unbalanced line recording using microtrack II

[Stratis]

Hallo everybody.
Could anyone tell me which is the best way to record unbalanced line using microtrack II ?
FAQ says "If you are recording from an unbalanced line level source or a microphone with an unbalanced (TS) cable, use the 1/8” input...".
I followed this instruction but there was so much noise (rec levels all way down).

Is there any way to convert unbalanced source (RCA) to balanced?

[JA]

A DI (direct box) will convert an unbalanced signal to balanced.

[0dBFS]

Stratis,

Lets assume you need to record from a 'hi-fi' CD player with phono output sockets.

You need a stereo screened cable with phono plugs for the CD player and TRS jack plugs for the Microtrack. Connect the screen of the cable to the ring of the TRS jack plug and the signal core to the tip of the TRS jack plug. Leave the screen connection on the TRS jack plug unconnected.

Set the record levels in the normal way. I have used this method to record from a cassette deck with good results. If the level (volume) from the CD player is too high it will need attenuating (reducing). It would be much better if the TRS inputs on the Microtrack had Line/Mic switching as the sensistivity of these inputs classes them as mic inputs.

To reduce the level you could use something like this:

http://cpc.farnell.com/sennheiser/hzr-6/volume-control-volume-control-unit/dp/AV00390

or a cheaper version:

http://www.maplin.co.uk/Module.aspx?ModuleNo=33144

If you get the clicking mentioned in the FAQ, you should be able to prevent it with this:

http://cpc.farnell.com/unbranded/b070/car-ground-loop-amplifier-filter/dp/CP03283

Connect between the phono sockets and the TRS inputs. It contains two 10k ohm 1:1 transformers. I haven't tried this with the Microtrack, but I have used it with computer audio inputs when a similar problem happens

Hope this helps.

[Stratis]

Thanks all.I suppose that D.I. gives better results. (or not????)

I also suppose that 0bdFS's 3 links are to be used via microtrack's 1/4" TRS inputs.Let me repeat that (according to FAQ) microtrack can record unbal. line signal via 1/8" input (not only via 1/4" TRS inputs). Is this correct?

http://www.m-audio.com/index.php?do=support.faq&ID=5d99c9ee03fa5f70bac4c743877145a7

Thanks again!

[0dBFS]

This:

http://cpc.farnell.com/unbranded/b070/car-ground-loop-amplifier-filter/dp/CP03283

does the same job as a DI box, i.e. 'converts' an unbalanced audio signal to a balanced signal. You may get a wider frequency response using a DI box. The 1/8 inch input always has 'mic power' on it, so I would be cautious about connecting an unbalanced signal to it.

[dutchboy]

This is the 'official' advice that I dispense around the web:

"I bought the MicroTrack II at Thomann and have been trying it out for some days (March 2009). This is one nifty little device. Sound quality is great. HOWEVER, unlike what M-Audio says, the MicroTrack II does NOT really support recording off an *unbalanced* line level source. M-Audio in their knowledgebase recommends to use the 1/8" input jack for unbalanced sources. This jack, however, passes 5V phantom power for microphones and this CANNOT be switched off. With a voltmeter I measured about 4V DC on each channel (L and R) to ground. This voltage can have a negative influence on your sound, if not CAUSE DAMAGE to your equipment. The technical support of Allen & Heath, the brand of my mixer, recommends to NOT connect ANYTHING line out to the 1/8" jack of the MicroTrack II. The 1/4" jacks are said to produce a clicking noise when connecting them to an unbalanced line level signal. A warning to anyone thinking of buying the MicroTrack II. M-Audio support DID NOT reply to questions I had about their questionable recommendations."

So yes, M-Audio is, in my opinion, being irresponsible by in their knowledgebase recommending users to connect line outputs to the 1/8" input jack.

Solutions are:

1) use a DI box (direct box). Although these boxes don't produce any audible signal distortion, even with only 0.05% THD I still think I could have a perfect signal but now I need to tool around with audio transformers.... sacrificing sound qualtiy that could have been optimal.
2) use a conversion cable: unbalanced line to balanced. Best sound quality solution --if it works!!-- and better go to the 1/4" inputs to avoid the 5V power on 1/8". Options are to leave sleeve unconnected or connect it to ring (on the MT side). I didn't try any of this... I use 3:
3) maybe your equipment offers not a true balanced output but a so called "impedance balanced" output. MicroTrack II seems to be able to handle it.
4) modification of your equipment's output stage into a (impedance) balanced output. Google.

Solution 1 and 2 are what 0dbFS also says. Thanks.

K.