Quav interacting with downstream pedals

[Fanyo]

One of my pedals is causing volume increase in pedals after it.

Added a new Quaverato to the board, and noticed it is interacting with other pedals downstream and causing volume jumps.
I’ve tried swapping all cables, power supply, power cables, etc.
I’ve tried rearranging pedals,, adding different ones, etc.
I am using a loop controller, so I can take each pedal and its cables completely out of the circuit.
Here’s what I’ve been able to parse out:

– The Quaverato is definitely the culprit. No other pedals in any other order cause this issue.

– The Quaverato only causes increased volume interactions with pedals downstream, not upstream.

– With buffer-always-on pedals, it makes no difference whether the pedal is on or not (to cause volume increase)

– With true-bypass pedals, the volume increase only occurs when the pedal is on

– The closest I can come to describing exactly how much the volume is increased is probably akin to turning the level knob of a typical dirt pedal up around 15%-20%

The volume increase is an issue because some of the loop controller patches will have the post-Quaverato pedals in the signal path, while some will not. This makes it impossible to maintain a consistent output signal level across all patches.

Has anyone ever experienced anything like this?

Would anyone care to posit the specific source of the issue? Could it be an impedance issue? I am truly dumbfounded at this point.

[brach]

Fanyo,
I have never heard of this issue before. There is nothing uncommon about the input or output impedance of this version of the Quaverato, so that’s not the issue. My only guess is that it has something to do with the frequency response of the Quaverato. If you have drives or other pedals that are sensitive to the frequency response of the input signal, they may be boosting those particular frequencies more than others. Have you tried changing the order of the pedals in your chain? Most people run modulation effects like the Quaverato toward the end of the pedal chain, partially for this reason…modulation effects often have a tendency to shift the phase of different frequencies. Another thing that might help is to keep a non-true bypass pedal directly after the Quaverato…like a tuner pedal or a buffer pedal or something.
I’m sorry about this issue. I hope you can find a solution that works for you. I’m sorry that I can’t be of more help.
Take care.
-Brach

[Fanyo]

Hey Brach, thanks for the reply. I want to be clear in that I don’t think there is anything “wrong” with your design. I am having an issue, and am hopeful that you can help me understand what’s happening. Also, I would hope that confronting stange issues like this could help you understand the circuitry even better than you already do.
I absolutely love the Quaverato and I really hope we can figure out a way to solidify its spot on my board.

I have tried every single conceivable routing scheme, in every conceivable order, in every conceivable combination, and changing/swapping every conceivable variable. Typing a highly detailed description would take hours, so you’ll just have to trust me when I say I’ve tried it all.
I had to build a true bypass single looper in order to remove buffers and opamps completely from the equation, and here’s what I’ve found:

– the issue in question is a roughly 20% jump in volume, and will be referenced to as the JUMP henceforth. It is DEFINITELY not an issue of certain amplified frequencies or the nature of modulation effects, etc etc etc. It is a highly noticeable, quite substantial jump in volume (by real-world stage performace standards, not bedroom mouse-fart levels)

– the Quaverato is the only pedal that I can add to the signal chain that causes the jump. With the Quaverato removed from the signal chain, no combination of any of my vast collection of pedals result in the jump.

– the jump only occurs when an opamp is activated downstream of the ON Quaverato (whether through buffer or otherwise. True Bypass pedals only activate issue when they are ON)

– the jump only occurs when output of the Quaverato is connected to my 8 channel loop controller (Joyo PXL LIVE). The Quaverato does not need to recieve signal from the looper, only sending signal to the looper to cause the jump. (Ex: guitar->Quaverato IN-[]-Quaverato OUT->loop 7 RTN-[]-loop 8 SND->delay IN-[]-delay OUT->loop 8 RTN-[]-looper out->amp). (nothing else is connected to the looper, anywhere). I feel like this is an important discovery that at least tells us that the issue definitely does not originate on the input side, but is isolated to the output side.

