Behringer UV300 Ultra Vibrato (or any plastic clone) - True Bypass Mod?

[scorchedcortex]

Hello everyone,

Has anyone performed a true bypass mod on the Behringer UV300 Ultra Vibrato, or ANY of the cheap plastic Behringer clones?

If so, can I be directed to the directions or a tutorial on how to do this? I DO NOT want to re-house the pedal. I just want to put in a true bypass foot switch in the existing enclosure.

I'm a bit of a noob at this, so any help is much appreciated.

Thanks!

[Mark Hammer]

Why do you want to install TB?

[DavidRavenMoon]

I agree with Mark. There's zero benefits on modding it to TB. It's all hype.


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[scorchedcortex]

I have seen various posts suggesting that the bypass on these pedals are noisy and problematic. Is it just a bunch of hooey?

[Mark Hammer]

It would depend on the pedal.  I have a few Behringer pedals.  Some are every bit as quiet as their commercial predecessors (i.e., Boss, MXR), and others have made poor choices of op-amps.  I have their acoustic simulator (clone of Boss AC-2), where they use TL064 quad op-amps.  Very hissy.  But input and output buffers in e-switched pedals are generally single-transistor affairs and very quiet.  If one has 8-10 e-switched pedals on their board, then the miniscule amount of noise that the buffers add, cumulatively, may not be studio quality.  One or two at a time, however, their hiss pales beside what the rest of one's rig adds.

So, I can see some limited arguments for wanting to convert to TB.  But outside of those specific contexts, I'm not seeing a strong argument for you to rip up the pedal and install a different switch.

[Redvers]

Just get a small TB looper for it. Then you could ab true bypass against buffered bypass to see if it's worth it.

[R O Tiree]

Sound aside, there are some important "engineering" points to be made if you "DO NOT want to re-house the circuit".

1.  There is not going to be enough room.  Designers/manufacturers are simply not going to supply an over-sized enclosure, because it costs more money when you're building thousands of pedals a month.  Underneath the stomp-button, there's probably a spike of plastic/metal, poking through a small hole in the main enclosure, that impinges on a small micro-switch soldered to the PCB.  It can't smash through the PCB, though, because the bit you tread upon hits the top surface of the main box, limiting its travel precisely to where it needs to be to make the switch but not apply excess force to the PCB - we're talking a couple of thou tolerance, here.  The hole in the main box under the foot-pedal is quite small (just big enough for the spike to get through to the micro-switch) so cutting out a hole big enough for the 3PDT switch is going to ruin it.  In addition, the very act of drilling this larger hole will inevitably mean that swarf will fall onto the board, leading to potential short-circuits if you don't get rid of it completely (unlikely) and, if a bit gets inside a pot, it's toast.  Try sourcing exactly the same pot (lead spacing and length, physical dimensions, shaft type and length, bush diameter, etc... oh, yeah, VALUE! because some of these bespoke pots have "weird" values/tapers/pinouts) - you're very unlikely to find one.  That's always assuming that your drill doesn't suddenly burst through the new hole and smash into the PCB with inevitable results.  The safest option here is to completely strip the box of ALL its contents, drill, vacuum it out and then try to put it all back together.  Ever tried to remove ALL the solder from all 6 pins of a PCB-mounted jack socket?  During pedal assembly, they put the jack sockets in first, nip them up, place the PCB over the pins and only then solder them up, so to disassemble, you have to reverse that process - remove all the solder from those key "locking" components, then remove the PCB.  If the holes are through-plated (and they almost always are, these days, given SMT components on double-sided boards) then you just won't get it all out - it's that simple - so it'll be time to get out the hacksaw, then you'll have to source identical jack sockets to replace the ones you wrecked.  <sigh>.  PCBs will be a stock size and shape, because they have to reach all the various jack sockets, pots and switch(es), because it's cheaper to manufacture by soldering everything to the PCB rather than have a small army of people to cut/strip/solder individual wires, then another small army of QA testers to make sure the people wiring them up did it correctly.  (They still need testers, but the chances for errors with PCB-mount manufacturing are vastly reduced, so fewer testers are needed.)  Simply put, the design  is robust enough as it is and, if the micro-switch fails for some reason (corrosion, too many cycles) then a replacement is uber-cheap to source and uber-easy to fit.  So, trying to shoe-horn a comparatively MASSIVE 3PDT switch in there bolted to the existing enclosure just won't work mechanically, meaning that a re-house is the only option.

2.  Rat's nest.  You will have to break out the input, output, LED connections, as a minimum, and then provide one more wire for each to go back from the switch to the board to restore functionality.  This gets messy and occupies more volume in that tightly-packed pedal enclosure.  Re-house, again.

3.  Where will those new connections have to go?  Invariably, the very first thing an input signal sees after the jack is a buffer in e-switched pedals, which is the very thing you're trying to cut out of the circuit.  Then it goes to the JFET/CMOS switching system.  Trying to just inject the input signal from jack->3PDT->first "useful" bit of the circuit may not work terribly well, as its input impedance may be fine for their buffer, but not for your guitar.  In addition, it will probably be mis-biased and lead to pops (at least) or ear-splitting BANGs when the 3PDT is engaged and disengaged.  This will need careful thought and will almost certainly mean a bundle of messy point-to-point wiring of several components to get the bias where it's needed.  More rat's nest and a massive chance that, when you pry it all back in the box, and assuming that you can get point 1 above to work OK, that point-to-point bundle will almost certainly compress and short out itself and/or something else on the board or the enclosure.  Lastly, unless you're confident/competent at de-/re-soldering on PCBs that are only (cheaply) designed for limited heating cycles (ie, one), you're probably going to wreck traces and/or components.  Re-house, again (or a costly re-build if you mess things up... or just buy a new pedal, 'cos this one's knackered).

Although I agree in principle with Redvers' suggestion, you'll need a buffered pedal in front of this whole A/B TB/"stock" setup.  Let's say you have a 20ft guitar lead (you gotta move around, right?) and another 20-30ft lead from your pedal board to your amp, then a couple of feet of patch cables... all told that's 42-52ft of lossy cable between your guitar and your amp.  As PRR has said recently in another recent thread, and undoubtedly many times elsewhere, guitar cable sucks tone much more than "good enough" buffers.  A buffer early in your chain sorts that loss out.  So, you'll probably find that the sound with "TB" selected in Redvers' suggested layout will "unfairly" bias you towards the buffered, original pedal.

That said, most buffers in our commercially-bought pedals are pretty dumb, but good enough.  There are much better buffers out there, for the extra price of less than $1-worth of parts but, bean-counters being bean-counters, they will mandate that the engineers put the cheapo version in there, because it's "good enough"... that is until you stack 20 pedals in a row, all with cr@ppy, cheapo buffers that are always in-circuit, and then you're clearly not in quite as good a place than if you only had 5, for example.  As Mark Hammer says, if it's not noisy/hissy, then I'd agree wholeheartedly with him that ripping it apart and messing with it to the extent that it cannot be restored, as I've hopefully shown, will be wasteful of time, money and effort and would, therefore, be pointless.

[DavidRavenMoon]

What "better" buffer could you have that would be quieter than one transistor?

That's low in cost, and the single stage keeps the noise down. 

Like Mark said, the rest of your rig will be noisier!


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[PRR]

A properly designed many-part buffer *may* be quieter than a simple buffer.

Design the output to drive the load well, design the input to take signal as nicely as possible.

Of course this path is not certain. Adding more parts to a bad design may be a worse design.