Looper Pedal Clipping

[7704A]

I picked up a JamMan Express XT to use for tech stuff, piping guitar into an amp while I'm poking around inside, and ran into what I think is a lack of headroom.

First sign of trouble: playback almost always sounded duller than the original signal.
Further investigation: ran from the looper directly into my audio interface's instrument inputs. Looked at waveforms, and played the original and recorded audio back-to-back.
Observations: the looper playback, as recorded by the DAW, is noticeably duller than the original signal, also recorded in the DAW. Playback waveforms look like they're missing transients, and are flat-topped in the worse cases. Audible distortion in the worst cases when compared to the original signal. Looper is set to unity gain.

Worst-Case Original signal:

Worst-Case Looped signal:

Yowza.

The looper manual says +4dBu (1.228Vrms) max input, and my DMM says my (high-output passive humbucker) guitar's transients peak around 4-5Vrms with hard playing, and around 2Vrms with normal playing, so I guess I can't blame the looper, but it was not obvious at the start that this would even be an issue to worry about. Sold it to MusicGoRound and bought a Boss RC-1. The RC-1 lists a nominal input level, not a max level, and I figured if anyone is going to get it right, it's probably Boss.

So far, that seems to be the case. Playing in the room, recorded loops can still seem duller but that just appears to be the fact that the strings aren't plinking when I'm not playing. In the DAW I can't tell the difference between the two, and the waveforms look near identical:

I had looked at other cheap loopers, in particular the TC Electronic Ditto Looper, but apparently that just has built-in compression to avoid clipping, per user reports. I need a pedal that can drive amps with same signal level as my guitar, so that wouldn't have worked.

Anyone else have this same issue with loopers?

 

[mentoneman]

yes. hate that.

 

[BeZo]

Have you tried buffers before it or putting other pedals in the chain?

 

[glpg80]

Id tried buffering before the looper. Pickups are just inductors and their impedance can change drastically over frequency which is not good for linearity going into a pedal that expects a certain voltage range. I agree that some kind of buffering into a compressor and then the looper pedal would have eliminated the clipping at the cost of degraded dynamics - but in a looper pedal that’s likely a worthy trade. At the end of the day a different looper pedal is just easier to get so I don’t disagree with selling the offending pedal and going boss.

 

[7704A]

Have you tried buffers before it or putting other pedals in the chain?

Nope, didn't try any of that.

Pickups are just inductors and their impedance can change drastically over frequency which is not good for linearity going into a pedal that expects a certain voltage range. I agree that some kind of buffering into a compressor and then the looper pedal would have eliminated the clipping at the cost of degraded dynamics - but in a looper pedal that’s likely a worthy trade.

In most cases, yeah I assume the tradeoff would be worth it. Anywhere the level of the guitar signal doesn't matter much. In this particular case I wanted the looper to hit the front end of my 4104 hard, the same way my pickups do, and generally perfectly replicate the signal, so any sorta gain reduction wouldn't have worked unless I added a gain recovery stage after the looper to bring it back to level, at which point I have three pedals which isn't as easy as just buying a better looper, like you said.

 

[cobrahead1030]

I’ve not done a close comparison like that, but the looping function on my Timeline & DL4 sound just a tiny bit quieter & darker than my RC1.

They all work fine for me, just playing something to noodle over. However, the boss is much more handy when I want to loop a phrase to dial in pedal or amp tones.