We know that the QC has no ground connection though the power connection. It is a 2 conductor power connector. Any other type of power supply will still connect to the QC via the same 2 conductor connector. I do not understand how people believe that a different power supply will solve any grounding issue. If the power supply is grounded, the ground connection will stop at the transformer that steps down the voltage. All you have from there to the QC is the 2 wire, 2 conductor jack. There can not be any grounding via the power supply.
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Are you sure the ground is isolated from the outlets on units like CIOKS DC7?
Obviously some users, including me, experience a significant difference in noise when no other grounded equipment is connected.
EDIT:
In DC, GND and (-) are usually the same. No 3rd wire needed.
I would be very surprised if any decent poweer supply intended for use on guitar pedal boards was not isolated. The ones that usually generate noise are the ones that are not isolated. My point was that I do not believe that the QC can be “grounded” via its 2 conductor power wire and connector. It is not designed to be grounded that way, even if a ground connection were provided by that route. I would also maintain that virtually all (if not all) of the alternative power supplies frequently suggested are incapable of providing a ground connection via the 2 conductor connection to the QC. And even if they could, the QC is not designed to utilise it.
Interesting point. I couldn’t find any information from CIOKS regarding the DC7 and grounding. Certainly worth investigating.
Yesterday I did some measurements and I can confirm, there is continuity between the center pin of QC’s power port (-) and the metallic case, as well as the footswitches (obviously) and the sleeve contact of the guitar cable. In other words, the QC can be grounded via it’s negative power terminal.
This could explain why it gets ground when powered by a notebook PSU, assuming, the negative terminal of the PSU’s outlet is grounded.
However, I was not able to measure continuity between the ground port of the inlet of CIOKS DC7 and the negative terminals of its outlets, thus no continuity between ground of DC7 and ground of QC. I don’t exclude user error on my side, though.
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Well done 2342. It is refreshing to have someone actually test these theories, rather than just blindly repeat them as fact. I agree that there is continuity between the centre pin of the QC’s power port and the casing etc. I can also confirm that the casing etc is grounded when connected to powered speakers via XLR. My QC is definitely not grounded via USB by my plugged in laptop.
It is obviously possible that the CIOKS is able to ground the QC, though you were unable to measure continuity. I rather doubt that the CIOKS does actually ground the QC, and I am pretty certain that the other commonly recommended alternative power supplies don’t either. Most of them don’t even connect to ground via their own power connections (2 pin plugs).
I don’t know what causes the noise issues for some users, but I don’t think that it can be solved by imagining that alternative power supplies can “ground” the QC whereas the supplied PSU does not. I don’t get any noise through headphones regardless of whether the QC is grounded via XLR - if I don’t get the noise I can’t eliminate it. It is possible that the noise is caused by dirty power, and there are possibly power supplies that have better filtering. Another likely cause is RF interference - many valve amps are simply unusable my house, and this was the main reason for me switching to digital solutions. But can we please stop blindly spreading the fallacy that some other power supply will provide the magic solution by “grounding” the QC.
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The problem with grounding on QC is that it runs off a wall wart and virtually every WW that I have ever measured has it’s output voltage ‘floating’ with no reference to mains safety ground. So essentially it was never intended to derive a ground from the power supply.
The only way it can ever get a ground reference is through another connection be it audio input, output or USB etc. That’s why some people report they need to have the USB plugged in as the QC is getting it’s ground ref from the computer through USB ground. A ground nevertheless but not ideal.
If the QC had used an IEC mains power IP socket as most other modellers do, → there is your ground.
Using a wall wart was obviously a cost cutting exercise but they also obviously overlooked some potential problems for example if you are using an electric guitar with grounded strings and the QC isn’t plugged into anything that it can get a ground reference from, you, the guitar and the QC are all ‘floating’ groundless in a sea of noise, RF and whatever. Theoretically if all of the devices have their shells and ground connected to each other, there should not be a problem, they can float away without a mains ground reference (connection) but theory and practice always seem to be some way apart especially when noisy, non ideally shielded electric guitars come to the party.
Depending on the setup the QC may need to have a connection to mains safety ground through the PS. To make things more complicated this same ground connection can cause a ground loop if QC is also connected to something else that is grounded. There are ways around this that many manufacturers use such as having a ground ref through a low value resistor (10-20ohms) from the PS and some high current diodes to conduct in the case of an electrical fault.
