No, part of the time I’ve had a USB wifi adapter connected, but removing it doesn’t seem to make any difference.
@khz, please thank your friend for looking into this. This is an isolating audio transformer which I consider the best and safest of solutions.
However, the one he points you to has a very low impedance (300-600 ohm) – probably because he builds audiophile systems, which require a lot less load than instrument amps. (The MOD input itself is 1 Mega Ohm)
Bear in mind that ‘isolating transformers’ per se can be cheap (~5 Euro), but for audio applications you are better off with one built specifically for that purpose. For high impedance applications they can cost alone some 40-50 euros each. (The MOD could potentially be fitted with these, but it would add about 100 Euros in price to the final product.)
I have no experience with Palmer gear, but this would be an adequate output for an instrument audio isolation device. Impedance mismatch is a problem because if the signal is too low for your amp, you’ll overload your MOD (which will try to overcome the resistance). Conversely, too hot a signal – say, connecting your guitar to a 1K Ohm or less input – may damage your preamp transistors.
(In recent years, some people have been tricked into buying high-impedance headphones because “the sound is better” according to some “specialised” gadget magazines. They then plug those into their phones, which results in poor audio and at times a burnt phone. The impedance of the headphones has to be directly related to the expected impedance of the amplifier itself. Phones and other mobile devices require very low impedances, usually 32 Ohm or less. Audiophile headphone amps may in turn require 250 Ohm or more. Please, don’t fall for that kind of “wisdom”.)
Palmer also has a 2-channel box like the one @mj_prod mentions:
I can wholeheartedly recommend Radial Engineering gear. I’ve used their passive and active DIs, they are superbly quiet and – more importantly – utterly reliable. Some will have phase, pad, and ground lift options. (Disclaimer: I am NOT affiliated with R.E.)
One important distinction here: ground lifting the AUDIO signal via DI box might be a necessity in some cases, and much preferable than lifting the ground of the amplifier. If your system has a safe and efficient path to ground through other equipment, it is something you may do at your own risk – though obviously I do not recommend it.
This short video of an audio isolation device made in the US is very clear in its depiction of the ground loop issue and has an awesome demo of isolating transformers in action (watch it with headphones).
Now, for those here using tube amps: you will ALWAYS get some hum. Always. It’s the nature of analog equipment operating at very high voltages – 6L6 tubes employ 450V – and it’s precisely this feature that produces their warm tone. MOD can be completely silent and fully grounded and you will get hum out of your tube amp (and some solid state amps too). Also, I do not know of a laptop that has a power supply with isolation transformers.
(Regarding balanced cables: the Duo X tech specs says outputs are “Balanced compatible”, whereas the Dwarf says “TRS Connectors Balanced”, so it might be the case the Mod Devices opted to build a device that will be used either straight into a computer or FRFR speaker systems, and not a guitar amp – we would need to hear from them on this topic.)
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I would also find it good to discuss this topic further here. There are so many situations where you can integrate the ModDevive into your setup that there are many possible solutions. Electronics is complex.
If one would insert the here won experiences of the different of the different users into the wiki it would be the most ingenious which we could compile together. 
SPDIF could be better documented in the wiki.
I will tell him (c/p) - any thoughts are helpful and may save time/testing. Thank you! 
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Your inputs would certainly make my work (and also the work of other MOD team members and overall our knowledge database) muuuuuuuch easier! Go ahead and give them I would be personally hyper thankful 
Regarding the better wiki documentation, it’s overall something that we are aware of. It’s on my plate, but honestly, I’m not having much time for that. I’m for now prioritizing the Dwarf documentation, but even that is kind of late at this point (although new OS versions will bring some upgrades and I’m also preparing to document already with the 1.11). On the SPDIF subject, what would you exactly suggest?
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Yes a wiki is constantly work, I know that. 
It’s constantly evolving after all.
The experience and knowledge from the forum can be very helpful for the wiki.
SPDIF: Ah just found under https://wiki.moddevices.com/wiki/Duo_X_Technical_Specs#Audio that it is a coaxial TS connector, I had only read the https://wiki.moddevices.com/wiki/Duo_X_User_Guide#SPDIF_out ^^.
