Archive for the ‘Electro Harmonix’ Category

EHX Small Stone EH4800 Phase Shifter

Sunday, September 28th, 2014


What is it?
Electro Harmonix Small Stone EH4800 Phase Shifter. Made in USA, possibly in early 00’s.

This wasn’t the first and certainly won’t be the last pedal i’ll buy as a broken unit. Sure there have been units that were beyond repair and those will always hurt, but usually i tend to be able to fix them. This particular unit has all the OTA chips socketed. The symptoms were that the pedal only worked with a battery, but not with a power supply. True. This was the case. But even though i suspected a broken connection from the DC jack, the truth was that everything started to work right once i pressed the ICs firmly back to their sockets. Which makes me wonder why all the chips are socketed in a unit that’s manufactured in this scale. Who knows, maybe not all the chips work perfectly in this circuits and they need to be swapped around.


Since the early versions of the 70’s, the design has always been using OTA chips to create phasing. There is a distinctive difference in sound of JFET-based phaser when compared to OTA-based design. According to the internet, the early units had CA3094 and CA3080 chips in them. The later versions, due to obvious reasons, are done with LM13600/LM13700 chips. If the reason is not yet obvious to you, the CA3080 was discontinued about 10 years ago, and the CA3094 even earlier. While there are a number of CA3080s available through auction sites, the price and availability isn’t exactly right for manufacturing of this scale. LM chips are still in production, even as surface mount chips.

As for most classic circuits, there is a schematic floating around the web. This one’s drawn by Bernandduur and as always with his work, it is a pleasure to look at it. There’s a quad opamp for in/out buffering and LFO, plus two dual channel OTAs for the phasing. Basic manufacturing methods on these units look ok.  Neat, but not too pleasing.

How does it sound?

A deep wobbler with definite personal sound. Decent range on the rate knob and depth of the phase goes way beyond what we are used to. Even though the sound is very good, don’t expect to get soft and mild slush out of this. This is a lot more like a shock effect than ambient phaser. Prime example of good EHX design. Something that’s not exactly like all the others, and successful at that.

EHX Holy Stain

Saturday, September 13th, 2014


What is it?
Electro Harmonix Holy Stain from XO series.Made in united states in 2010(ish).

Once again. Put a pedal, any pedal, for sale with a broken switch and a price tag around 20% of a new unit. You bet i’ll be there, bombing your email and throwing the little money i have against the computer screen. This was one of those. Simply swapped the defected 3PDT bypass switch and did a little cleaning. Unit works as it should. Or at least close to it.

Checking out the insides shows a DSP based big board. All done in current, dull EHX manner. I’m guessing the drive/fuzz/distortion is done with transistors and the rest is digital. It’s sort of like a modern hybrid.


Let’s talk about the features a bit. To begin with, the Holy Stain looks like a cross breed between a Muff and a Holy Grail Reverb, with a few added extras. The main stomp switch is our bypass that sets the overall effect on and off. The basic side is controlled by two rotary switches, a tone control and a volume control. The first rotary selects between clean, fuzz or drive modes. The second selects overall tone color between bright, dark and warm. Tone control acts pretty much like the one on big muff pedals and volume is rather self-explanatory. All that is used to set the base tone.

Then we have the rest. Foot switch selects the digital effect mode between room reverb, hall reverb, a pitch shifter and a tremolo. These four modes share the two controls for all of them, the mix and amount. Mix sets the blend of this extra effect against the clean/fuzz/drive tone coming from the first part. The amount acts as a decay time setting for both reverbs. It also sets the frequency of the pitch shifter mode and the rate of the tremolo. Amount can be rocked with a external expression pedal, which makes the tremolo mode a lot more interesting and the pitch shifter to have similar features to a Whammy.

Limited, but still quite a set of features. These usually come pretty cheap, even as new. But if you think about the features and compare them to what you actually use – or want to use. For me, i would probably gone for separate drive and effects sections with a stomp to engage/disengage the effects other than the drive side. Sure there is notable amount of outside the box thinking when the designer has set the features, but…

How does it sound?
I’ll start with the good and go on about the bad a bit later. The Fuzz mode is actually good with its crisp lead sounds. On fuzz mode, the color settings are usable too, even though i tend to leave it on warm. Both reverbs are ok too, with a slight note explained further…

Off to the bad. First off, to me (yup, may be heresy, but i’m talking about my taste) the clean and drive modes are just bad. First thing that comes to mind is the horrible distortion section found in Digitech RP6 multi-effect. Color and tone controls won’t save those, no matter what. Other reason why the RP6 pops up to mind is the latency. All the digital effect modes are fine if you have your mix control below 35% mark. Higher than that, the guitar signal has already gone out of the speakers before the verbs/shifter/tremolo even think about touching the signal. Similar digital lag as heard on RP6.

