or not. This will leave the beginning of transients a bit more intact, and it sounds different. (But very subtly different).


Two free exciter VST's that do this are
VOS Tessla Pro

TesslaPRO mkIV released

all the analog goodness in subtle doses Designed for mixing and mastering engineers navigating the digital realm, TesslaPRO strikes a balance between analogue character and modern precision. By rei…

varietyofsound.wordpress.com

You need to check the manual to see what it does exactly, I forgot. I think it was that turning Transient counterclockwise accentuates transients, and clockwise smooths transients.

TDR SlickEQ

TDR VOS SlickEQ | Tokyo Dawn Records

A mixing/mastering equalizer designed for intuitive use, musical flexibility and impeccable sound.

www.tokyodawn.net

On the right where it says "Out stage > Lineair", you can select a few transformer models for saturation (with Lineair begin the clean option). Set the calibration box below it to as high as it'll go (16dB) I think, to really pump out saturation. Output level will not increase btw, it's just an internal value.

 

[kemmler3D]

Let me clear this up a bit.

Exciters
Many exciter plugins work on level peaks. It's simply called saturation. Excitation is nothing more than subtle saturation, usually applied on the upper mids and highs. (But can also be done on bass).

As Level dependent saturation is the behavior of any piece of equipment reaching the end of its headroom. Tubes amp smoothly approach that 'break up' in a more pleasing way than solid state gear. Therefore any tube simulator will do level dependent excitation.

Edit: Btw this does not mean that all tube Hi-Fi amps will add saturation. If designed that peak levels never reach the headroom limit, no added harmonics will be added.

There are millions of VST's. Two free ones to try:

Softube Saturation Knob

Saturation Knob

Free VST analog distortion plugin. Fattens up drums and bass, adds harmonics and shimmer to vocals. Add grit and get your best mix with a single knob.

www.softube.com

Very simple, just one amount knob, and a type switch to select between for full bandwidth saturation, or only on the low, or only on the high frequencies.

VOS ThrillseekerXTC

ThrillseekerXTC mkII released

ThrillseekerXTC – bringing mojo back ThrillseekerXTC mkII is a psychoacoustic audio exciter based on a parallel dynamic equalizer circuit. It takes our hearing sensitivity into account especi…

varietyofsound.wordpress.com

The mojo and drive section specifically are an exciter. The Low, Mid and Air sections are an EQ with additional saturation as well, so you have multiple ways of adding harmonics.

Transformers.
Level dependent saturation is something different than transformer saturation. The main difference is that a transformer takes time to saturate, so it's not level, but the integral of level and time that decides wether a transformer will saturate or not. This will leave the beginning of transients a bit more intact, and it sounds different. (But very subtly different).


Two free exciter VST's that do this are
VOS Tessla Pro

TesslaPRO mkIV released

all the analog goodness in subtle doses Designed for mixing and mastering engineers navigating the digital realm, TesslaPRO strikes a balance between analogue character and modern precision. By rei…

varietyofsound.wordpress.com

You need to check the manual to see what it does exactly, I forgot. I think it was that turning Transient counterclockwise accentuates transients, and clockwise smooths transients.

TDR SlickEQ

TDR VOS SlickEQ | Tokyo Dawn Records

A mixing/mastering equalizer designed for intuitive use, musical flexibility and impeccable sound.

www.tokyodawn.net

On the right where it says "Out stage > Lineair", you can select a few transformer models for saturation (with Lineair begin the clean option). Set the calibration box below it to as high as it'll go (16dB) I think, to really pump out saturation. Output level will not increase btw, it's just an internal value.

Great examples, I mention VOS all the time for people who are interested in spicing up their sound, but oddly enough the people who are interested in that are rarely interested in cheap ways to do it. An interesting psychological / economic experiment in there somewhere...

 

[Timcognito]

There are other types of exciters you know:

 

[tmtomh]

The implication here being that the creative process ends - or should end - at this point? That playback should be a passive experience confined to reproducing as faithfully as possible exactly what's been recorded onto the commercial product? Hogwash!

If you like the effect of this or any other effect on your playback setup, then by all means use it and enjoy - the entire point of this hobby is to enjoy listening to music.

To the subject of the thread, though - is an exciter the "hidden holy grail of audiophilism" - the answer would have to be No because it doesn't restore anything or enhance fidelity; it's an additive effect. It's "creative" as you say. Nothing wrong with that of course - again, use one if you like its effects.

With that said, I've never felt the need or desire to add harmonics to the music I play on my system.

