Archive for the ‘Electro Harmonix’ Category

EHX Germanium4 Big Muff XO

Friday, July 22nd, 2016


What is it?
Electro-Harmonix Germanium4 Big Muff Pi. Made in NYC, USA in 1013.

Buzzword. Much like “cloud services” or “streamline” in some other contexts. For pedals it’s usually “Germanium”. Next and the biggest single question – how come this unit has nothing more to do with a Big Muff than its name.. Since late 60’s the Big Muff has mostly been the same four transistor circuit that can be compared to Tubescreamers to a certain degree, being somewhat a standard and a subject to numerous (hundreds, maybe) derivative clones over the years. So the marketing department at NYC has decided that in modern day it’s ok to sell anything with BMP name. Well, i don’t need to be this harsh. The designer team may have had a few people of prestige involved. But still. When i hear the name “Germanium Big Muff”, my initial thought will instantly move towards the classic four transistor circuit, with germanium transistors instead of the basic BC550C (or similar) that we see in all modern BMPs. Even the number 4 in the name would suggest this. But no.


In reality, the pedal is two separate circuits in series and there is basically nothing that would even point towards the classic Big Muff, except for the name. There is a trace at Freestompboxes forum (may not be 100% correct and to see it you’ll need to login), that’ll confirm the suspicion. Basically the distortion half uses the two NKT275s as clipping diodes in a feedback loop of a non-inverting opamp, where overdrive half has the two germs in a signal path, but still utilizing an opamp for recovery. This part has some similarities with the EHX Germanium OD released in XO series earlier. The transistors are those current repro NKT275s that EHX must have bought in as truckloads. For the rest of the components and board design, the unit is on par with all the other modern EHX pedals. Mixed SMD and through hole design.


But what comes to controls and other features, this isn’t as bad pedal as i first thought. The overdrive half offers very similar tones as the XO series GeOD, but with much wider controls. And the distortion goes with decent control set as well. To me, it seems that the biggest issue remains with “false” marketing and labeling. Another head scratcher is the price development of new and used market of these. Just a couple of years back you could score one of these used for $40€, but for some reason not explainable, the current street price is something notably higher.

How does it sound?
Not bad. Both halves are like peaches from separate cans. Neither of these may get the label of “musical”, but there are tons of those ye oldee school slightly misbiased germanium transistor tones available. Both halves activated, there is some high gainy/fuzzy sonic bliss in the air. Not enough to blast through the roof, but still very decent distortion with a vintage-like touch to it. If i wasn’t offended by the misleading marketing and labeling, i’d hype this pedal to a degeree that i rarely do. But since there is certain, slight feel of being swindled present, i hqave hard time of praising the unit.

It’s not bad, at all. It offers quite wide range of those misbiased old school drive tones that most of us love. Nevertheless, i believe this unit won’t be too popular and it’ll settle for the status it should have. A novelty, or a speciality, that’ll get one purpose covered nicely. Nice. Not shocking, but nice.

EHX Graphic Fuzz XO

Monday, April 6th, 2015


What is it?
Electro-Harmonix Graphic Fuzz with variable envelope response, from XO-series. Made in NYC in the late 00’s. Most likely in 2009.

A friend was letting this one go and i just simply couldn’t help myself. Pricing for an used Graphic Fuzz isn’t too cheap, but then again – it definitely isn’t one of your average straight up clones or slight derivatives of something else. The box is big, but there are ten large slide pots for the controls. Reasonable spacing for standard rotary potentiometers would have possibly called for even bigger box. That would also have taken the graphic EQ out of the equation. I took a peek inside once i got my hands on the unit.


I see six dual opamps and no inductors. This means that the EQ section is done with gyrators and in the same manner as found in most modern graphic EQs. Rest of the features are not that simple to see by just looking at the board layout. There is a fuzz that can be switched on and off and there is a “variable envelope response”, which acts almost as a compressor. But not quite. I’d say it functions closer to an envelope generator we find on synthesizers. No, it does not act exactly like those either. Still, the dynamics slide sets the attack of the tone and sustain sets the release.

So the set of features is pretty much a thought that comes from outside of the box. Original idea, but does it carry us far enough?

