Sunday, 27 January 2013

Emerson Custom Guitars Em-Drive

This is a really simple circuit looking at the board, but we didn't have a pic of the back and on the breadboard my suggestions didn't sound right, so I shelved it for a while until I could get a look at the unit myself or at least a decent pic of the rear of the board.

peavey_xxl on the forum posted a link to a schematic that he said someone who built a clone referred him to and so here's the layout based on that scheme. I have done the layout with the same mojo paper in oil caps in mind that were used in the original.

Updates 30th Jan 2013 - Pot value established and corrected, thanks peavey_xxl

Info about the original:

EM-Drive Transparent Overdrive:
Handwired, Handbuilt in Broken Arrow, Oklahoma USA using some of the finest quality & reliable parts available. This pedal does everything from a slight boost/sparkle to a nice, warm light OD sound. Good for use as a first stage OD or a nice boost pedal.... you may find yourself leaving this on the entire gig!

Specs:
-NOS PIO (New Old Stock Paper In Oil) capacitors
-Handwired Construction
-Quality High Tolerance CTS Pots (Hand Metered & Matched)
-Durable Turquoise powdercoated finish
-Davies knobs
-USA Switchcraft jacks
-3PDT True Bypass Footswitch
-Hand picked and matched parts for tone and durability
-Power: Standard 9 volt DC power supply with a negative center 2.1mm barrel, NO internal battery option.








and a compact version for those without mojo tastes :o)



141 comments:

  1. That's seriously the smallest one I've seen, for sure!

    Maybe do one compact layout, just for fun? =D

    ReplyDelete
  2. Have you seen what this is in retail for 160$, thats just sick! I better get into boutique business : P

    ReplyDelete
  3. Well.... it does something. I don't have any 2N5088s on hand, so I tested what I have. With a 2N3904, it's a boost (and not really a great one either). With an MPSA18, however, it creates a horrible glitchy synth-like monster that actually sounds really good!

    ReplyDelete
  4. I haven't been able to replicate the problem, so I'd say tag it. As a boost, it's actually quite nice. As an overdrive.... not that great. I tried upping the caps to 220n for bass, but that ended up making it extremely muddy.
    Cheers on 100, and here's to many more!

    ReplyDelete
    Replies
    1. Excellent cheers mate. We still need an extra two to do the 100 really because 2 of them are notifications, but no doubt Machine has another 20 to add :o)

      Delete
    2. Don't know 'bout no 20, but 2 i can probably do...
      +m

      Delete
  5. Just breadboarded this one and it works fine (used a 2N5088), but it doesn't like a hot input - sounds like ass with a humbucker. Sounds alright as a boost/light overdrive if I turn down the volume on my guitar, so it's probably nice with singlecoils. :)

    ReplyDelete
  6. Am I right in thinking that the gain pot is just doing the same job as the guitar's volume knob here? If so could we just omit it and have a really simple 6 component component boost?

    ReplyDelete
    Replies
    1. Yes it's just a pre-effect level control and you could easily do without it. But with what Fredrik wrote above, it may be useful if you play single coil and humbucker guitars so you can tame the input level a bit with the higher output pickups.

      Delete
    2. Oh, I see. I would probably use a trimpot for the gain and stuff it into a 1590A as a one-knob dirty boost, if I ever decide to box it.

      Delete
  7. Wow. For those of us who think the LPB1 is too complicated, I guess.

    ReplyDelete
  8. Finished a little test rig the other night and have been fiending for some instant gratification.

    In hindsight, I should've socketed, but used a 2N5088 and it's great! Just a few min to verify it as working, but my SHO is already scared.

    ReplyDelete
  9. This comment has been removed by the author.

    ReplyDelete
  10. On saw this video on youtube http://www.youtube.com/watch?v=S7XTk5bgc9Y 0:28 and noticed that contains 3 resistors and not 2

    ReplyDelete
  11. I built the compact version of this last night using a 2SA1815 transistor (somehow the only other transistors I have are JFETs), and I've gotta say, it's not too bad. With the volume control at max and the gain control at minimum, it sounds exactly like the bypassed signal (I'm guessing that's the "transparent" part). The pedal has a decent sound with an okay boost/overdrive up to maybe half of the gain. Above that, it starts to get a bit farty. It adds a fair bit of low end at higher gain. Still, though, for having all of 5 parts on the board, it's a fun little pedal. I wouldn't pay $160 for it, but it sounds decent ahead of my Champ and Carmen Ghia. Pushes the preamp a bit harder.

