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Robert Keeley Boss Mods Trifecta

Blues Driver Style OverdriveBoostBoost and OverdriveBossBrown Sound DistortionDistortionDriveEffects Pedal MakersFuzzFuzz-Drive and FuzzstortionKeeley EngineeringMarshall Style DistortionMetal DistortionMooerOverdrive+-

Robert Keeley has of course modified more than these three Boss pedals - yet I personally feel that these are the ones really worth having. I have featured both the Keeley Freak Fuzz Modded BD-2 Blues Driver and Twilight Zone Modded MT-2 Metal Zone on this site several times before. In fact the Freak Fuzz Blues Driver is my favourite overdrive pedal of all time! It cleans up wonderfully with your guitar volume control - much in the same way as a Fuzz Face, and it has that same sort of boost impact where it can lend additional sparkle and definition if used with the gain dialled right back.


The third Keeley-modded Boss I acquired was the DS-1 Ultra / Seeing Eye LED Mod - which is similar in a way to Robert’s tweaks on the Blues Driver and Metal Zone and significantly enhances the frequency response and output profiles of these pedals. Robert’s mods to me just beautifully ’beef up’ the tone - certainly lending more weight to lower frequencies - and they just give you a thicker, richer, more harmonically textured and overall much more satisfying tone - with better signal-to-noise ratio - not that any of these pedals don’t already sound great to start with - this is just more of a custom tune-up - tweaking parts values and upgrading essential parts with better quality noiseless components - which all have an impact on each pedal’s final output.


You can of course buy Waza Craft versions of the BD-2 and MT-2 - which are both excellent also, while I still have something of a preference for their Keeley predecessors - which supposedly had significant influence on Boss’s own Waza engineering decisions. I also have the MT-2W, and fully intend to acquire a BD-2W at some stage for sake of completion - while I don’t really feel I need it right at this moment - as the Freak Fuzz Blues Driver is as close to welded into my pedal-chain as any pedal ever will be.


I own numerous iterations of the Boss DS-1 - an original unadulterated orange one, an unadulterated Black 2017 40th Anniversary Edition, a DS-1X Multi Dimension Processing Edition, and DS-1 JHS Synth Drive Deluxe Modded Edition. I still felt that I had to have the Keeley-modded Ultra version - for the same reasons that I love the Keeley Blues Driver and Metal Zone. All the same Boss pedals have been brilliantly modded by Brian Wampler, Josh Scott and Mike Piera to name just a few of the greats - while overall it is generally Robert’s modifications and output profiles that I prefer - although I do have a lot of JHS mods too, and no doubt will add some Analog.Man editions at some stage - Brian’s earlier mods are just much much harder to come by.


Note that I also included the Boss SD-1 Super OverDrive Keeley Ge (Germanium) 5-Star Mod as a Bonus Round - it’s still right up there, but not quite of the status of the other 3 - and I could not readily find any kind of obvious or even vaguely matching mini alternative - I could have maybe gone with the new MXR Mini Timmy (also with asymmetrical clipping) - but I feel that it is its own thing really - and I don’t feel it entirely fair to associate obviously branded pedals with each other unless they are intentional clones or alternatives.


In terms of the second row of mini-pedals - those Mooers are the nearest equivalents to the above Boss pedals - in fact the Blues Mood and Ultra Drive MKII are both specifically modelled on the actual Keeley-modded Boss pedals. And my first ever ’Blues Driver’ type pedal for quite a while was indeed the Mooer Blues Mood - which I still retain and love, although it does not really quite reach the lofty heights of the Freak Fuzz edition - it does not have those amazing sparkly harmonics, yet does capture a lot of the same character and core tonality.


I have asterisked the 3rd mini pedal - the Mooer Micro PreAmp 001 Gas Station - as this is not based on the Metal Zone or an exact replica/alternative, nor is it yet in my own collection - I’m just waiting to snatch one up at a good price! I find the Mooer PreAmp 001 the closest match to the core output profile of the Metal Zone - it of course has 3-band EQ - which is close to the Metal Zone’s 3-Band EQ + Parametric Mids. In trying to find a near equivalent Mini pedal to the Metal Zone - it has to have at least 3-Band EQ and have that same degree of attack and potent mids frequency focus - and I reviewed all the mini metal pedals that I researched for my last piece on High Gain Pedals - and it became pretty quickly evident that the Mooer PreAmp 001 Gas Station was the closest match in that selection - based in turn on the Diezel Hagen amp. If you disagree with my third choice here or have a better candidate - please drop me a line and let me know why!


