Get rid of the fizz in multi-fx? (RadTone Harmonic Converger)

[JJRockford]

I read about a little box that would improve the tone of multi-fx such as Boss GT-8 or Line6 XT Live, called RadTone Harmonic Converger. Here is the review on harmony-central: http://reviews.harmony-central.com/reviews/Effects/product/RadTone/Harmonic+Converger/10/1

Does anyone have an idea about what this can be? I only guess, that since it is a passive box, it's not something very complicated, but my electronic skills aren't very good. Would be a great thing to try to build though!! Have a Boss GT-8 which a bought because it was the only multi-fx that provided a good harmonizer and some guitar synth sounds. It's sounds pretty good, but not as good as my previous Vox Valvetronix/Tonelab... :/ So something to improve the tone would be really welcomed.

[David]

JR:

It's not passive, it's not digital and it's DEFINITELY not cheap!  It's designed specifically to clean up and smooth out the audio output from the Boss GT series units.  I used a GT-3 for almost a year before I cashiered it.  After all the money I'd paid and all the frustration I'd endured trying to get good patches set up that did exactly what I wanted them to, I concluded that no GT-series unit was worth the extra cost of the HC, good though it might be.

It's intended for the gigging pro who's committed to the GT platform, has cash, but doesn't have the patience to program or tweak much...  IMHO.

[Processaurus]

Beside that is totally amazing and magical and worth every penny, it sounds like a multi-pole lowpass filter of sorts.  There are some DIY cab sim projects around that do that well.  The simplest low pass filter is a resistor and capacitor:
 

[JJRockford]

I thought I read that the HC needed no power, that's why I thought it was passive. So guess it's just me who missunderstood something, as usual

But I'm not quite sure I understand what you mean; You had a RadTone HC, but still didn't like any of the GT-pedals? There SHOULD be pretty huge difference between, lets say the GT-5 and the GT-8, since GT-8 is several years newer (compare software amp simulators from the 90s with todays Simulanalog GuitarSuite or NI GuitarCombos for example ). I have only tried the GT-8 though, so I'm not sure.

Anyway, I thought that the HC could be something like pretty narrow (high Q value) EQ and some sort of harmonic enchancer (something that adds harmonic overtones and maybe a little bit harmonic distorsion, like a tube).

Probably pretty silly reasons why I guess, but the first is because I read about someone who had achived the same results by adding a external (post) EQ.

Second guess is even for far-fetched, but it seems like the Vox Valvetronix/Tonelab series have been getting huge advantages from this; From what I understood, they added a valve at the end of the signal path, just before the transistor poweramp. Maybe just a psychological thing, I think that the Valvetronix amps sounds, if not lightyears, at least lightmonths better than other digital modellers in it's price range (and far above, like the Line6 Vetta-series).

And, I think this is important to point out, I'm not out for stealing or reveal Radleys secrets, just thought someone here could have an idea about how to build a similar fx-box? Most proffesional musicians I know would probably NOT spend 300 US$ in ordering some mystic magical box they haven't even tried, from the other side of the Atlantic Sea  (live in Sweden...).

[JJRockford]

Beside that is totally amazing and magical and worth every penny, it sounds like a multi-pole lowpass filter of sorts.  There are some DIY cab sim projects around that do that well.  The simplest low pass filter is a resistor and capacitor:
 

So you tried this thing as well?

What does "multi-pole lowpass filter"? (Remember, I'm a swede, or at least from Sweden!) A lowpass filter with several cutting frequensies?!!?

[d95err]

What does "multi-pole lowpass filter"? (Remember, I'm a swede, or at least from Sweden!) A lowpass filter with several cutting frequensies?!!?

A first order (or single pole) filter (like the schematic posted above) has a slope of -6dB per octave. E.g. if we have first order lowpass filter with a cutoff point of 1kHz, the signal level will be 6dB lower at 2kHz, 12dB lower at 4kHz, etc. A second order (double pole) filter will have 12dB reduction per octave, third order 18dB, etc.

So a "multi-pole" filter is a filter of second order or more.

[JJRockford]

What does "multi-pole lowpass filter"? (Remember, I'm a swede, or at least from Sweden!) A lowpass filter with several cutting frequensies?!!?

A first order (or single pole) filter (like the schematic posted above) has a slope of -6dB per octave. E.g. if we have first order lowpass filter with a cutoff point of 1kHz, the signal level will be 6dB lower at 2kHz, 12dB lower at 4kHz, etc. A second order (double pole) filter will have 12dB reduction per octave, third order 18dB, etc.

So a "multi-pole" filter is a filter of second order or more.

So it's like adjusting the Q value?

[David]

I thought I read that the HC needed no power, that's why I thought it was passive. So guess it's just me who missunderstood something, as usual

But I'm not quite sure I understand what you mean; You had a RadTone HC, but still didn't like any of the GT-pedals? There SHOULD be pretty huge difference between, lets say the GT-5 and the GT-8, since GT-8 is several years newer (compare software amp simulators from the 90s with todays Simulanalog GuitarSuite or NI GuitarCombos for example ). I have only tried the GT-8 though, so I'm not sure.