    ReplyDelete
  12. A really good booster. Tested with a 2N3904; With Stratocaster guitar with GFS Hot single pickups sound is fuller. Single-channel 5W tube amp got low gain overdrive channel. Recommendation for harp players.
    tnx IvIark

    ReplyDelete
  13. How much difference do you think the paper in oil caps actually make to the tone? I've never used any but have nice poly box caps.

    ReplyDelete
    Replies
    1. In my experience those tend to sound a bit softer, but the difference is not that huge or noticeable.
      +m

      Delete
    2. With caps some people swear they all sound the same, some people swear they all sound different, I lie somewhere in the middle. I don't think the differences are ever night and day, and I've never thought one type of cap sounded great in a circuit but another sounded crap, but I do think that there are some subtle differences between certain cap types. The best bet by far is to get hold of some, experiment and go with what your ears tell you. Anyone who is testing should always measure the cap values to make sure they are close enough in value so that any differences won't be simply due to tolerances.

      Delete
    3. You guys must have read my mind, when this went up I ordered a couple of PIO caps and some fancy carbon comp resistors so that, for myself at least, I could put the mojo theories to rest one way or the other. I'll build a totally mojo version, one using polyboxes and standard resistors and one using the cheapest nastiest parts I find and then A>B>C them to see if I can tell the difference. I thought this would be the perfect circuit to try it with as there's relatively few parts to buy. The caps came today and I think the resistors will be here tomorrow.

      Delete
    4. I think that what most people talk about differences in caps (audio) is really difference in real values (tolerance).

      While building some effects, I've had to swap mylars or mkts with monolithic ceramics due to final size of the board, both types measured and selected to the same values, and I can swear that NO difference is noticeable.

      The only real difference I've noticed is using ceramic round (lentil) caps over 1nf, extremely high tolerance (20%) that makes difficult to get a correct value and that are definetely more noisy.

      BR

      Delete
    5. The cheapy ceramic caps are the most obvious to me too, and I also could tell no obvious difference between polyester and multilayer ceramics, so I bought a boat load of multilayer ceramics! 100 for £2, thank you very much :)

      But I'm also not quite prepared to just ignore the theory like some people on FSB and other places would do. There are a lot of measurable factors with caps that some people will tell you don't make a difference without actually offering any evidence why that should be the case. Capacitance changes with frequency, temperature and age to varying degrees with different caps. Q, ESR, leakage and dissipation factor are all measurable and different in some cap types. I'm not saying all these factors are important when it comes to audio but I'm equally not quite sure they can all be dismissed.

      A good test is something like a Big Muff where there are a lot of caps, and their own characteristics could be compounded. Two identical boards with transistors matched for gain, one built with all polyester caps and another built with ceramics which are measured for close values sounds and feels different to me. Again I wouldn't say one sounded great and the other sounded bad but certainly different. Resistors aren't really a factor because if you use 1% metal film in both you know the tolerances are close enough not to have an impact.

      Whether subtle differences is enough for the builder to choose one type of cap over another is really then just personal preference.

      Delete
    6. Yes, you're right Mark, but the differences at least to my ear, are always subtle.

      On my first build, a Fuzz Face, I spent lots of money in caps, just wanted what was supposed to be the "best": AC128s, Panasonic electrolithic's and PIO 100nF output. For sure, this effect worked wonderful.

      hen I built another one, with AC128's, tayda electrolithics, and local store 100nF monolithic ceramic....and could hear no differences in sound, was a shock.

      I'll try the Big Muff, the one I've bouilt has been with polyester caps, will build another one with monolithic to a/b them, but I'd bet that the differences will be subtle too.

      BR

      Delete
    7. When I was talking about ceramics in a Muff I meant the cheapy 50V ones rather than the multilayer, I've never compared those and think the differences to my ears would be a lot less obvious. It wasn't a test for you to do by the way, more a test for people who believe there are no differences at all in any caps, because as you said already the cheapy ceramics are noisier, and to me they always have obvious artefacts in the decay. I actually think they are sometimes better in a fuzz pedal for that reason, they sound somehow more aggressive.

      Again this isn't night and day and none of them sound hugely different, but to me they can sound subtly different. There can be no doubt that changing values or transistor gain would have a lot more dramatic effect.

      Maybe the differences are more obvious at higher voltages in amp building but I'm not sure I trust myself with anything above 18V so have stayed away from that so far :o)

      Delete
  14. I've got some K42Y's on the way...I'll be sure to comment again after the mojo is complete.

