Archive for January, 2014

Boss GE-7 Graphic Equalizer

Wednesday, January 29th, 2014


What is it?
Boss GE-7 Equalizer, made in taiwan in may 2002. Otherwise in fair condition, but missing a few slider knobs (which seem to very hard to source as spares).

Schematic is online, courtesy of There are three DIP-8 and two SIP-9 opamps plus a transistor based output buffer that make up the circuit. There’s also standard Boss-style electronic JFET switching. All seven frequency ranges from 200 Hz to 6.4KHz are active filters that are able to boost or cut the desired frequency while keeping other frequencies well in tact. Plus the gain slider sets allover level and offers a reasonable amount of boost for all individual bands.


The board is your standard modern taiwanese specimen. Dull, ground/trace-filled, autorouted touch, which doesn’t raise much feelings. The (a)symmetry is more pleasing than most of the modern designs, but still quite boring.


Didn’t expect to see SIP opamps so this was one quite interesting things about this pedal. But now that i’ve been inside of various Boss boxes, the surprise isn’t that big. Other thing that in reality is interesting is definitely the board fastening. All the sliders have their own board, which is fastened to the main board and the enclosure with a single screw. With these few peculiarities boosting the otherwise low interest, this is not a bad tool to have.

How does it sound?
Loudish. Can be used as a clean boost in addition to frequency tweaking. Versatile 7 band eq. Doesn’t sound like “Wohoo”, but rather like “Yey.” One can definitely use this to pre- or post-eq other pedals  in addition to boosting one’s cleans. And distortions.

ENO Music PT-21 Guitar Tuner

Monday, January 27th, 2014


What is it?
ENO Music PT-21 Guitar Tuner, made in china 2013.

I wanted to try something tiny as a tuner for my personal pedal board. The price was one factor. I didn’t want to get another TC Electronic tuner as the old Polytune i have works reasonably well and i’m familiar with the use. Recently i’ve noted that i rarely use the polyphonic mode, so i was pretty interested in these new chinese mini pedals. First i tried it out. Works. Feels responsive.. A/B’d this with my old war horse, Boss TU-2. That Boss is the tuner i use at home for everything from re-stringing to fine tuning the intonation. TU-2 is good, responsive (sometimes too responsive) and very accurate tuner. This ENO is about as fast as TU-2, doesn’t go mad and doesn’t get mixed up in frequencies.


Opening the unit up shows pretty neat work. Everything has its place (ok, the couple red wires could have been replaced by better engineering). The rubber band making the DC jack fit perfectly made me smile. Simple solution, yet quite elegant. At this point i’m not getting deeper about how it works as it is digital design. Maybe i’ll revisit all the stub articles about digital stuff one day..


It seems like the ENO PT-21 is solid and well made tiny tuner pedal. I’m yet to test it on my own board, so we’ll see how it takes some real action – handling the temperature changes and if the frequencies stay accurate on real situation. For home use this cheap little thing seems to be a good choice.

Placed it on my board and used it for a few days. Even though it seemed to be as accurate as TU-2 in the first run, the Floyd Rosed Strat didn’t agree. It does get close, but not close enough. Sad. Sad indeed.

How does it sound?
It doesn’t. But it isn’t supposed to. It is true bypass though. But for the usage.. It’s not the worst tuner i’ve had by a long shot, but it simply isn’t accurate enough for me. Not bad, but i might sell it off rather than trusting it. Oh well. Guess i’ll just need to get that Polytune mini. On the bright side, this is definitely better than DOD FX12 Tuna.

Morley DDB Diamond Distortion

Friday, January 24th, 2014

Morley-DDB-DiamondDistortionWhat is it?
Morley DDB Diamond Distortion from so called “Jewel box” series. Made in US between 1995-98.

My passion for pedals and effects is something that i don’t quite understand myself. This series is perfect example. I seem to like stuff that may not be worth it. Morley is best known for their wahs and wah derivatives. But there are some non-rocker pedals in their back catalog too. The four units in the series all share the same project box. Thin, wide and very, very long. The measurements are far away from the sidelines, missing the ballpark completely when it comes to usability. The boxes take up a half of your pedal board, but they do look pretty cool otherwise.


Spacious board layout shows that the same circuit could have been fitted in 1590B (or MXR-style) enclosure without issues, even using through hole components including 0,6W resistors and still there’s enough room for a battery slot. As with a few other Morley distortion designs, there is TL074 quad opamp and silicon diodes as clippers in the feedback loop of the main gain stage. Standard three controls of Level, Gain and Tone. Nothing too special in the design, just straight forward buffer -> gain stage -> recovery stage -> tone control -> buffer. The schematic is available at Morley’s site. The schematic says it’s “revised” and dates back to ’97. Wonder what, if any, differences there are between that document and the earlier one.