One very good mode with almost usable multi-effect section – if you keep the mix down enough for it to work right. Otherwise… no.

EHX Nano LPB-1 Linear Power Booster

Saturday, July 26th, 2014


What is it?
Electro-Harmonix LPB-1 Linear Power Booster from EHX Nano series. Made in US in 00’s.

I’ve been over this units grandfather before in the form of EGO Microphone Booster. In its heart it is still the same simple one-transistor-as-amplifier booster. The base topology remains, even there are a number of modern additions to the box. First off, the bypass method is per modern standard, meaning a 3PDT stomp switch with true bypass. There are power filtering and polarity protection present and chokes for input and output. The tiny, simple circuit can now be powered by modern standard power supply or a battery. Board layout is really ugly and there’s acres of wasteland in there.


I had a conversation with one person who was looking for plain volume boost for his setup and asked me what he should do about it. Get a custom build from me or try some commercial solution? Or some other option? I said “i think the best way to see if a simple booster is what you want, is to buy a LPB-1 as used unit”. You know, since you can get one for 25€ post-paid. I also said that if it didn’t suit him, i’d buy it off from him with that price. And here we are. I wasn’t planning on buying one, but i guess it’s good to have one of these too. and now the dude knows that he can’t get pure, clean power amp volume boost out of any pedal. He’ll need an amp that can do that.

How does it sound?
Like a single transistor booster. Clever and nice way to get your vintage-style single coils to light up. Some might even use this as a boos for clean lead sounds. But still i’d recommend this only for single coil pickups with lowish output. Ive been playing around with these circuits over the years, but once i got this unit.. I though it was broken. On any setting over unity level, it started to break up the sound in not so great manner. I checked the unit over and it was (still is) fine. I took another guitar and, yup. The super high output Hagström customs were just too much for it. The distortion created by too high input level isn’t pleasing.

Overall tone? Clean, colorless, tasteless, odorless simple boost. A tool.

EHX Big Muff Pi with Tone Wicker

Tuesday, July 1st, 2014


What is it?
Electro Harmonix Big Muff Pi w/ Tone wicker. Made in NYC, USA. According to the serial number, this unit has been manufactured in 2013.

A Big Muff with added features? Sure i had to get me one. It’s not that often that i buy pedals as new, but when my interest is piqued and the price is right, who am i to argue with the collector inside my head. And as always, i needed to rip it up as soon as i had a chance. After a epic battle with the DC jack, here it is.


Otherwise all SMD, except for the aluminum electrolytics, diodes, main transistors and most interesting part of them all, the tone stack capacitors are ceramic. This could be a result of trying to recreate the feel of the old BMPs. This unit has BC550Cs for transistors. The same type we’ve seen on other modern reissues as well.

So the basic BMP is in tact, but what are the added features? First off, we have a tone bypass switch. A feature that was present in late 70’s / early 80’s IC version (also known as version 5). As the name suggests, the tone control is completely bypassed and full range of frequencies are pushed through. The old tone bypass switches had a resistor in the path of the bypass to compensate for a level boost coming from dropping the tone stack off the circuit. On this unit, there isn’t one. So the volume boost you’ll get by bypassing the tone is noticeable. The second switch is called “wicker”.


The “wicker” switch is quite peculiar thing. There is a CD4066 CMOS switch added on board and it’s controlled by other half of the “wicker” switch (the other pole of that switch is unused). What this switch does? It takes the small value hiss taming capacitors off from the first three gain stages. This results in increased noise floor, but it also gives a noticeable amount of more spike to the feel. Since there weren’t a schematic or anything definite about the wicker circuit online, i traced my unit. Check out the traced chematic here. I’d also suggest reading Kitrae’s notes and info about the unit on his awesome Big Muff page.

Box features EHX modern standard true bypass. To be honest, i’m not a big fan of current EHX board design or box/chassis grounding methods, but i am digging some of the sounds…

How does it sound?
Very nice addition to the BMP family. It can be used as a standard big muff with both, tone bypass and wicker switches in off position. In that mode it doesn’t differ a lot from any other Muffs. Or not at all to be exact. Once the Tone bypass is engaged, it reminds me a lot of the V5 BMP clone i built for myself (although my IC version clone tends to sound a bit more synthy, which is not a bad thing at all). And once the wicker is switched on, it basically takes the standard muff to a new, noisier level with added bite. So basically, we have four BMPs in one box. The standard sounds are intact, the tone bypassed, roaring Muff is in there and lastly we have something new to add to our palette. Seems like too many pedals get this “versatile” word out of me. On this occasion it is well deserved. The pedal, it simply sounds good.

EHX Doctor Q Nano

Saturday, June 21st, 2014


What is it?
Electro Harmonix Doctor Q Envelope Follower from Nano series. Made in NYC, USA around late 00’s.

