Getting this high pitched buzz in my Frankenstein rig. Troubleshoot exercise.

[DustyCat]

Ingredients:

Behringer QX1222 USB 8+ channel mixer

Apple Mac Book Pro 2015

SM57 w/Mic Stand

AKG 240K Headphones

Various cables (XLR, USB, stereo audio 1/8" + 1/8" to 1/4" stereo adapters)



So I'd like to make some play-a-long videos like I see other guitar players do on youtube.
Since I've had some synchronization issues by using an iPod to listen to the recording and then set my guitar playing recording to the actual recording (that i own) on iMovie, the song comes from the computer.

iTunes: song play
MBP headphone jack out to AUX IN
Mixer USB OUT into MBP USB IN (have to change the input signal in settings).

And still I get this high pitched buzz/hum.

 

[Logrinn]

Isn't there a risk for some feedback loop issue here?
Going from the headphone out from your computer in to the mixer and at the same time the mixer goes in to your computer. Right?
What happens if you disconnect the headphone out to you Aux in? Does the buzz/hum stop?

 

[mayfly]

I'd say yes you likely have a ground loop somewhere in all that.

 

[stratamania]

Can't you just use the USB for audio in and out and dispense with the Aux in. Or put the song on an MP3 player or iPod and plug that into the Aux port.

 

[Sovereign_13]

Let me see if I understand this:

You are recording your own playing as: guitar -> amp -> SM57 -> mixer -> computer
You are recording the original track as: computer -> mixer -> computer
You are recording video via computer camera.

I can tell you that it's pretty likely the folks on YouTube are recording audio via something similar to what you have, but probably using a dedicated camera for video only, and syncing the two in post with a cue.  That way they get better audio quality than what a video camera can produce.

A few ideas about the humming:

• The video recording is also recording audio, and what you're hearing is two out-of-phase copies of the audio
• Your re-recording of a recorded song is creating weird feedback/aliasing
• As others have suggested, possible ground loop somewhere or (less likely) stray noise.

Personally, I'd import the recording you have into your DAW of choice and "dub" your own playing on top of it as a separate track.  Take video of yourself playing via camera (standalone or computer), but no audio, and sync the two with your video editor.  I am not a professional, though I do have some amateur recording experience.

 

[mayfly]

Personally, I'd import the recording you have into your DAW of choice and "dub" your own playing on top of it as a separate track.  Take video of yourself playing via camera (standalone or computer), but no audio, and sync the two with your video editor.  I am not a professional, though I do have some amateur recording experience.

This is how I do it.  I record all the audio separate from the video.  I drop both into final cut to create the final video with audio.  I use a 'clap' or some such to help synchronize the audio to video.  This is how I did this one:

[youtube]https://youtu.be/Op8Anmt7U7U[/youtube]

 

[DustyCat]

AND THE BOARD COMES ALIVE!!!
Oh my goodness, thank you guys for checking up on me, I did not expect answers so quick.

Where to begin...no there's no significant/critical feedback issue. The high pitched hum diminishes when the level is turned down.

Ive experienced synchronization issues when if I originally play along with an iPod, then try to line up the guitar recording to the .wav of the song from iTunes and by 2-3 minutes they are slightly out of sync (digital I know, weird) and by the end of the song they are noticeably out of sync.

I was unaware that audio could be transmitted two ways simultaneously via USB. Also...weird, I will try it

Yes Mayfly, that's how I'm doing it, pretty...pretty ghetto lo-fi, but it has worked in the past and here's an example...

[youtube]32CD_0TEbaI[/youtube]

Good video, I totally thought you were going with Fleetwood Mac "Go Your Own Way" ~:50ish

Maybe I should start using GarageBand instead of iMovie as the basis for videos like you do in yours. Also, for any budding camera men out there if someone asks you to video the show, just a static shot is fine. Don't need folks zooming in, and the panning while fully zoomed in, but that's another topic...

I like the dedicated camera idea  :sign13:

GoPros should be coming down in price now a days, eh?

 

[Sovereign_13]

I think maybe I'm not explaining/clarifying myself adequately?  Don't play to the iPod.  Ignore the iPod.  Your DAW of choice (GarageBand, ProTools, Reaper, Sonar, etc.) should be able to do playback through headphones/monitors while you're recording.  That way you can record individual tracks, but only the first one has to play to a click/in a vacuum (we usually make the drummer do that since his part is usually more easily synced to a click).  Every track after that should have the option to hear some/all of the previously recorded tracks.

By dragging your recording into the DAW and letting it handle playback of the existing track and recording of the new one, you should reduce or negate any sync issues.

It's still possible that the artifact you're hearing is aliasing caused by the audio card resampling the existing .wav file.

My suggestion is:

Guitar -> amp -> SM57 -> mixer -> computer -> DAW -> playback through computer headphone jack
.wav file -> DAW -> playback through computer headphone jack

That way you have audio going into the computer via USB and audio coming out of the computer via the headphone jack.  You could alternatively use the headphone jack on the mixer and set your computer's audio output to the mixer, rather than the headphone jack.

 

[AndyG]

Ive experienced synchronization issues when if I originally play along with an iPod, then try to line up the guitar recording to the .wav of the song from iTunes and by 2-3 minutes they are slightly out of sync (digital I know, weird) and by the end of the song they are noticeably out of sync.

Actually, that's not weird at all ....
Every digital (or analog) device plays using its own internal clock.  When you listen to a song on your iPod versus on your computer, they are playing at slightly different speeds ... even though your ear would never notice it.  It becomes obvious when you take 2 separately record sources and try to sync them up ... they drift due to the difference in speed. 
I've been doing post audio for over 15 years, and this is something that plagues my work when location sound isn't shot properly.  Devices need to be locked to each other, where there is only one master clock, and every other device slaves to it.

Even when using the lo-tech method described, there will be some drift between audio and video.  But over a 5-minute song it would be roughly a frame or 2, which is barely noticeable.  If you were to record a half-hour epic solo, the drift between an unlocked camera and your DAW would be significant by the end.