hey,
thanks for the stuff on electrical interference.
USB devices are particularly prone to interference i have found.
This is the one major mistake that Apple have made. All maxed should have three 
Jack's microphone, headphones and line-in i believe.
Michael
> On 10 Feb 2015, at 8:10 am, 'Chris Blouch' via MacVisionaries 
> <[email protected]> wrote:
> 
> Related to this, there are four audio electrical levels. Mic levels are tiny 
> signals that come out of a mic and usually need to go through a pre-amp 
> before they can become usable 'line level' signals. Line level is typically 
> for signal routing such as patching the audio output from a DVD player to the 
> line input on your Mac. Next up is headphone which is a much stronger signal 
> as it's going to drive physical movement of something to make sound waves in 
> your ears. Last is speaker levels which, like headphones, range from a few 
> watts to thousands to drive room or stadium filling speakers.
> 
> All that is to say, if your TV output is for headphones, direct connecting it 
> to the line input of your Mac may give distorted sound. It shouldn't hurt 
> anything but you'll know it when you hear it. Most modern TVs have RCA output 
> jacks (or something digital on newer sets) which would be line level and a 
> better source for recording. If not then you'll need something called a 
> "direct box" which takes a headphone level input and generates a mic level 
> output which you can then run to a standard mic pre-amp to record. I have a 
> Mac-mini headphone output going to one of these to run it into a Mackie 
> mixing console.
> 
> The last bit it hum. This can be any number of things including bad cables, 
> ground loops and picking up interference from power lines. If it's a low 
> pitched humm that might be 60-cycle interference as alternating current flips 
> polarity 60 times a second in the US and 50 in many other countries. In the 
> case of a ground loop, you can google the explanation but it can sometimes be 
> when two devices are on two different power circuits. Sometimes as little as 
> plugging both devices into the same circuit can make that go away. The 
> aforementioned direct box can also have a 'ground lift' switch which can 
> eliminate the buzz in some cases. If it's from interference, the only 
> solution is to move the cables around to try and make it go away or use 
> better shielded cables.
> 
> Hope this helps.
> 
> CB
> 
> On 2/9/15 3:49 PM, Tim Kilburn wrote:
>> Hi,
>> 
>> On a Mac, the headphone jack doubles as a line-in jack.  You should be able 
>> to go direct using 3.5 to 3.5 from the out on your TV to the jack on the 
>> Mac.  Using an app like Audio Hi-Jack Pro would do the recording for you 
>> nicely.
>> 
>> Later...
>> 
>> Tim Kilburn
>> Fort McMurray, AB Canada
>> 
>> On Feb 9, 2015, at 12:34, Michael Marshall <[email protected]> wrote:
>> 
>> hey all,
>> i have a TV with a 3.5MM headphone jack witch i used to connect to the mike 
>> port on my windows computer and record the sound.
>> on the mac i have run into some significant difficulties with this.
>> Obviously the Mac has no dedicated microphone jack witch can be overcome 
>> with the iMike USB interface witch i have got. this has a mike jack so i 
>> thought i would be fine.
>> The main problem that I am having is that on that and any other computer a 
>> lot of USB recording devices including this one have an unpleasant buzzing 
>> sound. I have found this problem over multiple systems and multiple USB 
>> devices. My theory is that it is electrical interference between the 
>> computer and the USB interface.
>> what i would like to know is this, is there a way to use the 3.5MM patching 
>> cable connected to the headphone port on my television to somehow Connect to 
>> the Mac without USB? because i'm not getting the best Sound with my current 
>> configurations.
>> thanks for any help on this.
>> Michael
>> 
> 
> -- 
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