Prostheta

Ugh, this reminds me that I need to get to painting my two M-IIs. The black one is less of a priority than Pearly, maybe because I dread painting black.

Nice find in Birch! I often find it bland.

I'm unsure whether binding is cut or extruded. It could be a mixture of both dependent on manufacturer and material.

Those are the ones I love. In principle the output of this optical board should be able to replace the pot in these circuits, making a Morley format switchless optical Vox wah possible. The harmonics of those older models are sweet, especially when you grab sustain on notes. They bloom, which has become a big part of my preferred playing style. 

The board also corresponds very well with an actual BH1 board. It's very interesting to me to see both the incremental and the significant changes made between the BH1 and BH2 wahs.

The main things I looked for with this unit are the locations of the pedal mechanism bolts for retrofit optical board alignment purposes and also the optical silhouette card. These are in spec, so I can pretty much gut this unit regardless of what the original PCB was designed for. Interestingly, the LDR has 350 written directly next to it....whether this is some sort of nominal test value isn't known....measuring it in circuit produces over 2MOhm in darkness and 500Ohms or so when an LED flashlight is shone on it. This may be different with a red LED as the peak sensitivity may lay in that band, producing say....350R.

So it seems to be that the older Morley Power Wah was more or less identical in function to the subsequent revisions, and the rev.1 board is populatable to make it into a bad Horsie 1 switchless wah.

Alrighty, so we have this specimen of a Morley Power Wah, a rev1 board.

I put in an order to prototype a standalone optical board. Once this is proofed, I'll maybe add in a couple of trimmer pots to tweak the pedal position curve a little if that seems useful. (Fusion 360 board render)

As for the taper, I haven't actually read any commentary on that. Do you have any references that I can absorb....?

At the moment I don't know exactly what to think about the implications of an odd taper curve, whether it's a flaw or an aspect. I'd like to think it's a matter of "feel" (something I depend on with wahs when hitting a specific note sustain point) but that depends on which direction the curve is if it's an S. I do think that this can be controlled to some degree by adding in an adjustable brightness pot for L2 to reduce the maximum point and one in series with LDR2 to increase the minimum. These would be both opto board mounted, so fit in with my vision of a modular design.

As an aside, talking about tapers, the modern Morleys (20/20s?) use a nylon wire strung through the case to drive a linear slide potentiometer. I can't say how much I have an immediate dislike for this sort of arrangement....physical mechanisms seem so poor and prone to fault.

The silly imaginative side of me is thinking about alternative optical arrangements now....I thought about magnets for a while, however they're similar to optical in that they decay in range as a square of distance. The pedal moving a mirror or a diffusion card might be an interesting thought experiment. The contact-free passive mechanism of optical is just too cool of an idea, and I guess that is part of my attraction to the BH2 circuit....maybe the use of very-directional LEDs rather than old-style bulbs contribute to any weird taper phenomenon?

I'd put some thought into that. The immediate yet flawed solution would be to make a new silhouette curtain with a different aperture than the standard thin triangle. All sorts of people on YouTube (including the most obnoxious one) recommend modifying the aperture with knives, files, etc. Given just how small of an area this is, I don't think it's all that useful due to unpredictability. It seems that for many, any improvement is still an improvement!

My thought is that perhaps it really does not matter too much as long as there is an actual range. I'm in the process of designing a new board for the opto area in EAGLE CAD (bonus of getting AutoDesk educational access) so this should in principle allow me to perform a range test by measuring the resistance of LDR2 at various points in the travel of the pedal. Tweaking the L2/LDR2 positions on the board should reveal as to whether or not the aperture shape is in fact poorly implemented....I can imagine that this is not the easiest thing to set up in the factory and likely isn't done so optimally, however at the design level it may still be valid. Realigning L2/LDR2 may be all that is required.

Similarly, it shows how sensitive this design is to misalignments/tolerances. The aperture card is attached to the underside of the pedal, the pedal attached to the case using two bent metal brackets, the PCB to the case via these bolts spaced with a shake washer and a nut. The optical components are soldered to the PCB. This is a LONG chain of tolerances that could creep in, so misalignments are to be expected even if that is only in the range of half a mm. For an optical aperture measuring 5mm or so in length, that adds up. 

