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PostPosted: Mon Jun 08, 2009 10:23 am 
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Since the original BYOC Overdrive was the first DIY effect I ever built (or modified!), I have a special fondness for this circuit. After spending a fair amount of time here in the Overdrive forum in recent months--partly because of my aforementioned interest, and partly to help out the forum moderator, Fuzzdawg, who as a new dad doesn't have as much time to spend here as he used to--I've noticed a number of questions & problems that seem to come up repetitively with the new Overdrive 2 kit. So I thought I'd start an OD2 FAQ thread to capture some of the relevant information and hopefully prevent trouble/confusion/frustration for future OD2 builders.

Order of Effects & How the Controls Work

The Overdrive 2 contains two completely independent effects--an overdrive circuit based upon the legendary Tube Screamer TS808, and a boost circuit that can be built in a couple of different versions. As laid out, the order of the two circuits is overdrive first, boost second. You can run either effect separately or both together. If run together, the boost will just make the overdrive output louder, without adding further distortion, because it follows it in the signal chain. If you do get additional distortion, it's coming from your amp, due to the stronger signal hitting the preamp harder. It is possible to modify the pedal to reverse the effect order, as shown HERE. In that case, running the boost and overdrive together adds more distortion to the output, since the boost acts as increased gain for the OD circuit.

Controls-wise, the potentiometer at the top left controls the boost output level and the stomp switch on the left turns the boost on and off. The rest of the controls--three pots, two 3-way toggle switches and the right-side stomp switch--control the overdrive circuit. If you have the overdrive turned off, these pots and toggles do NOTHING to change the output of the boost circuit.

The top toggle controls the bass equalization in the circuit. When built to standard specs, the middle position will correspond to the stock TS808's frequency profile, with it's strong mid-range response "hump". To the left is the "Full" position, which allows more bass through the overdrive circuit, while the "Fat" setting to the right lets even more bass through. You may find that this can lead to some degree of "muddiness"/loss of clarity, particularly with humbuckers.

The lower toggle controls the signal "clipping" mode which is the primary way that the overdrive circuit adds distortion to the signal. To the left is the stock TS808 setting, using a pair of silicon diodes, and to the right is the second clipping mode--either red LED clipping (standard kit build) or MOSFET clipping, if the pedal is built using that option from the MOSFET Conversion Kit. The middle position is what's known as a "diode lift", so named because it "lifts" the clipping diodes out of the circuit and thus outputs an unclipped signal. More to follow on the subject of signal clipping later....

Wire Up That AC Adapter Jack!!

The layout of the new OD2 board, with the battery connections at the bottom of the PCB, leads some builders to believe that as long as they solder the two battery adapter wires into the PCB and hook up a 9V battery, then the pedal will have power. Au contraire, mon ami! The board merely routes the battery output up to be connected to the AC adapter jack. This is done because this type of adapter jack contains a mechanism that physically disconnects the battery from the circuit when an AC adapter plug is inserted. Cool feature, because it saves battery life. But the upshot is that, unless you wire the AC adapter jack into the PCB, the pedal will not have power, even when a battery is being used.

A Common AC Adapter-related Mistake....

A number of OD2 builders have reported that their pedal works fine when running on a battery, but goes dead when they plug in an AC adapter to the jack. This behavior is almost always caused by the same mistake--switching the wires connecting the two positive lugs on the AC jack to the two "+" eyelets on the tab at the top of the board. The problem occurs because of the design of the AC jack, which causes the battery to be physically disconnected from the circuit when an AC adapter plug is inserted, saving battery life. So if you incorrectly wire the right-most "+" eyelet to the "ring" lug of the AC jack, when you plug in an AC adapter, it disconnects itself!

Here's a diagram showing how the AC adapter should be properly wired to the PCB:

Image

Watch that Power Polarity!!