    ReplyDelete
    Replies
    1. Yeah I got a few a while ago too. Hey I'm an experimenter, so sue me! :o)

      http://i76.photobucket.com/albums/j6/IvIark_2006/DIY/Components/4.jpg

      Delete
    2. I dont think you got quite enough. I see open space in the photo. ;)

      Delete
    3. Oh that was only 1 box, I had another 400 in the other box :o)
      I think I may have a bit too much stuff hoarded

      Delete
  15. Hi, i've wired the pedal this morning, i used a vintage 2n3904 and 2 mallory 150 (100n) for caps. The effect sound like a ipercompressed fuzz, very dirty, and below a certain level of volume input don't saturate and the effect volume is lower than the clean guitar. When i turn down the volume or the tone pot of the guitar to zero i hear a sort of buzz.
    I followed the schematic and i verified all the solderings...Help

    ReplyDelete
    Replies
    1. I changed DC adapter (a original boss whit a musikding one), the buzz disappeared, i tried with a bc547 in CBE position and it works fine, then i tried with a 2n2222 in CBE position and it works bad (like a ipercompressed fuzz), then i tried with 2n2222 and a 2n3904 in EBC position and it works fine like demo, is a layout error or my transistor are bad =|? Thanks a lot

      Delete
    2. A lot of circuits just work better with certain transistors in certain gain ranges, than others. It would be almost impossible to make a layout error with this one :o)

      Delete
    3. And about the orientation? Thanks

      Delete
    4. The orientation is correct for the 2N5088 mentioned, and the C, B and E position are correct no matter what the transistor. So you'll have to check the datasheet for whatever you want to use to make sure the pinouts are correct to the layout.

      Delete
    5. I looked at the pattern, and certainly the layout you posted is correct; so I checked the datasheet of the transistor and the pedal works with all oriented in EBC way (not CBE)... i dont know why, tomorrow i'll test the transistors with my tester,I'm confused...
      Thanks for your patience and for all the layouts!

      Delete
  16. i've built this one, and i think it sounds best with lower gain transistors. at first i tried a 2N5088 and it kind of acted like Simone described, broken and farty, like a bad fuzz. i must've tried at least a dozen transistors, and i ended up with a really low gain BC337 that measured around 200hfe. that one sounds good. but if you want this tiny little circuit to sound great, put a cornish buffer in front of it!! holy crap!! i cant believe how soulful and blusey it sounds. someone else please try this combo and let me know what you think. Mark, Miro, i know this isn't the place to ask, but a cornish buffer into an em-drive layout would be pretty sweet.

    ReplyDelete
    Replies
    1. I built this with regular polyester film caps and it sounded pretty good up to 12 o'clock but after that it's just a messy boost/low gain fuzz. In saying that it sounds great before that. Then I did the same and ran my 'insert very expensive mythological' buffer in front of it and it just sprang to life!

      Delete
    2. Try to turn the transistor of 180 degrees (form CBE to EBC), mine in this way works fine with low and high gain transistors!
      This afternoon i try with the cornish buffer and with the klon buffer i've made!
      Thanks

      Delete
    3. I just built the EM.. I like the kind of fattening up of the sound, but it also takes away some top end, which I'm not so keen on... do you think the buffer solves this?

      Cheers.

      Delete
    4. Tried a few different transistors now.. the first 2n5088 I tried did the weird flatulent fuzz thing, and a 2n3096 worked better, but was losing a little of the top end. I also was using 470k lin pots with terrible torque.. so I ordered in some alpha 250k pots, and some other transistors.. the MPSA18 didn't give me any output.. a 2n2222A sounded ok, but a different 2n5088 sounds great - the best so far, no top end loss.

      Delete
  17. Ok this is going to be my next project after I finish troubleshooting my Musikding Fuzz Factory. With a Cornish buffer in front of it, it will shine for sure.

    ReplyDelete
  18. I'm guessing, from what I read, that this won't be a good match with a Red Llama clone. In fact, from the demos it looks like the both basically are made for the same purpose. What do you think?

    ReplyDelete
    Replies
    1. What do you think about musikding's f factory?

      Delete
  19. This pedal design allowed me to test the larger capacitors I have lying around normally used for Amp Builds. I first up used Orange Drops 600V 1nF and 0.68nF and to my surprise got a very Nice sounding Boost with minor distortion when the Gain is on Full. I am now going to try Large 200V+ Audience Caps, Sozo, etc. Caps. ie. Going to trial different Cap values on this pedal like you do with Guitar Caps to get different textures and Tone. Thanks for the Post. Great Stuff.

    ReplyDelete
  20. I am going to try this as my first pedal build. I am a bit confused however, where is the circuit input and output? Is it the same as the Jack Input and Output?

    Thanks

    ReplyDelete
    Replies
    1. It says in the notes of the layout, you have the input wire to lug 3 of the Gain pot, and lug 2 of the Volume pot is the output. These wires would then go to your stomp switch for bypass wiring, and then to the input and output sockets.