Anyway, I thought that the HC could be something like pretty narrow (high Q value) EQ and some sort of harmonic enchancer (something that adds harmonic overtones and maybe a little bit harmonic distorsion, like a tube).

Probably pretty silly reasons why I guess, but the first is because I read about someone who had achived the same results by adding a external (post) EQ.

Second guess is even for far-fetched, but it seems like the Vox Valvetronix/Tonelab series have been getting huge advantages from this; From what I understood, they added a valve at the end of the signal path, just before the transistor poweramp. Maybe just a psychological thing, I think that the Valvetronix amps sounds, if not lightyears, at least lightmonths better than other digital modellers in it's price range (and far above, like the Line6 Vetta-series).

And, I think this is important to point out, I'm not out for stealing or reveal Radleys secrets, just thought someone here could have an idea about how to build a similar fx-box? Most proffesional musicians I know would probably NOT spend 300 US$ in ordering some mystic magical box they haven't even tried, from the other side of the Atlantic Sea  (live in Sweden...).

No, not quite.  I had a GT-3.  It would do the fizzy thing just like its other GT cousins.  I belonged to the Boss GT forum at the time that Rad first released the thing.  He set a price tag of something like $200 or $300 on it.  I decided that I didn't like the GT enough to "fix" its sound.  I went back to analog and I am a much happier man.

[lvs]

I used a spare feedback destroyer to alleviate this problem. It contains a set of parametric filters that can be quite narrow. For each filter, I first set Q and A high, and hitting a chord through a gainy patch, I manually changed F until I heard a fizz jump out. Then I decreased A until that frequency wasn't disturbing anymore. And so on with the other filters, until all the fizz frequencies were found. But putting the destroyer in bypass mode revealed that alltogether the difference was a bit drastic, so I made a few different patches on the destroyer, containing the same filter frequencies but with various levels of attenuation. The GTs already being tweaking galore themselves, I can imagine one could ask for a simpler method. Besides that, I can't tell how it compares to different approaches, but the results weren't half bad.  I think you can get some idea how a destroyer (or a different device containing parametric filters) would work for you without a financial effort : get some free software from the web - a parametric EQ plugin and something to host it shouldn't be impossible to find - and connect the GT output to the PC's soundcard.

[Joe Kramer]

Go to Edcor and get yourself a 10K:10k transformer.

http://www.edcorusa.com/products/transformers/pc/index.html

That might help clean up the digital fizz.

Interesting how that HC box "self-destructs" if you try and take it apart.  I'd bet money there's a transformer in there.

[JJRockford]

Would a transformer work without power? I read a little bit more about the selfdestructing-thing; Think someones missunderstood this a little, from what I understood it's just that the HC interior is hidden in a plastic mass (like Greg Fryer and Pete Cornish do...). But of course, if you try to remove the plastic, there is probably a pretty big chance that the construction will be destroyed!!

Will definitly test the GT-8 with a parametic filter through my computer, haven't thought of that at all. Bought the GT-8 only for live purpose (use software amps for recording).

My first thought was too that it was some sort of filter. Spend some hours yesterday reading about this thing; The guy who builts them have no homepage, no pics, no soundclips. Only thing avaible is a few (not flawless...) mp3s that people who use the thing uploaded on different pages on their own. Anyway, someone who analyzed the files was talking about that it seemed like the HC also affected the phase in some way. This, along with that the constructor wrote somewhere that the HC was mainly for direct recording, and not that nessecary if you used an amp, made me think that it maybe could be something like a speaker cab simulator? Should try it with my H&K Redbox Pro next week (it's in our rehearsal room right now) and see what happens.

What passive curcuit do you think could make something sound more tube-like?

Which I could use analog stuff as well... But I guess I have to wait until some company release a harmonizer which is just as versatile as the one in GT-8, and don't cost as much as an Eventide!!!

[Joe Kramer]

Hey JJR,

I wouldn't be the expert on this subject by any stretch, but here's what I know.  Transformers have an inherent bandpass effect--a rolloff of the lows and highs.  Depending on how good/expensive the transformer is, the bandpass width can be smoother and/or more extended.  Because the aliasing effects of digital might add ugly high harmonics, I would hazard a guess that a halfway decent transformer might naturally mitigate some of that ugliness.  Transformers also add a small amount of benign distortion that many people (myself included) find pleasing to the ear.  And yes, in a coupling application, a transformer would be totally passive.

Here's an informative thread about transformers:

http://www.diystompboxes.com/smfforum/index.php?topic=40603.0

And lots of useful info/schematics here:

http://www.jensen-transformers.com/

Hope that helps!

Joe

[r080]

Recent development that I haven't seen yet here:

A guy from Fractal Audio got hold of a Harmonic Converger and characterized it.

http://uk.line6.com/support/thread.jspa?messageID=50450&tstart=0

[ANDYEFFECT]

schematic?

[puretube]

does that "fizz" appear in all and every of the effects, or only in those where "dry" is being mixed with "wet"?
(like in flangers, phasers, delays, and reverbs, etc.).

sorry for this digital noobs`question, if this should be an obvious phenomenon known to everyone that uses such machines...