You also have to remember that using a wall wart side steps a lot of issues with safety compliance because the device itself doesn’t have direct 120/240V mains connection.
IMV NDSP should come up with an optional outboard power supply that provides some noise immunity
through a low resistance ground reference but still complies with safety regs.
I haven’t looked in detail into safety compliance of an external PS floor box with direct ground connection to the player through the guitar ground.
This may well be their main headache and the reason for their (lack of?) response to the issue.
I’m looking at getting a QC in the near future and as such can investigate further into these noise issues.
I’m also interested in a few other areas that may or may not affect sound quality of these modellers such as AD / DA converter quality, analog stages and clocking etc. From what I can gather, most modellers seem to be viewed as a ‘black box’ and all the quality is in the DSP power / algorithms but IME servicing / upgrading / designing many HiFi and Pro Converters, the converters, analog stages and clocking can have quite an impact on the sound quality.
PS sorry for long technical (boring to most 
) post.
Cheers
Terry
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Thanks for sharing your technical insights. My answer, you cited above, was just to share my findings with the CIOKS DC7 that has a grounded AC connection but apparently no ground on the outlets.
Other than that, as far as I remember, NDSP explicitly states that the QC has a non-grounded power connection to avoid ground loops and that it is designed to take it’s ground from other equipment, it is connected to.
The issues, you mentioned regarding ‘groundless’ floating should technically apply to any pedalboard, right? I have the feeling that QC was designed to live on pedalboards, using pedalboard PS and getting its ground the same way, pedalboards do.
Virtually all wall wart and guitar pedal type power supplies have isolated or ‘floating’ secondaries.
Exactly. That’s why the main issue is when it is used with headphones and no other ground connection.
Guitar strings are connected to player and player makes a great antenna for hum and RF.
Only if they are not connected to an amp and it’s chassis ground which is rare.
Not necessarily. QC can be used in many varied applications but they will *almost always provide a ground, even the USB will usually provide a ground. It seems the issue is when headphones are used
with no ground connection.
TCD
Grounding can be a no-win compromise. If QC provides its own ground through its power supply, then that can create ground loops when connected to other equipment that has different sound references. If QC doesn’t provide a ground and relies on connected equipment to get a ground then there’s no ground when its used by itself, inherited grounds from other equipment can be lost on power off, and if you connect to other equipment like a power amp that also doesn’t have any ground, then there can be dangerous voltages created in QC.
Getting grounds right is critical for high-gain units like QC. I think QC made the right compromises. It is better for QC to derive its ground from things it is typically connected to. As users, we have to know what that means in terms of connections and power up/down sequences. In practice this isn’t too hard.
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In the thread above, @MP_Mod has referenced a Glob-Tek grounded PS from Digi-Key, Part 1939-1233-ND, manufacturer no TR9CE3000T00-IMR6B. Looking at its datasheet, it has a three pin IEC power cord in, and “Grounding Configuration : (E1) Earthed Output”. This would seem to be a grounded power supply, and @MP_Mod states (s)he and other users have had good results using it.
This would seem not to be a fallacy of a power supply grounding the QC?
But as other commentators have said in this thread, could this power supply then result in other ground loop noise being introduced, if the QC is connected to other components, eg (in my case) to the FOH sound desk via XLR cables?
Note, I purchased the Globtek due to other recommendations for a more robust PS and personally do not have ground noise (never have fortunately). The PS works great, long lead and very robust etc.
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Sometimes what you hook it to might not be grounded either. I hooked up headphones to the QC, ran USB from QC to MacBook Pro (which also has a 2 prong)
The noise was worse than a First Act Strat into a poorly grounded tube amp.
I ordered the Ciox7… and you are rightS it is whisper quiet when plugged into the board (which is grounded)
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This setup (in the attached picture) doesn’t have a 3 prong between the QC, Apollo X4, or MacBook Pro, and the noise is horrible. I have the Ciok7 on order, and I also ordered the power supply from Digi-Key that the Mod recommended.
I have a Temple Audio board, and just ordered the XLR pass thru module. I would get that anyways for a cleaner look, but it will ground my XLR to the pedalboard.
There is another (over priced) IEC plug module for the Temple Audio board. If worst comes to worst, I will install that, and that would definitely ground the pedal board
The noise with setup is unusable in it’s current configuration.