Here follows a little more about each of the above pedals - including the circa prices at which I acquired them and condition/wear. All are in extremely good condition and the least aesthetically pristine pedal has only the tiniest of marks upon it. Japan-sold ’Very Good’ condition pedals are typically in pretty excellent nick - and I have some which are almost impossible to separate from ’Excellent’ status. Note that the Freak Fuzz edition is increasingly rare and difficult to track down and decent examples can fetch 2 or 3 times the amount I paid for mine back at the start of 2018 :

Boss BD-2 Blues Driver Keeley Freak Fuzz Mod including Phat Mod - c£160 Very Good Condition - via

This to me is just an incredibly versatile and beautifully organically sounding - slightly fuzz-edged box of tricks. In its original format it does 3 things amazingly well - pristine sparkling clean boost with gain rolled back, lovely fuzz-edged bluesy overdrive, and richly-textured Marshall-esque crunch / distortion. The Keeley Phat Mod adds in better bass response - and the frequency profile just sounds thicker, richer and better balanced - while the Freak Fuzz Mod give you a really classy Fuzzy-Drive - like the Overdrive end of a Fuzz Face. I actually use mine mostly with the Phat Mod (right-switch engaged) and with gain around 1 or 2 o'clock and then use my guitar's volume dial to adjust to need. The two little cylinders on the pedal face are TO-1 Can AC188 Germanium Transistors used as clipping diodes for the Freak Fuzz voicing. There's lots of us that love the Blues Driver - much less that actually have this version, and far too many that weirdly don't go for this flavour at all - it is very much a bona fide classic - and as distinct a Boss voice as its DS-1, Heavy Metal and Metal Zone. In this particular version it has just the most fantastic degree of richly textured harmonic content - which sounds wonderful to me ears!

Boss DS-1 Distortion Keeley Ultra Mod / Seeing Eye LED - c£85 Mint Condition - via

Again a really beefed up and more richly textured better components modded pedal - which utilises the visible Red LED as a clipping diode. With the toggle switch up you are in 'Seeing Eye' mode and can see the degree of saturation illuminated in the LED, while flipping the switch down gets you into even fatter and beefier 'Ultra' mode territory. Both this and the above Blues Driver have quite distinct Marshall-esque voicings when cranked up. For me the Blues Driver has somewhat better range throughout its dial, while I tend to prefer both pedals cranked beyond the mid-way point. The DS-1 works best when pushing a little gain already in the signal chain - while the Blues Driver is more versatile and works equally well on a clean signal. Some players have a preference for one or the other - and while the Blues Driver edges it for me all-round, I still like the Keeley DS-1 almost as much!

Boss MT-2 Metal Zone Keeley Twilight Zone Mod - c£140 Very Good Condition - via

Boss MT-2 Metal Zone Keeley Twilight Zone Mod - c£140 Very Good Condition - via

I acquired this pretty much at the same time as my Freak Fuzz Blues Driver - the BD-2 came from California, while the Metal Zone was acquired from Ishibashi Music Store in Tokyo (via I luckily received this before the Blues Driver - which obviously kind of went on to dominating proceedings for me for a while. Robert again has worked his magic on this rather finicky and potentially aggravating circuit - brought about largely by the expansive range of the Parametric Mids frequency dial - where tiny movements make significant changes. For all Metal Zones - even the new Waza edition, you have to be careful when dialling in the mids! This is another beefed up edition - with a better balanced frequency response profile which reduces some of the fizz of the stock version, tightens up the low end and gives you more amp-like saturation. The 3-way toggle-switch gives you two further modes over and above the left-position stock variation. Toggle right for 'Triple Diode' Mode which gives you a more realistic amp-like molten guitar saturation. Move the switch into the centre position for the extreme 'Ultra Tube' mode for a 4x12 cabinet style ultra low bass response with even more tube saturation simulation and increased 2nd order harmonics in the distortion. I believe both the BD-2W and MT-2W were based to a degree by Boss Engineers on these Keeley reference models, while the Boss pedals don't quite deliver the exact same degree of texture (harmonics) or bass response. The Boss models typically tend to be much less bassy - which some players prefer.