There are a lot of recycled designs in EHX catalog. This is one of those that has been around since 70’s and later made its way to nano series in cost effective and more usable sized enclosure. Of course the board design has been reduced to SMD as well to keep manufacturing cost low. The design on the other hand, remains very close to the original unit.


There are a few schematics available. The first one looks like original factory schematic, but the scan quality isn’t too great. I’d prefer to read the redrawn one. As the design has been rather popular in DIY crowd, there are number of additions available. Some of those add very good features and address the shortcomings of the original (like J. Orman’s Dr. Quack or Nurse Quacky that includes M. Hammer’s mods). In essence, the original design has input impedance on rather low level, resulting in possible pickup loading. That is, unless you have a buffered pedal placed before the Dr. Q. Other improvements are for stability of the trigger and for the effective range of the filter part. Original works fine, but for those building their copy, i’d suggest reading about the improvements before doing anything rash.

For the basic functionality, the incoming signal is splitted in two. The other part rushes to the filter for being modulated and the the other is sent for the trigger. Output is taken from the filter.


The board is standard and modern EHX design. Nothing to write home about, but it works. The range trimmer is rather sensitive. To get it perfectly in tune with your chosen instrument (bass, guitar, organ, whatever), you’ll need to spend some time screwing with it. You can tune it throught the board, so there’s no real need to detach the board from the enclosure. The main differences between this Nano unit and the vintage ones are the added power filtering and parallel polarity protection.

How does it sound?
Usable, but pretty squishy. The design contributes to some noise, which will be present at all the times when filter sweep activates. Squishy noises do, however, leave us with sort of an vintage feel to the sound. So we could argue that this is not a “studio quality” effect, but it’ll serve well for vintage vibes on stage. Sure. There are other envelope filters that you might want to consider over this, but if the effect isn’t used that much.. Then the price range and quality should be right on que. Yes. That’s an idiotic pun.

EHX Satisfaction Fuzz

Tuesday, May 13th, 2014


What is it?
Electro Harmonix Satisfaction Fuzz from Nano series. Made in USA in early 2014.

Noticed this unit’s release on the web and it seemed quite promising. Seems like the idea behind the design was to recreate that well know fuzz sound from one well known Rolling Stones track. According to the stompbox historians, the unit used on the original track was in fact one of the early Maestro Fuzz Tones. Solid idea to recreate that sound. These unit sell for cheap as new, so there wasn’t much choice for me but to get one. Of course i teared it right open as soon as it landed on my desk.


Modern EHX design. No surprises there. Super dull and extremely boring design. But wait a minute! What are those empty pads just above the input jack? C7 and D2-D3. Print next to those holes say <++clip> and <++bass>. Now that’s something you don’t see everyday. As there are no hidden components on the other side of the board, i thought this should be easy enough to trace. So i did. Does that look familiar to you?


Yes. That is, in terms of topology, pretty much 1:1 with good old Jordan Bosstone fuzz with NPN/PNP pair as the main attraction. Design here has nothing to do with Maestro Fuzz Tone. Only a few cap value changes to Bosstone and voilá, there’s your new design. Smaller values for input and output caps, plus missing diode clipping at the output are the main differences, but EHX has cleverly left us with six empty pads and clear instructions what to do. Upping the output cap for 22n (10n and 12n in parallel) and adding two silicon signal diodes for clippers makes this so close to the Bosstone that it makes this unit very, very interesting. I think this would be the greatest and cheapest way to get yourself a Bosstone. Buy yourself a cheap EHX fuzz and add one cap and two diodes.

I’ve heard stories about some synthesizer makers leaving empty pads for user to try mods on. But i’ve never before seen this behavior in guitar effects before. I do hope this is something that we may see again in the future, maybe even from other manufacturers too. This does make EHX look better in my eyes…

For my own unit, i tried on the clippers, but decided to leave them out. I did place a 22n cap for C7. Now it isn’t exactly EHX Satisfaction nor Bosstone. (Maybe i should try it with only added diodes, but no cap at some point..)But it is something useful. And to be frank, it is cool.

How does it sound?
Out of the box – not so super. It has some qualities that could be reminding some of us of that desired Satisfaction tone. Thin, loudish, but not mushy enough fuzz. With output cap value increased – wow. Added body and mush. Think of mushroom clouds viewed through a kaleidoscope. Yup. It sounds like that. Fat, massive, loud and devastating fuzz. With both, clippers and cap added, it sound pretty much exactly like all the demos of original Bosstone i’ve heard. (Yup, i haven’t had a pleasure of playing with the original Bosstone unit. At least not yet.) Overall. Satisfaction Fuzz sounds good and it is definitely worth the money.