As the strip side picture of the board shows, the strips are a little wider than usual. The component side shows the massive room between the components without any symmetry or other visual candies.

As a side note – if you’re about to open your box up for any reason, keep in mind that the grounds for the left and right side of the board connect only through the weakest part of the board, between the battery hole of the PCB and the bottom end of the box. This is very stupid decision for the PCB design as the thin stripe of board can be easily broken. One can of course take a wire from jack ground to another to ensure that the box stays running for ever, even if that strip of board was to crack at some point due to opening the box up.

How does it sound?
Not bad overdrivish distortion. Not too great either. For your standard driven Marshall JCM900 sound, just turn the volume and tone to the max. It is usable, but with nothing special. The overall tone reminds me a lot of original MXR Dist+. The gain knob takes you from mildish overdrive to heavier overdrive. Other controls are pretty much useless. Nice novelty item as everything in a “jewel box” should be. It just doesn’t sound great enough to leave an impression. Talk about severe meh-factor.

Boss BD-2 Blues Driver

Wednesday, January 22nd, 2014


What is it?
Boss BD-2 Blues Driver. Made in Taiwan. Unit has nice road worn on the casing. Manufactured in april, 2004.

Although i’m not deeply in love with Boss boxes, there are a few designs that i find interesting and usable at the same time. This is one of those. Discrete opamp  and well designed JFET sound in compact box. There are a lot of these milder overdrives available from various manufacturers, but still only couple of really good ones come from big names. Boutiquers and few high end brands offer similar JFET-based vacuum tube analogy, but practically none of the mass producers do it.

For those interested, Gauss Markov has the redrawn schematic up on his site, so check it out. There’s factory schem available at Free Info Society too.


Under the hood shows the reason why most of the Boss boxes give me a severe case of meh. Autorouted, neat and clinical. These are made to last, but not to please the eye of an aesthetic electronics freak like me.


There’s a lot of spare room on the board, even though the discrete opamp stage is at least as complicated as using a standard opamp. That’s the key to the sound.

I really don’t get it why this pedal is listed high on big name modding lists. In my opinion a pedal should not be fixed if it’s not broken. And the Blues Driver is definitely not.

How does it sound?
Like one of the greatest low gain overdrive/distortions. It nearly captures the feel of overdriven old Fender tweed or Gibson amp. Quite edgy, articulate and dynamic. With low gain settings this is shining as one of those always on effects. Reacts quite dynamically to the way you play. It simply sounds great, even for someone who isn’t a fan of Bosses.

Ibanez AW5 Autowah

Monday, January 20th, 2014


What is it?
Ibanez AW5 Autowah in plastic enclosure from later soundtank series. Made in taiwan around late 80’s.

This model has couple things that are unique. First of all, it is the only Soundtank with analog opto-isolator on board. The box and the component layout itself is quite neat. It’s pretty well made and placing high on build quality in the series.There is a schematic up at Dirk’s page.


The schematic shows the basic signal path to be a buffer splitting the signal to bypass, modulation filter and the trigger part. The trigger part is close to something we’ve seen as a trigger in many other designs, like couple of EHX autowahs. It Includes half of an dual opamp and two diodes rectifying the triggered signal to two transistors which in part control the vactrol (or opto-isolator). The filter part is not too far off from WH10 and others. Then there is, of course, a output buffer and all the standard Ibanez electronic JFET switching components. All in all. Elegant design.

By the basic design, this should be very nice autowah. But is it?

How does it sound?
Sad. For obvious reasons one could have AF9 or AFL in mind once seeing this unit. It does not sound anything like the early 80s Ibanez perfection from 9- or Master series. It gets the job done, but overall it is sounding like a hollow, cheap thing. I may not be the greatest expert on autowahs, but i apparently have quite a few effect boxes from that genre. This one? Definitely not one of the greatest. Actually. One of the worst. You’re after a usable autowah in low price range? You should be looking at Dano French Fries instead. This one is much more of an nice novelty effect or a collector’s item than usable effect pedal.

Danelectro CV-1 Vibe

Saturday, January 18th, 2014


What is it?
Danelectro CV-1 Vibe from Cool Cat Series. Original version, no level trimmer under the battery slot.