      Delete
    2. Thank you for clarifying that. I was thinking that is how it was but was not sure.

      Delete
  21. Hey can someone direct me to some other good sounding small veros to try besides this and SHO? Just honing some skills.

    ReplyDelete
    Replies
    1. If you want just an easy nice overdrive, do the Lovepedal Woodrow - quick, easy build and sounds pretty decent.

      D*A*M Meathead is a great pedal regardless of small parts count. Devi Ever Hyperion as well. Those are both fuzz circuits so they are not too subtle ( is that an understatement? ). But they were both a good start for me in the Fuzz appreciation realm. If you build these 2, you will be sucked into the fuzz world....

      Delete
    2. Thanks Tim. Really appreciate it. Sounds like a great list to start off.

      Delete
  22. This comment has been removed by the author.

    ReplyDelete
  23. Another noob question. When I put this into an enclosure I an guessing the gain gets grounded and shorts everything out. Is this suppose to happen or did I screw something up?

    Thanks

    ReplyDelete
    Replies
    1. I said that wrong lol, obviously its not suppose to short. Is there a trick so it doesnt short out if its correct.

      Delete
    2. I don't understand, why would it short? The input wire goes to Gain 3, and Gain 1 and 2 connect to the board.

      Delete
    3. I got the mojo version working! My gain pot is a bit funky and I fried my LED somehow, but it works so I am calling it a success for my first build and leaving it alone before it no longer works haha. Thanks for this schematic, it was a good learning experience.

      I tried the condensed version and I found out 2 things. 1, I can not tell the difference between the Caps and 2, I did not know pots could catch fire. I think its a sign to not press my luck and stick to the one that works.

      I am hoping to have a functioning S.H.O. this weekend!

      Delete
  24. Sounds a bit trebly to me. Could trying a different transistor fix this or perhaps some other part value change?

    ReplyDelete
    Replies
    1. Change the 100nf caps to something a little higher (220? or 150?) that should allow more bass through.

      Delete
  25. This pedal work with BC547B?

    ReplyDelete
    Replies
    1. Should be just fine.
      +m

      Delete
    2. When I bread boarded it I stuck a bunch of different trannies in there and it worked with nearly all of them on different levels. 2N5088, 2N3096, BC548, BC558. Whatever NPN I had laying around. Personally I preferred a lower gain one to the 2N5088 but in saying that it sounds beautiful with any of them.

      Delete
  26. Build it! Works fine! Sounds better with my 2N2222A instead of the 2N5088.
    The 2N5088 was more bassy than the 2N2222A, it offers more clarity of the guitar signal when it comes to overdrive.
    Nice Build!

    ReplyDelete
  27. I've a question i tested it a second time and recognize, that the effect level is mostly lower than the clean-signal and with volume and gain full it gives not the overdrive sounds like in the youtube-vids. I used 200k pots, does it affect the sound so hard. I#m bit disappointed. I tried a bunch of trannies and checked the soldering twice. Any ideas?

    ReplyDelete
  28. What is the thing on the schematic that says cbe ( I am new to building)
    Thanks!

    ReplyDelete
    Replies
    1. It is where the transistor goes. The transistor will have three legs. They are called the collector, base and emitter. The CBE lets you know which way to orientate the transistor you are using when building the circuit. If you need to look up which leg is which Google up the transistor eg 2N5088 and you'll find heaps of datasheets. Note not all transistors are the same so always double check the orientation before you solder it in. Best thing to do is solder in some sockets so you can pop the transistor in and out, especially if you realize you have orientated it the wrong way.

      I use sockets like these and just break off however many I need. You can socket tranistors, diodes, caps, anything really. Allows a safety net and some flexibiity.

      http://www.taydaelectronics.com/30-pin-dip-sip-ic-sockets-adaptor-solder-type.html

      Have fun.

      Delete
    2. Oh and the transistor type is the part listed as Q1 underneath the vero

      Delete
    3. Thanks! Can I get an exact description of the thing that says 100n? I am trying to see if I can find it.

      Delete
    4. It's a capacitor. 100n refers to the value. 100n is the same as 0.1uF. n=nano farad and u=micro farrad. There are a few types around from ceramic to mylar fim to polyester box ones. I tend to use the mylar film ones personally for no specific reason except the balance of price and they look a touch cooler than the ceramic ones. Here's an example of what your looking for and a few types.

      http://www.taydaelectronics.com/catalogsearch/result/?q=100n

      As far as shops if Tayda Electronics is no good for you, try Small Bear Electronics, Mammoth Electronics or Mouser. It's all about the shipping price really.