The new update sounds very good. Thank you for continuing to develop the hardware and software, it’s so nice about the device, about ModDevice and about us users.
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Perfect. The inputs and feedbacks from you guys are also valid on the organization side. Do you think that makes sense or would you rather put it on the User Guide? We basically divide it into:
- Tech Specs: where you can find physical info about the devices, meaning, dimensions CPU power, type of connectors, etc.
- User Guide: How you use the device, different modes, etc.
- Device Settings: everything that you can set up on the device settings so it better fits your music setup and workflow.
You’re welcome Your inputs help us a lot
It might be the case that the Dwarf has only balanced outputs, as per the wiki: Dwarf Tech Specs
As such, the connection Dwarf => Amp will always have some considerable noise.
Your testing routine, namely
is also an indication in that direction.
Therefore – if that is indeed the case, the use of a DI box that will convert balanced to unbalanced will ease the strain on the amp side, and if that box has an audio isolating transformer it will also take care of the hum. But, again, amps will always have some hum, tube or solid-state. My hand built, ultra-grounded tube amp, when turned on, alone in the house, produces hum. I would say that the digital-quiet operation of a MOD device could be expected on a studio setting or when connected directly to one’s computer, just like BOSS’s units (my GP-10 into the computer and amp produced a hellish noise until I employed an isolating audio transformer.)
Amps that take a balanced input are somewhat rare.
Sadly, there is no definitive and one-size-fits-all solution for ground loops and noise in general that is both safe and cost-effective. The combination of DI box + audio isolating transformer is the nearest best solution, but if the electrical wiring is not good and earthing is poor, it can only do so much.
(Those of us residing in Europe should also bear in mind that most homes still have electrical wiring in which earth and neutral are connected, either throughout the house or at the distribution point.)
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Thanks for the detailed explanation. It’s staring to make sense.
This, however, seems to be a major design flaw for a product that seems to be aimed at the guitar stomp box market.
To quote the Dwarf landing page:
Just plug it!
From vintage style low output pickups to hot ceramic hambuckers.
From mic level to line level.
Into instrument amp or directly into PA or mixer
I’ve ordered a cheap stereo isolation transformer. We’ll see how that goes. It sort of defeats having a pedal board in a box if you also have to take another box in order to plug it in to anything without noise. Fortunately the transformer is passive so it doesn’t need extra power 
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Makes sense. I just overlooked it or I do not always read everything so carefully.
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You have a point there. Let’s wait for Mod folks to chime in. It could be simply bad wording, for I don’t see a reason why the outputs of the Dwarf should be different than those of the X.
That being said, just once in my life I was on stage with more than 2 pieces of equipment that I didn’t get some hum (it was a brand new theatre built circa 2005 in the US, where the full earthing of electrical installations has been mandatory for a long time.) Every other time, either we’d put up with the hum or we would use DI boxes, hence why I bought my Radial.
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Agree, what a strange decision 
Just plug in was certainly ironical.
I am not sure that an inverted DI Box will do the trick in front of my guitar amps accepting only TS input line with a guitar level, not the one delivered by a DI box ???
I must say that I just received my Dwarf, plug into it my HH guitar, and plug a TS jack between Dwarf and the amp : the hum in OD mode of my blackstar is huge .
I will try with a DI box ???
I will name the Dwarf my delay and hum box…
EDIT : with a DI box the hum level is reduced to the ‘normal’ blackstar OD level, this will be my first guitar effect needing a DI box to be plugged in the amp ???
Great for direct audio interface connection but strange for amp.
Just to reiterate: it’s an assumption on my end, based on the wiki. But let’s wait for Mod folks to give the official scoop on this one.
It does, and also it can get pricey. That dual channel Palmer box I posted earlier costs around 100 Euro.
But in all fairness we need to consider this: ideally, current audio equipment could simply have isolating transformers inside. But the retail cost of a good, toroidal, wax potted one is in the 50+ Euro range.
