Topic: Micro Track problems

[Md2545]

I'm borrowing a MT from a buddy and after transfering the show I noticed a clicking/digi noise. is this due to the unit or the jack getting bumped around, I also ran it though soundforge 9 to add some volume but I checked the raw file and it was on there too. I'll post an example, any help is much appreciated. I know very little about this unit.

using DSM-6S/M>PA-6>MT

[guysonic]

Sample is kind of short, but I heard two 'clicks' about midway. 

These seemed not a digital noise or deck fault, but sounding more like some sound in the ambient the mics picked up (in stereo) that got recorded live, but maybe not noticed or heard during the performance? 

[JoeKiller]

yeah that sounds like a wook hitting the pole or something

[Md2545]

Lent the unit to a buddy and came back to find all the tracks have little repeative "second ticks" when I don't even have a mic plugged in and I hit record and I listen through head phones I still hear the tick. It's louder on the RCA than on the 1/8 mini input settings. Do I just need to update the firmware or is the card bad. Please help, and thanks in advance.

MD

[guysonic]

Lent the unit to a buddy and came back to find all the tracks have little repeative "second ticks" when I don't even have a mic plugged in and I hit record and I listen through head phones I still hear the tick. It's louder on the RCA than on the 1/8 mini input settings. Do I just need to update the firmware or is the card bad. Please help, and thanks in advance.

MD

Yes, it can be the card, but truth is something in the digital system is getting into the front end of the analog on this deck due (I think) to a PCB design ground-loop fault.  With some cards drawing more power, and maybe generating a more intrusive ground-loop noise, the MT2's design fault can be more a problem with certain cards than with others.

I tested the MT2 using an older run of Sandisk's 8 GIG CF that worked flawlessly with older MT1, and seemed to be fine for not polluting the minijack input on MT2 deck.  However, the dual 1/4 TRs input was totally unusable in unbalanced mode due to the noise fault of the deck, and only the balanced input was able to suppress the noise to inaudible levels, but could still be seen in the spectrum graph I again post shown below:

[Husker Du]

However, the dual 1/4 TRs input was totally unusable in unbalanced mode due to the noise fault of the deck...

I've been back and forth with M Audio on this and they keep telling me it's not a defect. Their advice continues to be use only balanced sources for the 1/4" inputs. 

[Church-Audio]

This is a typical "wook waveform" notice the spike at 500hz this is a typical "wook frequency" you can tell this is the work of a wook. I would invest in some wook repellent. 

[guysonic]

However, the dual 1/4 TRs input was totally unusable in unbalanced mode due to the noise fault of the deck...

I've been back and forth with M Audio on this and they keep telling me it's not a defect. Their advice continues to be use only balanced sources for the 1/4" inputs. 

If its not a fault, then what is it?  Certainly not a feature.  Maybe a shortcoming, and an avoidable/fixable one if enough owners/prospects want for better.

I'm now thinking the MT2's TRS inputs are ONLY balanced mode QA'd; as likely directed by 1st tier design engineering. 

Engineering would ONLY know of unbalanced mode noise (the shortcoming) if actually having tested the final production PCB assembly where most times such problems are first seen to appear. Mostly due to wrongly run/connected ANALOG/DIGITAL/POWER ground/commons copper traces, and sometimes COMPONENT proximity in low level audio sections. 

I suspect most functions are inside a single CODEC IC  that may or may not have provided, or if properly featured, had (by engineering/PCB designer) fully implemented separate power, digital, and analog ground/commons paths so generated noise doesn't pollute the analog audio process.  In other words, slight possibility there's a design shortcoming in the CODEC IC, AND/OR design error in the implementation of the CODEC IC as it connects to the PCB board.

And yes, balanced input mode has provided over 45 dB of internal deck ground-noise noise rejection to make the shortcoming inaudible.  Unless, maybe possessing golden ears hearing low level/low frequency repetitive noise modulation of audio signals.



As the graph shows, the deck's internal noise character (seen as ripples) is effectively suppressed by the rejection action of balanced input common mode rejection action. 

Normally, this common mode rejection has advantages to reduce induced noise expected with extended lengths of input cable, and here we see it being used by M-Audio to reduce a huge amounts of internal deck noise.   

And it really works!  Way to go M-Audio! 

[guysonic]

Got word yesterday from M-audio tech my sent-in-for-repair or refund is NOT repairable for known issues, and purchase price for MT2 is being refunded.

So for sure unbalanced input noise issue is now officially an MT2 'product feature' as explained by M-Audio.

However, although not mentioned, the 88.2K bandwidth shortcoming with MT2 applying wrong filter may still be firmware corrected, but I'll never know for not getting the unit back to bench test.

I hope for owners of MT2 using 88.2K mode at least this issue is not a 'standard feature' and will eventually be fixed with a firmware update.  So those using 88.2K sampling rate might still have a non-addressed problem with ~ 20,000 cycle bandwidth limitation until further notice.

So no MT2 technical review, and I will continue to use my MT1 as the better Microtrack model version for acceptable analog input performance reasons.
(See MT1 review at www.sonicstudios.com/mt2496rv.htm