-the jump does not occur when loops containing active opamps are off/inactive (as in disengaged—-the loop is out of the circuit)

-The jump only occurs when the Quaverato is ON, it’s output is connected to the PXL LIVE via an on/activated/engaged loop, and there is an active opamp introduced in the circuit downstream of the Quaverato.

-The jump does not “seem” to occur if there is an active buffer/opamp connected to the output of the Quaverato before the PXL LIVE. But specifically, the jump is always ON regardless of additional opamps/buffers introduced/unintroduced downstream.

I don’t specifically know if there are buffers/opamps within the PXL LIVE, but there are no potentiometers on the unit to control level, and the signal level/strength at the output is indiscernible from the signal at the guitar’s output. I can’t help but assume there are buffers present.

The jump is a problem because sometimes there will be buffers/opamps in the signal path post-Quaverato, and sometimes there won’t. It would be fairly undesireable to experience a 20% jump in volume between using the Quaverato by itself, and using the Quaverato with reverb or delay. I’m sure you can forsee a problem here.

You may be on to something; I may have to permanently connect a stand alone buffer to the output of the Quaverato to sort of perpetually keep it in JUMP mode. I’d like to avoid this if at all possible, for several reasons.

Synopsis:
The Quaverato’s output is reacting with the combination of the PXL LIVE and downstream opamps/buffers.

Any suggestions for solutions are welcome, but I would really like to understand what exactly is happening….regardless of whether it’s a truly fixable issue, or nature of the beast grin-and-bear-it, or whatever. For me, the practical solution is secondary to understand exactly what is causing such a crazy reaction.

What do you think is specifically causing this issue?
I have multimeters and the ability to use them, but I don’t exactly know what to test for or how to interpret the readings. I’d be happy to take any measurements upon your request.

Thank you for your help!

[brach]

Fanyo,
Thanks for the detailed info. I don’t feel defensive about my design work or the Quaverato. I’m constantly learning and I would probably even design the Quaverato somewhat differently if I was to do it over again these days (after all I’ve learned in the years since I designed it). I’m always wanting to learn and be a better engineer, so thanks for letting me be a part of this troubleshooting process.
One thing that I’m curious about is to remove the looper from the equation…have you tried using the Quaverato and other pedals together outside of the looper? According to the user manual the PXL live does have “buffered bypass.”
I know you said you tried every conceivable combination of pedal orders and it happened on all of them…but If the Quaverato is the very last pedal in the chain (hooked up to the looper) before the amp, does it still cause this issue? What about if it is the last pedal in the chain after the looper, where the looper output is plugged in to the Quaverato input and the Quaverato output is going into the amp, does the volume jump happen then, when other pedals are turned on?
Have you tested the Quaverato when it is just plugged into the amp and your guitar? I’m curious if the boost you hear is really the normal volume level of the Quaverato, and the volume level is being reduced when it is in the pedal chain.
So far, from the list of facts you gave, none of them disprove my original hypothesis of it being a frequency sensitivity issue. I don’t know how you can say this is definitely not true. This type of thing can be experienced with an overdrive or distortion pedal that has the tone know all the way up…there is often a large boost associated with that adjustment, most of the time at least 20% boost. Most of the time, when modulation effects have this issue it is at a much lower volume level than what you are experiencing here, but it doesn’t always have to be. The same principles could be at work here. Unfortunately, it will take more than a multimeter to test it…you would need at least an oscilloscope and signal generator. You could experiment with the crossover switches, changing the frequency to see if that has an impact on the boosted/jumped signal. If it does, that’s a clue pointing to what is happening.
Let me know what you find when you have the opportunity to check these things out.
Good luck!
-Brach

[Fanyo]

That’s a great attitude to have, Brach!
I believe you’ve created a very special thing in the Quaverato. If there’s a better sounding, more feature laden, easier to use, more versatile tremolo pedal out there, I’m not aware of it…nor could I imagine the possibility. And the kit was a ton of fun and highly rewarding, not to mention the absolutely flawless and very well thought out build instructions. Kudos, my good man!
I’d LOVE to see what you could do with a phase or chorus circuit!