I did get pretty far with my collection without having a single vibe-only pedal in it. This unit finally changed that fact. Danelectro made a number of itself with the vibe from its mini series. And for a good reason. It was very cheap and very good sounding vibe that many people simply true bypassed and rehoused. The success of mini-series univibe clone set pretty high hopes for this unit too.

This is also an good unit, but it has couple of reported faults. The first issue is with the delay of wet signal. I do get the idea of disconnecting power from the circuit when bypassed. But it is a very stupid idea on a circuit which operates on four LDR (light dependant resistor) stages that all need notable amount of current. Yes, that’ll save you from swapping the battery every 4 hours, but then again – who uses batteries anyway? Now, when we cut the power and push it back on when bypass switch activates the circuit, there’s bound to be a short, less than half a second delay before all four LDR stages are running properly. That is a fault. Not that it would bother me in any way, but that still is a fault.


Second issue reported is the rise in output level when activated. Later units have a trimmer pot under the battery slot, which lets you adjust the level to perfect. The original units don’t. The issue comes from the dual opamp seen on the gut photo’s main PCB on lower right corner. That simply applies slightly too much gain for the output signal. This is another issue that doesn’t bother me at all. But someone who would use this vibe as a everyday effect on his/her board, would suffer from these faults. Two “errors” on one design has never been a good thing for the pedals (nor for manufacturer’s) reputation.

Both issues can be addressed with relatively small effort. Just take the power continuously to the circuit, bypassing the switch. And change the value of one resistor to get the unity level back. Both are simple procedures, but i personally don’t see a reason to perform either. One can and should probably use this for recording instead of live performing. The issues mentioned do not bother you in studio and there’s a very good reason to use this for recording…

How does it sound?
And this is that reason. The overall sound is very close to the classic Uni-Vibe, but here we have added personality and overall feel of the sound is slight darker. Three controls can tune it from mild phaser-like atmospheric slow sweeper to super-wobbly wild child. Both extremes take the whole signal and put it through the blender with your morning smoothie.

For the price and construction (disregarding the two faults), this is in fact a very good catch. One should still look for revision two, rather than the original. For me, i’m keeping this as is.

Digitech DBM Bad Monkey

Wednesday, January 15th, 2014


What is it?
Digitech DBM Bad Monkey Tube Overdrive from Distortion series. Made in china around 2008.

Bought mine for a very low price as an broken unit through ebay. As usual, my first suspicion was that the unit had gotten a jolt from wrong polarity supply. This wasn’t the case. Seller stated that he “don’t know what’s wrong”. But just seeing the unit gave an explanation why this pedal wasn’t working. It had been either thrown around in anger or kicked with intention to break it. The gain and level knobs were broken from getting a hit. I opened the box up and probed to confirm. Yes. Both of those pots had internal damage. In fact, the sweepers were simply ripped off from the carbon strips inside the pots. Took me a while to track down the exact pots and new original spare part knobs. Those did not come cheap, but overall, i still got away with about 25% less money spent that i would have used on a new unit at cheapest.


The board apparently uses the same base layout as all the other Distortion series effects (Screaming Blues, Death Metal, Grunge and Hot Head). Mix of Panasonic metallized polyester caps and standard small surface mount components. The design and almost everything about these boxes are just too modern for my taste. So these are not my favourite things to collect, but once i happen to find one for a reasonable price or as broken challenge – i can’t seem to help myself.

How does it sound?
Not too great. Very deep mid honk accompanied by similar tone controls found on DOD Grunge. I would say it sounds very much like a Tubescreamer alternative. Can’t say if it is any better than a TS. For my style of music and playing it is more or less useless. The EQ section offers more versatility than most other TS alternatives/clones,but let’s face it. The tone controls on this particular design have not reached the level of “any good”. If you’re looking for a TS with more bass, this might be your choice. Due to the fact that it sounds exactly like TS with more bass and the price of a new unit is somewhat unbeatable when compared to quality. Not great. At all. But for the price.. Very good.

Boss MD-2 Mega Distortion

Sunday, January 12th, 2014


What is it?
Boss MD-2 Mega Distortion, made in Taiwan in february 2009.

Got the unit in very good condition for a fair price – without a box and papers, but still nice. Actually i got this on the same day as the Morley Crystal Chorus. So, of course, i hooked them both up for testing at the same time. Oh boy. Let’s return to that in a bit.


