Bleeding from the Mixer

FruitarGeek

Hi Guys

A friend of mine is the producer at Stellies MFM and he has a bit of a problem that no one can solve. He is trying to overdub vocals over an advertisment, which is track one, however whenever he tries to record it, the sound from track one is bleeding into his recording, however he is not using any speakers and the headphones are well 'shielded' from allowing noise to escape. He fears it may be the mixer itself. He phoned some sound guys and they suggested he routes his PC OUTPUT which is channel 13/14 to the MAIN MIX, or something like that, however the bleeding is still there.

Does anyone have knowledge of this issue?

This is the desk he is using

Thanks

AlanRatcliffe

Where is he taking the input to the PC from? If it's the main mix, then he's going to record whatever the mixer is sending to the monitors.

It's a four bus desk, so there's an easy solution: hook the mixers sub out to the PCs inputs, main mix output to the monitors. When he wants to send a channel (or channels) to the PC to record, just assign that channel (or channels) to the sub mix.

To monitor what is being recorded, leave the channel assigned to the mains unless it's an either/or situation with the assigns, then use the sub to mains switch (if there is one). Failing either of those being an option you can use the through setting in the software to pass the input to the output of the interface (although it will then be subject to both the input and output latency of the interface, which is not ideal).

And yes - always a good idea to bring the outputs of the soundcard to an aux input directly to the mains - bringing it back into a channel means there is a chance of setting up a feedback loop if the channel is assigned to the subs. That ends up blowing either the mixer of the interface (I've done it!).

Riaan-Combrink

Alan Ratcliffe wrote And yes - always a good idea to bring the outputs of the soundcard to an aux input directly to the mains - bringing it back into a channel means there is a chance of setting up a feedback loop if the channel is assigned to the subs. That ends up blowing either the mixer of the interface (I've done it!).

@ Alan: just to make sure I understand.

In my live set-up I run (2x) jack from channel 13/14 on my mixer to the usb interface (connected to PC)'s outputs (RCA). As long as I'm only using the mains for playback, there's no danger, right?

I've now set up to record in exactly the same way; but now also running back to the mixer's 'tape' RCAs from the RCA-inputs of the interface. Similarly, no issues there?

Is there a more efficient way you would set up to record in this scenario? Interface only has 1 x RCA out and 1 x RCA in. Mixer as follows:

Riaan-Combrink

Riaan C wrote but now also running back to the mixer's 'tape' RCAs from the RCA-inputs of the interface.

Sorry, its not called 'tape', but 'REC out'.

AlanRatcliffe

Riaan C wrote In my live set-up I run (2x) jack from channel 13/14 on my mixer to the usb interface (connected to PC)'s outputs (RCA). As long as I'm only using the mains for playback, there's no danger, right?

That will be fine. No chance of a feedback loop if you are only using the outs from your interface and using a pair of channels does give you more control over your playback source in a live situation, in case you need a bit more gain or some EQ. In recording, you want to keep the signal paths as short as possible for fidelity, so the extra gain and EQ circuits are undesirable.

BTW - try get into the habit of thinking of your connections as running the same as your signal flow. i.e. Your PC's Out runs from the interface to the mixer's inputs and the tape out runs from the mixer to the interface. Makes it easier to understand and especially troubleshoot (both for yourself or others you are describing it too).

I've now set up to record in exactly the same way; but now also running back to the mixer's 'tape' RCAs from the RCA-inputs of the interface. Similarly, no issues there?

Actually there are. Your tape outs are (usually) mirrors of the mains for live recording, so get the entire mix, including what is being played back, which will cause the "bleed" the OP was complaining about. Rather use one of your buss pairs (/Groups in your mixer) as outputs to get only the tracks you need to the PC. Then as described above, you simply assign (the assignment switches are the three small pushbuttons next to the fader) to the relevant buss for recording and also to the main stereo buss for monitoring while recording. No problem with the tape ins though - they go straight to the main buss.

Mixer as follows:

Nice. The built in channel compression and six output busses are great for live.

Riaan-Combrink

Alan Ratcliffe wrote BTW - try get into the habit of thinking of your connections as running the same as your signal flow. i.e. Your PC's Out runs from the interface to the mixer's inputs and the tape out runs from the mixer to the interface. Makes it easier to understand and especially troubleshoot (both for yourself or others you are describing it too).

