Here's the available gear - Make it sound good

[whyachi]

I'm trying to record some bass clips on my 2008 MacBook with Garage Band. I have a passive bass, an amp with 1/4" and a DI out, some 1/4-1/4 cables, a DI-1/4 cable and a 1/4-1/8" adapter. The MacBook has a 1/8" line-in and a webcam mic.

I cannot seem to get anything but buzzing through the recording. The webcam mic picks up sound but has obvious limitations for low notes. Running the 1/4 out to a 1/8 adapter results in constant humming which Garage Band assures me is actually me playing a low B. The DI>1/4>1/8 seems worse.

I'm not planning on using this for a band or anything, I just need something moderately workable for recording what a couple different pickups sound like.


Thus far I've tried running GB's compressor, but I'm a complete newb with Garage Band so I'm a bit lost on what to try next. The obvious solution would be to buy an interface but I really need to get by with what I have currently, an extra $60+ is out of the question.

 

[Superlizard]

Have you utilized the DI out yet?

oops... hold that thought.

Does the DI have a level knob?  Perhaps the signal is too hot into the Line In (Mac) and therefore clipping.

As well, is the Line In (Mac) stereo? (my guess is yes)... more than likely the Line Out is mono (verify this)... make sure
you have the proper 1/4" 1/8" adapters in mono, not stereo.  (or vice-versa - all depends)

 

[whyachi]

The line-in is stereo as is my adaptor, but on the Mac I have the option to set it to stereo or mono. I tried the DI level from 0-10 and got the same thing all the way around the dial.

 

[Superlizard]

- try all mono adapters if you have them, set Mac line in to mono.

- for DI route, verify DI is actually working and isn't f00ked.

- the sound you're hearing, does it change pitch as you play, or a constant-pitch hum?

:icon_scratch:

 

[GoDrex]

now that I think of it, I've heard of some people having trouble with some line out stuff - where the ground had to be lifted... for example:

this is in reference to a Weber attenuator.

The DI (line out) feature and associated controls turned out to be very useful, however I ran into the same exact same problem that I encountered when I had previously tested the THD Hot Plate. In some situations, to avoid a ground loop (or plainly put, a really bad, fizzy tone), you may have to “lift” the ground off of one end of the cable that hooks between the DI and the device it’s being connected to. I had to do this as well to alleviate the problem, but after doing so, I found that the tone network was nicely tuned.

 

[whyachi]

- try all mono adapters if you have them, set Mac line in to mono.

- for DI route, verify DI is actually working and isn't f00ked.

- the sound you're hearing, does it change pitch as you play, or a constant-pitch hum?

:icon_scratch:

How can I verify the DI is working? Its a brand new amp, and I've never used it.

I've only got the one adapter but I can probably trade it out tomorrow at GC for an all-mono one..

The sound stays the same unless I'm playing, then it lowers in volume. It doesn't seem to matter what note I'm playing, it always does the same thing. Loud buzz when I'm not touching anything, quieter buzz when I'm playing. It doesn't seem to be picking up anything as far as actually bass goes though.

 

[GoDrex]

try disconnecting the shield on one end of the cable...

 

[whyachi]

There is a ground lift switch on the back of the amp, is that what you're referring to?

 

[GoDrex]

perhaps if it's related to the output you're using.

if not, I'm talking about physically disconnecting the shield from one end of the cable you're using.

 

[AndyG]

Yeah, it sounds like you have a good old-fashioned ground loop happening ... laptops can be notorious for this.

Since you're using a laptop, the easiest way to see if that's what it is ... just run the laptop on the battery .... unplug it from the wall altogether.

If this works, you will need an isolation trasformer between the DI out and the Macbook in .... or do all your recording with the battery!

 

[whyachi]

Yeah, it sounds like you have a good old-fashioned ground loop happening ... laptops can be notorious for this.

Since you're using a laptop, the easiest way to see if that's what it is ... just run the laptop on the battery .... unplug it from the wall altogether.

If this works, you will need an isolation trasformer between the DI out and the Macbook in .... or do all your recording with the battery!

...that's a bit of a problem, as this laptop has got some kind of superfunky issue where if the magnetic power cable isn't plugged in and running, it powers off instantly. Battery charged or not. Happens on multiple batteries and chargers, and the thing is out of warranty.

Come to think of it, I did use a similar setup to this one on a 2007 MacBook running on the battery without this issue at all. I'll try it on another computer.

 

[Superlizard]

The sound stays the same unless I'm playing, then it lowers in volume. It doesn't seem to matter what note I'm playing, it always does the same thing. Loud buzz when I'm not touching anything, quieter buzz when I'm playing. It doesn't seem to be picking up anything as far as actually bass goes though.

You might have the issue where because you're dealing with both stereo and mono items, the connection isn't right.

I've had this before where I was say, sticking a mono adapter into a stereo adapter/jack (or vice versa) and all you get is buzz... apparently
the connectors inside the adapters were not lining up right; signal might have been touching ground, etc yada yada.

Since your DI is most likely mono, my suggestion is do an all-mono signal path up to the Line In jack.

So, assuming you're using a 1/4" mono cable from your DI:

- get an all-mono 1/4" female end to 1/8" male end adapter

That's my best guess.

 

[AndyG]

...that's a bit of a problem, as this laptop has got some kind of superfunky issue where if the magnetic power cable isn't plugged in and running, it powers off instantly. Battery charged or not. Happens on multiple batteries and chargers, and the thing is out of warranty.

Come to think of it, I did use a similar setup to this one on a 2007 MacBook running on the battery without this issue at all. I'll try it on another computer.

From what you're describing, I'm almost convinced that it is the laptop.  Those wall-wart chargers are the worst for dirty power.
There have been several occasions where I've had to interface a laptop with pro audio gear, and the buzz goes away as soon as you're running on the battery.  That's one of the problems of using the line-in as your record input.  With ANY kind of USB or firewire interface, the problem won't exist.  Isolation transformers aren't exactly cheap .... but they will solve the problem.  You'd be better off getting something like a Presonus Audiobox .... much less expensive than a new laptop!

 

[Rouse]

I've had many problems with DI on amps in the past. Use a mic, much more consistent.

 

[GoDrex]

uh... try disconnecting the shield on the audio cable...

 

[AndyG]

uh... try disconnecting the shield on the audio cable...

That trick will only work on balanced, line level inputs .... when coming out of a DI, the signal is still mic level, and much more prone to outside interference.  And if the DI (on the amp) is an unbalanced output (which it probably is) that trick will not work at all.