Amp Line Out to PA

[gfa]

I just agreed to a last-minute fill in running sound for some friends. I've only run sound for my band, and we just use a couple of LDCs, so it's very simple. This gig will have three people running line-outs from small amps to the PA, for a mix of acoustic and electric string instruments. Where in the signal path does that line out pick off the signal? Is it weird for a given instrument's sound to be coming both from the amp and from the PA? What's the "you don't know that you don't know this" stuff to watch out for vis a vis the line outs?

Thanks.

[shufflebeat]

Q1) Line out.
- Jack - TS (unbalanced) or TRS (balanced) or,
- XLR - balanced?

Q2) Is there a ground lift switch? You may not need it but good to know.

If there are no notices to the contrary a line or DI out often comes after all the controls except the master volume, which means the player can set their amp volume without messing with signal to PA. They also may choose to adjust channel volumes that will definitely mess with signal to PA, have that conversation when you're hooking up the amp.

The speaker often plays a significant part in the amp sound so be prepared for the signal to PA to sound very different to the amp. If it's a problem a mic in front of the amp can be an easy fix.

If the amp sound is unusable you may prefer to use a DI directly on the instrument with a link out to the amp.

Duplication of sources can be a problem, specially for guitarists who insist on pointing their amps to the back of their knees. Consider placing their amps in front of them like monitors so the audience only hear the PA or angling them up. Be prepared for players not to like this.

At the end of the day most people won't hear or care anywhere near as much as you think.

[gfa]

Thank you, Shufflebeat. No idea the answers to your questions. I'm showing up with my mixing board (QSC Touchmix), mains (RCF HD-32), and rolling case of miscellaneous cables and hardware, and it's up to them to bring the rest. We're all friends and it is a low key gig. I'm nerding out on it because I'm normally performing at the gig while trying to do the sound, so this is a fun opportunity to fiddle around with the PA gear.

I LIKE the idea of having them point the amps at themselves, would not have thought of it myself, and am appropriately grateful to you for suggesting it.

[YamahaGuy]

Some amps have a Pre- and Post- DI output.
If you use the pre-, the guitar's raw signal goes to the PA. If you use post-, all the work the amp's EQ and effects do are reflected in the signal that goes to the PA.

It's not necessarily weird for sound to come from both the amp and the PA. Many players prefer using their amp as their monitor and will position it facing them. The bad part can be when the bounce back of the sound from the amp is louder than FOH from the PA. You get a weird delay action. Try to have the PA sound louder than the amp to avoid that.

If an amp has no direct out, you can sometimes get away with using the SEND from an effects loop if so equipped. Different amps do different things as far as that goes, i.e. some amps SEND effects loop is dry (no EQ or effects from the amp), some put out the wet (EQ'd) signal.

If the amp has no effects send or no output, you'll obviously need to mic it.

Finally, try to have all electrical equipment plugged into the same electrical circuit. Ground loops are nasty, and easily avoided if the amp, mixer and powered speakers are all plugged into the same outlet.