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Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-20 13:57:30

Hi, I just bought a POD X3 Live for comparing it with my old Tonelab SE. When playing around with some of the Robben Ford patches from the GuitarPort page, I was confused about some odd harmonics.

I tested more on this issue and came up with this: For some amp models e.g. 1998 Brit Plexi Bass 100, 1967 Class A30 Tob Boost, 1993 Match D30, 1960 Tiny Tweed, 1958 Tweed B-Man (this was the one from the Robben Ford patches) I get an additional odd harmonic tone when playing a single note. See the attached example, where I used the 1998 Brit Plexi Bass 100. The first tone is ok, the 2nd one - with increased drive - has a second odd harmonic tone.

As a workaround I can reduce the drive, then the second tone disappears. Those patches are unusable with high gain, from my point of view. Is this a common problem or rather intended?

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by tbrisson on 2010-02-20 17:54:07

Wolfgang, thanks for posting this.  I have noticed the same thing and posted about it some time ago with no answer. Hopefully a new question will get some attention. I've noticed the same harmonic thing on many of the Marshall models.

-Tim



Re: Odd Harmonics with some Amp Models when Increasing Drive
by pgm86 on 2010-02-20 18:50:19

hi, since you have a new pod x3, i'm guessing you have flash memory v 1.21 installed in your pod. in this flash memory, line 6 tweaked their tube amp models in terms of harmonics. here is the change log:

     POD X3/POD X3 Live/POD X3 Pro Flash Memory V1.21 Release Notes:

     Enhancements/Fixes:

  • Momentary display of the amp tone knobs has been added to POD X3 and POD X3 Live.
  • POD X3 Live and POD X3 Pro now support MIDI via the external MIDI jacks. Please see the MIDI CC Reference doc (posted in the Manuals section of www.line6.com for more info).
  • Setting POD X3 Live or POD X3 Pro MIDI Channel to Omni now causes the unit to respond to MIDI CCs on any channel. If in Dual Tone mode, both tones are affected by the MIDI CCs. While MIDI channel is set to Omni, Tone 1 MIDI CCs are sent out Channel 1 and Tone 2 MIDI CCs are sent out channel 2.
  • Tone Toggle has been added via MIDI. Please see the MIDI CC Reference doc (posted in the Manuals section of www.line6.com for more info).
  • Ultra-Cool Line 6 Power-up splash screen has been added to POD X3 and POD X3 Live.
  • Minor change to our digital tube models to improve higher harmonics.
  • POD X3 Live FX Loop parameters are now tweakable via the onboard expression pedal.
  • POD X3 room reflections no longer sweep from left to right.
  • Assignable FBV Loop switch can now control Tone 2 for POD X3 and POD X3 Pro.
  • Buttons test in Test Mode restored.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-20 23:48:19

I found that problem with the default settings of these amp models: 1966 Brit Plexi Bass 100, 1990 Brit J800, 1992 Brit J900 Dist, 1987 Brit Gain SLVRJ, 1967 Class A30 Top Boost, 1999 Match D40, 1965 Plexi 45, 1968 Plexi Variac D, 1960 Tiny Tweed, and 1958 Tweed B-Man. I started with an emtpy patch and browsed through the amp models without changing any parameter.

When I reduce the amp's drive, the problem dissapears (or is not recognizable). When I then add a tube distortion stomp box, the problem is back. So I think it is really related to the modelling of the "drive" parameter.

I started with flash memory version 1.21. Later I have updated to 2.00, no change.

I'm not yet sure if this is ok for me or if I should return the thing and stick to my tonelab.

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-20 23:56:16

Hi pgm86, I think your post did not make it to the forum. I got 'an E-Mail notification with a text intro, that is not visible here ...



Re: Odd Harmonics with some Amp Models when Increasing Drive
by Crusty_Old_Rocker on 2010-02-21 00:55:41

This is part of the accurate amp modelling that has been done by Line 6.  When they model an amp they model everything all the nuances and undertones that characterise each amp.

You will notice it a lot around the 12th fret with the Vox AC30 model and you will find vintage Vox owners talking about it.  Little Champ amps are also notorious for it.  They have also modeled the "cone cry" on the Marshalls too.

Take a look at this: http://www.thegearpage.net/board/archive/index.php/t-236949.html

Thesetones are part of what makes the amp models sound so authentic.  If you don't want those authentic nuances then try using the Line 6 original amp models, they are based on some of the more popular amp models but don't have all the idiosyncrasies of the originals.

Cheers,

Crusty



Re: Odd Harmonics with some Amp Models when Increasing Drive
by Crusty_Old_Rocker on 2010-02-21 01:03:05

wbruessler wrote:

I'm not yet sure if this is ok for me or if I should return the thing and stick to my tonelab.

Wolfgang

If you want amp modelling that doesn't sound authentic then go with the Tonelab.

Seriously, if you want authenitic modelled vintage tone the Line 6 modelling has it.  If however you want some weak, sanitised approximation then use another brand.

As I stated in the previous post, the Line 6 originals will give you sanitised valve amp tones, so you can use those instead.

