Thinking about using MOD Dwarf with Laney L5 Studio, or

a Mesa/Boogie Express Plus 5/25. I use an HX Effects currently with the Boogie. I get hella noise when USB is plugged in. I got a USB isolator but the one I bought (while it does prevent hum) also prevents USB operation. Apparently there are different levels of functionality of these and I probably need the $60 one instead. Or I just only plug it in when I need to. As it turns out I barely use it anyway.

I’ve been through a few things in pursuit of DIY DSP nirvana for guitar.

  • I did a LOT of stuff on the FV-1
  • got an “Elk Blackboard”, but (a) not a pedalboard ready format, (b) company seemed to shift focus to “Aloha OS”, leaving support/future of Elk Audio OS uncertain (IMO). I used the OB-X sequencer demo. It’s cool. I never developed anything for it.
  • Tried Raspberry Pi 3 running “SooperLooper” with USB audio, total disaster.
  • Tried MacBook Pro running Ubuntu Studio, low latency, RT kernel, USB audio. Built SooperLooper, Hydrogen, a few other things. Made some DSP patches in Faust. Could not get acceptable latency without XRUNS (glitches). XRUNS drive me crazy. My Windows machine has been cranking audio into USB interfaces all day for years so I can only surmise that Linux audio needs a LOT of help to work properly. I’d accept that the Pi’s USB implementation may pose some insurmountable obstacle, but a MacBook?

So, I’m a bit concerned about (a) ground loops caused by connecting various audio bits together with different ground references, (b) generic digital electrical interference based noises (e.g. whines that change depending on what the device is doing), and (c) glitches or artifacts caused by misbehavior of the software such as XRUNS. I’m just planning on using mono in - mono out. in the effects loops of whichever amp. As a bonus I might try stereo, returning to the FX return of the “other” amp which would just be for amplification and a possible trip through a cab simulator.

Some people are having troubles and it’s not clear what the breakdown is between (a), (b), and (c). I would really like to develop and offer some plugins, and I would like to use the box. I know that people don;t generally come to the forum to say how happy they are. So this is an opportunity for someone with a similar setup (i.e. using it in the FX loop of a tube amp) to tell me how great or awful that is. For example I think these are just unbalanced 1/4" in and out. So if going balanced solved the whole problem I don’t know how I’d adapt to that.

I do have a stereo passive DI box which I got for the other setup but I have never used it since disconnecting USB solves the problem.


Well, plenty of things to consider here.

1. Will I get noise?

Most likely.

Impedance is your enemy here. There is no set value for what the ideal impedance value would be for an effects loop, so most manufactures choose what they want within a typical range. Those who manufacture effects as well (Boss, Vox, etc) will choose the one that suits their other gear best. One may end up needing a buffer at the return, if the signal gets too low (which brings in more noise).

It is impossible to say how much and what can be done to curb it in that scenario. Balanced cables may not be of help since most loops will be unbalanced. This kind of noise caused by impedance mismatch – which may force you to increase gain so as to bring the signal up – is not related to ground loops.

2. Will I have a ground loop issue too?

That would not be a surprise. I hope not, but it might as well happen. The more you have “stuff” connected to AC, the more are the ‘paths’ for a ground loop to occur.

Here, breaking the loop is a must, either by employing an audio isolation transformer or simply a DI box that will lift the ground.

3. What about digital interference noises?

These easily get overamplified when using tube amps. If the turn of an encoder produces some digital noise, even if very light, you will hear it quite well through your amp.

Bear in mind that tube amps are NOT quiet machines, no matter how clean and low powered they are. Even those Class A single-ended amp heads that are designed for smaller settings and usually spit out less than 10 watts will produce some noise. It’s the nature of a tube amp. Pedalboards like the HX came to the market precisely to cater for an ever growing need of a portable rig that can either go straight to the mixer or into a flat-response speaker.

(The MOD is to some extent similar to the HX in that sense, and I would guess it works better with a full range amplifier than a tube one – but don’t take my word for it and also I don’t know exactly how it was marketed.)

I know nothing of C (XRuns), so I can’t comment.

A lot of the users report that once they disconnect the ground from the AC plug our use the ground lift switch in their DI boxes, the noise goes away. That is a very telling sign of a ground loop (A).

