pranav_mox6 - 14 July 2014 02:11 AM

I just want USB connection noiseless when I’m doing line in recording from soundcard. That’s it!

For that I asked is that level of noise normal or not?

There’s no such thing as a noiseless connection - there will always be some noise. What determines the audibility of that noise is its level relative to that of the signal…

 

pranav_mox6 -

When I play on MOX, the peak level gets up to -24dB.

...and as best I can tell from the information you’ve provided so far, the noise level is approximately 80 dB below the peak signal level you’re currently obtaining (about 80 dB signal-to-noise ratio [SNR]). It should be possible to do better than that (over 90 db SNR), but don’t concentrate on numbers and spectrum plots.

If you can increase the MOX levels so that the peak is closer to 0 (zero) dB without significantly increasing the noise level, then that should improve the situation. Even an 80 dB SNR may be acceptable if your music doesn’t have much in the way of quiet passages. How does a recording sound to you?

Recording sounds good but not clean. I hear minor noise when there is a quite passage in music. Or at the end of music track I hear it.

I want to make it clear. You mentioned there is nothing as noiseless. That means the last image, is that noise considerable? And I shouldn’t worry about it and ignore it?

You’ve been very clear - you want to make as noise-free a recording as possible. It’s an understandable goal.

If the noise shown in the most recent image had been relative to an actual peak signal recording level near 0 (zero) dB, then it would certainly be acceptable. However, you indicated that the peak level you are getting from the MOX is -24 dB. If you can’t increase that level without bringing up the noise at the same time, then what’s in that image can likely be improved on.

I can’t be certain from the plots you’ve posted so far, but it looks like some of the noise is related to the power line frequency and its harmonics ("hum"/"buzz"). Can you post an image similar to the previous one, but instead of an FFT plot, 1/3 octave?

Sure, here it is.

Plus I want to know will DI box solve this problem?

Click thumbnail to see full-size image

pranav_mox6 - 16 July 2014 02:42 AM

Sure, here it is.

Thanks, nothings stands out on this plot.

 

pranav_mox6 -

Plus I want to know will DI box solve this problem?

Before you try a DI box, what have you done to raise the MOX signal levels? Since you’re using an external audio interface, what happens if you raise the Master Volume level on the MOX? That should increase the signal level, but does it increase the noise as well? If the noise increases at the same time, then a good quality DI box might improve things, but eliminating noise induced by ground loops isn’t always straightforward. Also, if you try one, you might need to go back to using an unmodified USB cable.

I kept the MOX and interface level all up high to the maximum, and then the images were uploaded. And yes, the noise level would also get louder or lower, when I slide the master fader. Well not that much. But its easily audible and noticeable.

Can you suggest any DI box? I’m not familiar with it. I was, in fact newly introduced when I got this issue. Well I came to know some of them as Live wire and samson’s DIs.

pranav_mox6 - 16 July 2014 12:08 PM

...Can you suggest any DI box?....

I don’t know if a DI box will solve your problem or not, but I can recommend This Unit from personal experience.

It is a very good quality and effective DI box.  This is a stereo unit, which you will definitely need if you decide a DI is what is required...unless you plan to purchase two single channel units.

cmayhle - 16 July 2014 12:42 PM

I don’t know if a DI box will solve your problem or not, but I can recommend This Unit from personal experience.

It is a very good quality and effective DI box.  This is a stereo unit, which you will definitely need if you decide a DI is what is required...unless you plan to purchase two single channel units.

That looks to be an excellent unit… and as it uses transformers you are guaranteed ‘galvanic isolation’ ... so no earth loop noise at all!
You may need to use a second unit if you introduce any inputs via the A/D input though?
We had along discussion about that a while back (see here:
http://www.motifator.com/index.php/forum/viewthread/458593/ )

and you can read in that thread about the alternative option of breaking the USB ‘gnd’ connection.

As others have said, losing ground loop noise completely can be a matter of trial and error, but transformer isolation has got to be the easiest - and probably the best - option.

pranav_mox6 - 16 July 2014 12:08 PM

I kept the MOX and interface level all up high to the maximum, and then the images were uploaded. And yes, the noise level would also get louder or lower, when I slide the master fader. Well not that much. But its easily audible and noticeable.

If keeping the MOX output level and the interface level at maximum results in only -24 dB peak level from the MOX (as you previously reported), then you’re not setting levels for your mix correctly.

See:
http://www.motifator.com/index.php/forum/viewthread/471747/
http://www.motifator.com/index.php/support/view/midi_velocity_and_audio_record_levels
http://www.motifator.com/index.php/support/view/mox6_mox8_recording_tips_from_bad_mister

Not all of the above will apply to your situation, but it should help you get considerably higher record levels, and therefore an improved SNR. When you get the peak record levels up (closer to 0 dB), then determine whether you need to do further noise reduction.