Modern looking traces on a filled board. This time, a space well used. The amount of gain the two SIP opamps and a handful of transistors deliver is respectable. The design that has basically five stages amplifying and/or driving the signal, with no diode clippers and manages to keep the massive noise content away is quite respectable too. Aside the buffering and standard Boss electronic switching, there’s a discrete JFET opamp acting as first gain stage. This stage offers the Gain Boost control too. Which is followed two standard gain stages. After that there’s very peculiar looking differential stage, followed by active tone control leading to standard level control. Not simple in any way. You can check the schematic out at FreeInfoSociety‘s page.


That peculiar differential stage i mentioned.. I’ve not seen that configuration exactly like that before. If it is something standard i’ve missed, please let me know. I may dig deeper in to the idea at some point to satisfy my curiosity. Anyway. This is standard Boss box that would normally, even with one interesting stage on the signal path, raise not much more than meh. But this time…

How does it sound?
Like a very pleasant surprise. I don’t think i’ve heard distortion as thick and saw waved before. Massive amount of gain with sufficiently low noise levels. The amount of sheer distortion is so high, that the sound is no more distorted in traditional sense. It reminds me a lot more of a tight and thick saw wave synth sound. And as i previously didn’t know where or when to use chorus effects to get something decent out of them.. This box solved it. Place a soft analog chorus in front of this one and be prepared for total angry synth mayhem. So far, this is the greatest distortion to me in all of Boss’ lineup. So. I’d sum this one up as so over the top distortion, that it isn’t one in the vast number of normal distortions. Quite nice to run into something like this instead of thousands of standard distortions.

Ibanez CD5 Cyberdrive

Thursday, January 9th, 2014


What is it?
Ibanez CD5 Cyberdrive, fixed wah distortion from later Soundtank series. Made in taiwan late 90’s.

Ok. I’ve said this before. There’s one sub-genre of distortions that just isn’t for me. This being the fixed wah distortion. And here’s the Ibanez’ take on one with modern, dull traces and nothing earth shattering. Well. Not completely like that. There are couple of interesting things in there. That won’t mean that the unit is anything more than piece of unusable junk, but those couple of pointers are good to know before throwing your 15 year old birthday gift away. You won’t be in for a bucketful of cash, but just don’t throw it away yet.

Funny how this and my Dano Grilled Cheese are the two units in perfect condition. Both are quite old units, but it seems like neither of them has seen any real use since they were bought from music stores years ago.


Once i opened the bottom plate, the feeling of “meh” was overwhelming. To my eyes, this is the ugliest board in the whole series. But now that we got most of the trash talking out of the way, we can dig in and see what we’ll find. Dirk Hendrik has drawn a schematic, so take a look at it next. Now. You can see the red LEDs for clippers and that the main gain stage is sort of like a Rat/TS hybrid. Those LEDs are in feedback loop of an non-inverting amplifier and the gain setting components at the inverting input are creating two frequency/gain networks alá Rat. The distortion side is quite simple but still appealing, even there’s nothing special about that.


Some of you may have noticed that the input buffer splits the signal and passes it to tone “tone” control driven by another dual opamp. That topology reminds me of something. Now where have i seen that before.. Here. So you have a decent distortion and a tone control that is in fact 1:1 with Ibanez WH10 (and WH10v2) Wah pedal.

Now you know what it’s made of. It is a curiosity. Quite unusable one, but still a curiosity. One could take a wah enclosure and mount the board inside and probably even make it switchable with standalone WH10 circuit. Would make pretty cool high gain distortion wah.

How does it sound?
Engineers have been after something new and this is the result. It sounds like a high gain distortion and a inductorless wah in fixed position. That’s what it is and that’s what it sound like. Sad that we can’t separate the two. The distortion by itself wouldn’t be bad and the wah by itself isn’t bad – we know this from playing around with the reissued WH10v2. But these two combined.. No. I could see myself using this pedal in a studio, if i was to record some thrash- or mathmetal solos. But there’s not much chance of that happening, so the unit will probably stay in the cabinet with all my other Soundtanks.

Suitable for hair metal of the late 80’s and early 90’s. For anything else? There are other pedals.

Colorless writings, part 6 – The Diode Breakdown

Thursday, January 9th, 2014

What on earth are you talking about this time?