If you want to power your OD2 with an AC-to-DC power adapter (often affectionately referred to in these parts as a "wall wart"), be sure it is the standard center-negative variety used by the vast majority of effects pedals. Center-positive adapters are common for powering a wide variety of other electrical devices, so if you have a number of these devices around--especially if located in the same area--be careful that you don't mix them up. If you plug a center-positive adapter into the OD2, there's a very high probability that you'll fry the opamp and either render your pedal totally mute or at least sounding very sick. The overdrive portion of the OD2 circuit is based directly upon the classic TS-808, and like many effects, it has no polarity protection built in. So if you have both types of adapters lying around, PAY ATTENTION to which kind you're about to plug into your OD2!! Look for the symbols below on the body of the adapter:

Image Image

Mounting the I/O Jacks

Because it's a pretty tight fit up at the top of the enclosure where the input and output jacks are mounted, some care is needed to orient them properly during installation. The main thing to avoid is any contact between the "tip" of the jacks (see diagram on page 28 of instructions)and other metal surfaces. If the tip of either jack contacts a grounded metal surface (e.g. the enclosure itself or the backs of the pots), the audio signal will short to ground. Also, keep in mind that just because the tips don't contact anything when you first mount them, that may not be the case when an instrument cable is plugged in. The cable plug deflects the tip outward so that the resulting tension maintains a good contact between the plug and the tip. That deflection--about a 1/16 " or so--may be enough to cause the tip to touch a grounded surface. And remember that the solder lug for the tip must similarly be kept from touching a grounded surface. If you mount the jacks with the orientation shown in the diagram on page 29 of the instructions, you should have no problem.

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PostPosted: Mon Jun 08, 2009 10:26 am 
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Clipping Options & Observations

The stock OD2 configuration offers two switchable clipping choices--the traditional TS808 pair of silicon diodes (1N914 type), and a pair of red LED's as used in the highly touted (and, IMO, ludicrously expensive) Landgraff Dynamic Overdrive and numerous other "boo-teek" OD pedals. The MOSFET Conversion Kit offers the option of substituting a pair of BS170 MOSFETs for the red LED's, giving a different distortion character. The third position of the clipping toggle switch is what's known as a "diode lift", in that it lifts the clipping stage out of the circuit and passes the signal through unclipped.

In point of fact, you can modify the clipping configurations in a myriad of ways. Clipping is the term given to the process of inducing distortion into an audio signal by cutting off, or "clipping", a portion of it. Check out THIS ARTICLE by effects guru R.G. Keen for a good overview of musical distortion. A pair of diodes--essentially one-way current gates--are a convenient way to induce signal clipping. They're installed in a circuit in such a way that, when a signal voltage is applied that exceeds the diode's turn-on or "threshold" voltage, the portion above that voltage value is dumped out of the signal path, usually to ground. Think of it as working like a safety relief valve does, only with voltage rather than pressure providing the device activation.

Because an audio signal is an AC signal, clipping diodes are nearly always installed in both polarity directions, so that both the rising and falling portions of the signal are clipped. The simplest and most common way to do this is just a pair of diodes of opposite polarity wired in parallel. This exactly how the stock OD2 clipping is set up, with a pair of 1N914 diodes and a pair of red LED's. A clipping stage set up this way--an equal number of the same type of diodes wired in parallel but opposing polarity--gives what is called symmetrical clipping, since the rising and falling audio signals are clipped in the same way. If different types or numbers of diodes are used on the two opposing polarity sides, the resulting clipping is called asymmetrical, because the rising and falling signals are processed differently. According to the conventional wisdom, symmetrical clipping gives rise to odd order harmonics that impart a raspier edge to the clipped tone. Asymmetrical clipping generates both odd and even order harmonics, with the latter having a smoother and somewhat more musical sound; the more asymmetrical the clipping, the more pronounced the even order harmonics become. Asymmetrical clipping has become very popular, due to its perceived/reputed quality of sounding more natural and "tube-like". But you really have to experiment and see what sounds best to you, because these are extremely subjective matters.