BTW, I as a hobby I build point to point hand wired valve amps the old fashioned way, so I do know a bit about what I'm talking about.

Cheers,

Crusty



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-21 11:42:03

Hi Crusty, thanks for the explanation. So coming back to my original question: This ought to be an intended effect. Is there an official statement from Line 6 regarding this issue? You are referring to the "1967 Classic A30 Top Boost"? Yes indeed, that one shows the discussed ghost tones. I definitely prefer the "Class A-30 Fawn".

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by tbrisson on 2010-02-21 11:50:07

Crusty, thanks that makes sense.  I own some old amps and indeed the overtones are similar, and occur at the fretboard locations described in the post you linked. I've also notice the overtones are less noticeable at gigging levels, they only really 'pop' when playing at home.

I should have figured this out, as I noticed and *love* the Marshall speaker cone cry. Getting that effect going direct into a PA without blowing the patron's heads off is very cool!

Thanks for all your posts here, I've been successfully gigging my X3L for over a year due in part to your informative posts here. I played a corporate gig Saturday morning 8AM(!), walked in sleepy-eyed, plugged into PA and played-no problems!

-Tim



Re: Odd Harmonics with some Amp Models when Increasing Drive
by tubealot on 2010-02-21 13:24:25

Crusty, those ghost notes you are calling 'authenitic modelled vintage tone' are rather a symptom of a suboptimal power supply than a likeable feature. Common thing with old amps, where PS capacitors have aged and drifted too much. Ugly sub-harmonics appear the more you drive the amp, that's when your tech should do cap job to take care of that.

BTW, otherwise highly regarded Mojave Amps' early Sidewinder models had the problem fresh from the factory and could be cured by throwing a few dozen more uF at the B+. VOX ACxx amps are known to produce noticeable ghosting by design, that's why you try them all before you buy one (Les Paul anyone...). Old Marshalls often have curable ghosting, as do clones where PS cap values were chosen true to original specs instead of matching them to the non-original iron.

Every tube boffin will agree that prominent ghost notes are indicative of bad design or aging/mismatched components. The sacrilege of ripping out the beloved vintage mystic mojo '54 caps and replacing them with modern age parts is easily outweighed by the fact that after re-capping it you'll have better sound, bass response, s/n ratio and no more ghost notes.

Then again, we are talking about a DSP here, so it may well be an artifact of the algorithms used, Much like a root+5th power chord contains sum and diff frequencies of the original notes, a DSP algo is prone to producing weird (dis-)harmonics, aliasing, and any number of funny side-effects based on input frequency and sample rate ratio.

Given that L6 does not talk about fight club their technology (impulse response? component simulation?) it will remain a mystery whether they sampled (IMO) broken amps or the ghost notes are a by-product of the employed math.

TL;DR I will happily repair and sanitize your tube amp and get rid of ghost notes for good / I personally don't care for authentic reproduction of brokenness and would kill to get my hands on L6's devel software and solder around in the code a bit



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-21 23:12:58

So is there any Line6 statement about those ugly harmonics? If they really choose to emulate those "tube amp bugs", I would consider this as a bad decision. Luccily there are enough amp models without that "feature". Overall I'm happy with the device right now.

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by Crusty_Old_Rocker on 2010-02-22 01:24:21

wbruessler wrote:

So is there any Line6 statement about those ugly harmonics? If they really choose to emulate those "tube amp bugs", I would consider this as a bad decision. Luccily there are enough amp models without that "feature". Overall I'm happy with the device right now.

Wolfgang

There was an official statement from Line 6 way back when they first released the original POD and the article has long since disappeared from the internet.

What you call a bad decision I call an amazingly fantastic and clever decision.  Seriously what better way to model a vintage amp in a truly convincing way.  If you don't like the accurately modelled vintage amps then use the modern ones or the Line 6 originals.  There is something there for everyone.

Cheers,

Crusty



Re: Odd Harmonics with some Amp Models when Increasing Drive
by Crusty_Old_Rocker on 2010-02-22 01:42:11

You're right, they are perfect models of imperfect amps.  It is definitely the power capacitor idiocyncrasies that have been modelled.  They modelled the classic old amps the way they received them.  They didn't send them off to be updated and modified before modelling them.

As for your suggestion that it's the algorithms rather than accurate modelling - don't you think it's a massive coincidence that what you describe as digital artifacts only appears on the amp models that are known to produce these ghost notes, that the ghost notes sound the same as on the vintage originals and are most prominant under the same circumstances as the ghost notes on the vintage originals???  That some pretty selective digital artifacting, don't you think?

If you go and check out a Variax you will gain a deeper appreciation for just how clever Line 6 modelling really is.  Any experienced guitarist knows that the position of the neck pickup in the Fender Stratocaster results in it not properly picking up harmonics when played.  The Variax Strat model does exactly this.  What's seriously impressive is that if you move the position of that pickup using workbench you can move it to where it will pickup the string harmonics.  So Line 6 didn't just model the sound of the Strat they actually MODELLED THE PHYSICS of the guitar.  Just like they modelled the physics (including the old power caps) of the unadulterated vintage amps.