As ive previously stated, I’ve tried several combinations of several different pedals in several different orders….with and without the PXL. Different cables, different power supplies on multiple pedals, etc etc etc etc. I changed and swapped and substituted every conceivable variable, and I mean EVERY SINGLE THING (without disassembling pedals and changing inner components).

My statement still stands. There is only one very specific situation in which the JUMP occurs, and that is:
Signal (either straight from the guitar, or from an activated opamp pedal, or from the upstream PXL loops, or from the guitar input of the PXL….SIGNAL ORIGIN DOES NOT MATTER UPSTREAM OF THE QUAVERATO)-> Quaverato IN [] Quaverato OUT->PXL loop RTN [] PXL loop SND (from the next loop downstream from the Quaverato)->(any) pedal (with an activated ((energized and in the circuit)) opamp (via buffer or otherwise) IN [] pedal OUT-> PXL loop RTN [] PXL OUT-> amp

In the following scenario, the jump DOES NOT occur:
Guitar->PXL IN [] PXL loop 7 SND->Quaverato IN [] Quaverato OUT->PXL loop 7 RTN [] PXL loop 8 SND->true bypass pedal OFF->PXL loop 8 RTN [] PXL out->amp.

In the following scenario, the jump DOES NOT occur:
Guitar->PXL IN [] PXL loop 7 SND->Quaverato IN [] Quaverato OUT->PXL loop 7 RTN [] PXL out->amp.

In the following scenario, the jump DOES NOT occur:
Guitar->PXL IN [] PXL loop 7 SND->Quaverato IN [] Quaverato OUT->amp.

In the following scenario, the jump DOES NOT occur:
Guitar->PXL IN [] PXL loop 6 SND-> (any) pedal (with or without activated opamp…it doesnt matter) IN [] pedal OUT-> PXL loop 6 RTN [] PXL loop 7 SND-> Quaverato IN [] Quaverato OUT->PXL loop 7 RTN [] PXL loop 8 SND->true bypass pedal OFF->PXL loop 8 RTN [] PXL out->amp.

In the following scenario, the jump DOES NOT occur:
Guitar->Quaverato IN [] Quaverato OUT->loop 7 RTN [] loop 8 SND->true bypass pedal OFF->loop 8 RTN [] PXL OUT-> amp

In the following scenario, the jump DOES NOT occur:
Guitar->Quaverato IN [] Quaverato OUT-> (any) pedal (whether on or off, whether true bypass or not, buffer or no, etc…doesn’t matter)IN [] pedal OUT-> amp. This scenario 100% completely bypasses the PXL.

In the following scenario, the jump DOES NOT occur:
Guitar->PXL loop 6 RTN [] PXL loop 7 SND->Quaverato IN [] Quaverato OUT->PXL loop 7 RTN [] PXL loop 8 SND->true bypass pedal OFF->PXL loop 8 RTN [] PXL out->amp.

This is how to ENGAGE the jump:
– OUTPUT SIDE of Quaverato MUST be connected to PXL in some operational fashion, through either the front/main guitar input, or through the return side of one of the loops.
– There MUST be an active opamp in the circuit downstream of the Quaverato->PXL combination. Where the signal goes from there is inconsequential. As long as the signal path is Quaverato->PXL->active opamp, the JUMP occurs. There can be 100 active OR bypassed opamps in the circuit upstream of the Quaverato, or 100 active OR bypassed opamps in the circuit downstream of the first initial active opamp in the circuit POST the problematic Quaverato->PXL->active opamp combination. It does not matter. The key is the Quaverato->PXL->active opamp combination.

I say again, THIS IS NOT A FREQUENCY SPECIFIC ISSUE. The volume is increased by roughly 20%, across the entire frequency spectrum…evenly.

The JUMP occurs whether a pedal is “effecting” (as in PHASING or CHORUSING) the signal or not. The “effect” is not important. The OPAMP is what is important. A clean buffer will cause the JUMP if it is inserted Quaverato->PLX->clean buffer (ACTIVE OPAMP).