Two properties of the diodes themselves affect how the clipped tone sounds--the aforementioned threshold voltage, and the speed at which the diode turns on when the threshold is exceeded. Diodes that turn on quickly are said to give "hard" clipping, while slower ones clip more "softly". Hard clipping typically sounds more distorted and harsher in character than soft clipping. That can be good or bad, depending upon what tone you're going for. Different diode voltage thresholds determine how much of the signal is clipped, affecting both the degree of distortion and the volume of the clipped signal. A diode with large voltage threshold, like an LED (typically in the 2 - 2.5V range), clips far less signal than a low voltage threshold diode like a 1N34A germanium diode (~0.3V). Consequently, the output of the LED clipping would sound less distorted and very noticeably louder than the 1N34A clipped signal.

Things other than simple diodes can be used to generate signal clipping. The BS170's included in the MOSFET Conversion kit are a perfect example. Though these are a type of transistor and not a diode per se, their structure is such that they contain an internal diode called a "body diode" that gives them signal clipping capability when appropriately wired into the circuit. MOSFET clipping has become quite popular, due to its somewhat warmer, fuller sound compared to silicon diodes, and is used in some very popular pedals, including the Fulltone Fulldrive 2 MOSFET and the Hermida MOSferatu. I've used J201 JFET's in some other pedal circuits for clipping, and there are many other possibilities.

The bottom line is that you don't have to stick with the two stock choices or the optional MOSFETs when you build your OD2. Feel free to experiment. A good way to do this is to install sockets in the diode connection eyelets on the PCB, so that you can try different types and combinations of diodes without needing to desolder/resolder the components. You can even solder multiple diodes together head to tail to make asymmetric combos. For example, one favorite of mine is a 1x3 1N914 diode array. Do keep in mind that you can use either the LED or MOSFET mounting locations but not both simultaneously.

Uh-oh! The diode "lift" sounds just like the LED setting!?! What the....

No, you didn't do anything wrong. This apparent similarity in tone is for real, at least under many circumstances. The reason is that LED's have a high forward voltage threshold--typically in the 2.0 - 2.5V range--so it takes a BIG signal going through them before they clip any of it. So unless you have things cranked up pretty high--a hot signal into the pedal, the OD gain cranked up, and slammin' those strings pretty good--the LED's may very well be generating little to no signal clipping. And if that's the case, then they're functioning just like that diode lift position does, and the two settings sound the same. The fact that little to no signal is being lost via clipping is why they're both noticeably louder than the stock TS clipping setting.

But wait a second! If the diode "lift" isn't clipping any signal, how come you can still hear distortion? Well, that's because not all the distortion comes from signal clipping. The opamp gain itself adds a certain amount of distortion, plus the hotter output of the OD circuit may be generating distortion downstream in your signal chain. The preamp stage of your amplifier is getting pushed harder by the OD2's overdrive output and may be generating some degree of distortion just from that.

Because of this tonal similarity between the LEDs and the diode "lift", I prefer to build my OD2's with BS170 MOSFETs in the second clipping position. I like the warmer, smoother tone of the MOSFET clipping, and the middle "lift" setting on the clipping toggle gives you very close to the same tone as the LED's would anyway. So using the MOSFETs gives the pedal a broader range of different tones.

BTW, there's a simple way to see if your LED's are clipping, because when they do--they light up!! Not very much, and generally only for a fraction of a second at the initial attack of a note or chord, but if you remove the back of the pedal, turn it upside down, and darken the room, it's visible.

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PostPosted: Mon Jun 08, 2009 10:37 am 
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Careful with those trimpots....