How does it sound?
Almost but not quite. We are stuck with relatively faceless graphic EQ and a fuzz/overdrive that’s quite close to the one knob Muff Overdrive. Not any version of Big Muff. The one knob Muff. You know, the one that comes in red and green from the nano series. The EQ works well, while it is rather generic. Then agai, no of us might even want a graphic EQ with a personality. It does, however, make the fuzz/overdrive a lot more usable. For the envelope part.. I do not have that many good words about it. It works like nothing else, so it’s hard to wrap your head around it. Versatile, yes. Usable, well, ok. Good? Maybe i wouldn’t go that far. Interesting. That would be a good word to describe the unit.

Nice set of features and these could serve a purpose for those who want something different ™. Wide set of features, but the tones leave me somewhat cold. Not the worst EHX box, though.

EHX Memory Man with Hazarai XO

Wednesday, March 18th, 2015


What is it?
Electro Harmonix XO Stereo Memory Man with Hazarai. Made in new york in early 10’s.

Got this unit used with a defunct tag in a trade. I was sort of skeptical as most of the modern EHXs are just plain dead and there is very little that can be done. But i went for it anyway, out of curiosity. Pedal was and is in decent condition with a few marks of use. Since the old school lab supply on my desk can only put out 100mA i figured this wouldn’t the one to be tested on that supply. After checking the manual, i set up one of my old power supplies with 500mA output and tried the pedal out. Nothing. No sign of life. Oh well. These things can happen and some trades leave me on the win anyway, so getting one brick isn’t going make much of a difference. Still i wasn’t convinced. I took out my modern favourite power supply that can put out 1A if needed and tried again. Took the pedal about 20 seconds to perform its power on self tests, but this time everything seemed to be running smoothly.


I do recall running into similar issues with other all digital designs. If the circuit is fed with too low current, things can get weird. Seemed like the case with this one. My guess is that someone had used low current supply and this has caused the digital circuitry to act in an undesired manner. Others could still think that the unit is broken and i’m not disputing that. It’ll work just fine if it has a power supply that’s capable of satisfying its needs. The damage has been done and it’s not getting any younger. But it works.

As the photos show, there is very little us lumberjack-style effect enthusiast can do if the pedal is really dead. This is partially a sad thing as the people qualified to repair these things are scarce when compared to old through hole manufacturing methods. Meaning that there will number of units that will get trashed due to not being cheap or viable enough to repair when something goes wrong. One of the biggest culprits of modern times. Unsustainability.


In heart of it all lies an digital signal processor manufactured by Analog Devices. Yup. I’d call that an oxymoron. Although AD chips and processors are top notch and those tend to be used for many audio applications. This design is all digital and size of the chip tells us that it’ll beat your Commodore 64 in a heartbeat.

Next up i was to try the unit out, now that it was working. Five pots with a digital rotary switch and two stomps. Unit can be used as a standard delay, but that will leave a load of features out. We have our multi tap and reverse delays in addition to the expected ones. The looper function is in there too. I must admit i had to search for a user maual to get any real testing out of it. If you want an overview of the features, i suggest you do the same. It would take me quite a time to explain everything, so let’s just get on with it.

How does it sound?
Pristine. Designed in a manner that the unit could be usable with synths and organs as well as with guitars. Frequency responce doesn’t discriminate and the buffering at the beginning of the signal path doesn’t care wether you push it hard or with vintage guitar pickups. One could truly earn a cape of a wizard if one was to learn every feature and use them in a live set. Good clean tones and repeats are well controlled. This truly isn’t your average delay and i believe the designer has done his/her work by chasing the features that are not found on every single delay unit out there.

Sound good and works fine with suitable power supply. Some of the features still elope me, but that’s just me. You should try one out to see if you like it. For me, i’m a lumberjack.

EHX Big Muff Pi Nano

Sunday, February 22nd, 2015


What is it?
Electro-Harmonix Big Muff Pi Nano. Made in NYC, 2013.

Ok. This took them long enough. The massive Big Muff enclosure is sort of an visual trade mark for this obviously classic fuzz/distortion, but there’s been Little Big Muff out for a long time. Little BMP being the same circuit, but just in a 1590BB-sized box and with mostly SMD construction. We all know the circuit doesn’t require the huge box, even with through hole parts since dozens of other brands and boutiquers have been offering their tweaked clones ages. And usually in a smaller, 1590B, or 125B sized enclosure. In my opinion, the size form factor does matter to a degree. B-box always trumps the bigger ones (but if we go smaller than that, my interest drops lower than hell). So, in a sense, EHX releasing a BMP in a smaller form was just a matter of time. Chinese cloners are currently selling similar circuits in A-sized boxes, but i do hope that EHX doesn’t go there. Ever.