Point taken! I see the logic and value therein.

Alan Ratcliffe wrote Rather use one of your buss pairs (/Groups in your mixer) as outputs to get only the tracks you need to the PC.

May I be really dof :-[ Groups (Busses) 1-2 is a pair, right (as is 3-4)? I'll thus plug a L-jack into the slot marked '1' under 'Group Out', and my R-jack in '2'? This makes the pair '1-2' which is then assigned by depressing the '1-2' button next to whatever channels I wish to record. The 'Group 1-2' fader is then used to set the level of the group-record signal, whereas the Stereo Out fader (of which the stereo outs are connected to my amplifier by XLR) will simply provide me with reference or monitor playback (but not effect the recording signal path)?

One last one whilst you are looking at the mixer pic: I could run to my usb interface from either the jack sockets above channels 11/12 or 13/14, right? At the moment I'm using 13/14, but that channel has no gain adjustment. 11/12 seems identical (as does 9/10 in fact) - no idea why I never saw that. The issue with 1 to 8 is obviously that they are not stereo, but intended for either a mono jack line connection or an insert (for Graphic EQs and similar units) - do I have this right? But barring channels 1 to 8, I could use 9/10 or 11/12 instead of 13/14 (and get the gain adjustment as a bonus)? I'm starting to see the logic, I think - as channels 1 to 8 have the compression feature, whereas one would never apply compression to eg. a composite backing track (keyboards, bass, strings, drums all together). So those three combined channels seem perfect to run to the PC.

AlanRatcliffe

Riaan C wrote Groups (Busses) 1-2 is a pair, right (as is 3-4)? I'll thus plug a L-jack into the slot marked '1' under 'Group Out', and my R-jack in '2'? This makes the pair '1-2' which is then assigned by depressing the '1-2' button next to whatever channels I wish to record. The 'Group 1-2' fader is then used to set the level of the group-record signal, whereas the Stereo Out fader (of which the stereo outs are connected to my amplifier by XLR) will simply provide me with reference or monitor playback (but not effect the recording signal path)?

All correct! Now you have that in hand, an added wrinkle: your busses are paired, but your panpot controls which buss in the pair the channel is routed to. This means that by hard panning two channels, one all the way "left" and the other "right" you can isolate the two from each other for recording onto separate tracks in your DAW (most tracking is done in mono and the stereo imaging only comes in at the mixing stage).

One last one whilst you are looking at the mixer pic: I could run to my usb interface from either the jack sockets above channels 11/12 or 13/14, right? At the moment I'm using 13/14, but that channel has no gain adjustment.

Aside from being from interface to mixer ? , correct. 13/14 and 15/16 are preset at -10dB for tape/CD players, so don't need extra gain/trim.

The issue with 1 to 8 is obviously that they are not stereo, but intended for either a mono jack line connection or an insert (for Graphic EQs and similar units) - do I have this right?

Almost, but it's either jack or XLR input and the inserts are used for adding EQ, compression or gate (or any effect that needs to be in series rather than parallel) to that channel.

But barring channels 1 to 8, I could use 9/10 or 11/12 instead of 13/14 (and get the gain adjustment as a bonus)?

Yes.

I'm starting to see the logic, I think - as channels 1 to 8 have the compression feature, whereas one would never apply compression to eg. a composite backing track (keyboards, bass, strings, drums all together). So those three combined channels seem perfect to run to the PC.

Exactly. They also have a fixed frequency midrange control (easy to use), while 1-8 have parametric mids (handy for "tuning" the mid EQ to problem frequencies).

All-in-all, it looks like a nicely thought out mixer for live use, providing everything you would need from a small board. A few small compromises, but mostly intelligently chosen.

FruitarGeek

Thanks Alan

I will let you know if it worked out. I forwarded this topic to my friend

Riaan-Combrink

@Alan: as always, thanks! ?

FruitarGeek

Alan, My friend got it working. He said he had to apply a bit of logic to fully grasp what was going on, but he says I must thank you.

So here it is :"THANK YOU" ?