The three internal trimpots added to the OD2 design are a very cool feature that allows you to "dial in" the tonal character and response that you prefer, but fiddling with them is not without consequence! This is because they do NOT function wholly independently--they interact with each other and/or other parts of the circuit. Specifically:

  • The LOUDER trimpot has a fairly strong interaction with the tone stack, and when dialed up high can make the tone unpleasantly harsh and generate some weird/unpleasant signal decay behavior. I like to run mine at or below 5 Kohms, which is pretty low on the stock 50K trimpot.
  • The MIN trimpot does set the pedal's minimum gain, but does so in combination with the MAX trimpot setting. It's the ratio of the two that actually determines minimum gain. So, for example, if you reduce the MAX trimpot setting by half from the TS stock 4.7 Kohm value to 2.35 Kohm to double the pedal's available gain, you'll have to reduce the MIN trimpot setting by half as well, to keep the same minimum gain (i.e. the gain with the OD drive pot all the way down). Many people are unconcerned about the pedal's minimum gain, but this is something to keep in mind, in case you do like to dial the pedal gain way down to clean up the output.
  • The MAX trimpot is by far the trickiest of the bunch, because it affects both maximum and minimum OD stage gain as well as how much bass is passed through. This one gets fairly involved, because of how this trimpot interacts with the OD2's switchable tone capacitors. Let's look at this critical interaction in more detail (WARNING! Techno-geek content):

    The MAX trimpot and the switchable capacitors controlled by the 3-way "Fat" toggle switch together form what is known as an "RC low-pass filter". Signals with higher frequencies are blocked from passing, while lower frequencies pass right through. The transition point between what gets through and what doesn't is referred to as the "bass rolloff frequency" (BRF, for short). The lower the BRF value (in Hertz, i.e. cycles per second), the more apparent bass response the pedal will have. If the MAX trimpot is set to the stock TS808 value of 4.7 Kohm, then the BRF at the "normal" toggle setting (middle position; 0.047uf capacitance) will be ~720Hz. For the "Full" setting (left; 0.094uf), it's ~360Hz and for the "Fat" setting (right; 0.197uf), ~172Hz.

    But if you start dialing down the resistance in that MAX trimpot to get more gain from the circuit, those frequency values change proportionally. For example, say that you dial the resistance to half of the TS stock, 2.35 Kohm. The relative gain of the pedal doubles, but the BRF's do, too! Now the rolloff values at those three toggle settings change to 1440hz, 720Hz and 344Hz respectively--significantly more bass being rolled off at each setting! So if you want the same low-end performance that you had with the original 4.7Kohm pot value and the toggle set to "Normal", you have to run the toggle at the "Full" position instead. And if you want the bass rolloff point you were getting with the stock pedal gain on the "Fat" toggle setting (172Hz)--well, too bad! The BRF at the "Fat" setting--the lowest you can go--is now 344Hz. The "Normal" toggle setting begins rolling off bass at 1440Hz. That's getting pretty thin sounding to be considered "normal", eh?
    Bottom Line: If you like to crank up the OD2's maximum gain with that MAX trimpot but still want to keep the pedal's bass performance comparable to the stock gain setting, be prepared to install different caps in those three switchable slots. For example, if you set the MAX trimpot to 2.2Kohm, you'll get a bit more than twice the stock gain. Substituting cap values of 0.1uf, 0.1uf and 0.33uf for the stock 0.047uf-0.047uf-0.15uf caps will yield rolloff frequencies of 723Hz, 362Hz and 168Hz--very close to the original stock gain values. So you'll get your extra available gain, but still maintain bass performance pretty close to "design specs".

    The theory and mathematical relationships upon which this interactive gain-bass rolloff behavior is based are discussed in R.G. Keen's excellent article The Technology of the Tube Screamer, found at THIS LINK on his website.


Stock TS build, full MOSFET conversion, and everything in between....

The Overdrive 2 kit comes stock with the components to build the overdrive portion of the pedal to vintage TS808 specs, though the second clipping position and the three trimpots offer tonal flexibility that the original never had. However, the MOSFET conversion kit lets the builder take the OD2 into some new tonal territory, both in the overdrive and boost portions of the circuit. The conversion kit includes MOSFET and ancillary componentry to modify four portions if the circuitry:

