Upper-end Overdrive Head-to-Head: Klon Centaur vs. Maxon OD-820 Pro
by Dave Szabados

Perhaps the most frequent question we receive here is, "What type of overdrive should I use?" or more specifically, "Have you tried Brand X? If so, what do you think?" The Klon Centaur's name has come up on quite a number of occasions, so we thought it would be good to give it run. But in addition to the Klon, I wanted to spend time with another pedal also designed and marketed to provide similar characteristics so we chose the Maxon OD-820 Pro.

The Klon Centaur is really one of the first of the "boutique" overdrives to be created that has spawned the current popularity of boutique makers. Built in small numbers, the Klon since the mid '90s has been continuously backordered, according to the website and owner Bill Finnegan. Indeed, our own Klon Centaur did take approximately 10 weeks to receive.

Both the Klon Centaur and Maxon OD-820 are designed to be used primarily with tube amplifiers for best effect. Both models boast having full transparency. While this is an often over-used marketing buzzword, we'll listen to how transparent these units truly are. Essentially, will they color the tone of the guitar signal when the overdrive is engaged, or will they maintain the sound and feel of the guitar and amp and simply add overdrive gain? The answer to that question will truly determine how transparent each of these units is.

Clean boosting is another effect that both units provide. In fact, both the Centaur and OD-820 deploy dc-converter circuits that deliver great headroom with their increased voltages that helps create a strong boost to push the tubes on the front end of a tube amplifier. We'll again compare both and see which unit does a better job of this task as far as delivering transparency and low noise.

Klon Centaur

The Centaur is widely used by many players and has enjoyed great popularity since its inception in 1994. Klon's Bill Finnegan sells the Centaur direct via his website and units must be pre-paid. Bill spends time with each customer who contacts him, primarily trying to get an idea of the equipment and playing style of the customer, to help determine if the Klon Centaur would be a good match.

I play a good deal of rock and blues music through a number of vintage amplifiers with both Fender Stratocasters and Les Pauls. The Centaur would be right up my alley, according to Mr. Finnegan.

When I received the unit some 10 weeks later, the first thing that struck me was the size. The Centaur is rather large, much more so than I expected and of course more than the common Boss or Ibanez floor box. Housed in a heavy die-cast enclosure, the silver finish looked like it was a simple polishing job and I'll admit that for the amount of money spent, I was a bit put off by the scratched-up look of the finish which looked like it needed to be painted or polished further to smooth it out. It gives the Centaur a "used" look. Looks aside (not THAT important anyway I suppose!), the Centaur's basic controls are for overdrive, treble, and volume. Switching is done via its Carling DPDT which does not provide True Bypass. Finnegan stated that an explanation of why he opted to not use True Bypass would "take about an hour to explain", but in essence he feels a well-designed buffer helps drive any additional pedals on the board and won't color the tone if created properly. Indeed, I'll admit that I could not hear any tonal loss when bypassing the Klon as I would with a unit like a wah pedal so I have to presume that the Centaur indeed has a well-designed buffer stage.

The bottom of the Centaur has a large turn-screw door for the battery that can be opened with a large flat-head screwdriver or a coin. A 9v DC jack is included, but it is the 1/8" plug type which has become a bit less common than the standard 2.5mm DC jacks used with most other power supplies. A male plug however was included for retro-fitting another DC adapter. A photo-copy of a simple hand-written one page "user guide" is also included. Perhaps it is to give the "boutique" feel, but again I felt a little more effort could have been made in this area based on the money that was spent. All in all though, remember that these are just minor gripes.

As I do with all pedals I review, I decided to peak more closely inside the unit. The circuit, much to my surprise, was completely covered in a black "goop" material to hide the various component values and circuit design. This is another area that is a put-off in my book and makes the Centaur basically impossible to service or have repaired by anyone else if Mr. Finnegan ever opted to leave his business. I suppose the reason for the goop is so that nobody could be tempted to copy the design - however, with that said, if a designer wanted to copy the Klon Centaur bad enough, that designer would find a way to remove the goop. But enough of this, let's get to the tone and now go and play with the Centaur!

I went with the classic Gibson Les Paul and Marshall Combination first. Setting the amp for mild overdrive and setting the volume on the amp to go comfortably along with the drummer, I then kicked on the Centaur for a boost. The Les Paul equipped with our favorite Seymour Duncan Antiquities (see earlier PAF-style humbucker shootout in the "Guitars" section) has a characteristic creamy-smooth midrange that really enhances the Marshall's tone, but with the addition of the Centaur, it became a bit much as it added additional mids that gave the tone an overall "mid-bumped" tone. When adding additional overdrive, the mids became even more pronounced and upfront in the mix.

One positive element of this first setup is that the Centaur did retain the characteristic punch of the Les Paul, but otherwise this was a sound that didn't suit my interests personally. I then ran the same guitar through a Hiwatt DR103 set clean to listen to the overdrive by itself. This is not where the Centaur shined at all, and in the Centaur's defense, there aren't many overdrives that can sound good in front of an amp that's set 100% clean. I have to suspect that fans of the Klon enjoy it because it retains a sense of punch to the guitar's signal, but the biting high-end of the Centaur did nothing to provide a sense of warmth in its drive.

So far, well, not so good. Next up, I went with a Fender Stratocaster plugged into a Fender Super Reverb, Marshall, and Hiwatt respectively.

The Fender Stratocaster's naturally glassy tone has a lot of top end bite with a bouncy bottom end. Boosting the Super Reverb with the Klon for a lead solo, I then heard the magic - the punchy Centaur's mid-boost was powerful and a nice complement to bring up the Strat's midrange and presence and now brought the guitar out in a more pleasant light.