If keeping the MOX output level and the interface level at maximum results in only -24 dB peak level from the MOX (as you previously reported), then you’re not setting levels for your mix correctly.

No the level I mentioned is the average. Otherwise I am undoubtedly happy with the output I get from MOX.

And I’m going to try a DI box. Well its worth. If it wont work for MOX, I’ll use it for my acoustic guitar.

Thnx for helping.!!!

pranav_mox6 - 17 July 2014 03:58 AM

No the level I mentioned is the average. [...]

OK, but that’s not what you said before… “When I play on MOX, the peak level gets up to -24dB.” ...and the terms “peak” and “average” have quite different meanings.  :-)

 

pranav_mox6 -

And I’m going to try a DI box. Well its worth. If it wont work for MOX, I’ll use it for my acoustic guitar.

Thnx for helping.!!!

Best of luck in obtaining a satisfactory noise level.

I don’t know what’s wrong with, I tried Behringer Ultra DI20 DI box. It didn’t reduce the noise, but it did boost the noise too much. Tried ground/lift switch.

Why? Is it because its an active DI?

Well thank god I didn’t buy it. I borrowed it.

pranav_mox6 - 03 August 2014 02:34 AM

I don’t know what’s wrong with, I tried Behringer Ultra DI20 DI box. It didn’t reduce the noise, but it did boost the noise too much. Tried ground/lift switch.

Why? Is it because its an active DI?

Well thank god I didn’t buy it. I borrowed it.

Although it relates to a Motif XF (not a MOXF), and was not a USB-related noise issue, you might still find this interesting:
http://www.motifator.com/index.php/forum/viewthread/472326/P30/

pranav_mox6 - 03 August 2014 02:34 AM

I don’t know what’s wrong with, I tried Behringer Ultra DI20 DI box. It didn’t reduce the noise, but it did boost the noise too much. Tried ground/lift switch.

Why? Is it because its an active DI?

No, it’s because that box doesn’t offer ‘galvanic isolation’. That means either transformer coupling the audio path, or opto isolating the USB path

In cmayhie’s post above he links to a Radial PRoD2 device which is a transformer isolated DI box that should work. You don’t appear to have seen that post?....

In this thread: http://www.motifator.com/index.php/forum/viewthread/461757/

The OP links to a USB opto-isolator which should also solve your problem.

Your response on that thread suggests you’re not interested in that item either?....

You may get lucky by trying different ‘ground lift’ options.....but at best you’ll probably only reduce the noise, not eliminate it.

‘Galvanic isolation’ may sound like a fancy term. It’s very simple.  If you isolate the electrical ‘ground’ routing by using either a transformer coupled unit (in the audio path) or an opto-coupled device (in the USB path) then you will guarantee to lose the noise in your ‘ground’loop…

If you’re really on a tight budget, you might like to consider galvanic isloation by using a Toslink conversion? ..

Connect your your audio line outs to something like this Toslink A/D converter
and then connect an optical Toslink cable to the output. Connect the other end of that cable to the input this Toslink D/A converter and connect the RCA outputs from that unit to your audio interface ‘line in’ connections.

I don’t know how good the A/D unit is (Edit: see post below), but I have used that type of D/A unit on several projects, and it works well.

Bit over the top perhaps, converting to digital via an A/D and then straight back to analogue with a D/A?… but it would give you galvanic isolation, and it is cheap.....

Further to the last suggestion in my post above, I can confirm that the Toslink A/D converter linked to above - together with it’s associated D/A converter - works very well, and eliminates hum completely, without compromising any ‘safety’ earths.

So, you can guarantee to eliminate ground loop ‘hum’ by using ‘galvanic isolation’ in several ways.....

The ‘passive’ transformer solution with the Radial ProD2 suggested by cmayhie above is probably the best way. But it will cost you around $150.
There is a much cheaper passive ‘hum eliminator’ - the HD400 from Behringer - which seems to be transformer coupled ( most reviews say it is.. the spec doesn’t actually say). That should be OK?  - (I haven’t actually tried it myself - yet! I’ve ordered one to see. I’ll report on how well it works after I receive it...)

The USB opto-isolator solution from Olimex should work fine, but it needs to be shipped from Bulgaria, so would probably take a while to arrive. With shipping costs, that option should cost about $50. How well it works, I couldn’t say....should be OK…

Probably the cheapest option is to use a Toslink connection - which I can confirm works fine. That should only set you back about $25, including free shipping, if you buy from Ebay.