  • 2nd clipping position - Instead of using the stock pair of red LED's for the 2nd clipping position, the OD2 PCB is all set up to take a pair of BS170 MOSFETs instead. They install in their own 3-eyelet mounting positions, though be sure to insert them backwards from the orientation shown on the silkscreen image on the board. See the Clipping Options & Observations section above for more details.
  • Input/output buffers - The main point here is to allow the builder to leverage the MOSFET's higher input impedance vs. bipolar silicon trannies to preserve top end response. Personally, I find the advice of effects guru Jack Orman compelling on this point--he suggests using a MOSFET input buffer if you're looking for maximum "sparkle", but sticking with the bipolar tranny output buffer for its stronger drive performance. Also, as noted in the OD2 instructions, MOSFET buffers are a bit noisier than bipolar transistor type, so that may factor into your choice, too. You can also raise the buffer impedances in a different way--by substituting 1M resistors for the stock 511k's.
  • Opamp - The MOSFET conversion kit includes a CA3260 BiMOS opamp to give you another "flavor" of IC that can be run in the OD2, along with two provided with the base kit. IMO, changing opamps in this and other TS-based overdrives is among the more subtle changes you can make, tonally. But if you're looking to maximize the MOSFET-icity of your OD2 built, here's another way to do it.
  • MOSFET Boost - It really comes down to a matter of personal taste on whether you go with the BS170 MOSFET in the boost stage or stick with the kit's stock MPSA18 bipolar tranny. Again, the impact is top-end chime and clarity with the MOSFET. The stock MPSA18 bipolar tranny boost--essentially the same as the vintage EH Linear Power Booster circuit--still has good top-end clarity, definitely gives you more authority in the bass and lower mids, and has more innate output capability. But if it's a "squeaky clean" boost you want, the MOSFET option is tops for that.

It's important to note on the MOSFET conversion that it's not an "all or nothing" decision--you can go with the MOSFET conversion in some of these parts of the pedal's circuitry and not in others. For example, in my personal OD2, I have MOSFET clippers and a MOSFET input buffer installed, and I socketed the components for the boost circuit so that I can switch back and forth between the MOSFET and bipolar tranny boost versions. The output buffer is stock MPSA18 transistor version, and I pretty much stick with the Burr Brown OP2134 opamp all the time for its excellent clarity/fidelity.

One last thing on this--if you decide, for example, that you're really only interested in having the MOSFET clipping option, then despite our universal support for Keith's early retirement to a life of leisure & luxury, it doesn't make a lot of sense to be paying him $8 for the full MOSFET conversion kit. You can buy BS170 MOSFETs for about 50 cents each at any number of places.

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Last edited by duhvoodooman on Mon Jun 08, 2009 12:40 pm, edited 2 times in total.

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PostPosted: Mon Jun 08, 2009 10:40 am 
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Here's a marked up diagram of both sides of the OD2 PCB, showing the +9V, +4.5V, and ground traces. The through-sides of the eyelets are highlighted, as well. If you notice anything I missed, let me know by PM and I'll update the image.

OD2 PCB +9V, +4.5V and Ground Paths:

Image

** EDIT 7/28/10 **

Here's another couple of color-coded OD2 PCB diagrams I've put together, which some builders may find helpful.

The first highlights the two effect circuits--overdrive and boost. The switchable components within the overdrive stage (clipping and EQ switches) are also shown in different colors. Components that are wholly within the circuit are outlined in the circuit's code color. Components that interface to another element of the overall pedal circuitry (for example, to the +9V power trace or to ground) remain outlined in white. Traces are only shown on the side of the PCB where they're actually located.

The second diagram is the "whole enchilada"--basically the consolidation of the first two diagrams into one. Almost all the major elements of the pedal circuitry are color-coded on this diagram, with the exception of the indicator LEDs, most of the footswitch connection eyelets, the signal input and output traces, and some of the biasing on the boost transistor. This can get pretty confusing, so I'd recommend that novices approach this complex diagram with caution.

OD2 Overdrive and Boost Circuits:

Image

OD2 "Whole Enchilada" PCB Diagram:

Image

All three diagrams are available for download as a single PDF document at THIS LINK.