Other have reported that by either changing the display brightness or removing some plugins from the chain, noise is reduced or goes away. This is an evidence of B. Some plugins may have bugs that generate pops and clicks.

Apologies if I can’t offer a solution for your problem ahead of your spending money with either the Laney or Mesa. If someone here has that experience, it would be great to hear about it. I myself have a tube head but it’s in another country and I have no idea when I’ll be able to go there and fetch it.

Some side notes:

I came to the MOD precisely because I too had very high hopes on Elk OS becoming a leading operating system for music applications, but development has not moved forward in a while. The lack of suitable boards and sound cards makes prototyping impossible.

If one day MOD decides to load VST plugins, that will be the key to my everlasting love.

Macs can deliver roundtrip USB latencies as low as 1.9 ms with RME interfaces. I’ve seen that in action myself. (Using MacOS).

They must have thought that, ultimately, unplugging your amps from AC also kills hum. :face_with_hand_over_mouth:

If you reach it master, please enlighten the rest of us!! :raised_hands: :raised_hands:


OK I’m going to offer various thoughts.

I’d be really surprised if IMPEDANCE is an issue with the effects loops. I mean, I think if input impedance is 10K or over and output impedance is 100 ohms or lower it’s not going to be enough to worry about. The Laney documentation doesn’t list the FX loop impedances. It has a 0 dBU and -10 dBU setting. I’m not currently using anything in the Laney’s loop.

Ground loop isolation on two unbalanced 1/4" jacks (sigh) I guess reality dictates this is really the best solution in the event any problem arises.

Regarding amplification of digital interference in the tube amp, gain is gain, so if noise is coming in and gain is applied, louder noise goes out.

I suppose what I’m getting at is that something like the HX Effects and the MOD Dwarf are electrical boxes that have a certain amount of conducted and radiated interference. Depending on what you connect it to, you have a chance of making it worse, mostly, but the system suffers from the weakest link still. There are known ways to optimize or progressively debug complex audio setups so as to minimize the artifacts. So, when all those things are done, is the Dwarf in the same league as the HX Effects, or not? Many years ago I was an electronic designer and I know that reducing analog noise and controlling spurious radiated/conducted energy are among the most challenging aspects of the job.

I’m OK with the way the HX Effects behaves even though noisy with USB connected. If I get a Dwarf it will probably have USB connected most of the time because I will be developing plugins.

The other thing you’re telling me, and maybe this is true as well, is that most Dwarf users are going straight in the unit from the guitar and then straight into the board? And NOT putting it into an amps FX loop. Nobody from MOD is weighing in that they tried it or use it in this configuration. I looked at some of the YouTube videos and you can’t tell what is plugged in where, but no amp is seen.

Well, from your response I’m inclined to think that you knew the answers you were looking for already! I appreciate your inputs and expertise.

When you say


it becomes clear you are aware of the multitude of issues at play when it comes to optimising an audio system.

Now, I mention impedance not because it is a problem with the values set as you describe – though they vary woefully from maker to maker – but because the Dwarf within that loop might have problems. If the SEND is 100 Ohms and the Dwarfs input is 1MOhm, that might be an issue.

(That is: the effects loop is not the problem, placing the Dwarf there might be).

I didn’t exactly say that. I said my guess was that it could be plugged straight to the mixer – since the wiki says its outputs are “TRS balanced”. I even mention that I’m not sure how MOD advertised it, if it was supposed to be a pedal before your amp or not. I actually own a Duo X connected to the audio interface and haven’t been able to test it with an amp. In my setup, ground loops taken care of, I get ZERO hum or hiss, even with USB plugged in. (My interface is a RME, and they are notoriously good at preventing hum from ground loops).

Boy, that is quite a question.

Not owning either makes any answer more (an educated) guesswork than anything else, but here is my take: as a product I would think the HX (and Headrush, GT1000, etc) is more mature. I’d think with the investment and development muscle those companies have, they must have figured out a number of the ‘bugs’ one would encounter when developing such a product. Mod Devices is a small company and, as much as they might have prototyped and tested it, it might be the case that hardware improvements are needed.

