Any reason not to use a USB audio interface as a mic pre and fx loop?
October 26, 2021 12:36 AM   Subscribe

I want to run a condenser mic through my guitar effects pedals. I'd rather not pay $300-$350 for a box built for that purpose. Is there any reason not to use a USB audio interface that has an effects loop at 1/3 the cost?

I have some guitar effects pedals, and I have an acoustic violin that I would like to run through those pedals. I have a cheap piezo pickup I could use, but I'd rather use the microphones I already have. And I don't want to buy new vocal-specific effects pedals that use a mic-level XLR signal.

The more expensive solutions for this that I know of are the Eventide Mixing Link ($350) and the Radial Voco Loco ($310). But I notice that the Behringer UMC204HD USB audio interface ($110) has insert jacks for effects loops. I don't need the wet/dry mix or effects loop toggling functions of the Radial or Eventide boxes, and the output of the effects would be going into a USB interface for recording 95% of the time anyway.

Is there a good reason not to use the Behringer for its mic pre and effects loop? For recording, I'd plug the output of the effects chain back into the return of the interface, and for live use (when that ever happens again) I could plug it into the amp or DI. I'm pretty sure that the interface functions without a connection to a computer, as long as there's power, so I'm a little surprised I haven't seen anyone suggest this when the question of how to connect a mic to your guitar effects comes up.
posted by hades to Technology (11 answers total) 1 user marked this as a favorite
Best answer: I think this is a great idea and you should try it. There are pluses and minuses, and one showstopper potential problem.

The showstopper - if this particular interface needs an active USB connection you are stuck tethering to a computer.

- cheaper
- interface has many functions unlike the single task devices, use your good condenser mic on your next zoom call and amaze your friends/coworkers with the melodious tones of your voice!
- headphone out for practice or monitoring without amp
- input/playback mix knob for practice along with sound from your computer
- you will need a usb power source but thanks to smartphones and tablets you probably have many lying around
- sound quality will probably be excellent as modern Behringer gear tends to be good

- more components and points of failure
- gain staging, this is subtle but could mean the setup works OK but doesn’t sound as good as the components do alone. Your mic through the Behringer preamp may sound best at a high gain setting, but that signal going out the effects loop might overload your effects pedal. Same goes for the effects pedal output, it may be too high or low for an ideal level recording into your computer. A really well designed circuit with good components can provide excellent sound quality at any setting of the gain knob. Cheaper gear usually has a sweet spot or sweet range for gain controls, and outside that hiss or distortion.
The behringer does not have independent trim controls for the output and input on the effects loop. Also, most effects pedals are designed for instrument level signals, close but not exactly the same as line level signal. If your effects have their own input and output gain, you will be in a better position to get the best sound. If not you may have to find a compromise gain setting that doesn’t sound as good as the gear should.
- Snobbery, Eventide and Radial stuff is cooler and more pro/serious than behringer so in the way that purely technical gear is somehow also a fashion statement, this is in the knockoff handbag zone.
- Reputation and reliability, this is the seed of truth from which audio snobbery blooms. Behringer gear used to be the absolute garbage for reliability and an older generation of musicians and technicians may silently shudder as the sight of the Behringer logo brings back bad memories.
posted by sol at 5:31 AM on October 26, 2021 [4 favorites]

Best answer: This should work, but the big question is whether it'll work without being connected to a computer. I would suggest talking to Sweetwater and asking them. They're very knowledgable, and they'll take it back if it doesn't do what you want.

You'll need to use a special cable for your effects, since that interface has an insert, not an effects loop (with an insert, the signal goes out and comes back in through the same jack). The cable will have a 1/4" three conductor (TRS) cable on one end (that'll plug into the interface), and two 1/4" plugs on the other end. One will go into the input of your effects pedal chain and one will go to the output, so you'll need to take into account the spread of the cable.
posted by jonathanhughes at 5:34 AM on October 26, 2021 [3 favorites]

Best answer: Thirding that conceptually it should work, along with the caveats that that particular model definitely does need a USB connection to a computer to function - otherwise there's no electrical power (pdf manual for that line of interfaces, only the larger 4-channel unit has a separate power supply input) - and that the inserts are TRS and you'll need a specific "Y cable" like this one to put your guitar pedals in the loop.