Looking at the circuit and checking out the treasure cove for BMP information, The KitRae’s Big Muff Page, the design for this one is the same as for current huge box reissue and Little BMP. Our basic four gain stage design with the middle ones having diodes for clipping. Exactly like all the other discrete semiconductor BMP versions. Circuit is actually very close to Little BMP with through hole transistors, diodes and a few key capacitors. And since this is electronically the same as current ones in bigger boxes…

How does it sound?
It sounds exactly like the others. Big and creamy with decent output levels. As with all BMPs, the  sound is at its greatest with clean amps and medium to low output pickups. The design and the sound it represents has endured time extremely well. There have been some changes in the design over the decades with all of them having a lot in common, while still sounding different. This and all the others post-2000 units sound more or less the same. With a few exceptions. Still, no surprises. Just the classic tones in a extremely usable format.

EHX Hot Tubes Nano

Sunday, February 8th, 2015


What is it?
Electro-Harmonix Hot Tubes Nano. Made in NYC, 2013.

Some time ago i stumbled on to a schematic of this CD4049 hex inverter based OD/Dist unit. Played around with the design and noticed it had some real potential. There are numerous drive designs with hex inverters on the wild and while the CD4049 distortion is quite distinct in its tone, most of the circuits still have their own kind of face. Since i had played around with the old version of the circuit and loved it, i had no choice but to get the modern original. Rare occasion, but since the new EHX nanos are priced very reasonably, i got this one as a new unit. For all you DIY’ers out there – get the original. It will be cheaper than building your own from the schematic.


Quick eyeballin’ of the board shows that the circuit is the same as for the old, big boxed Hot Tubes units, just executed with SMD components. Everything from board design to the box scream “EHX” from miles away. Nothing special in the insides. There is a schematic up at Gauss Markov’s site. Plus a documentation for you to build your own. Like i said above, it may not be economically viable, but still. If we recap the design, there is JRC4558 after the input. Both channels of this chip are used to drive the first gain stage of the hex inverter. The gain of the design is set by simply placing a variable resistor between the dual opamp output and the first inverter input. This is followed by a second stage and next up is the switch for bypassing the tone stack. Both option outputs are driven by hex inverter stages, which means we have two of the inverters not in use. The tone control itself is pretty close to the variable high pass/low pass filter we see in all the Big Muffs and derivatives. It’s always a pleasure to look at an electronic design that makes sense.

How does it sound?
Vintage-like. Not too trebly in any way, but focusing on the lower frequencies for the overtones. It does sound very powerful. From mild boost to soaring distortion. I think some of the bass players will enjoy this more than average guitarist due to its relatively dark tone. Like stated, the tone focuses on lower frequencies, but i find this very usable nevertheless. The tone bypass is a novel idea too and will add to already high usability. Very good sounding unit. And since these come cheap, i can’t help myself but to recommend it to you all. It may not suit to everyone’s taste for a main overdrive, but it will have its use.

EHX The Mole Nano

Friday, January 30th, 2015


What is it?
Electro-Harmonix The Mole Bass Booster from Nano series. Made in NYC in 2013.

As the one transistor, simple boosters in the EHX family go, here we have the “Bass Booster”. Circuit has pretty much the same topology as all the other simple boosters (LPB-1 and Screaming Bird). The component values are the ones that determine the frequency response and thus, determine if the circuit boost full-range, bass or treble. On full-range, we cut nothing out. On bass, we cut out the high. On treble we cut out the bass. Simple, isn’t it. I was expecting to see the same board as for LPB-1, but no. The Mole has its own design, even though the circuit is still simple, one transistor booster.


Here we have our modern EHX board with most of the design laid out in SMD, while couple of the caps are through hole. And the transistor is a classic TO-92 packaged device too. BC550C. I think EHX has bought those to last a lifetime. At least this type seems to be the weapon of choice for most EHX pedals calling for NPN transistors. Overall, simple and useful. Why?