One interesting application of an exciter I've heard (and experimented with myself) is on bootleg recordings, specifically old 1970s Led Zeppelin soundboard recordings where the combination of the recording gear/technology of the time, possible azimuth misalignment, and generational loss from dubbing, result in an attenuated high end, and in some cases entirely missing harmonics for the high-hats/cymbals.

An exciter plug-in can add much-needed sparkle and harmonics to such recordings, and you could even argue that in such a case the exciter is a kind of forensic restoration tool that does potentially add to the fidelity - for example we know with 100% certainty that cymbals do have audible harmonics and we also know with 100% certainty that when those harmonics are missing from an old bootleg source, it's not about artistic intention.

The problem, though, is that the exciter plugin adds harmonics to everything. Even if you restrict the volume level and frequency range, it still adds harmonics to the entire sound at those frequencies and those volumes. So you get all kinds of added harmonic distortion of... existing harmonic distortion in the source. And it sounds awful and becomes super-fatiguing to listen to after a few minutes in my experience.

So for me - and this is just my personal experience and preference - the only recordings screwed up enough to need or benefit from an exciter are also screwed up in other ways that usually make an exciter do as much or more harm than good.

Now, an AI-based version of an exciter that could more accurately distinguish between music and distortion on an old source - that might be quite useful for certain very specific restoration projects.

 

[Smaestro]

Great examples, I mention VOS all the time for people who are interested in spicing up their sound, but oddly enough the people who are interested in that are rarely interested in cheap ways to do it. An interesting psychological / economic experiment in there somewhere...

Haha absolutely! I have the same experience. VOS is an honest developer, I've downloaded all his plugins in case he one day decides to call it quits.
I've come across plugins that add 1dB just by turning them on, and people swear it sounds great. Good saturation can't be that noticeable people. A higher price and a nicer interface is just so tempting it seems.

 

[Smaestro]

If you like the effect of this or any other effect on your playback setup, then by all means use it and enjoy - the entire point of this hobby is to enjoy listening to music.

To the subject of the thread, though - is an exciter the "hidden holy grail of audiophilism" - the answer would have to be No because it doesn't restore anything or enhance fidelity; it's an additive effect. It's "creative" as you say. Nothing wrong with that of course - again, use one if you like its effects.

With that said, I've never felt the need or desire to add harmonics to the music I play on my system.

One interesting application of an exciter I've heard (and experimented with myself) is on bootleg recordings, specifically old 1970s Led Zeppelin soundboard recordings where the combination of the recording gear/technology of the time, possible azimuth misalignment, and generational loss from dubbing, result in an attenuated high end, and in some cases entirely missing harmonics for the high-hats/cymbals.

An exciter plug-in can add much-needed sparkle and harmonics to such recordings, and you could even argue that in such a case the exciter is a kind of forensic restoration tool that does potentially add to the fidelity - for example we know with 100% certainty that cymbals do have audible harmonics and we also know with 100% certainty that when those harmonics are missing from an old bootleg source, it's not about artistic intention.

The problem, though, is that the exciter plugin adds harmonics to everything. Even if you restrict the volume level and frequency range, it still adds harmonics to the entire sound at those frequencies and those volumes. So you get all kinds of added harmonic distortion of... existing harmonic distortion in the source. And it sounds awful and becomes super-fatiguing to listen to after a few minutes in my experience.

So for me - and this is just my personal experience and preference - the only recordings screwed up enough to need or benefit from an exciter are also screwed up in other ways that usually make an exciter do as much or more harm than good.

Now, an AI-based version of an exciter that could more accurately distinguish between music and distortion on an old source - that might be quite useful for certain very specific restoration projects.

This already exists. Mastering exciters (software: TDR SlickEQ Mastering https://www.tokyodawn.net/tdr-slickeq-m/) add saturation while filtering out nasty IMD. If you need to go really deep on your full spectrum (a full song), than this will let you go much further than a traditional exciter.

 

[anphex]

SMSL has some DACs that allow for Sound Color, and there are options for emulating actually scientificaly ideal tube amps, creating only perfect 2nd harmonics, no bad 3rd harmonics.

So if you wanted to, this option could beat a +100k tube amp easily, made possible by one single neat chip. But for me this sound color option, even if scientifically perfect, causes faster hearing fatigue.

 

[tmtomh]

This already exists. Mastering exciters (software: TDR SlickEQ Mastering https://www.tokyodawn.net/tdr-slickeq-m/) add saturation while filtering out nasty IMD. If you need to go really deep on your full spectrum (a full song), than this will let you go much further than a traditional exciter.

Interesting - thanks!