Doesn’t the title say it all? Ok, ok. I admit it’s somewhat ambiguous. I’ll start by talking about the diodes in general and you just try to hang on. Is that ok? Good.
Most of you know the basic use of diodes in stompboxes. First one everyone has encountered is definitely the bright red LED that lit up when your first guitar effect pedal was first engaged. The LED is a diode as much as all the other diodes are diodes. As the name Di-ode suggests, there are two terminals to every diode. If there were more, it would not be a diode anymore. It would be a triode or pentode and so on. At simplest, the diode will pass the current and/or voltage from one terminal to the other, but not the other way around. Most of you have played with an overdrive or distortion type of pedal? I know you have. The common way to create distortion is to use back to back diodes to make the signal clip, as in distort. Other very common use for diodes in guitar effect pedals is to use them for polarity protection. This use has two different applications. In series and in parallel. The diodes are also commonly used in electronic switching as rectifiers for switching JFETs. And then, of course, there’s the humble indicator LED. These must be the most common uses for diodes. While there are some applications for zener diodes to lower the voltage and a few others, the ones listed above are the most common.

The diode is simple semiconductor that is based on the idea of semiconducting material passing the voltage and current only in one direction. When someone had the eureka moment of placing two in parallel and in opposite direction of each other, the world changed. Earlier we had to rely on transistors driving each other to get the dirt out of our electronic guitar addons. After that moment we started having lots of harmonic distortion with ease.

All of the diodes used for clipping have their own character to the clipping. The most usual 1N914/1N4148 (or any other similar Si diode) has the tight feel on the breakage. Other commonly used clipper diodes are 3mm LEDs, germanium diodes, other small signal diodes like 1N60P and schottkys. LEDs compress the signal more and offer more output level. Schottkys are quite similar in character, but slightly tighter and more bassy. Germaniums tend to offer softer sounds to the clipping, but they drop the level a lot more than any other type. Different germanium diodes also have slightly different responses, but they all share the level issue. 1N60Ps are close to 1N4148, but they sound more brittle and glassy.

Some of you weren’t probably aware that any transistor can also be used as a diode? Just omit, snip or maim the collector and use the base as an anode and emitter as a cathode. Same thing applies to FETs as well. The current will pass from base/gate to emitter/source, but not the other way around.

So that’s for the clipping configuration, how about other purposes?

From the common ones, the one that’s simply more important than indicator LED to me is the reverse polarity protection. To protect the circuit from wrong power supplies, engineers have used diodes to rectify the supply voltage. There are two common, yet completely different ways to achieve this. This protection is very good thing to have, as some amplifying semiconductors are very delicate devices. Meaning that they will burn up in seconds if they get + voltage to where – should be and vice versa.

First, these is the method of placing a diode anode to ground and cathode to supply. This method has a valid point, as it doesn’t touch the voltage at all. But as a huge downside, the wrong polarity causes the diode to be only thing between positive and negative lead of the supply. Meaning that all the possible current that the supply is capable of giving out is shorted through that diode, leading it to literally break down. If there happens to be a fresh 9V battery as a supply, all the juice is pushed through that diode in just a few seconds. In worst case, the diode practically explodes and takes a chunk of the board with it. In best case the silicon semiconductor just burns up leaving the diode to act as a sort-of resistor. Either way, the effect will be completely fried if it gets the wrong polarity as its power supply. Sure it can be fixed, but it’ll need at least wire cutters (preferably an solder iron and a new diode) to get it running again. Unless the board is done for. Sadly, i’ve seen those cases too.

The second method isn’t as popular in main stream big brand designs as it is for boutiquers and small brands. This is to take the diode in series with the supply. Yes. It’ll affect the supply voltage. In worst cases, when using a diode that isn’t meant for this application, the voltage drop could be a Volt. That is usually way too much of a drop, so using a proper diode is more than crucial. 1N5817 Schottky is one of the good ones. The drop stays low and as with any diode using this method – the board or the diode itself doesn’t get hurt if it gets the wrong polarity. Circuit simply won’t work at all. In other words, a diode in series with the supply will eliminate all current flow from the circuit without breaking anything up.

 What about LEDs and the other types then?

The indicator LEDs are diodes just like their other counterparts. The just happen to emit light when current passes through them. Thus the name, Light Emitting Diode.

By other types in this context, i mean zener diodes in particular as those are the ones we commonly find in pedals. In addition to small signal diodes, schottkys and LEDs. Zeners have one very nice feature. They can be used to lower the voltage. In simplest terms, placed in parallel with the supply (anode to ground, cathode to supply), the supply voltage will be reduced to the value of the zener diode. If you use 8.2V zener in that position, the excess voltage will get dissipated through the diode, leaving the supply at 8.2 volts.

I feel like i haven’t even started on this diode subject, but the usual 1000 words are already up. So, against my standard behaviour, i’m going to leave you with a wikipedia link that explains more than you ever need to know about diodes. In detail.