feedback looper questions

[FAP]

For some context, I recently purchased this rather mediocre piece of gear:

Viewed 1211 times

It toggles between two fx loops e.g. put a mic in the input, a distortion thru "A" and a reverb thru "B:" now you can toggle whether the mic gets distortion or reverb. This of course is just a rudimentary example, but that should be all that's needed.

Two questions:

1. When both "A" and "B" fx loops are occupied, and both fx loops are active (i.e. the pedals in each loop are on), I can hear some faint feedback. This feedback only disappears if one of the two fx loops are made inactive/turned off.
I'm guessing this happens because all jacks share the same ground via the chassis–-they're not connected irregardless of the switch in any other way--so could I eliminate this issue by isolating the grounds of the "A" and "B" sets of jacks (e.g. with a plastic enclosure)? And if not, how?

2. Is there a way I could add a true bypass i.e. input->output switch? I've attached a [crude] schematic below for reference: basically, the leftmost side of the 3PDT toggles the LEDs, the center toggles INPUT->SEND jacks, and the rightmost side toggles OUTPUT-> RETURN jacks.

[¾ dead]

Please don't be annoyed that I don't have an answer, but a comment on the idea that this otherwise generic box might actually be designed specifically as a tool for A/B testing Klone pedals, which I find pretty disgraceful as a marketing gimmick. The assumption is based solely on the centaur graphic, of coursr.

I could go on hijacking your thread... Suffice it to say that the general Youtubification of everything has ruined gear-buying forever. I'll see myself out... >_>

[FAP]

On the contrary, I learned something new today: I had no idea “Klone” was a brand! I doubt it has much to do with my predicament but it’s good to know regardless.

[¾ dead]

On the contrary, I learned something new today: I had no idea “Klone” was a brand! I doubt it has much to do with my predicament but it’s good to know regardless.

lol. I didn't know either! Man, a whole company ostensibly taking its namesake from a neologism forged out of pure hype hysteria.

We live in a silly, decadent time. Pip pip cheerio.
(says the guy who bought a fart pedal)

[crochambeau]

Klon. The Klon Centaur is the drastically overpriced pedal that has birthed the (general term) Klone...

Unless someone has formalized that as an actual name, which would be hilarious.

Anyway, when you've got two active lines that meet at a switch that just selects one line you hear feedback/bleed from the other, unselected line? ...and nothing else inside that box should be shared among them.

Are the wires inside the enclosure shielded? If not shielded, can you manage something close to a twisted pair (of signal/common-ground)?

If you have a good ground, signal disappears on it - so a shared ground is not inherently bad. Bad grounds, however, can exist - but inside a single enclosure is often something else (like capacitive coupling of unshielded wires or LACK of solid ground reference).

If you're rocking shared power between the two branches that could, conceivably, also be a bleed path - but power should be a black hole to signal as well and my money is on poor layout or lead dress.

What is the word in the upper left corner of your diagram?

[FAP]

The shielded wiring is a good suggestion, I’ll look into that. It shouldn’t have to have that but it certainly wouldn’t hurt; I think I’m just going to have to take this thing apart to get it to sound how I want anyways.

The power thing is also true: I’ll see if using battery power resolves the issue, in which case the solution will be a whole other kettle of fish.

The word in the upper left is “Chinese.”

Let me ask you this: if I just bridged in+ and out+ leads, would that bypass whatever fx loop is selected?

[crochambeau]

Let me ask you this: if I just bridged in+ and out+ leads, would that bypass whatever fx loop is selected?

No. It'll short across it which is different than bypassing it altogether. I mean, you might essentially "bypass" the effect, but that path will have the input and output node of whatever chain you have selected connected to your audio path - meaning any loading present at those sections will be seen as a parallel load with whatever the input impedance is of your following stage.

If I were adding a switch for bypass, I'd simply add another footswitch in standard bypass configuration and employ a switch per loop so you can have them both active in addition to both off.

The shielded wiring // It shouldn’t have to have that

Why not?

One thing I like to do when wiring bypass is shunt both the input to circuit (being bypassed) and output from circuit to common/ground when the effect is bypassed. This reduces noise generated in circuit from spilling over into the bypassed signal path. I have had to resort to using shielding a time or two when the circuit could manage oscillations even with input and output shunted to ground.

Some time spent basking in AC power delivery theory and how it pulls on the ground plane (when starved for a common path return) made for a decent reset to my approach on this sort of thing.

[NoiseWiki]

For some context, I recently purchased this rather mediocre piece of gear:


It toggles between two fx loops e.g. put a mic in the input, a distortion thru "A" and a reverb thru "B:" now you can toggle whether the mic gets distortion or reverb. This of course is just a rudimentary example, but that should be all that's needed.

Two questions:

1. When both "A" and "B" fx loops are occupied, and both fx loops are active (i.e. the pedals in each loop are on), I can hear some faint feedback. This feedback only disappears if one of the two fx loops are made inactive/turned off.
I'm guessing this happens because all jacks share the same ground via the chassis–-they're not connected irregardless of the switch in any other way--so could I eliminate this issue by isolating the grounds of the "A" and "B" sets of jacks (e.g. with a plastic enclosure)? And if not, how?

2. Is there a way I could add a true bypass i.e. input->output switch? I've attached a [crude] schematic below for reference: basically, the leftmost side of the 3PDT toggles the LEDs, the center toggles INPUT->SEND jacks, and the rightmost side toggles OUTPUT-> RETURN jacks.

What's hilarious about this is that the only reason it needs battery is to power the led.

[FAP]

Hell, I’ve done that before:
[Insert image of my AxB switch box with a partially exposed ground lead here]

Also confirmed it’s not an issue with power: I get the same oscillations on battery power that I do with a wall wart.

It bears mentioning I had a digitech grunge on “A” and a DOD grunge on “B,” both high-gain pedals. The oscillations didn’t occur (or at least weren’t noticeable) if I swapped one of them out for, say, a digital delay or something. Perhaps I’m being childish, but maybe the high-gain stuff is just that powerful enough to cause some cross-contamination.

[NoiseWiki]

Also confirmed it’s not an issue with power: I get the same oscillations on battery power that I do with a wall wart.

Well this thing is basically a passive switch.. it doesn't need power to operate except for the LED so for the sake of argument is there any noise if no power is connected.

Also just for the sake of mentioning it.. I have had issues with certain pedals being connected with other pedals to a one spot adapter.

Theoretically the least noisey route is battery power for everything