http://lamkins-guitar.com/music/article/hd500
David Lamkins picked up his first guitar a long time ago. As best he can recall the year was 1967: the year of the Summer of Love. Four decades later David has conjured up an amalgam of folk, rock and jazz solo guitar music for the occasional intimate Portland audience.
location: Portland, OR USA

Facets: Line6, digital, evaluation, review, technology, @musings info
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Line6 Pod HD500

Here's the story of my five days spent with a Line6 Pod HD500. If you're impatient, I'll save you a lot of reading: there's a lot to like about the HD500, but not enough for me to spend $425 (I had a fifteen percent discount coupon).

I arrived at Guitar Center on a recent Saturday morning shortly after opening, before the metal kids all got their `rents to taxi them in from the `burbs. I had the better part of an hour to play an HD500 through headphones without any audible distrctions.

I'm glad that I had read the HD500 manual ahead of time: that made it easy for me to set up a patch that I'd be likely to play. I didn't spend any of my time at the store auditioning presets. The HD500 sounded "good enough", so I bought one to take home.

This was the first time I've seen an HD out of the box. I must admit that it seems well-constructed despite its (IMO) somewhat cheesy appearance. I've always been concerned about Line6 stomp switches, in particular; having had a chance to see them up close, I'm hopeful that this design won't suffer the fate that has plagued legions of DM-4 users since the product's inception.

The expression pedal seems particularly robust. That was a pleasant surprise.

The display seems a bit small to me, but it's usable.

Once I got the HD500 home, I auditioned all of the presets. I know that the quality of the presets is an area of contention for many users; I won't be the one to step up and say that all of the presets would have met my immediate needs. I will say, though, that all of the presets are at least interesting. Many of the FX-heavy presets have quite arresting and engaging sounds. While they're not my bread-and-butter sounds, I could imagine using most of those oddball presets in film scores where the intent is to set a mood. In all honesty, a bunch of the FX-heavy presets had me wondering why the HD500 isn't giving the Axe-FX more a run for the money. Also, Adrenalinn fans could probably use an HD500 instead... there are quite a few beat-synced filters among the factory presets.

I found it very interesting that there are several factory presets having nothing but wah, volume and amp. Line6 is often criticised for hiding the weaknesses of their amp modeling beneath a thick frosting of effects. Not so with these "bare" presets. And... they sound good.

I experimented with the various lower-gain amp models and with setting up some patches of my own. I programmed entirely on the board; I prefer to know how to program my gear without the aid of a computer-based editor.

I did borrow Mary-Suzanne's MacBook Pro to use Line6 Monkey to upgrade the HD500's firmware from 1.3x to 2.02. That experience was pleasantly uneventful, particularly considering that I had forged ahead without even bothering to read that section of the manual. The Line6 Monkey walked me through every step of the process. Kudos to the folks behind the software and systems that made all that possible!

On day one I found little to criticise and a lot to like about the HD500. I had a few "what the heck moments" while building patches; they all turned out to be a result of either user error or inappropriate expectations.

The only things that I would have liked to have seen done differently are the gold-on-black lettering (that's difficult enough to see in daylight; I can only imagine its invisibilty under stage lighting) and the lack of complete markings (or prompts in the LCD) to illustrate all the functions of the buttons that respond differently to a press, a long press and a double-press.

By the fifth day of using the HD500 I had mixed feelings about the unit. On the one hand, it might have been nice to keep the HD500 around for the weird SFX. On the other hand, I slowly arrived at the conclusion that the HD's amp modeling is "close, but no cigar" relative to my expectations.

I'd spent way too much time over the preceding several days trying to dial in what I'd consider to be an accurate Fender Twin sound. A clean amp should be a walk in the park for a good modeler. But Line6, in my past experience, has never been outstanding in the low-gain realm.

My benchmark tone for a good Fender Twin sound is a patch on my Eleven Rack. If you've read my comments about the Eleven Rack, you know that I consider its modeling to be quite accurate.

Using the Eleven Rack as a reference, I was able get the HD's EQ really close by ear. The HD's controls don't correspond to the settings on the Eleven Rack, but I never really expected that they would.

In addition to matching EQ, I'd been careful to match levels. For normally-plucked notes, the tones were close enough that the HD and the Eleven Rack sounded indistinguishable from one another.