      Delete
    5. even here in the US - i use tayda for the bulk of my parts. The trick with them is to go ahead and plan 3-4 builds you want to tackle and then order the parts for all of them. You'll buy 5-10 of everything, but at pennies per piece rather than .50 - $1 per... Shipping is pretty cheap - even if you go with the cheapest, you'll get it in about a week. People seem to like smallbear too but i've never bought anything from there. My other favorite source is mammothelectronics.com - awesome prices on enclosures there - and it's not too expensive to get them pre-painted either.

      Delete
    6. Just wanted to add I love and use Tayda stuff a lot. Cheap and quick to ship.

      Delete
  29. This is one of those builds where wiring up the box takes 10 times longer than building the circuit haha. This is a milestone - the first build that worked the first time, no tweaks. Of course, with 5 components, i should hope it worked. It's a little ugly because I didn't have a 2M resistor and had to link two 1Ms together haha.. looks like a little teepee sitting on the board.

    Question for the vero experts - This seems like a circuit that you could modify pretty easily. I breadboarded it first and was playing around with adding a little diode pair to make a clipping option. I can visualize where to put it in a schematic, but as for the vero - i'm not sure where the best place is. I could shunt the output and get the clipping i want, but not without a big volume drop. If I basically added two columns on the right side of the board and put the shunt in between the input capacitor and the collector of the trans, would that yield better volume results?

    I really like the low part count projects - helps to learn a lot more about what is going on. This would be a pretty versatile pedal adding a simple diode clipping circuit with a pot to blend it in and out.

    Thanks!

    ReplyDelete
    Replies
    1. Hey Marcuspl

      I'm sure the circuit experts can add some more ideas but I built the compact version and slapped a pair 1N4148 on the output. Volume drop, yes but not enough to warrant not trying it. Unity gain came in at about 2 o'clock after diodes added. Sounded alright. Mind you the MXR Distortion + on here has a low parts count and sounds heaps better than an Em-Drive with diodes if you are after a simple build.

      Another option is chaining two Em-Drive circuits one after the other and seeing if it gives some added clipping.

      Delete
    2. Thanks - that's what I noticed. I was going to check out the MXR distortion at some point - mostly i'm just trying to get to where I actually kind of understand what is going on haha. The volume drop isn't too big of a deal unless i'm fading the diodes in with a knob.. kind of strange for the volume to drop as the distortion increases.. I'm not 100% sure what kind of diodes I even used - i bought them from a local store (tube and ham radio supplier). I think they are 4001s but they are huge. It was a very smooth distortion.

      Delete
  30. I see Lunchie has reported back about the Mojo version. Has anyone else completed the Mojo version? If so, are you hearing the farty low end when turning up the gain?

    I've built the compact version with the 2N5088 and I'm hearing the farty fizzy low end. Sounds great before that and I plan to build a Cornish buffer to place before it to see what that does. My order has just been shipped from Tayda with the 2N2222A and other trannies to try out.

    Thanks guys...I'm a daily reader very part time builder.

    ReplyDelete
    Replies
    1. Sorry for bringing this back up a month later, but did you end up trying other trannies?

      This circuit seems to be designed with low headroom so that with a guitar-level signal, it quickly goes from cleanish > mild distortion > fuzz. With the right signal level going in and the right transistor gain, that makes it feel super sensitive in a good way. With hot pickups or transistor with too high gain, it sounds, as others have put it, "like ass". If it's fuzzing for you, the lower gain of the 2N2222A might be a better fit for you than the 2N5088.

      Delete
    2. Thanks for in reply. After I posted my question I actually starting thinking it may be due to my humbuckers pushing it too much. After playing with the transistors, at the moment I'm jamming with the a 2N4401. The 2N2222A sounds excellent but I still wanted a little more gain, and the 2N4401 brought that. The 2N4401 also sounded a little more natural to my ears. I think I'm going to go back to the 2N5088 for awhile and just not crank it to see how it feels. I've been throwing around the idea of putting a switch in there to swap transistors. And/Or, place a resistor in series with the gain pot to see what what will do. I love DIY!

      I will say, when I plugged my Strat into it...it brought a really big smile to my face.

      Delete
  31. I built both mojo cap and compact versions and A/B'd them on a couple amps. I applied signal to both builds for several hours to allow for any initial "burn in" on the caps (if there's truth to that). I also tested component values to make sure that everything was within +/- 5% between the two builds. The mojo caps used were Russian K42Y-2 250V PIO (roughly $2.50 each plus shipping if you buy several), and the modern caps were Epcos blue poly box caps ($0.11 each from Mouser).