Boss, for instance, had subsonic filtering in some of their VG units for those using piezo pickups. At some point, they decided that the actual number of users was so low that they would have to deal with poor performance by themselves or buy a Boss GK pickup. The circuitry for one such filter probably costs no more than 15 USD per unit. Other manufacturers stepped in (RMC, Wayne Joness, etc) and sold boards or boxes that fixed that, at more than 150 USD. Then RMC decided to include subsonic filtering in their Poly-Drive X (2011 and later) so those previous workarounds were no longer necessary.
If a company like Roland/Boss – which has a lot of money to spare – cannot provide a $15 board to fix something that is entirely their fault (poor tracking of piezo pickups), how can we demand any manufacturer to include $100 worth of audio transformers for something that is not their fault and may not happen?
Think of 1/5th of the Dwarf price being just those 2 output transformers. Some RME interfaces have isolated inputs, but they come at a hefty price. (By the way, RME’s Babyface only has balanced outputs.)
So, if one manages to use it and have no ground loop issues, hooray. The rest will need some workaround.
Let’s wait for the final word on Dwarf’s outputs.
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I would say that the choice of having balanced output, which I did not noticed when reading the first specs, seems to be a clear intention to use the Dwarf plugged in an audio interface rather than in an amp because very few guitar amps have a TRS jack for guitar input…
That’s not a matter of costly isolating transformers.
Maybe the people who have been designing Dwarf have less experience with guitar amps than with synths or audio interfaces connected to a DAW ?
EDIT : as this thread is marked as solved, apparently Mod team seems to consider it is closed.
Thanks for your inputs, @CSurieux.
Could be. And to some extent it makes sense. Mod devices might be willing to position their products as competitors to modelers like Line6 Helix, Kemper, Headrush, as well as some of the latest Boss GT and SY units. These are all designed to be connected straight into FRFR speakers or full range amplifiers, both of which will have balanced TRS/XLR inputs. It seems to be the direction the market is going now.
(Boss’ excellent MS3 unit is more of a traditional multi-effects box, and in spite of being cheap, incredibly flexible and powerful, it’s selling so bad that it might be discontinued soon.)
Also, MOD boxes also have sequencers, midi instruments, audio players, noise generators, synths, …, all of which require full range amps.
I would not think that to be the case, since @gianfranco, @jon and others at MOD Devices are essentially guitar players. I would bet on what I said above.
The OD mode of most amps start by having some 12-15dBs of extra sensitivity to the input signal (and not by boosting the signal internally, which would be preferable but is more expensive). If you already have hum, using OD mode makes it much worse, sadly.
That is not the point I was making. Balanced or unbalanced as the audio may be, isolating transformers would be required to remove hum from them (they do not only convert impedances). My point was that, in order to prevent hum straight out of the box, they would need those. And it doesn’t make sense to employ them, unless you have a super high-grade device like RMEs, Apogee, Universal Audio, etc.
As I said before, we need to wait to hear from them as to if the outputs are balanced only and, in that case, their reasoning for that.
(Disclaimer: I did not participate in either Kickstarter or Indiegogo’s crowdfunding effors, so I don’t know for sure what was promised for the Dwarf.)
I think it was marked “solved” back in 2018, when the first posts got in. It’s just that we kept talking about it and others peeked in searching for the same answers.
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Ha Ha we are on different planets.
I accept the cumpliment!
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No native Fx loop and balanced TRS stereo output, this product is clearly not conceived for use with any guitar amp ?
There seems to be much talk on here of the need for a DI box to kill the hum, but a hum destroyer will perform the same task by getting rid of the ground loop. Less than £20 for one that will work on two channels.
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Sorry - we - not robots-
But I agree that adding a cheap DI box seems to do the trick, but very unusual for most of us using more often amps than audio interfaces, and it is one more piece in the puzzle.
I agree it’s unusual, but the Mod boxes aren’t like other pedals that I’ve come across in many ways, and I don’t object to a balanced out. As I said, a hum destroyer works fine, and is cheaper than a DI box.
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