Example of routing schematic:
Guitar->PLX IN [] loop 6 SND-> Boss Reverb IN [] Boss reverb OUT-> loop 6 RTN [] loop 7 SND -> Quaverato IN [] Quaverato OUT -> loop 7 RTN [] loop 8 SND -> Boss EQ IN [] Boss EQ OUT -> loop 8 RTN [] PLX OUT -> amp

In this schematic, all loops are engaged, all Boss pedals are OFF, and the Quaverato is ON…..
When taking loop 8 out of the signal path (disengaging), the output volume drops 20%. Toggling between engaging and disengaging loop 8 the output volume jumps up and down by 20%

I used Boss pedals in this schematic because they use clean and transparent always-on buffers (ACTIVE OPAMP).

I am trying VERY hard to be as clear and as detailed as I can possibly be. You keep assuming I’m confusing compression, distortion, modulation, frequency spikes with volume (SIGNAL LEVEL) And/or I’m running the Quaverato into a bunch of clipping stages and/or frequency/phase modulators.

I have tried very hard to leave ZERO room for assumption. What I’ve described, is exactly as described.

I hope I’ve made the issue clear. The length and redundancies are unfortunate, but seem necessary to negate any further confusion, and really drive the point home.

Thank you again for your time and willingness to investigate cause of this issue. I truly do appreciate it.

[Fanyo]

Also, maybe I should describe the intesity of the jump a little clearer since there seems to be some confusion there as well.

Initially, I stated it was akin to turning the LEVEL (volume) knob on a typical dirt pedal (not gain or distortion knob) up 20%. So that means from half (or noon) to 70% (or 2:00).

I would also be confident in using the same metric as applied to a clean 15w solid state amp.

Another accurate way to describe it would be to say that if you were watching your television at a certain volume, and the volume increased as much as THE JUMP, it would most certainly illicit a “WTF!?” response.

Yet another way to put it: the jump is almost twice as loud as I would ever want a lead boost, in comparison with the base volume.

I don’t know what to measure, or if I have the proper equipment to measure such low voltage signal level. This is the best I can do to clarify.
As I said before, it’s a significant jump.

[Fanyo]

Also, to reiterate:
Every loop in the PXL can be populated with any pedals from my significant pedal collection, im ANY combination. at ANY settings, in ANY order, and the JUMP only occurs if the Quaverato is 1.) IN the circuit and upstream of the PXL OUT, 2.) ON, and 3.) Upstream of ANY pedal with an ACTIVE OPAMP (energized and in the circuit). And anytime I say “any”, I mean LITERALLY ANY.

To clarify even further:
When I say ACTIVE OPAMP, I mean an opamp that is energized (powered/ON/active) and in the circuit (guitar signal path). This includes ANY AND ALL PEDAL CIRCUITS THAT USE AN OPAMP:

When I use the term OPAMP, I am not using it as a colloquialism to describe “distortion”, or “gain” or “loudness” or “compression” or any sound effect, artifact, or descriptor of anything other than an actual physical DC-coupled electronic voltage amplifier with a differential input; also known as an OPAMP.

I realize it may be possible that the OPAMP itself may not be the true culprit that is causing the JUMP reaction with the Quaverato’s output section…that it could in fact be that a buffer (in its entirety) could be the culprit, and an opamp just happens to be an integral part of that circuit. Maybe it’s the specific collection of components that make up a buffer, or the order in which they are placed in the buffer circuit, or a particular way they react with each other within the buffer circuit. I don’t know enough about guitar pedal engineering to know the difference. What I DO know is that without an OPAMP placed in the guitar signal path circuit as I have described many times here, there is no JUMP. And unfortunately, I don’t own any pedals that do not use any buffer circuitry (AFAIK) to experiment with.