Whether or not the HX sounds better than the MOD is an entirely subjective thing, but as a platform I would think the MOD offers more opportunities for developers. I am not sure if in the end it will thrive and become a de-facto platform for which bigger companies would develop plugins – my hope, as I mentioned, is that MOD instead bows to VST format at some point! (please MOD team, forgive my evil intentions!!)

Also, having tested a Headrush (arguably not as good as the Line6), I have to say that I was able to pull sounds and guitar tones from my Duo X that owe absolutely nothing to that unit. What’s more, I scared a Fractal Axe 2 owner with the clean sounds I’ve got out of my MOD. Amplitube doesn’t come close to sounding as nice (to my ear, obviously.) So, right now I am giving MOD a fair trial and so far I cannot complain.

If you instead are happy with Line6 and get what you need from it – sadly not the DIY Nirvana we’re both searching, evaluate carefully your need for a Dwarf.

Making the Dwarf more amp ready right out of the box is certainly something that needs attention from the MOD team, but I’m not sure what’s to be done there. I don’t think they can get an authorization to sell it with 2-prong, unearthed power supplies. In Europe that is a major battle.


This is basically a super-accurate answer (and thanks for the help once again @QuestionMarc!). Basically, users are reporting noise as a single “thing”. The problem is that there are a lot of different types of “noises”. Some are indeed ground loops, others are actually generated by some plugins and obviously, some others may possibly be caused by some sort of faulty device. Having them all put on the same bag, makes our work a bit harder to tackle every single type of noise (anyway we are working on it) and each particular situation.
For example, we received already noise reports where the users discovered after some tests that the noise was actually not caused by the MOD Dwarf, but either by a device connected to it (for example they discovered this by completely taking the Dwarf out of the setup…the noise stayed there). I can tell you that these reports happen with fairly known and disseminated guitar devices.


If you instead are happy with Line6 and get what you need from it – sadly not the DIY Nirvana we’re both searching, evaluate carefully your need for a Dwarf.

Well yeah, clearly I can’t program the Line6, which is frustrating.

I also have to calibrate my own symbiotic relationship with such devices. I did an experiment last year which involved buying the HX effects and getting rid of several individual pedals I had. Just to see what would happen.

The way I use the HX effects seriously undercuts the flexibility of its features, but at a creative level I have no need for many of them. I don’t perform live so I don’t need any performance oriented things. When I am recording, lots of times I just take a basic relatively dry amp sound into the DAW and whatever ambience or modulation is added there. I also don’t set up lots of different wild sounds. I have ONE PRESET and I turn the “pedals” on and off. Sometimes I change what one of the pedals does. So I mostly use it when just noodling and less for recording.

In a way, it seems like I should just go back to having a few pedals, but given that the HX Effects only cost me $450 (about the same cost of an Eventide delay or reverb pedal), it hardly makes sense, even if I just use it in this very limited way.

So, when I see the demos which show this amazing spider web of different virtual pedals all connected together, I know that I would do that a few times but it would not figure into how I personally would tend to use the device. I think I would most likely use it for single sounds that I am developing myself. As with the market positioning of the HX effects, and some other devices like the TC Plethora, they toss the amp modeling to focus on time, filter, pitch and modulation effects. I like the basic sounds I get from the amps I already have.

That said, I am not a metal kind of player and most of the time am in low or medium gain territory. Who knows? In any case, if I don’t EXPECT that hooking up a device in the amp FX loop will be problem free, it’s less of a shock when that comes to pass.

So now I have to think about whether I see myself either:
- setting up a third guitar recording chain
-maybe getting rid of one of the ones I already have

Part of the problem here is that I already have a Captor-X hanging off the back of the Boogie, so I’ve got a good recording interface and don’t need IRs in the FX box. I don’t (yet) feel like getting rid of that so I can use the one in the Dwarf.

I understand the difference in resources between a startup and a larger company. I recall working in a hardware startup where we had one hardware engineer but he was REALLY good and we engaged consultants for specialties as needed. A startup CAN do excellent design work but it depends on the people and budget (e.g. for revisions), and in this case it may also depend on their goals, such as whether or not they intended it to be used in the FX loop of an amp. And it really sounds like the intended use case of this device is guitar straight in and then outputs to your mixer.

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