Digital and analogue sync

Lestratcaster

Ok here's the situation. I do my guitar lessons on Zoom, which has been going alright.

I have 3 basic audio feeds, my voice via an xlr mic, my guitar out of a Kemper, both into a Focusrite interface. Then any backing track stuff is usually off Spotify or YouTube. Unfortunately Zoom only detects the interface's analogue ports 1+2 as an audio input, otherwise I would have used an SPDIF connection. 

Now, when I have to demonstrate parts in songs along with the original recording I would normally use the share audio function on Zoom to play the music straight off my computer, but several students have noticed the guitar sound isn't quite in time with the track. I have concluded this is because digital (Spotify) and the analogue (my guitar) signal's are going to be converted at different speeds hence why they won't be in sync.

I tried Voicemeeter which is like a virtual mixer thing but due to the digital/analogue thing I still had the same problem. So I deleted that off after hours of frustration.

My only solutions I can think are:

1. Use my webcam (Logitech C920) mic to pick up the live in the room sound mix of the Kemper and Spotify out of my monitors.

2. Have a 2nd xlr mic positioned next to a speaker monitor to pickup the mix so I can do this and get my voice running analogue through the Focusrite.

3. Get some form of hardware mixer to mix everything before it hits Zoom, as it then messes around with the audio. I am willing to get a physical mixer if it means the audio and my guitar signal will be in sync. Just need to know which one and how to hook it up.

I would like that direct sound as its clearer and more professional. Temporarily I will have to go with the first option however.

Has anyone got any other ways I can get my guitar sound and audio playback to be in sync? 

Danny1969

I haven't gone back to zoom teaching yet but when I was doing it before i used a small Alto mixer  and connected that into the line in then Zoom used the line in.  I had a room mic for talking, my guitar and phone for running youtube plugged into the mixer. That's the best you can do I think ... all audio will be in sync then but zoom will still get the video to audio out of time .. least mine did 

Lestratcaster

Hmm....Zoom picks up a line in? I wonder if I could plug in my iPad then into the back of the Focusrite? But then again when I click on the box for audio input in Zoom it still only shows analogue 1+2.....

Video and audio sync isn't too bad as I have a good internet connection and most of my students do as well.

I wonder if there's any other video call apps that will take a digital guitar signal perhaps, preferably SPDIF.

Danny1969

I used an iMac, brilliant zoom teaching machines ... no audio interface just mixer straight into stereo line in. 

Lestratcaster

See I'm on a laptop using Windows 10 which have crap sound cards and drivers.

Would it be possible to rout the interface into the mixer with an iPad playing Spotify audio then sending all this to Zoom?

Danny1969

Yeah that will work fine, this is the little mixer I use ... it's got phantom power which I need for the room mic ... 

https://www.ebay.co.uk/itm/Alto-Professional-Audio-Zephyr-ZMX52-Compact-5-Channel-Mixer/174507930048?epid=1205350117&hash=item28a17bb1c0:g:FEwAAOSwKFlfcJzj

Lestratcaster

Ok, or even Kemper straight out into the mixer? Cos that's what soundguy's would do live at venue's right? Xlr mic into the other port then music off iPad into aux?

Funnily enough I was looking at that same ZMX52 mixer.

Danny1969

Yeah everything into desk then desk out into audio interface.  If you get one of those desk make sure it comes with the power supply as it needs roughly 16V AC ... not DC. It won't work with DC as it use's 2 half wave rectifiers internally to create a dual 15 0 15 supply. 

Branshen

Which focusrite do you have? Audio loopback is how I would go about it if possible. 

https://support.focusrite.com/hc/en-gb/articles/360006883140-How-do-I-use-the-Loopback-feature-on-the-Scarlett-3rd-Gens- ;

Lestratcaster

Right ok, just watching a little video on an ART Pro Audio and it seems like the mixer can take all the input sources, mic into 1, Kemper into 2 then music off my iPad into channel 3. Send to Zoom and it should work.

https://www.long-mcquade.com/101666/Pro-Audio---Recording/Mixers/ART-Pro-Audio/4-Channel-USB-Recording-Mixer.htm

For the one you linked me its got a power supply, this one is USB powered I think. But I presume it'd work the same way with the inputs.

Lestratcaster

Branshen said:

Which focusrite do you have? Audio loopback is how I would go about it if possible. 

https://support.focusrite.com/hc/en-gb/articles/360006883140-How-do-I-use-the-Loopback-feature-on-the-Scarlett-3rd-Gens- ;

The 8i6. I have heard about the loopback function but I wasn't sure how to rout audio from Spotify into it, and I don't currently use a DAW. 

Lestratcaster

Ok I’ve gone for the Alto zmx52 5 channel that @Danny1969 suggested.

A couple of questions though. The output of the mixer is unbalanced whereas the Focusrite inputs are balanced (I think). Is the stereo trs cable I would plug into my speaker monitors ok to connect mixer to interface? I will monitor using headphones.

And if I plug an electro acoustic into the mixer should I switch the input on the interface to instrument or leave it as line? 

Danny1969

Yes should work fine as the mixer jack will short the sleeve of the TRS cable to ground making the TRS lead unbalanced. There is no advantage to balanced audio over very short distances unless you're routing the cable through a very noisy environment. 

If the acoustic has a built in pre amp then it might be happy at line level, if not use the instrument input. Basically the difference can be the input impedance and the gain on some mixers but just the gain on others. 

I'm back to Zoom teaching tonight so my rigs coming out again too

Lestratcaster

I really ought to have got the xm862 as it has a balanced output but too late now...

If I’m connecting both outs of the mixer to the the front 2 ports of my interface them I should be switching both ports instrument? The electro acoustic is a Takamine EG321c that I’ve used live a few times and sounds good.

Lestratcaster

Right, mixer arrived earlier so proceeded to hook it all up. Took me a while to figure out connections and controls but got it working in the end. Started off with electric guitar, the Kemper signal is coming out of main output with an instrument cable into channel 2 (mic is in 1). Music is plugged into 3 off a phone using a dual 3.5mm to 1/4" cable. Guitar is now in sync with guitar, which is great! All direct and mixed from one device.

Now for my electro acoustic, just plugged straight into channel, however I get a horrible hum noise as if there's static interference or something. Whenever I touch the TRS cable plugged into either the interface or the mixer the humming stops. Is this linked with the unbalanced out - balanced in thing? I've seen those pseudo cables that one end is TS (unbalanced) and the other is TRS (balanced) for connecting different types of gear.

Why am I getting this hum though?

Danny1969

Are you using a simple mono unbalanced instrument cable to connect the acoustic ?

Lestratcaster

Yes I am.

It doesn't hum whenever I plug it straight into my Focusrite though.