I'm a little surprised I haven't seen anyone suggest this when the question of how to connect a mic to your guitar effects comes up

Well, IME, mostly when folks are connecting a mic to guitar pedals for budget or stylistic reasons, they're using a dynamic mic (like a Shure SM58) plus a barrel impedance transformer. So you don't really need a preamp, because you don't need phantom power.

Or, y'know, if they're just looking for effects kinda in general and not invested in specific tonal qualities inherent to specific guitar effects pedals, they record a dry signal and add the effects in the recording program during mixdown. And even if they want something specific from a specific pedal, they'll still record a dry signal and then send that specific track out of the audio interface to the pedals and back in to a new track in the recording.

IOW, condenser mic into guitar effects pedals is kind of an edge use case.

Another option for you would be to use a standalone phantom power supply, and then a Female XLR to Female XLR coupler (plus a mic cable) to run a passive DI "backwards". As in your mic signal goes in to the DI "output" XLR via the female XLR coupler, then out of the 1/4-inch "input" jack to the pedals. You can do this with a passive DI because passive DI's are basically just transformers, there's no real "direction" to the signal flow.

and for live use (when that ever happens again) I could plug it into the amp or DI.

I gotta be honest, as a live sound tech this kinda makes me go "yikes." Condenser mics certainly have their place in the live sound world, buuuuuuuuuttttt . . . whether this will actually be practical depends very much on context.

Condenser mics being generally more sensitive and with a wider useful frequency range, especially on the high freqs, are more prone to feedback and picking up the sounds of other instruments on stage, and adding the various tonal and frequency peaks and valleys and phase shifts inherent to effects pedals doesn't exactly help the situation. And the further away you are from the mic, the more problematical it is.

Not saying it's impossible, but every violinist I've worked with who plays live with effects connected to the instrument uses some kind of pickup system and/or a mic that can be clamped to the violin.
posted by soundguy99 at 6:57 AM on October 26, 2021 [4 favorites]

Best answer: In theory, most guitar pedals are designed for a different impedance and line level than what you'd get on an insert jack after a mic pre and the sound you get might be suboptimal. In practice, I've known many people doing more or less what you're proposing without a problem. It will depend on your specific pedals and the sound you want to get. You can get reamp boxes at various price points that will correct the level and impedance issues.

I'm not familiar with that particular unit so I don't know if it will work when not plugged into the computer. Some definitely will not, as they rely on certain settings being controlled by software on the computer. The other potential problem with using a USB interface for live performances is whether it would induce latency. Probably not in this case but it is possible. As an alternative if performance capability is important, you can find small Behringer (and other companies) mixers that will let you do what you're proposing as a standalone device.
posted by Candleman at 7:00 AM on October 26, 2021 [1 favorite]

Best answer: Soundguy 99 is right, a condenser mic into effects into an amp on stage is a recipe for great frustration. I understand the desire for the nicest hifi sound possible, but once on stage some sacrifices should be made sometimes for stability and clarity.

I play banjo in a band, and struggled for years trying to find a good "acoustic" sound when amplifying it. A condenser mic seemed the obvious choice for fidelity, but quickly proved to be a TOTAL NIGHTMARE as soon as the PA got turned on and the room filled up with yelling drunk guys. I have ended up with a setup which prioritizes feedback stability, and a fairly severe EQ which allows it to sit in the mix without fighting the other instruments in the band. The end result sounds very little like the acoustic instrument, but works very well in the context of the full band.

This is a pretty big digression, but food for thought nonetheless.

Also, assuming you are playing a quiet room and/or have a good sound tech, you could use your pickup to drive the amp/pedal chain and also play into a mic. There is a whole pile of other issues this could introduce, but it could be fun to experiment.
posted by TheCoug at 8:01 AM on October 26, 2021 [6 favorites]

Best answer: Speaking as someone with an acoustic fiddle that I sometimes run through pedals (although it's been too long since I did much of it, and I'm absolutely not doing it professionally!): If you're open to playing with your pickup, I'd consider just getting a basic, bombproof preamp and running from that through your pedals to the amp or audio interface. Feedback is likely to be lower with a pickup (especially in a live situation), and if you're running your sound through pedals anyway, the slightly less acoustic sound isn't apt to matter as much. Annoyingly, the basic Fishman preamp I have seems not be produced anymore, but violin-focused stores list some other options for high-impedence pickups, some of which are in in a similar price range to that audio interface.