    We switched between the two builds with a toggle switch placed where my friend could not see it. Through his setup (Deusenberg Starplayer TV through a Vox-like Morgan DAG15), my friend liked the warmth of the poly caps in the compact version. The mojo caps sounded just a little too bright. Through my setup (G&L ASAT Deluxe through a weird homebrew amp I built), I thought the poly caps sounded a little muddy; I liked the clarity of the mojo caps.

    IMO the difference isn't large enough to pay the extra money and separate shipping for the mojo caps. On the other hand, there is something cool about opening it up and showing your bandmates the fatty green Russian caps mojo caps. ;)

    ReplyDelete
  32. This is my first build - just completed the layout, but everything sounds farty & distorted (I have the "real" EM-Drive to compare it to).

    I've read through some of the comments, and noticed some change the values of the resistors or change the transistors, etc... but what could be causing this bad tone if I followed the layout exactly? Is it faulty wiring or a bad component? Thanks in advance for any advice!

    ReplyDelete
    Replies
    1. First I would check all your solder joints and make sure they are fresh and shiny. Also make sure none of them have run over the grooves and are connecting adjacent tracks together. If they appear to be (or even if not) run a stanley knife down each groove to make sure they are clean and all solder error is cut apart.

      Next I would also check your transistor pinout. Sometimes having the transistor in backwards will give some noise but not the noise you were expecting.

      I've been pretty rough on resistors, caps and wires in my time building (burning all sorts of things haha) and it has never been a bad one of them for me. It's generally user error on my part that I don't see on first glance.

      Delete
    2. Oh and congrats on the entry to the world of building. So addictive. :)

      Delete
  33. I have built the mojo version twice now. My first version worked perfectly, but my second version seems to have a very low output. Im not sure what it could be. I get a good signal if both Pots are maxed, but when i start rolling the pots back, it becomes very low. What d you think it could be? I used the 2N5088 for my second build, but i forget if i used a 2N5088 or 2N2222A for the first. I have suspicions it was the 5088.

    ReplyDelete
    Replies
    1. Maybe it's a bad transistor?

      Delete
    2. That's what i thought. Im going to try both 2N2222 and a new 5088, and will report back.

      Delete
    3. Tried it with a 2N2222A and it works perfectly. Must have been the Transistor! Great pedal!

      Delete
  34. I've made this before and I own the real thing as well. It's a great booster but not a good overdrive. I don't turn the gain knob anywhere past 3 o'clock because then it'll sound farty with my single coils (haven't tried hum buckers yet). I personally use it with low gain and moderate volume just to fatten up the tone and it does a good job!

    ReplyDelete
  35. I am relatively new to building clones. I have built to the smaller diagrams specs to a T and when activated the effect is very quiet, glitchy, and the gain knob has pretty much no effect. Any idea what the hell i could be doing wrong?

    ReplyDelete
  36. I had a look into my EM-Drive (original one) and after scraping the black nail polish off the transistor I found out that it's an MPSA18. There you go!

    ReplyDelete
  37. shit I could have saved a lot of trouble a while back...yep mpsa18 it the ticket

    ReplyDelete
  38. Could someone post an Oscilloscope shot of the output of this thing with a 1Khz 400mV sinewavel going through it.
    I have verified that my circuit is built properly, then I put it in a software electronic simulator, and I have tried all of the transistors mentioned above, and it still sounds like a herd of cattle after 50 gallons of laxative. The simulator looks just like the output on my scope. It looks much like a half-wave rectifier (bump..flat..bump..flat...). What the crap fellers????!!!

    ReplyDelete
  39. Thanks for this schematic, but I'm sorry, IMHO it just sounds bad.

    I can't believe somebody likes this one with 2n5088. Very farty. I've also tried another 2n5088(I thought that first one was bad) - same unpleasant sound.
    Also to me it seems like it has some threshold with 2n5088, I tend to pick heavily so it has signal spikes, I mean its very silent, but when I pick hard it attenuates signal too strong, in unpleasant way. I've also tried 2n3094 and 2n4401 - both didnt have that threshold issue, 2n4401 sounded the best to me (clearer?). Its nice for solos, but I wouldn't care for rhythm playing (too fat).

    So speaking shortly: if it sounds bad, try other transistor.

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. The original one uses MPSA18 transistors.