So in that respect, I think that adding in some adjustability to dial that out, which isn't bending wires makes sense. By fitting the new optical board using two of the four pedal bolt locations, I can add in a thumbscrew or set screw at the far end (think, fine adjuster on a Floyd) that bears against the inside of the case, the entire board can be deflected accurately to bring it into location. Using rubber o-rings or washers in the main mounting bolts should provide enough give so as not to stress the PCB.

Splitting the board into two halves is fairly logical, and the way I look at it agrees with the method used by the guy making the rackmount BH2 with a pedal for control only.

The components in this section of the board, plus LDR2 (wah position) can be brought out with five wires. Two for power, two for logic outputs to drive the JFET bypass section and one for the LDR itself. Sensibly, the author of that modification also added in a power smoothing cap to that board which makes good sense rather than not.

So in principle this means that this board could provide the basis for any sort of optically-controlled pedal. All that is required in the "effects" board is the JFET switch section and the processing itself. Very cool. It would be nice to see what is possible for this arrangement beyond just a wah....

So here's our fully populated board. I ordered in components that were easier to acquire without the usual massive delivery fees, otherwise I'd have gone for top notch components across the entire board. Kemet poly boxes are fine.

Oh FFS. I seem to have accidentally bought myself a second Power Wah

Alright, so let's look at what I can do with this one. I am unsure as to which PCB revision this board is, however that is pretty much academic since I won't be using it. I'll recover the inductor from the board, and perhaps the footswitch also. Beyond this, we're looking at the pedal housing and optical mechanism alone.

Looking back at the schematic, we've got distinct areas of the board that can be split up amongst smaller PCBs. Primarily, the optical side which deals with the signal routing aspect of the pedal and the effect section itself. The two 2N5484 N-channel JFETs are controlled by the CMOS inverter logic that interprets the state of the L1/LDR1 heel-position detection pair via U1, charges up C2 when "on" and provides a falling charge when "off" via R2/TP1 to ground. When this falls below the threshold of the next inverter, the JFETs select between the unmolested (well, as unmolested as "buffered" gets) signal and the effected signal. Cool.

So in principle I can isolate the switching into a smaller PCB mounted using the four bolt locations from the pedal. This is pretty much what this guy did when converting a BH2 into an external optical controller and rackmount unit: http://griffineffects.blogspot.com/2014/05/morley-bad-horsie-2-wah-into-rack-wah.html

The processing part of the circuit can also be shrunk and fitted inside the enclosure using small standoffs. The jack sockets, DC socket, pots, LEDs and footswitch can then be brought out via strain-relieved cables to their respective locations.

I'd like to try out a different inductor in this circuit, perhaps even switchable between the Morley inductor and alternatives if space permits. To my understanding, the Morley circuit is based on the Crybaby, which itself is based on the original Vox circuit. Given that I have a lot of love for that Chrome Custom model in the Helix, being able to bring this character out into an external analogue pedal sat one of the four send/return paths of the Helix is just too cool.

https://catalinbread.com/blogs/kulas-cabinet/vox-cry-baby

Morley Bad Horsie 2 Schematic (1).pdf

Alright, so the board is populated, assembled, set up and appears to be functioning! Not bad for first time. I was dreading fault-finding a board that is not my own, but I'll take it. A rough playthrough last night revealed a few changes that I think I would make in addition to the basic build issues that I found.

Firstly, the "quality of life" adjustments I made. These are general popular modifications often seen with the Bad Horsie 2. Things like the input cap being raised in value so the wah doesn't lose so much low end, etc. Nothing that really affects the basic function or character of the product. The LDR/LED positions were set up so that the wah turns off within the last few mm of heel travel, and the range is better from the in point through to the toe. It's pretty nice, however I agree with a lot of people's comments that the range isn't that linear through the movement, with a lot of the action being bunched up into a very small end of the range. This can be fixed to a degree by moving the appropriate LED/LDR pair, but is mostly a job involving modification of the optical silhouette.

It's also worth mentioning that the the BH2 went through at least two revisions. I have a board that is labelled Rev. B that doesn't fully correlate to the schematic, which was Rev. A. A couple of blogs out there referring to modifications/repairs of the BH2 that I used as a guide for the project were based off Rev. A, however the real differences are simply component values.