If you're really prefer microphones regardless, there are also some similarly affordable mic preamps (e.g. this ART one or this Presonus one), which - with XLR input and 1/4" output - could be plugged into guitar effects pedals too, and depending on your desired sound and the pedals you'll be using, that might be enough, with some of the caveats others have mentioned? (Can't vouch for these personally, though.)

I can and do plug my fiddle into my USB audio interface (or use my SM58 mic), but I'm.... not actually sure whether said interface would function without being hooked up to a computer, and I'm not sure I'd be sanguine about the Behringer one working either, unless you find reliable reports that it does, or the company confirms that it does? (I might also be a bit biased by the iffy reputation of some of Behringer's lower-end products, but I'd also wonder why you wouldn't first look into other similarly-priced offerings from Tascam or Focusrite or something, especially if you ever will use the audio interface attached to a computer.)
posted by ASF Tod und Schwerkraft at 9:34 AM on October 26, 2021 [1 favorite]

Best answer: Also, for recording purposes, unless playing with the effects going in your monitor mix is an essential part of your thing, consider recording it dry and then adding the processing later so that a slight off setting on the effects don't ruin a killer violin take.

I would not recommend a cheap tube mic pre - they're using starved tube designs to keep costs down which creates a sound that's sometimes interesting but as an effect rather than an everyday thing (unless that interesting sound is your jam). The same money in a solid state mic pre will sound better overall.
posted by Candleman at 9:57 AM on October 26, 2021 [1 favorite]

Response by poster: Excellent points, all. On second thought, if I were going to do anything like this live (I do this professionally in only the loosest, most technical sense -- sometimes there's pay involved, but mostly it is a hobby), I'd definitely want to use the electric violin, not the acoustic. And it hadn't occurred to me that of course rack effects that loop is intended for would be operating at line level and guitar pedals would be operating at instrument level.

What prompted the question is that I have a Boss RC-30 looper which has a mic input in addition to the usual instrument jack, and I was thinking it would be fun to use that with the fiddle, which I think sounds better using a LDC than a SM57. But I'd like to put the looper towards the end of the effects chain, rather than the beginning, and it doesn't have its own effects send/return path.

I think I probably will get the Behringer and see if it works for this, but I need a backup USB interface anyway, so if it doesn't work well in this application I won't be too disappointed.
posted by hades at 10:59 AM on October 26, 2021

Best answer: I have that exact Behringer unit and can confirm that the insert loops and main outs work just fine without an active USB connection (just power).
posted by davidest at 3:28 PM on October 26, 2021 [2 favorites]

Best answer: Our occasional guest violinist uses a cheap small Lavelier-style microphone clipped onto the bridge. It's like a condenser but uses a watch battery instead of phantom power, mini jack adapted to 1/4 jack. Easy to run into fx & amp, sounds okay.

Personally, if it was me I would invest in a better Violin pick-up, maybe better quality than your cheap piezo, like a mid-price piezo or something. This seems like a simpler solution than some of the other options considered, if that works with your signal chain.

Getting an electric violin is more expensive, and more fun.
posted by ovvl at 3:39 PM on October 26, 2021 [1 favorite]

Response by poster: An update: I can confirm that the UMC204HD does work in this application, with USB powering it from a charging brick and the send and return of a TRS to dual-TS insert cable plugged into the input and output of my pedalboard. If there any ill effects from impedance mismatches between the interface's effects loop (100Ω send / 10kΩ return, according to the manual) and the pedal chain, I'm not hearing them, at least not with these pedals. Being able to use the pedals with arbitrary instruments (or vocals), not just the violin, opens up possibilities for fun experiments.

That said, if I had done better searching earlier, I would have turned up the Zoom A1/A1X Four, a multi-effects pedal which comes with a device they don't seem to be selling on its own but which is exactly what I was looking for: the MAA-1 mic adapter, a battery-powered mic preamp with an XLR socket on one end and a 1/4" instrument plug on the other. So maybe I'll pick one of those up as well and wind up with a spare multi-effects pedal that looks reasonably interesting, still for less than the cost of doing it with the more purpose-built stuff from Radial/Eventide.

(And I do have an electric violin, which it makes much more sense to use with the effects. But now I can also play around with using them for, I don't know, pennywhistle, dulcimer, autoharp, kazoo, or whatever.)

Is it weird to mark everyone's answer as "best answer"? Because I feel like that'd be appropriate here.
posted by hades at 1:13 PM on November 4, 2021 [1 favorite]

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