I would never suggest that Line 6 put the ghost notes into the modern amp models and render them un-authentic.  Just as I would not suggest they remove them from the vintage amp models, thus rendering them un-authentic.

People who don't like this level of accuracy in their amp models would probably be happier with a ZOOM or Behringer device.

Cheers,

Crusty



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-22 04:42:51

Hi Crusty,

this turns out to become a philosophical discussion. Personally, I'm going for a digial amp modeller in order to have an unexpensive, light weight, flexible pre amp. I just want to have the tone, I'm not interested in having that very authentic sound of a specific valve amp. Right now I'm probably preferring the Pod over the tonelab, since the pod has - from my personal view - way more usable sounds. The Pod's Wah is way better than the Wah of the Tonelab. In addition I have the XLR outputs, an Post-Amp-Compressor & EQ ... So I'm happy with it.

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by tubealot on 2010-02-22 07:31:18

I'm in too good a mood to take that Boringer remark personally. Believe it or not, some unsuspecting sap bought my Vamp2pro for 140Euros off ebay, to each his own.

Comparing pickup modeling with amp modeling does not compute on many levels.

Following your argument the removal/omission of microphonic feedback and stratitis from the pickup emu, renders them un-authentic too. /s

Of course I want the utmost level of accuracy, still, I wouldn't play a ghost note riddled 12xxx Plexi just because of it's nameplate and serial number. I'd take it to the bench and restore intended functionality, or buy a properly serviced amp in the first place.

Overly prominent ghosting cannot possibly be a desirable characteristic. If L6 is modeling/emulating/simulating/approximating a circuit down to the component level they might as well have fixed that.

To name a few, do you hear much ghosting on the Plexis of EVH, George Lynch, Michael Schenker? Why not? Because they have cherry picked a good one. Or hire a J. Arredondo or R. Smith et al to fix it.

The best view under the hood I found so far is http://www.gearwire.com/marcus-ryle.html

Hasanyone ever found more in depth info?

BTW, sanitized , have a listen to ZZ Top - Rhythmeen - Loaded.

Is this a broken amp, cable, overloaded input, master on 11?

Does it even matter in lieu of the outcome?

Note to self: shut up and play yer guitar.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by wbruessler on 2010-02-22 14:06:38

Hm, he says that they have tried hard to find the best amp of a series as the master sample for modelling. But they have even modelled so called "defects" in order to get authentic sounds ... but they would take out what might be potentially less desirable.

I would read it like this: When there is a speficic behavior of an amp series, they would try to reproduce it (so called signature sound). But when an certain effect is - by the community - more regarded as a fault, they would not resample that.

Nevertheless: In the manual I don't read something like "we have modelled those cool ghost notes" ;-)

Wolfgang



Re: Odd Harmonics with some Amp Models when Increasing Drive
by raab90 on 2010-02-22 16:59:32

>>To name a few, do you hear much ghosting on the Plexis of EVH, George Lynch, Michael Schenker? Why not? Because they have cherry picked a good one. Or hire a J. Arredondo or R. Smith et al to fix it.<<

  Because the guitars are mixed.

The sound changes a lot when mixed in a song.

And believe it or not, those harmonics are what in most cases makes you say "what a cool vibrato", when you hear a thick, strong note in old rock songs.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by tubealot on 2010-02-22 17:26:19

I can see how ghost notes can hide within a mix, but when it's time to put one foot on the monitor wedge and play Eruption I'd rather play an amp that doesn't have ghost notes a mere 10dB below signal level. Preferences. Taste. Whatever.

http://www.youtube.com/user/VanHalenStoreDOTcom

class="active_link" href="http://www.youtube.com/user/MasterTracks18">http://www.youtube.com/user/MasterTracks18

orgoogle "Guitar+Hero+Van+Halen+XBOX+Tracks+Normalized+Pitch+Tempo+fixed" (I'm not linking because of questionable legal status of those files)

Happy ghost hunting, peace.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by poynt99 on 2012-09-09 12:58:04

That's difficult to swallow.

Further research into the so-called "ghost-note" issue has revealed that it is extrememly unlikely that these discordant notes are ghost notes modeled from the amplifiers.

There are at least a dozen amplifier models in the POD X3 and Spider IV amplifier (and probably many more products) exhibiting this problem, and the suspicious fact that makes it difficult to believe these are modeled after the amplifier itself, is that every one of these models exhibits the exact same discordant note. One would expect each amplifier that was being modeled would exhibit its own unique-sounding artifact, yet this is NOT the case with these modeled amplifiers.

Have a listen for yourself and come to the only logical conclusion available.

PS. I have not yet listened to the POD HD, but I will report back what I find in this regard.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by poynt99 on 2012-09-10 15:57:33

Yep,

The POD HD has them as well.



Re: Odd Harmonics with some Amp Models when Increasing Drive
by poynt99 on 2012-09-12 19:27:09

Some positive news; it seems that many of the amplifier models in the POD HD have a "HUM" adjustment, and when set to 0%, most if not all of the ghost note disappears. Why hasn't anyone (hello L6, you out there?) suggested this?

Too bad this feature is not available in the POD X3.




The information above may not be current, and you should direct questions to the current forum or review the manual.