How does it sound?
Useful due to how it sounds. Want to cut the high end off and give some volume for the lows? For very cheap nano series pedal, this is the way to go. While i don’t see myself using this on my main board anytime soon, i think of the unit as a tool to shape the tones in studio sessions. While it is very good unit, the lows tend to need a lot more power to get amplified. You know, your 50W all tube guitar amp will be louder than your 100W all tube bass amp. In reality, this isn’t exactly true, but due to how we humans perceive frequencies, it might as well be. Due to this, the Mole seems a bit sluggish for its output level, when compared to LPB-1 and Screaming Bird. It could be louder, but still. This one gives you decent kick for your lows while cutting the top end. Usable. Tool.

EHX Octave Multiplexer (XO)

Friday, November 7th, 2014


What is it?
Electro-Harmonix Octave Multiplexer from XO series. Made USAaround late 00’s

No. I’m not writing everything about this again. Just check out the post about EHX Octave Multiplexer Reissue. The main points for the design are written in there. There are a few differences between these two units, mainly on construction methods – that’s why i’m posting these separately.


From electronic point of view, this is exactly the same effect as the big box reissue. Only differences are the manufacturing methods and the type of components. While the reissue tries to stay true to the vintage Octave Multiplexer, the XO series version just tries to add more user value to the design.


The main difference in features is the “Dry out” jack placed next to the “Wet” output jack. This allows the user to split the signal to two paths. First for the sort-of bypass and second for the processed signal. Nice feature, but has few applications. Supports experimentation though. And that’s not a bad thing.

How does it sound?
Exactly like the huge box reissue. Both of the versions sound exactly like each other, so in reality there’s not much point in having both. Unless you love down octave divider effects and are a pretentious asshole, also known as the collector. Again – For a bit more in depth article on this circuit, check out my Octave Multiplexer Reissue post.

EHX Germanium OD

Saturday, November 1st, 2014


What is it?
Electro-Harmonix Germanium OD, “Vintage Overdrive” from XO series. Made in USA around late 00’s.

Creativity. A threat or a possibility? Sometimes it manifests itself as both. And at the same time. I got mine as used for a fair price with velcro on the bottom. By the way, you can use the detached strip to get the residue glue off the metal. Anyway. The internet had only a few guesses of how this circuit was made. This was one of motivators in play when i decided to buy one. Opened it up as usual.


And traced it. If you take my drawing and mirror it vertically, there are some similarities with Arbiter Rangemaster – but not much. The point of the design is PNP transistors reversed with negative ground and odd controls that affect resistance on both, emitter and collector side of the main transistor. Which looks a lot like remake of NKT275. Or possibly even a re-branded NKT275.


Everything about the circuit and the build quality is more or less on par with all the other modern new york manufactured EHXs. No handwiring involved and most of the circuit is made with SMD components. I brought up the creativity in the first paragraph, because this design falls easily into “drunk or genius” category.

How does it sound?
Unusual. Wouldn’t call it good, but it offers that broken 60’s tone when applied in front of a decent tube amplifier. But folks looking for an overdrive.. This may feel like an awful mistake if you are not exactly sure you know what you are getting into. OD may not be a perfect description for the sound this produces, in my opinion. I’d rather call this Germanium Warmer. If considered as a “warmer” instead of an overdrive, this might be a useful tool to nail that sixties teenage garage punk clean tones. Think of this as a Rangemaster style treble booster with full frequency range and less boost. With rather senseless controls, of course. That should land you in the correct park.

Not bad at all. But i still wouldn’t call this an OD.

EHX Octave Multiplexer (RI)

Sunday, October 26th, 2014


What is it?
Electro-Harmonix Octave Multiplexer Reissue. Made in USA around 00’s.

For starters, EHX Octave Multiplexer was originally an apparent move to compete with all the other octave divider boxes that started to emerge in late 70’s and early 80’s. I have no idea when the very first down octave effect was produced and by who. Still, the basic idea of driving a flip-flop circuit over the top produces the analog octave down effect we know and love today. Sure, the technological advances have bumped us to the point where small footprint pedals can produce polyphonic octave down effects. But there’s still nothing like trying to get these flip-flop based octave dividers to track your signal properly. As a caveat, this type of circuitry can easily miss the note you wanted to add the effect to. When that happens, the tone produced is just wild and completely senseless. This behavior is something that can’t be digitally modeled. And it is a feature, love it or not. So is a modern polyphonic down octave better than its analog counterpart with its own flaws? I’d say no. Musicians have created a tons of great sounding guitar tones for tons of great albums with effects like these. To love the mistracking means that you have to be a person with adventurous mind.