The most relevant of which is R42 which is the resistor providing the base resistance for the contour control in series with the 100k potentiometer, giving a value of 33k-100k. In Rev. B this was increased to 68k providing wider range. This control doesn't seem to be as effective as one might imagine, so it may provide some scope for future character modification.

The second difference I noted was R37; a resistor that is part of a voltage divider setting a bias voltage for the contour portion's op-amp. Oddly enough, in Rev. A the pair R37/R38 are 1M and 1M2 respectively; not identical values as you'd expect for a voltage divider in this sort of circuit. In Rev. B this was changed to the expected value of 1M2, however swapping out R38 to 1M would yield the same result. The offset doesn't make any difference in practice, so just a minor note.

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So, the changes that I would make if I were designing this pedal.

The two pots added are soldered directly to the board using pins soldered flat to pads which is terrible. The mechanical retention of the pots is based entirely on how strongly the copper will stay on the PCB! Ideally the pots would be of the "solder tag with flying leads" sort of configuration, or pins in through holes at worst. I may have had lifting traces because of this, which may explain the less than effective natural of the controls as they stand....

The same applies to the LEDs. I understand that an integrated PCB is a great idea for component reduction and manufacturing simplicity, but only to a point. I would say that some of these decisions undermine the durability of the end product by placing too many demands on the PCB that they're just not designed for.

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What next?

I'm in danger of taking this project way too much to heart when in reality I think my Line 6 Helix' built-in expression pedal is more flexible and provides more than an external pedal can. I do like the switchless option of the BH2, however this is also something that the Helix' pedal can be configured for. My go-to model in the Helix is the "Chrome Custom", which is itself a modified version of a Vox Wah and that thing just screams feedback sustain when you dwell in the sweet spot of specific notes. I would love to outboard this to an analogue pedal that I can leave in a send/return to save DSP, but a wah is rarely that much of a hog that I need to consider this.

So about me taking projects to heart....I'd love to improve and modify this pedal, even to the point of breaking up the PCB into 2-3 boards to improve functionality and durability. What can I say? The product designer in me wants to see how far this can be taken, and watertight perfection being sought-for. I love the optical design, and that appeals to me on a level that probably has no real world use. It's just cool.

I don't think that I want to disassemble and reassemble this pedal continuously. The stresses on the PCB from the board-mounted components is going to hit a point where something will break. I would however like to make my own "ultimate" BH2, even if it's just for the sake of it. Whether that's buying a second-hand Power Wah for the mechanism or building up a wah around a Crybaby-style diecast enclosure....not sure.

Modifications I would introduce would involve making the range of the pedal controllable; once the silhouette is tweaked, making the heel and toe frequencies controllable. These are the Helix models' strong points. Additionally, pushing the inductor into producing even order harmonics would make it scream more. That matters. I'm not a WANK-WANK-WANK style wah player, but more of the vocal expression during leads sort. Catching the vowel.

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Let's see whether I get the bid on this cheap PW that I put in.....

Sure, take as much from this experience on to the next build. The body looks fine even if the neck has issues. At least you know the cause and solution.

A bit of an update on this one.

Firstly, parts are on order. I'm populating the entire board with 0,6w 1% metal film resistors as mentioned, plus replacing all of the capacitors with Nichicon and poly boxes.

The first thing I'll be doing is bringing in the Bad Horsie 2 "into spec" by populating it with the original factory values. As nice as having a series of modifications is, I don't particularly want to go straight into modified form and have no frame of reference to what changes were made. I'll likely dial these in anyway, but not initially.

I'd also like to take this board slightly further by incorporating the modifications that I settle on into the PCB design. At my place of study, we have access to a PCB router which is perfect for this sort of prototyping. Couple that with an educational licence for EAGLE CAD and we're golden. This will allow me to take the original schematic and layout, then modify it with the component changes (for things like bringing resistors out to pots, adding in switches, strain relief, etc) plus baking in specific lead pitches of say, WIMA and Nichicon caps for a V2 drop-in.

The difficulty is the parts that I cannot source too easily. Morley LDRs are out there, however they're not cheap or standard. The inductor is specific to Morley. In spite of this, it would be a nice idea to try out a few different inductors. I prefer a more vocal-sounding wah with a wider Q to pick and hold notes into sustain, especially the Vox V847. If the Morley sounds too modern for my liking, I could drop in a Fasel yellow or a Halo inductor to try these out to taste. Or make them switchable on the same board.

