I’m using the Quad Cortex as a multi-effect unit for my Fender Blues Junior IV. I’ve noticed that the QC produces a constant hum that can be heard through the amp.
When I disconnect the QC from the Blues Junior, the hum disappears. When I connect my guitar directly to the amp, there’s no hum either.
To troubleshoot this, I created a completely fresh preset on the QC, connected to the Blues Junior. The preset is literally empty – no effects, no amp simulation, no cabinet – and the hum is still there. Interestingly, it doesn’t matter whether the guitar is connected to the QC or not.
The amp and QC are connected to the same socket. The Ground Lift function is off. When I turn it on, the hum becomes much louder and sounds a bit different.
I expected that an empty preset would make the QC transparent to the signal. What could be causing this hum? How can I get rid of it?
An empty preset in any multi effects, or even a normal guitar pedal in bypass doesn’t always mean it would be transparent to the signal.
I would check multiple things here.
-are you using a power conditioner? Not the cheapest livewire version or a no name brand from Amazon. Those things are basically a power strip in a rack mount. They aren’t real power conditioners.
-have you checked your cables?
-are you using the power supply that came with the Quad?
-do you have anything else connected to the quad? Some people have experienced noise with the Quad if the USB is plugged in to their laptop, etc
Thanks for the suggestions.
Yes to all — I’m using a power conditioner, proper cables, and the original power supply.
I disconnected everything, but nothing changed.
However, I may have found the issue. I had the input gain set to +24 dB to center the signal on the meter. When I changed it back to 0 dB, it helped. There’s still slightly more hum compared to plugging the guitar directly into the amp, but it’s much better now.
Is this normal behavior?
How can I make the QC fully transparent? Will setting both input and output to 0 dB achieve that?
I could do that, but what about the level meter in the I/O settings for the Input?
When I set the input level to, say, 1, the signal is very low — almost unnoticeable on the meter bar.
The sound from the amp is also much softer compared to plugging the guitar directly into the amp, bypassing the QC.
When I set the input level to 23, chords fit perfectly within the meter bar, just barely touching the red zone.
I find I rarely have to adjust the input gain on the QC. If your level is super low, then that just means you have lower output pickups or play lightly. It isn’t supposed to always be at a level right before red on the meter. It doesn’t work like that when you’re playing through your amp either. The amp is just seeing whatever level the guitar or pedals in front of it are providing. By boosting everything as much as you are, you’re basically just giving a massive clean boost to all of your playing lol. The level of the visual meter shouldn’t even be considered in this situation aside from making sure you have signal + it isn’t peaking.
If your level is very different going from the QC to your amp, vs just guitar to amp- you can try boosting the level. Possibly the input a little or the output. It shouldn’t need that much of a different level, but it’s normal for some pedals to have a slight volume difference. For example many choruses will slightly boost the signal when engaged, etc.
There’s no reason to be boosting the signal 23db though. That would mean you have a cable issue or routing issue. A boost like that is raising the noise floor a ton.
with no blocks on the grid, the output level is VERY low. The QC levels incrementally increase as you add blocks to the lanes. Managing those gain stages is crucial to getting a healthy but clean output level across the grid.
The 1/4" outputs (3 and 4) can increase your headroom if you’re connecting to balanced inputs on an amp; this will boost your levels by 6dB, but still- with nothing on the grid you’re not really using the QC how it was designed to be used. Even if you just put a gain block on the grid, that can increase your level enough to get a good noise floor without changing your tone or having to boost your input so high (which is what was causing the extra noise- if the QC isn’t really adding anything you are only boosting its noise floor which unsurprisingly will raise the level of background noise)
If you have rather low output pickups it’s perfectly normal that the meter stays in the lower half, but “almost unnoticable” sounds strange.
Do you by chance use a TRS cable instead of TS to connect your guitar? If so, you should definitely try a TS cable.
Depending on the electronics of your guitar that could make a difference. For example I just tried it with my active pickups and had no sound at all, while another guitar with passives worked, but was missing a few dB of input.
I always thought an empty preset would be unity from input to output without any boosts or cuts. Is that not the case? Weird design choice by neural IMHO if that’s true
Regarding the low input signal: with +23 dB, the level is just right (on the border of red line); with 0 dB, the peak reaches only about halfway maximum whan play loud and dynamically (when I previously wrote “almost unnoticeable,” I meant that only a significant level increase results in a visibly stronger signal).
So, based on what you’ve said, it seems that my signal at 0 dB is totally acceptable, and I should try slightly increasing the I/O levels (just a couple of dBs at most), and then maybe add something like a clean booster to the grid.
Yes. The input signal does not have to reach the red area. Halfway is totally fine as long as the amp models react as they are supposed to (/ as you want them to)