The unit we’re looking at here is the 00’s reissue of the original 80’s Octave Multiplexer. The circuit has similarities to its predecessor, but there are modernized parts to it. The sub switch is not present on the original and this is the biggest difference between a reissue and the vintage unit. This switch takes the low octave in and out of the processed signal. If taken out, the “High Filter” control lets one use this as a up octave. Sort of.


The low octaves are created with a 4013 16-pin flip flop circuit. As seen in most of the effects in this genre. EHX couldn’t have done a better or worse job with their circuit, since it’s all about the 4013. The tracking aspect can vary with the rest of the circuit and in my opinion EHX does this remarkably well. Actually the Octave Multiplexer ranks at least as high as Boss OC-2 in my personal favorites list. The way this flip-flop works is that the signal pushed through it has to be huge. But if it’s too big, the tracking won’t work right. And if the signal is too weak, the octave divider doesn’t work. One can, of course push a massive fuzz through the flip-flop like done in MXR Bluebox, but to create all analog, distortionless, well tracking octave down effect isn’t as trivial as one might think. Some people prefer to use a compressor in front of this kind of effects to help the tracking. It works to a degree.


Board design and manufacturing methods look exactly like all the other reissues in EHX catalog. Not a pleasure to look at, but not ugly by any means. Massive sized box will definitely keep a few future fans away. But for that, there is XO-series version with otherwise the same electronic circuit. Just made with baked-in SMD components instead of the real deal.

How does it sound?
Wild and mean with a decent tracking. I think the size and the of the box may have been contributing factor to why Boss OC-2 has always been considered as a classic and EHX Multiplexer hasn’t. To my ears the Octave Multiplexer sounds at least as good, but with added craziness in the form up octaves as well. It sure is a beautiful sounding octave down. Every time i need an octave down when recording it’s either this or the XO version i take with me. Unless it’s a dirty down octave that is needed. Then the choice is DOD Buzz Box. Not much sense in trying to feed clean down octaves with wild distortions. So. For clean down octaves. EHX Octave Multiplexer is the king.

EHX OD Glove

Friday, October 10th, 2014


What is it?
Electro-Harmonix OD Glove from EHX nano series. Made in NYC in 2013.

An overdrive that sounds like nothing else on EHX catalog. That’s the catchphrase from the marketing material. Sure enough. It isn’t close to anything from current or past EHX catalog. But it is rather familiar from somewhere else. Take a look.


The chip on the right is ICL7660S, a DC-DC converter, which doubles the incoming 9V to 18V(ish). There’s a slide switch for selecting the use of standard 9V or doubled. I suspect the 18V doubled mode will eat your battery a lot faster than the standard voltage mode, so a switch may have been a nice idea. How does it affect the operation or sound.. That’s another story. But let me say – not that much. There is a distinctive difference, but t actually hear it, you’ll need to be somewhere else than your rehearsal room with the rest of your band.

The main circuit looked pretty simple when the function of the other chip was established. Couldn’t help myself but to trace the whole thing. Here are the results. Does it look familiar to you? Non-inverting gain stage with gain control, hard clipping done with two MOSFETs (shunt to VRef instead of ground), a recovery stage and a two mode switchable, simple tone control. All that followed by a standard level control.

If you haven’t seen this before, i guess it’s time for you to get yourself a 18V running, MOSFET clipped, tone control added derivative of a Voodoo Lab Overdrive. Or in other words, a very nice and super cheap derivative of something related to an obsessive compulsion disorder.

How does it sound?
Fat and distortion-like overdrive. Very nice sound that sits well in somewhere between a Voodoo Lab OD and a MI Audio Crunchbox. High gain overdrive that’ll suit many occasions with its good controls and good range from near clean to overwhelming drive. The 18V switch adds some headroom, which lets the pedal to live a bit more than it does running on 9V. Treble cutting the tone knob does may be useful to most as well. I’ll keep this short. It sounds good.