[brach]

Thank you for trying to be so clear in your communication….sorry for my lack of understanding very well. I’m not sure what is going on here. Somehow the Quaverato is interacting with the PXL in a weird way, seeing that when it’s not in the signal path the issue doesn’t occur, no matter what pedals are in the signal path. I would love to find the schematic to the PXL to see what buffer circuit they are using.
You were very clear that the pedals that have been part of this issue contain opamps (“an actual physical DC-coupled electronic voltage amplifier with a differential input; also known as an OPAMP”). But you also described the buffer in a non-activated Boss pedal as “an opamp”. From the Boss service manual schematics we can see that Boss pedals use common collector discrete buffers, so I’m a little confused about what you are calling an opamp…are you just calling an active pedal, despite it’s particular circuitry, an “opamp”?. Either way, you said the jump does occur when a bypassed Boss pedal is powered on downstream of the Quaverato, so I’m assuming this volume jump also happens with discrete, non-opamp based pedals like a big muff, or LPB-1, or mosfet boost are on downstream of the Quaverato…is this correct?
One thing this might be related to is the phase of the Quaverato signal. If you look at the Quaverato schematic, you will notice that the output signal is out of phase from the input signal. But I’m not sure why only the Quaverato would cause a jump in the volume and not other pedals that flip the phase (like the LPB-1 set to unity gain, for example…which I suppose is something to check out). There is a way to mod the Quaverato to have in-phase output…it requires a lot of trace cutting and jumper wire running.
Another thing that crossed my mind is that the “silent switching” circuit on your pedal may not be operating correctly…possibly causing impedance issues. You can check this by removing C17, which will remove that circuit from the signal path. You’ll need to use a solder sucker to clean out the PCB holes (heat it up from one side of the board, suck from the other side of the board).
That’s all I can think of for now. Good luck!
-Brach

[Fanyo]

Thanks for the reply!

Sorry, I was under the impression that all buffers used opamps in their circuits, and most every pedal used opamps somewhere in their circutry. I’m not a pedal engineer, and I know just enough to be dangerous. I didn’t want to use the term “buffer” by itself bc I didn’t want to mislead you into thinking I was referring to a stand-alone buffer every time I used that word.

I’m not 100% sure if I have any pedals that don’t use buffers…or opamps, for that matter…in its circuit. I don’t currently own any of the pedals you mentioned.

I’m also not sure if any of the pedals in collection flip the phase.

For now, I’m just going to run a stand-alone buffer permanently in-between the Quaverato’s output and the PLX. If I find another pedal that causes the jump, or pedal that doesn’t activate the jump post-Quaverato, I’ll let you know.

There was another symptom, but I didn’t want to add to the confusion until we got the big issue clarified, which it looks like we now have:
When the JUMP is activated, the taper on the Quaverato’s volume pot changes. It goes from a relatively smooth 0-10 transition in normal operation, to increasing drastically from roughly 7-10 (while not increasing much from 0-7) when JUMP is active.

Thanks again for your patience and willingness to help me figure this weird issue out. I brag on you and your designs every chance I get.

[brach]

Fanyo,
Well, I guess that is one solution. I wish we could have figured this out. This is still very puzzling to me. It’s also puzzling that the taper of the volume control reacts to factors outside of the pedal. I still would like to see the schematic to the PXL. I think that would tell us something about what is going on here.
Anyway, good luck using the Quaverato in this way. I hope it’s not too annoying for you.
Take care.
-Brach

[Fanyo]

Hey, Brach. Hope you’re doing well.
Just an update to add some data to your diagnostic toolbox:

I purchased a stand alone buffer and placed it between the Quaverato’s output and the PLX loop return to keep it in JUMP mode. It worked well, but all of the footswitches of the PLX started “popping” loudly when actuated…..that is, until I replaced the stand alone buffer with an OFF Boss pedal, and then the popping went away. Since I don’t have room on my board for another pedal, and Boss doesn’t offer a small stand alone buffer, and hardly any buffer manufacturer states whether their circutry is opamp based or discreet transistor based (i took a peek under the hood of the one i purchased, and it was an opamp based circuit), I decided to swap out the Quaverato with a recently acquired Walrus Audio Monument, and it had the exact same issues as the Quaverato. So out of the 50 or so guitar pedals I own, only the Quaverato and the Monument cause/reveal the JUMP issue.