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PostPosted: Sun Oct 18, 2009 5:44 pm 
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i have an OD-2 set to mosfet stats and i was wondering if i could just change the mosfet op amp out for the burr of the jrc by just poping one off and snapping the other in or are there other mods that have to be done before i could change the op amps?
sorry if the query seems ignorant, but i'm a musician and in no way a electronics wiz.
thanks


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PostPosted: Sun Oct 18, 2009 6:56 pm 
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No changes needed. Pop one out and the other one in.

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PostPosted: Fri Nov 13, 2009 12:08 pm 
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i have the od2 with full mosfet conversion. just wondering if i can turn up the boost with the trimpot without affecting the regular overdrive.


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PostPosted: Fri Nov 13, 2009 12:24 pm 
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The three internal trimpots affect ONLY the overdrive stage and have no effect on the boost, which is a completely separate circuit. Think of the OD2 as an overdrive pedal and a boost pedal that just happen to share the same enclosure and the same PCB.

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PostPosted: Tue Feb 23, 2010 12:57 pm 
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With a big tip o' the hat to Stephen, here's his excellent markup of the PCB, showing the various component locations labeled with the designations corresponding to the schematic shown on page 38 of the OD2 instructions. You can see this diagram along with the OD2 schematic and the component list in Stephen's posting HERE.

Image

Incidentally, the resistor immediately below the "Louder" trimpot, VR4, is labeled as "R9.5" because it was mistakenly left off the BYOC schematic and would logically be listed between R9 and R10. It's a 220 ohm resistor that is placed between the tantalum cap connected to the wiper of the OD tone pot and ground.

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PostPosted: Sat Apr 24, 2010 7:41 am 
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I'm planning to follow your recommendation to use the MOSFET mod for the input buffer and clipping, while sticking with the BJT for the output buffer.

Could you please tell me whether you normally replace the 511k resistor in the output buffer with a 1M in this case? Does increasing the impedance at this stage make any difference?


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PostPosted: Sat Apr 24, 2010 3:44 pm 
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I always just build the BJT output buffer per stock configuration with the 511K resistor. With the higher impedance of the MOSFET input buffer, I don't think 1M resistor in the output buffer really buys you anything.

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PostPosted: Sun May 23, 2010 2:31 pm 
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Hi,

I'm interested in trying DVM's recommendation for 1x3 assymetrical diode clipping in my OD2. I've got several 1N4148 diodes left over from a partial MOSFET conversion, and I'm wondering if I can just daisychain 3 of them together and put them right into the slot that Stephen's supercool markup lists as D3, leaving a single one (with opposite polarity) in slot D4. Anybody know? This mod just sounds so easy (too easy?), and I hate to waste the components by chaining 'em up if this won't work.

Thanks!
j.

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PostPosted: Sun May 23, 2010 8:11 pm 
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Yes, just solder 3 of them together head to tail, bend them in a U shape, and insert into either the D3 or D4 spot. A single 4148 then goes into the other diode spot, oriented opposite in polarity. Very simple.

EDIT: I had to do a couple of these 3x1 clipping arrays for some customer builds anyway, so I took a couple of photos. The first shows the three 1N4148's (a.k.a. 1N914) soldered head to tail. I give the two leads one full twist around each other and then apply a small dab of solder. In the second photo, the excess leads have all been trimmed and the 3-diode chain has been bent to the shape needed for eyelet insertion. In this case, I've bent the middle diode over 90 degrees to the plane of the other two to minimize the overhead room needed--helpful if you're using compression eyelets on the PCB, as I was in this case, since they add about 1/4" of height. You can also slip a sleeve of heatshrink tubing over the diodes, if you want to insure they're insulated from surrounding components.

Image Image

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PostPosted: Wed Oct 27, 2010 10:38 pm 
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I was curious about having the "asymmetrical clipping". So I tried chaining three 4148 diodes like this, leaving a single one in the D3 spot and the trio in the D4 spot. When I put it back together and turned it on there was this awful "whining" sound and it sounded like a fuzz pedal with a lot of sustain instead of an 808. Weird.