Whichever direction I take a V2 "Amazing Horsie" board, there's a bunch of things to learn here....

It does seem redundant, however there may be implications when it comes to fitting pickup rings, covers or routs? It still doesn't make sense to me as off the top of my head I don't remember there being any external dimensional changes such as those....just appropriate string spread coverage.

It's probably something non-meaningful. Maybe we should ponder something else?

Minor progress. I depopulated the PCB other than the parts I don't want to replace. Probably ordering parts on Monday since I've got a stock enquiry in....

There's a wealth of info on mods here:
http://www.goethert.com/FrostBottomBoys/AndyHowe/WahPedals.htm

It's best not to go too crazy with these at first, however for the purposes of buying in components for this project I'm selecting a few mods so at least I have the components on hand to experiment. I have limited space for additional switches and pots, so I'm either going to have to bake in some ideas or select those that I want to be adjustable.

• Swapping out R12 (68k) to 56k is a popular one to "give the wah some balls". This can be switchable with a 56k and shortable 12k in series. Easy enough to construct the resistors around the switch bring out flying leads from location R12 on the board.
• R15 can be altered in the same way out to a 50k pot with a 10k resistor in series to provide a 10-60k range over the original value of 33k. This alters the Q value of the filter, however I am going to read into this a little further or directly experiment later in the game to get an idea of feel.
• The DC blocking input capacitor C7 (10nF) can be increased by either adding more capacitance in series or switching between different values. This allows more low frequencies through into the circuit, equating to a "deep" switch of a sort. Again, switches are cheap real estate compared to pots so this one is likely.

So it seems that there's a few simple mods that are just component changes.

Desoldered the battery snap and added in a couple of strain relief holes. I'm not reattaching a snap until the rest of the board has been populated. The two wires go through the first hole, then out through the second. Simple and effective. I use desoldering braid to remove old solder, then clean the board from flux residue with DNA.

The same applies for the four footswitch wires. These are in lesser need of strain relief since they don't get waggled around like a battery snap does.

Time to stop procrastinating and get the component order in.

Alright, I dug around a few basic specs and the general order of things is that the TL08x is the "standard" that nobody really uses, the TL07x is the lower noise version that has more or less established itself as the common general standard, and the TL06x backtracks towards the TL08x by having lower power consumption but is more noisy than the TL07x.

I just had a dig around and I have a few TLE2064 and TLE2074s. I'll probably use the latter since a few mA isn't going to break the bank. Wall warts lose more than this in their general level of inefficiency anyway I bet.

Since I'm going to be buying so many components, I'm going to draw up a total swapout if better quality components present themselves. In general all the resistors will be swapped out for Vishay Beyschlag MBB-SMA 0,6W metal film. This is a single unit, so a few cents on the component for buying on-brand makes sense. In time I may change out the battery box area and fit Li-ion battery with a buck boost charging circuit, simply because I've been doing non-guitar projects with Li-ion stuff recently. This is an afterthought though, and one that rates lower than the Amazing Horse case art.

At some point this weekend I'll review a few modifications on the Bad Horsie 2 and see what may be useful here. It seems that a few mods to the original Bad Horsie came from the Bad Horsie 2 so beyond a few basics I think it'll be fairly plain.

In my experience it never made any observable difference other than noise in high gain situations. Slew might be an issue, as that seems to be a common one with micropower op amps, but I'd really need to look at specs to draw any real conclusion beyond what I'm pulling out of my ass. I've always used them interchangeably and gone for TL06x when it's specifically a battery powered device. Not sure why the TL08x exists, however a TL07x is a good known quantity for most things.

Not all the case art.

I plan on using a power supply as this will be a secondary wah in ond of my Helix's loops. I'll be using a TLE2074 since I have a few, although I have TL064s, TL074s and OPA2134s kicking around unused.

The spec shows TL064, so for the purposes of quantifying what needs to be done I'm describing in those terms for simplicity.

I've decided that this in its finished form will not be a Bad Horsie 2. It will be an Amazing Horse, including case art.