I had an A/B switch feeding the the two rigs, with the rigs going into a mixer and then to the QSCs. I was able to switch back and forth while playing and not notice a change. That's a good thing, and I have to give props where due to Line6; I'd felt that most of their earlier low-gain amp models, while playable, didn't bear much resemblance at all to their namesake amps.

But - and this is why I didn't pick up right away on the discrepancy between my expectations and what the HD is capable of delivering - when I really dug in, say with a strong backhanded strike with the nails of three or four fingers, the HD's Twin amp model failed to deliver. With my Kritz single-coil (very much like Tele pickups) guitar into the Eleven Rack, that strong attack produced almost a "zing" kind of sound from the strong string harmonics. This is what I expect a Twin to sound like. That same stroke through the HD500 produced no "zing"; the higher harmonics simply weren't there. The "zing" on the HD500 was replaced by more of a "thwok".

I'd tried EQ to bring out the zing, to no avail. I could crank the presence and get a lot more upper harmonic content on normally plucked notes, but when I hit the HD's Twin model hard it was as if the amp had put up its hands in a defensive posture. Something in the model clamps down hard on that upper harmonic content, producing a "thwok" instead of a "zing".

As far as FX go, the ones on which I lean most heavily - reverb, echo, chorus and Leslie - didn't grab me the way the same FX do on the Eleven Rack. The HD effects are fine as effects, but fall quite short in realism when one considers the nuances of a physical device. This is especially true of the HD's modeling of effects that attain their signature sound from mechanical behaviors. The Leslie and the tape echo are both particularly unconvincing.

I really wanted to like the HD 500, but came away with mixed feelings. The goofy FX are almost worth the price of admission. But the poor dynamic behavior of the Twin - which should be the easiest amp to model - bothered me a lot.

On a positive note, I found the HD500 very easy to program. I'd avoided Line6 units for a long time because the Line6 UI designers had seemed hell-bent on peppering the user experience with hidden options, multi-button functions, and nested menus. By way of contrast, the HD's user interface is quite intuitive and easy to use. I did all of my patch editing right on the board. It only takes building and tweaking a patch or two to get the hang of the tap, double-tap and press behaviors of the navigation buttons; once you've internalized that everything else is right in front of you on the LCD.

I never did try the computer editor; there really wasn't any incentive to complicate an already simple programming experience with the added burden of firing up the computer, wiring the boxes together and learning a new software application.

If I didn't have the Eleven Rack for comparison and was "moving up" from one of the lower-end Digitech RPs, I think I might have been ecstatic with the HD500. (I must note, though, that a number of RP users had argued that point with me upon reading my comments in a post upon which this article is based. Several correspondents had returned an HD after a side-by-side comparison with their RP.)

The HD's modeling is not outstanding, but it's very good. The industrial design seems solid; much better than anything I've seen from Line6 in the past. The HD's onboard UI is - particularly for a Line6 product - outstanding. I've only owned a couple of Line6 products, but I've played most of them; this one's a standout.

I had really hoped that the HD500 would serve as a downscaled but still great-sounding live rig for "hit and run" performances. It would have been a big win to throw the HD500 and a couple cables into a bag to carry to one of those twenty-minute showcase performances.

The reality of the situation is this: I've been spoiled by my Eleven Rack rig. Everything that the HD500 does well, my Eleven Rack rig does better. Obviously, the Eleven Rack rig is larger, bulkier and more expensive by roughly a factor of five in each attribute.

On the other hand, the Eleven Rack can't hold a candle to the HD's diverse selection of effects and routing options. If you're an effects maven and can live without the constant search for the latest new pedal and weekends spent rebuiling your pedalboard for the umpteenth time, the HD could be an excellent choice. I am honestly surprised that I haven't heard more about the HD as a "poor man's Axe-FX".

From my perspective the HD is somewhat comparable to the Axe-FX. The similarity between the HD and the Axe, both relative to the Eleven Rack, is that you have a lot to tweak. More amp choices, more FX choices, more routing options, more parameters... You get the feeling that tonal nirvana is possibly just "one more" tweak beyond your grasp, if you could only figure out which parameter to adjust or what blocks to combine in just the right way to add that one tiny little bit that's missing...

Perhaps that's actually true of the HD: that long hours spent searching for just the right combination of parameters will yield one's Holy Grail sound. If I had to bet on my, or anyone else's, ability to come up with an accurate Fender Twin patch, I'd bet against it. I've long said that having lots of parameters to adjust is no guarantee that some combination of those parameters will yield the desired outcome. And of course the more parameters you have, the larger the search space; the more parameters you have, the less likely you are to find that "magical" combination.