      Delete
  40. Hey guys, so I got this thing to work with a 2n5088 (And sounds about as lame as described above), but with an MPSA18 I get really quiet signal (no gain), actually below unity on max volume, and it only gets loud with the gain cranked, but it sounds total pants. Any ideas? Did I get a bad batch of MPSA18 from Tayda? I tried 4 or 5... I'm getting an HFe around 800 (seems like the data sheet says it should be more around 400.. but then again I'm not sure my tester is working :)

    ReplyDelete
  41. I get the same results... I'm sure your tester is working properly.. I played around with several different transistors and the only thing that changes is the width of the bumps in the signal. I ordered some of the larger oil filled caps on ebay. That's the only thing else I can change. As I mentioned before, even my software circuit emulator shows the same output as I get from the breadboard... Oil Well!.... Pun intended.....

    ReplyDelete
    Replies
    1. Yeah, thanks Chuck. I'm using the exact PIO caps that he uses in the original, so I don't think that's the issue with mine... Gotta be the transistors...

      Delete
    2. I've been playing around on a breadboard with this and I am finding that it is the transistors. For some reason, if I swap the transistors with the same transistors (all MPSA-18s), they all respond differently. I can make it work on the breadboard (at least my scope shows it to be Ok), This is the weirdest build I have ever seen. It is so simple (basic inverting transistor amp), but I am having so much trouble with it. All I can say is RUKM (Are You Kidding Me???) LOL!

      Delete
    3. This design is extremely sensitive to changes in transistor hFE. In the originals, they must be testing & sorting the transistors very carefully in order to get any sort of consistency from one pedal to another. If you test the hFE of each of those MPSA18s you tried, you'll probably see that they measure differently enough to be causing the variations you're hearing, even though they're the same model of transistor. It's just a really finicky circuit.

      Delete
  42. just built the non-mojo version until my mojo caps arrive. it sounds awesome and has none of the issues that others are having. I modded mine with a trimmer for the collector of the MPSA18 so I could dial it in exactly how I wanted it to clip.

    pic of my board:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Emerson/EMdrive-circuit.jpg

    my modded vero layout of IvIark's non mojo version:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Emerson/Em-Drive.png

    ReplyDelete
    Replies
    1. Hi John, link doesnt seem to work, I ' d like to take a look at your vero and insides! Thank you,
      Sergio

      Delete
    2. I thought about rigging something up like this. I am almost in love with this thing but it's just not there yet. I'm going to try this out...board looks great, nice work John.

      Delete
    3. here's a link that works for my vero:

      http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Emerson/Em-Drive-with-trimmer.png

      Delete
    4. Hey John, out of curiosity, what collector voltage did you shoot for on the transistor? Half supply, or something else?

      Delete
    5. I just tuned both of mine by ear and haven't measured them, but I believe that they're at about 1/2 the supply voltage.

      Delete
    6. Hi John,
      Just wondering where you got hold of that "socket" for the transistor? What are they called please?

      Delete
  43. Just out of interest (trying to learn more about what each component does..) what would happen if the cap values were raised or lowered? how would that effect the sound?

    ReplyDelete
  44. I've now built both versions. they pretty much sound the same. the mojo version seems to have a little bit sweeter top end harmonic content at max gain but IMO, the tiny one actually sounds just as good.

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
  45. This comment has been removed by the author.

    ReplyDelete
  46. This comment has been removed by the author.

    ReplyDelete
  47. I get the sound from the board but not the dry signal...Can somebody tell me where to connect the input and output from the 3PDT to this board?
    10X

    ReplyDelete
    Replies
    1. Hi Gogiche, the input and output are connected to the pots not the board.

      Input will connected to the third lug of the gain pot
      Out put will come from the middle lug of the volume pot.
      Those will go to the switch
      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html

      Delete
    2. Hi mate.10x. Yes I know...so in order to connect everything with the switch I have to:
      1. Put 2 wires to the 3 lug of the gain pot one will go to the jack the other to the switch.
      2. 2 wires from the middle lug of the Volume pot. One will go to the jack the other to the switch.
      Is this correct?

      Delete
    3. Hello, apologies for the late response i live in the Pacific northwest.

      The way you want to wire it is have one wire coming from the pots to the switch and one from the jacks to the switch.

      So one wire from lug 3 to switch fro input
      then the input jack wire to the switch

      Out put wire from the middle lug to switch
      output jack wire to switch.

      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html


      ok so dont laugh but i made this quick little thing
      http://i.imgur.com/osEJFKK.png

      Delete
    4. 10X Mate, works like a charm :) Thanks A- Gain!

      Delete
    5. Great!!! I just finished this one tonight.

      I ended up using a 3904 and a 33n cap.

      I will try the mpsa18 when i put in the next order once i get more funds.