Going through the Marshall, again set with mild overdrive and decent volume, the Stratocaster-through-Centaur setup again performed and sounded exceptionally better than the Les Paul/Centaur rig with the overdone midrange. Leads came through boldly and it was apparent now why the Centaur is a favorite with many rock/blues players.

Through the more-challenging Hiwatt setup set clean, the Stratocaster's natural low-end did help the Centaur to warm up more in this environment, but it was definitely in its weakest area. The Centaur, as do virtually all overdrives, will perform best when there is already some tube overdrive breakup occurring with the amp. At that point, an overdrive's push can enhance and increase the gain of the amp. Left to provide overdrive on its own and the Centaur is a bit sterile.

At the end, I was left with a bit of disappointment with the Centaur. It sounded o.k., but it would have been nice if the Centaur had been a bit more neutral, especially with the Les Paul/Marshall setup rather than taking over with its own coloration. As my ears listen the Centaur, the unit's high point is its clarity and definition that it provides as well as its strong amount of headroom, no doubt courtesy of the increased voltages within. Rock and blues players that want added presence and mids when going into solo sections will enjoy what the Centaur has to offer - for those looking to increase their amp's gain in a more transparent fashion however, will do better looking elsewhere.

Maxon OD-820

Maxon's OD-820 is part of its Vintage Series effects and is also a bit larger than Maxon's other more-compact designs. According to Maxon, the intention of the Vintage Series is to provide the absolute highest degree of fidelity and lowest noise and so the larger size and the resulting larger amount of space between certain components and the power supply for example help achieve this goal. The OD-820, like the Centaur, operates from a 9-volt battery or a DC power supply. A power supply is included with the OD-820 which was a nice touch.

Controls on the Maxon are for Drive, Tone and Level and is setup in the same fashion as the Klon. Switching on the OD-820 is accomplished via a DPDT footswitch that is built into the signal in a bit of a different way. According to Maxon, though the unit does not use a 3DPT switch commonly found for true-bypass switching, the functionality is said to be similar to a true-bypass signal but with actually improved resistance characteristics. The included manual with the OD-820 is informative and also provides suggested settings for the user.

I opened up the OD-820 and the construction is indeed good as it tends to consistently be with Maxon products. For those of you that didn't know, Maxon is also the manufacturer of Ibanez' Tube Screamer TS9 and was the manufacturer of the famous TS-808 model produced in the late '70s through early '80s as well so there's indeed quite a long history of design expertise from the Maxon folks out of Japan.

I again went with the Les Paul/Marshall setup first and set up the amp for mild overdrive at a good volume level suitable to go against my drummer's own volume. The OD-820 responded with strong clarity and retained the punch and drive of the Gibson, but this time around, the strong mid-range hump was not so highly emphasized. As I increased the overdrive on the unit for stronger overall gain, the distortion took on a bit more of a bold tone, but the Marshall and Les Paul still retained the sound and feel of the Marshall and Les Paul. In this environment, the OD-820 literally smoked the Centaur. The tone control served up a bit more presence and bite if desired for aggressive playing, or when turned to about 10:00 position, warmed up the signal for a bit more of the classic Clapton Cream-era tone when also deploying the neck pickup. Yes, there was some great tone to be had when using the OD-820 with the Les Paul and Marshall - tones that made the OD-820 a true pleasure to use.

The drive control, according to Maxon, functions as a dual function "clean/blend" control. So when set at zero, the unit is sending only a clean signal through to the amp, then when at half, it splits the signal 50/50. Lastly at full clockwise is overdrive only.

Next up with the Hiwatt set sparkling clean, the OD-820, while capable of biting top end when the tone control is increased to the right, faired better with the Hiwatt when set at a warmer position around 9:00. The usability of the OD-820 was much better than the Centaur, which was more selective about the environments it's used in.

Strapping on the Stratocaster and making the rounds through the Fender, Marshall, and Hiwatt amps, I could conjure up very convincing bluesy tones a la Stevie Ray Vaughan. The OD-820 in this environment didn't have quite the amount of midrange boost on top of the signal as the Centaur, but I personally preferred it this way as it felt like I was now playing a guitar and listening to the amp's overdrive, and not feeling like I was playing through a pedal. Clarity and presence along with strong headroom is available in ample supply similar to the Centaur.

One interesting area I picked up on was the noise level at higher volume with the OD-820 was a bit less than the Centaur. Another point in favor for the Maxon: The bass response throughout all the tested environments retained tight and focused and in some respects I thought of the OD-820 and the Centaur as types of "high-fidelity Tube Screamers". The OD-820 perhaps shares more of the Tube Screamer's heritage as it employs dual JRC4558D chips. While I'm unsure of what the Klon uses in its circuit, company President Bill Finnegan assured me that the Centaur is nothing like the Tube Screamer so I have to presume it uses a different type of Op Amp or transistor.


Though both the Maxon OD-820 and Klon Centaur have apparently different designs of circuitry to some degree, they both do share some common characteristics with regard to their headroom, fidelity, and capability of maintaining a strong and vibrant guitar signal. Between the two units however, I found that the Centaur's coloration strongly favored environments where greatly added mids would be desired, whereas the OD-820 worked in a much larger range of playing conditions.

At prices of $306 (including shipping from Klon direct) for the Centaur, and $210 (Street price) for the OD-820, neither unit can be considered inexpensive. However, in the case of the Maxon OD-820 in particular, you do get what you pay for - AND at a price nearly $100 less than the Centaur. The OD-820 wins out in this review hands-down for its combination of quality construction, transparency, value, and overall good tone when playing through a range of gear. For more information about the Klon Centaur, visit www.klon-siberia.com. For more information about Maxon's OD-820, visit www.maxonfx.com.

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