Bonus Round! Boss SD-1 Super Overdrive Keeley Ge 5-Star Mod - c£80 Very Good Condition - via

The SD-1 Keeley Ge (Germanium) 5-Star Mod gives you a beefier asymmetrical Germanium diode clipping for more overdrive gain saturation and increased 2nd order harmonic distortion. In many ways it functions similar to the Blues Drive Mod - better frequency profile with better balance and more satisfying low-end and distortion texture. Much like the Blues Driver it also works really well across the dial - from boost through to crunch. Voicing-wise it's not quite as distinct as my selected above trifecta - but there are plenty of fans of this pedal too. For a variety of reasons it's not quite as iconic as these others and probably because of that has less of a following and to date no readily identifiable mini clones! Obviously the brand new MXR Mini Timmy has an asymmetrical style clipping option - but its main character is quite different really to this particular SD-1. I like all 4 of the Boss Keeley Mods, but based on my own preferences and usage patterns - this is somewhat understandably in 4th place. Again there are several players for whom this is their favourite Boss flavour - and the Keeley variety is a more evolved and refined version of that.

Mooer Blues Mood Micro (based on BD-2 Keeley Phat Mod) - £47 New

This was my first actual 'Blues Driver' variant - Mooer's take on the BD-2 Keeley Phat Mod - I was kind of sold by the Mike Hermans demo (as above) - and albeit not quite as articulate and dynamic as the actual Keeley modded BD-2 - the Blues Mood is nevertheless a fantastic proposition and a very viable option at its size. You have a two-way toggle which activates Fat (Phat) or Bright Mode - the former accentuates the low end, the latter the top-end. There's plenty of volume and range on tap here and I've recommended this pedal to lots of players wanting a bluesy style of drive - and all have been very satisfied with the results. It pays to shop around with Mooer as there can be a significant difference in pricing and if you research well you can often find one at a really fantastic price! As a backup to a proper Kelley Phat Modded BD-2 - this is really excellent.

Mooer Ultra Drive MKII Micro (based on DS-1 Keeley Ultra Mod) - £41 New

This is pretty much the same deal as the Blues Mood above - in that you get a really great clone of the Keeley Modded Boss equivalent - with not quite as good dynamics or range - but close enough to be worthwhile. In fact with the Ultra Drive you get some additional versatility in that you gave 3 modes available to you - Original / Extra / Ultra - with the Original being the DS-1 Stock variety, Extra being the Seeing Eye Mod, and the Ultra exactly as its name implies. It's a different character and voice, but much improved over the stock Boss version. I personally prefer both the Mooers over the stock Boss BD-2 and DS-1 varieties - while the actual Keeley varieties featured above are the apex of the pyramid as far as I'm concerned. It's no surprise to me that Mooer also has a preference for the Keeley Mods out of all the different mods available.

Mooer Micro PreAmp 001 Gas Station (based on Diezel Hagen 4-Channel Amp) - £75 New

This one is obviously the odd one out here as it's not a specific clone variety of the referenced Boss pedal, but in fact a clone of the Diezel Hagen Amp - which is a typical 4-Channel Diezel Metal Monster. The Metal Zone though really doesn't have any direct alternatives - and certainly not at the mini enclosure size. So as I mentioned in the intro I reviewed all the Mini Metal Pedals I'm familiar with to find the closest match to the Metal Zone output profile. As mentioned - the Metal Zone features 3-Band EQ plus Parametric Mids - where no Mini pedal has that feature set yet as far as I'm aware. Mooer's Mini PreAmp Pedals though do have 3-Band EQ, and in my Mooer PreAmp Overview and in the more recent High Gain Roundup - I singled out a number of those Mooer PreAmps - including the 001 Gas Station variety. This I believe comes closest to sounding like the Metal Zone - although it's by no means a totally perfect fit. A number of the Mooer PreAmps have been on my wishlist for a while - I'm just waiting for the price to come down a little more on the 5 or so ones I like - including the above one of course. Some people have been rather disparaging about the Mooer PreAmps - but if you use them correctly and dial them in appropriately they can sound really great - which is why a number of Metal bands use them in their compact fly-rigs.

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Stefan Karlsson
Stefan Karlsson
Guitar Pedal X
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