I spent roughly five hours over as many days trying, and failing, to dial-in the HD to achieve one great amp sound. In retrospect, that's about four and a half hours too many.

Look at it this way: do you bring a tube amp home and spend the next week trying to make it sound good? No. The amp either sounds good in the store, or you give it a pass knowing that you'll eventually find something that makes you grin and say "heck yah!" when you play. You don't think: "well, maybe if it I just gave it more of a chance..." (With notable exceptions for certain Mesa/Boogie users...)

The trick with modelers is that there are so many things to adjust that the "burden of greatness" implicitly becomes the responsibility of the consumer. The vendor has given you more controls than you've ever seen before; if you can't make the unit sound good, then it must be your own darned fault, right? That sleight-of-hand sells a lot of modelers. Consumers don't buy the sound; they buy the options with the expectation that some combination will serve up the perfect sound.

I love the Eleven Rack because it sounds like I expect an amp to sound with absolutely no fuss on my part.

I've (repeatedly) been underwhelmed by the Axe-FX because I haven't yet played one that's convinced me (for the way I play, at least) that I'm plugged into a "real" amp. I know other folks feel differently about this, and I respect those viewpoints. I'm certain that if an Axe-FX fan and I auditioned the same "real" amps, we'd likely reach different conclusions about the amps. It's a matter of expectations...

In a sense, I'm glad that I spent this time with the HD because I was able to form a hyphothesis about what Line6 is "doing wrong", which helped to reinforce my understanding of how DSP distortion works and how making certain design decisions might affect the outcome.

A friend speculated that perhaps the shortcomings of the HD's amp models are a matter of computing (in particular, DSP) resources. I don't remember where I saw the data, but someone (on TGP or DUC, most likely) did a comparison of the "power" of the DSPs in the various units. My memory may be faulty, but I think I recall that the Eleven Rack and the HD were closer to each other in terms of DSP power than either was to the Axe-FX.

More likely than a difference in hardware power, I think, is that there's a difference in algorithms. If I had to guess, it'd be that Line6 engineers (maybe in the interest of preserving DSP cycles to run effects, or maybe to push less-than-optimal code out the door to hit a marketing date) had intentionally truncated the polynomial that they use to model distortion on the Twin in order to be able to use a lower oversampling rate.

I don't know enough about DSP to write a decent sim, but I understand a bit about some of the principles and invariants. A polynomial function of degree N will generate overtones up to the Nth harmonic. When your distortion (or amp) modeling uses an Nth-order polynomial, you have to oversample the computation at N times the rate of the incoming clean signal. If you don't, you'll end up with horrible-sounding non-harmonic "aliasing" frequencies.

The biggest problem with modeling is the same as the biggest problem with darned near any software: simplifying assumptions always come back to bite you. The "can't happen" cases do happen.

In the case of the Line6 Twin model, I'd be willing to bet that the engineers made a simplifying assumption along the lines of "this is a clean amp that won't - in normal use - generate many upper-order harmonics". With that, they probably measured the transfer functions at "normal" input levels and observed, e.g. no "significant" HF energy above the Nth harmonic of the input. Then they implemented a truncated transfer function that simply stops at the Nth harmonic.

The problem with that particular simplifying assumption is that eventually some joker (like me) is going to hit the input of the sim with a signal that's 20 dB hotter than "normal", which clearly exposes the engineer's shortcut.

Now I don't know that this is definitely the underlying cause of what I'm hearing on HD, but it's - based upon my observations and the math behind distortion modeling - at least a plausible explanation. There might be another actual cause for the observed behavior. Software is like that; you can speculate endlessly about what caused a failure, but you never no for sure until you watch the code run "under a microscope"...

Line6 had always been weak on the transitional models. Personally, I think they've done a lot better with the HD.

In this case, I suspect that I've discovered a cheat that the engineers bet no one would find.

BTW, it's not that Line6's design (assuming the correctness of my unproven hypothesis) is actually wrong. It's just that what they did - with the engineering tradeoffs they seem to have made - doesn't meet my needs. Likewise, in the world of physical amps a Dual Rectifier isn't a good amp for me, but that doesn't make it a "bad" amp.

One week to the hour after having bought the HD500, I returned it to Guitar Center for a refund.

April 15 2012 03:43:44 GMT