EHX Lumberjack Log Overdriver

Monday, April 21st, 2014


What is it?
Electro Harmonix Lumberjack Log Overdriver. Made in NYC. According to the serial number, this unit has been manufactured in 2013.

Someone was selling this one as next to new unit for an ok price. As some of you may already know, i’m not a EHX fanboy. At all. Other than Big Muffs and a few odd birds, the EHX designs tend to reach for the skies. Only to find their hand stuck in a pile on manure. Meaning that the designs are always trying to break the limits and to come up with something profound – but usually ending up as a novelty special effects rather than a good sounding, usable guitar pedals. The official youtube demo shows a professional guitarist praising the sound. But somehow i think i sense a hint of doubt in his presence. There’s also a short part with a bass on that demo. Anyway. As usual, i ripped the bottom plate open as soon as the unit landed on my desk. Demos suggested the unit be be somewhat a modernized overdrive version of the bad old Gretsch Controfuzz. The controls Volume and Boost do what you expect them to. The Log Factor adds distant background distortion in the spirit of the Controfuzz, but doing  it in a post 1980 manner.


Nope. That’s not anything like Controfuzz. There are five dual opamps and a few transistors in there. While i was hoping that this would possibly be something simple, something i could use to learn’a thing or two, tthe reality hit me hard. With the sound the unit has, and the complexity of the circuit.. No. I’ll just screw the bottom plate back on and put this back to its original retail cardboard box. It can stay there and wait if the sound will have any merit after couple of decades of waiting. On a brighter side, the unit does come with a power supply. So all of the money wasn’t completely wasted.

How does it sound?

Horrible. The Overdrive never grows to be completely around. Instead, there’s always clean signal present. So as an overdrive effect for the guitar, i must say that this is definitely one of the worst. For a bass? Haven’t tried it for myself yet, but there is some hope for this being a decent (or maybe even great) bass pedal.

Makes me wonder.  If a design goes south due to blatant over engineering, why do they keep marketing it as something that it clearly isn’t? Now, slap a sticker with “For Bass” on top of the retail box and it might sell. There is a chance that over engineering has resulted is cutting some of lower frequencies off. If that’s the case, then this unit isn’t suitable for anything.

Except for novelty special effect.

Electro Harmonix Ego Microphone Booster

Sunday, March 9th, 2014

Guess i haven’t been this deep into producing vintage pedal porn before…


What is it?
Electro Harmonix Ego Microphone Booster. Made in US around 1969, according to pot labels.

Got this unit as a defunct gift from J. Stolpe of Väinö Grön (and numerous other bands/musical outfits). Story is the he found this unit from his father’s belongings and kept it. As we got into talks about my favourite subject in the world, he just decided to give it to me. The signal was passing on “bypass” mode and when the battery was connected and the boost engaged it acted as a dirty buffer. After looking into the design, it became clear that the design is 1:1 with all the original LPB-1s and 2s. All it takes to create a one transistor boost is an input cap, two resistors from supply to base and base to ground (these two form a bias voltage for the transistor), gain setting resistor from emitter to ground and a resistor from supply to the collector. Oh. And a output cap. Boost control is your standard 100K pot (output cap to lug 3, lug 1 to ground and lug 2 is your output). By the way, Beavisaudio has a perfect one paged article/image about how the single transistor booster works. If you’re not familiar with the subject, check it out here.


The fault in this unit was with the resistor from transistor emitter to ground. It was completely burned out and cut in two. Looked like someone had already tried to fix it with not so great results. I was afraid that the 36999 branded transistor was dead due to the heat. Those transistors are  apparently Fairchild made clones of 2N5088, that they manufactured for EHX in late 60s. I have no way of verifying this information, but it was on the internet, so it *must* be true.

Anyway. The burned resistor seemed like 330R in value, so i went through all my boxes and drawers for similar carbon composition resistor to match the original. Nope. I didn’t have any. So i just fixed it, no matter of the cost. As you can see in the photo above, there’s one resistor that doesn’t quite match the others. I used the standard 1/6W 1% metal film resistor in its place. Works. And even the original transistor works perfectly!

Then i thought to myself, “what makes this a microphone booster, as the circuit is 1:1 with Linear Power Booster?” The jacks. That must be it. The LPB has the other end as a plug – you know, to be used with a guitar. If there are two jacks, then it must be for the microphone. Damn i just love vintage stuff like this!

How does it sound?
Exactly like the linear power booster(s). Clean and loudish  to the ~90% of the knob sweep. And then badly distorting at the end. The circuit keeps the frequencies well in tact while the line driving capabilities are worth a mention. Not great thing, but very cool little tool to have. In fact, i’d recommend every guitarist to use one of the LPB-1s in their lifetime. It should at least open ones eyes to the idea behind loud “clean” boosters.