I currently have the Quaverato in the last PLX loop, and have found that it is, in fact, in JUMP mode. I know this because of the volume pot taper change. It’s a practical solution, and I’m fine with it. Initially I was hyperfocused on tracking down and figuring out such a stange issue, but the shine has worn off on that escapade, and now I’m just happy to be able to keep the Quav on my board.

Thanks again for all your help and patience, and I look forward to future Zepplin designs.

[brach]

Fanyo,
I’m sorry about this annoying journey. In finding out that this same issue happens with another pedal, I’m thinking that there is something fishy going on with your PXL. Normally the footswitch popping occurs when there is a DC offset on one side of a bypass capacitor. When the pedal is engaged the bypass cap allows some of the DC voltage change to momentarily flow through the cap, causing the pop. Pull down resistors can be used to help keep the charge from accumulating on one side of the cap.
If you just need a Boss style buffer, they are really easy to build. You can just follow the schematic from one of their service manuals (look at the TU-2 service manual, for a very simple schematic). You just need one FET and one BJT and a few other supporting passive components. You may consider trying to build one yourself, on some perf board. It would be very small and you could even install it inside the Quaverato chassis, so you could use the Quaverato’s 9V rail to power the circuit with. Perhaps a better solution would be to find out what kind of circuit the PXL is using and modify that. You could even install the buffer circuit in the PXL chassis so this problem doesn’t occur, no matter what tremolo pedal you use.
…I’m just throwing out ideas here. I hope your Quaverato ends up serving you well, despite this annoying issue.
Take care.
-Brach

[Fanyo]

Ok, I’ve been semi-steadily working toward figuring these issues out. I’ll try to keep this a succinct as I can.

Here’s what I know for sure:
1. The Quaverato and the Walrus Monument are the only 2 pedals from my 50+ arsenal that react to the rest of my rig this way (the Monument to a slightly lesser degree)
2. Nothing I do at or anywhere before the Quaverato’s input changes anything.
3. The Quaverato and the PXL are being affected by the Quaverato’s interaction with components post-PXL (DI box and/or mixing board)
4. The symptoms have been drastic volume increase or decrease with the Quaverato in the guitar signal path, and switches popping on the PXL (all depending on what’s in the signal path post PXL).

The only way I’ve been able to reduce these symptoms as much as ive been able, and not end up with a suboptimal routing scheme (really don’t want to run the Quaverato after the PXL. Kinda defeats the purpose of having a loop switcher) is as follows:
Guitar-> PXL (lots of random pedals in all its loops)(Quaverato in loop 8)-> off Boss pedal (after the PXL’s output)-> mixer’s Neutrik 1/4″ channel input. I have a “Y” cable splitting the PXL-> Boss buffer signal to a DI box, before the mixer input.

Omission of the Boss buffer, using the parallel inputs of a DI box as a splitter, placement of the Boss buffer at the Quaveratos output (within the same loop)…all resulted in some form or level of issue (volume jump, volume dip, and/or popping switches).

I enlisted the help of the members of diystompboxes.com forum and the general consensus was that the 100k output pot of the Quaverato causes it to have an unusually high output impedance, which was affecting/interacting with downstream components. I’m not sure that explains why the Monument causes/contributes to the same issues (to a slightly less degree) when it’s output pot is 10k.

Until somewhat recently, I have never been much of a pedal guy. I had no idea these circuits were so sensitive to other things within the same signal chain.
I don’t know if the already high output impedance of the Quaverato, connected to the low impedance input of a mixer causes the overall operational impedance to increase almost exponentially? I also don’t understand why using both parallel inputs of a DI box would cause issues such as drastic decrease in volume, drastic treble rolloff, etc.

I wish I had a better understanding of these things so I could pinpoint the exact cause of the problem and relay that info to you so that you might be able to help other folks, should they ever run into the same weirdness I have.

Anyway, thank you so much for trying to help me get it figured out. I have found a good and practical solution that doesnt involve getting rid of my Quaverato, and I guess that’s what really matters.

[Author]

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