Software instrument audio output woes...

[SlapLikeTheWind]

Hello all,

I'm an old-school, very analog bassist, but recently, I've acquired a Roli Seaboard Block to use to add some sound dynamic on stage; I have no experience with amplifying/routing sound from a software instrument to various receptacles, so I'm hoping for some wisdom from my fellow bassists... that said, here is my setup, and my issue:

I use the Seaboard to control software instruments in Logic Pro (Apple OS), on a 15" MacBook Pro; Logic is routing my sound output through a USB recording interface (PreSonus AudioBox 22VSL)... here's where I'm struggling with rig issues: on the rear of the interface are two 1/4" outputs (Left and Right); one output is routed to our practice PA via a 4-channel mixer (this connection sounds gorgeous over the PA), and the other PreSonus output is routed to our 16-channel recording interface (connected to a seperate PC, NOT my MacBook). Even though the PA connection sounds great, the same cannot be said for the line from the PreSonus to the 16-channel interface, which gets this gross, underdriven, distorted keyboard sound (very quiet unless PreSonus output volume brought up to point of clipping, which causes distortion as expected). Both lines from the PreSonus are mono 1/4" on the PreSonus end, and XLR on the PA/16-channel end (unbalanced, I believe).

What I know so far:
-Swapping the output lines on the PreSonus has no effect; the PA feed sounds great, and the recording interface feed picks up gross muddy whispers, no matter the output on the PreSonus
-Tried both mono and stereo cabling, with no positive effect
-No issues with any other part of our 16-channel recording rig (bass and guitar come in great, as does our Moog Sub-37 and electronic drum kit... room and analog drum mics sound great as well)

What I suspect:
1.) I need a DI box... but which variety?
2.) Alternatively to a DI box, I wonder if I instead need a digital/analog converter ("DAC")
-I suspect the signal coming from the PreSonus might be a high impedance signal, and so the PA mixer can sort of pre-amplify it, but the 16-channel interface appears not able to do the same.

Do I need a DI? A DAC? Any recommendations?

Any wisdom would be greatly appreciated!

Cheers!

 

[Jimbob Jones]

Hi there,

First off, your Presonus IS a DAC - it converts the digital info from your Mac to an analogue audio output (the two 1/4" sockets you mentioned).

It sounds to me like you have a balanced output from the Presonus being fed to your recorder that's not expecting a balanced input, or vice versa. This will essentially cancel out almost all of your signal. Mathematically it will cancel out perfectly, but in the real world a tiny bit usually comes through, and it always sounds terrible!

You're on the right track in troubleshooting so far; it's also worth unplugging the offending cable from the Presonus and plugging it into a different source (your bass, a regular keyboard, just about anything) and seeing what happens. There's always a chance there's something up with the input of your recording interface.

Assuming the recorder is ok, it's worth trying a DI. All things being equal, in theory you shouldn't need a DI to make this work, but it is a reliable way of converting a 1/4" connection to an XLR connection without running into all the wonderful issues you can find yourself with when working with balanced/unbalanced & stereo/mono signals together.

There's a small chance you have a bitrate issue, but I've never heard a bitrate mismatch cause this much of a problem, it usually just sucks all the life out of your signal but doesn't compromise levels IME. Check the bitrate of your recorder (probably 48k) and make sure that the MacBook is set to the same as the recorder in Audio MIDI Setup AND in Logic's Project settings. You'll probably need to check the same in the PC's DAW, but I caught fire the last time I touched a Windows computer, so I'm afraid you're on your own there.

 

[SlapLikeTheWind]

Hi there,

First off, your Presonus IS a DAC - it converts the digital info from your Mac to an analogue audio output (the two 1/4" sockets you mentioned).

It sounds to me like you have a balanced output from the Presonus being fed to your recorder that's not expecting a balanced input, or vice versa. This will essentially cancel out almost all of your signal. Mathematically it will cancel out perfectly, but in the real world a tiny bit usually comes through, and it always sounds terrible!

You're on the right track in troubleshooting so far; it's also worth unplugging the offending cable from the Presonus and plugging it into a different source (your bass, a regular keyboard, just about anything) and seeing what happens. There's always a chance there's something up with the input of your recording interface.

Assuming the recorder is ok, it's worth trying a DI. All things being equal, in theory you shouldn't need a DI to make this work, but it is a reliable way of converting a 1/4" connection to an XLR connection without running into all the wonderful issues you can find yourself with when working with balanced/unbalanced & stereo/mono signals together.

There's a small chance you have a bitrate issue, but I've never heard a bitrate mismatch cause this much of a problem, it usually just sucks all the life out of your signal but doesn't compromise levels IME. Check the bitrate of your recorder (probably 48k) and make sure that the MacBook is set to the same as the recorder in Audio MIDI Setup AND in Logic's Project settings. You'll probably need to check the same in the PC's DAW, but I caught fire the last time I touched a Windows computer, so I'm afraid you're on your own there.

Thank you so much! That’s the most useful explanation I’ve been able to find; gah, I didn’t even think of the cancellation from a balanced cable! I’m so used to unbalanced-land!

Thank you for your knowledge! Rock on!