Tomorrow I'll go over it again and see if I find anything obvious. Polarity is correct. All three diodes have the black stripe in the same direction. Opposite polarity from the single diode (like it was originally).

Thoughts?


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PostPosted: Thu Oct 28, 2010 4:44 am 
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Don't know. I use the 3x1 diode array all the time and have never seen this behavior. It certainly doesn't increase gain, it just clips less of the signal on one side. If the middle diode lift position of the toggle (no clipping) doesn't do the same thing, I can't understand why the 3x1 would cause a problem. If it persists, open a new thread in the forum and post some photos.

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PostPosted: Thu Oct 28, 2010 6:02 pm 
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I think I've found the culprit. The positive square for D4 pad has lifted off the pcb entirely. Entirely my fault for getting it too hot. I had trouble taking out the existing single diode and when I put the 3x1 diode array it just pushed it right off the pcb. Live and learn I guess.


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PostPosted: Thu Oct 28, 2010 8:17 pm 
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Easily fixed--just bend over the diode lead that goes through that eyelet and "tack" solder it to the round solder pad joint of the D3 diode right next to it. The two pads are connected with a trace anyway, though that's probably broken now. If the lead is already clipped off too short to do that, try to just apply a blob of solder that will connect the two.

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PostPosted: Fri Oct 29, 2010 6:31 am 
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Wow. Thank you! It worked great with a little blob of solder. Saved it's life.

I wasn't sure how the 3x1 array would make it sound so I wanted to try it. So far it's making the 808 setting way cleaner and louder??? It sounds eerily similar to the boost side when it's used alone and cranked. I have to just about dime the gain to get obvious overdrive. Is that normal for the 3x1 array in place of the stock 808 section of this pedal?


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PostPosted: Fri Dec 03, 2010 6:31 pm 
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Built my overdrive2 to mosfet and loving it!! Just have one question about something that is bothering me with the decay of the overdrive signal. The overdrive sounds great but after I strum a chord and let it ring out it decays and sorta sounds like a dead battery as the over drive dissipates. I can still hear my guitar fine i was just wondering if there was a place i should trouble shoot to see if there is a bad connection. Curious what the culprit of this might be? Any suggestion as to what might be causing this? It happens in all 3 modes.

I have my trimpots set fairly low. The "louder" is all the the way turned down The other two are set at about 6 o'clock. I've looked for bad solder joints and haven't found any. You guys have any suggestions?


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PostPosted: Mon Feb 07, 2011 7:40 pm 
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So what good is the bottom toggle switch set in the middle taking out all the leds? What tone is this like? It responds really bad into my Vox and my Bassman, Really badly!

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PostPosted: Tue Feb 08, 2011 3:46 pm 
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It should be louder (because none of the signal is being clipped) and cleaner/less distorted. The signal gain is increased by the pedal's opamp, which will introduce some distortion, but it certainly shouldn't sound "bad". What exactly do you mean by "really bad". Can you describe the sound in more detail?

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PostPosted: Tue Feb 08, 2011 9:18 pm 
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Well neither amp takes OD's well, they are very picky, so I think this is just me, but it seems to boost the highs into a shrill like territory. I will be playing on a very OD friendly amp tommorrow and I plan on trying this setting.

So is this the TImmy like transparent setting? Or what would you describe this setting like, if there is a comparison available?

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PostPosted: Wed Feb 09, 2011 9:31 am 
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Well after doing some research on here, it sounds like I need to dial down the tone knob, after I did that it mostly solved this problem, thanks. THat tone knob gets a little krazy.

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PostPosted: Thu Feb 10, 2011 2:37 pm 
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Is it possible to use transistors other than the mosfet in the mosfet spot on the board for clipping? Ie NPN silicon. If so would they still go in backwards from the silkscreen like tthe Bs170's?


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PostPosted: Thu Feb 10, 2011 4:21 pm 
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You can use JFETs, like J201's, but not, to my knowledge, BJT's (NPN or PNP). They don't have the quasi-diode internal structure to function as clippers. Ref. THIS ARTICLE by Jack Orman.

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