      Delete
  48. I built three of these with some off-cuts I had lying around!! One has ceramic caps with a 5088 in it, very nice! Second one has poly film caps with 3904(my fave!). It has a kind of ragged decay to the notes that I really love! The third one has poly caps with a 150nf output cap with a BC109 in there. All three sound really great!! The hard thing now is deciding where and with what to put them. A few duel pedals coming up, I think! Pairing one with a Purple Plexi 800 will be the first test!!!

    Cheers, Thommo.

    ReplyDelete
  49. This comment has been removed by the author.

    ReplyDelete
  50. How much of a difference would there be if you used two 250k linears instead of one linear and one log?

    ReplyDelete
  51. Mine does not work anything right: (
    low gain, but gives sound with volume at most
    Tested two 2n5088 and is equal ....
    What would recommend?

    What voltages C B E??

    ReplyDelete
  52. No forum freestompbox one user says that the transistor is MPSA18.
    I put this circuit directly? or we have to change something?

    ReplyDelete
  53. I tested an old 2N4401 and has given sound
    The sound without the effect is more bass than with the pedal on.

    ReplyDelete
  54. Tested a 2N4401 and 2N3904
    2N4401 - More bass than the 2N3904 and has more gain
    2N3904 - Clean and balanced (with little gain compared to 2N4401)

    ReplyDelete
  55. my "Em-Drive"
    https://dl.dropboxusercontent.com/u/51252869/Pedais/DSC_7243_800.jpg
    I'm still in testing, I use it to boost volume but I need more volume ...
    I will lower the resistance 4.7k to test

    ReplyDelete
  56. Hi. First time poster here. I have been following this site for awhile with great interest. I have built 4 pedals, this being one of them and a Cornish buffer being another (thanks atomicwombat). The Em-Drive sounds fantastic with the buffer running into it, but a bit dull without it when I turn the gain up.
    Here's my question: Can I build both circuits on the same vero and put it in one box? Like, add 6 more lines above the buffer to build the non-mojo version. How would I connect the two together and run the leads out to the pots?
    Thanks for such a great resource.

    ReplyDelete
  57. I wonder how it would sound with the slightly higher gain 5089, instead of 5088, or mpsa18 :)

    ReplyDelete
    Replies
    1. I've tried the MPSA18 and it seems to have too much gain. Very light strumming seemed to work effectively, but as soon as you slight dig in, it just farts out big time. From what others have noted above, the design seems to have a narrow threshold of effective operation. I'm currently using PN100 which is supposedly an equivalent of 5088. It performs pretty much how the demo describes, although may have a bit more grit. I'm going to try the 2N2222A is it's slightly lower gain again.

      Delete
    2. Yes, the mpsa18 almost makes it a fuzz, but the 5089 sounds really nice :)
      When i used the mpsa18, in addition to being farty, it acted like there was very little battery power left, although it was a fresh battery. Strange

      Delete
    3. Yes, I had the same "very little battery" type experience too

      Delete
  58. mark help! i've build this one with a vox repeater in the same box(input to vox-to boost-to output).seperated they both work fine.(i've build vox ones before so it's the same with that one). but connected together i have a a really lound sound like a metronome from the repeater's rate even whene i have only the boost on and the vox off..i've used bc550 everywhere in both boards and 2n4853 in vox also.do u have any idea?please tell me what to solder or to destroy(!) to throw this sound away!!!!!!!thanks...

    ReplyDelete
  59. just finished mine... it works... but i get a good amount of white noise coming out from it. but when the gain pot is close to max or at max, the noise actually disappears. any ideas as to why this is happening?
    thanks

    ReplyDelete
  60. Anyone have a parts list from mouser or alliedelec?

    ReplyDelete
  61. Great boosting pedal.
    I had to make another for my friend, too. :-)

    Here is my EM-drive.

    http://weplaymusic.co.kr/entry/EMdrive%EC%99%80-%EC%BC%84%ED%83%80-%ED%81%B4%EB%A1%A0

    ReplyDelete
    Replies
    1. Hi Jaemin,

      Your demo sounds great! How did your clone compare to the actual EM-Drive itself? Did you use 2N2222s as well?

      Delete
  62. Breadboarded this last night with some interesting results bearing in mind all that's been said in this thread:

    With 5088 it sounds really good after a tele and into my dc3 but with an mpsa18 I'm getting that dreadful glitchy thing going on that others have mentioned.

    I agree it sounds a bit farty when maxed but I'm pretty sure it's not built for that. It sounds pretty farty when maxed in the demo bid to be fair. Use it where it does sound good and it sounds... Well... Good!

    I went for Mylar caps and they sound pretty good to me. Think curiosity will get me eventually and I'll probably go for a second build with PIOs.

    I've built a whole bunch of kits but this will be my first vero so wish me luck!

    Thanks for this IvIark

    ReplyDelete