Differing sounds between R24 and Ardour

I use a Zoom R24 as multi-track recorder and/or audio interface.

I record a signal on the R24 and import the WAV file into Ardour, track 1.
I also record a very similar signal directly in Ardour using the R24 as auto interface, track 2. Same guitar, same settings, same cable, same R24 inputs, same gain.
I normalize both recordings to the same level. When played back, there is a noticeble difference in sound. The Ardour recording sounds slightly muffled.
I played with the gain settings (as mentioned in thread Mixes sound a bit different then using daw) but the difference remains.
The LSP spectral analyzer shows a significant diffence in the harmonics.

AFAIK the signal is digitized by the DAC from then on it’s bits and bytes. Since in both cases it is the same DAC (the R24) I would expect only minor differences.

Sounds to me that the recording quality settings might be different between the R24 and Ardour. Have you double-checked that both are using something sensible like 44.1 or 48k and 24-bits? Perhaps there was some resampling on import to Ardour from the R24? It might be something else but it’s perhaps a place to start? :slight_smile:

Thanks for the suggestions.
Everything (R24 and Ardour) is set up for 44.1kHz / 16bit. No conversion upon import.

To make things more complicated, I redid the exercise with a function generator using a 440Hz square wave, and this shows no significant differences between the recording on the R24 and the recording via the R24.

So it could have been anything… I’m quite sure all settings (guitar, pedals, …) were the same for both recordings but it wasn’t really set up as a reproducible experiment :slight_smile: .

One possible explanation, though a bit farfetched: when you plug the R24 into your computer as an interface, does it switch to running on USB bus power? Presumably when you’re using it as a standalone recorder it’s powered by batteries or by mains power. If the unit switches to bus power when you use it as an interface, this could conceivably explain the difference.

I notice this difference on my Sound Devices MixPre 6: when I record directly to the recorder using four phantom-powered mics, everything sounds normal. If instead I use the recorder as an audio interface, it switches to bus power and it doesn’t seem to be enough to properly power all four mics; there is a very noticeable difference in sound. This may have been fixed by a very recent firmware update (in the last few days), but there’s also an option to override the automatic switch to bus power and use mains power instead. When I do that the sound quality is comparable to that recorded directly to the recorder.

Actually looking at the R24 user manual, the USB bus power may indeed be the culprit; see excerpt below. My guess is that you’ll experience the difference in sound no matter what DAW you use, it’s not Ardour. You will need to run the unit on batteries or mains power. If you’re already doing that, though, then I’m not sure how to explain it. Even if you’re not using phantom power, it’s possible your guitar and pedals are drawing enough power to degrade the sound if it’s using bus power.

The audio interface and control surface functions of the R24 can be used by drawing power
through a USB cable from the USB bus.
• We recommend always using the latest R24 system software.
• When using phantom power, we recommend using batteries or an AC adapter even when the
unit is used as an audio interface.


That’s a very interesting point. My R24 is usually connected to the power supply (and has batteries) but when it is switched off and then connected to USB, it draws power from the USB bus. When switched on and connected to USB it draws power from the power supply. I never paid attention to this but I will now.

Have you tried using it with another DAW, or just a recorder e.g. Audacity?

That would be an easy way to figure out if the issue is with Ardour or the soundcard.

I tried recording using the R24 as Audio I/F, both USB powered (usb, see below) and mains powered (pwr, see below), and I couldn’t hear a difference.

@x42 I couldn’t get Audacity to record, but I suddenly remembered that my effects pedal (Boss ME-25) also has a USB connection. Recording using the ME-25 as Audio I/F yields a result that is almost as bright as the original recording.
As a bonus, I threw in my Zoom H2n.

Overview of configurations and summary of results:

  1. Guitar → ME-25 (phones) → R24 (recorder) SDcard → Ardour (import)
  2. Guitar → ME-25 (phones) → R24 (I/F, pwr) → Ardour (recorder)
  3. Guitar → ME-25 (phones) → R24 (I/F, usb) → Ardour (recorder)
  4. Guitar → ME-25 (I/F) → Ardour (recorder)
  5. Guitar → ME-25 (phones) → H2n (recorder) SDcard → Ardour (import)
  6. Guitar → ME-25 (phones) → H2n (I/F) → Ardour (recorder)

Best results: 1
Runner up: 5 and 6
Slightly less: 4
Muffled: 2 and 3

In practice I think only 2 and 3 will be audibly different. The differences between the other alternatives are very small (as far as I can hear).

Disclaimer: This was fun but in no way a scientifically sound experiment.

Okay, the only other variable I can think of that might be causing the difference is the audio driver. What operating system are you using? It’s possible that the audio driver for the R24 is causing the difference you’re hearing when you use it as an interface. The H2n would be using a different driver.

I’m using Linux and as far as I know all devices use the same out-of-the-box audio driver.

I’m not an expert on audio interfaces, but I assume that the R24 DAC converts the incoming audio to a series of bits and bytes, and either stores this on the SDcard (when recording), or sends it via USB to the PC when used as Audio I/F. In either case I would think the bits and bytes would be identical.

Hmmm, okay. Linux is not listed as a supported operating system for the R24, which leads me to believe that it’s not a class-compliant interface. But I see in the Mixbus forum (see link below) that there’s a way to make it work in Linux; I assume you’re doing something similar? There’s a difference between having it work as a control surface and having it work as a true audio interface with recording capability. Linux and Zoom R16+R24

LOL. It is good I didn’t know this all these years I’ve been using the R24 :joy:.

Seriously, the Zoom R24 is fully supported by Linux and has been so for ages (the thread you refer to is from 2016). It works as a card reader, as an audio interface (2 out, 8 in), as a midi device, as a control surface (Mackie and OSC). Unlike Windows you don’t need special drivers on Linux.

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