high pitch frequency on motu 896mk3 hybrid inputs

[romanamor]

hi there, i have one of the recently released motu 896mk interfaces. when i connect any gear (mic, instrument pickup) to any analog input, i get a high pitch sound around 1527 hz that becomes more noticeable the more i push up the trim knob. this high frequency pitch does get recorded. due to this problem i exchanged the motu 896mk3 hybrid for another unit, but the problem is the same.

i don't have this high frequency pitch on my motu ultralite mk3 hybrid nor my apogee duet2 - same setup (cables, mic, headphones).

the high frequency pitch disappears if i unplug the mic from the cable (balanced xlr), but the cable still connected to the 896. if i plug in the mic, the pitch reappears.

the pitch gets louder the more i turn up the trim knob or the more i approach the mic to the cuemix display on the 896.

now, THIS IS REALLY INTERESTING:

mic connected to my motu ultralite - no high pitch sound. now, i turn on the 896 (nothing connected to it except the power cable, the 896 stands next to the ultralite) the high pitch sound at 1527 hz reappears and does get louder the more i approach the mic to the cuemix display on the 896. turning off the 896 makes the pitch disappear.

i have tried other cables - no success...

I DON'T KNOW WHAT TO DO!

are there users that have experienced similar problems?

every advice is greatly appreciated!

thanks in advance.

[Spencil_Splodge]

Hi,

I have also just purchased a Motu 896mk3 Hybrid and I am experiencing the same issue, only mine is occurring at more like 1670Hz.

I have raised a support issue with Motu (and my supplier). Did you ever get to the bottom of this or receive any additional information from Motu?

Best Regards.

[Klaus]

Hi,

I have also just purchased a Motu 896mk3 Hybrid and I am experiencing the same issue, only mine is occurring at more like 1670Hz.

I have raised a support issue with Motu (and my supplier). Did you ever get to the bottom of this or receive any additional information from Motu?

Best Regards.

Yes, please report back here about 896mk3Hybrid issues and reports from MotU / techlink answers

Best

Klaus

[Johnnybell]

Any word on this? i am having the same problem...

[Spencil_Splodge]

Still note received anything back from Motu - guess it's Christmas afterall.

Also note, without anything connected, not even a cable, switching on the PAD causes the tone to occur...

[Klaus]

Still note received anything back from Motu - guess it's Christmas afterall.

Also note, without anything connected, not even a cable, switching on the PAD causes the tone to occur...

You are right..
Also the 1k65Hz tone appears when an external input termination is applied, i.e. 500 ohms, or a mic.
I measured this and here are screenshots of Smaart,

http://redmountain.ch/896mk3H-input%20t ... 20gain.pdf

and for level reference

http://redmountain.ch/896mk3H-full%20le ... 20gain.pdf

If I calculate roughly, this is a s/n ratio of only 78 db related to 0db analog...
at +35db gain... so an input noise of 113db...

Me thinks this is inacceptable.

My 896mk3 ( firewire only ) don't have this problem...

and then the 896mk3H also have this problem :

http://www.motunation.com/forum/viewtop ... 98#p407642" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
( slow loading of files from computer )

And the old 896mk3 files can not be imported...

I'll probably send it back.


Best

Klaus

[Spencil_Splodge]

Very interesting stuff... maybe it's a Hybrid only issue!!??

I'm wondering if the PSU in the unit has changed for the Hybrid as the literature talks about an 'International 100-240V, 50-60 Hz autoswitching power supply. '...

Thanks for the extra info.

[Spencil_Splodge]

Or, of course, it could be something to do with the changes in the preamp section or indeed the addition of the USB stuff...

[Klaus]

Or, of course, it could be something to do with the changes in the preamp section or indeed the addition of the USB stuff...

Me thinks it is related to the new input section... and it's supply rail on the PCB

The Display is probably drawing current thru the PCB and the preamp is sensing this...
only if the input is terminated ...
Just guessing and remembering my hardware career ...

I'm wondering when MotU will chime in...

Klaus

[Spencil_Splodge]

Sounds like a good theory - I'm actually a firmware/software engineer so my hardware experience is limited to coding chips rather than putting them together

It wasn't so long ago I was looking into why a display was 'leaking' current and raising our power consumption... slightly different, but sometimes there are firmware fixes that can get around these issues (in my case there wasn't :-S it involved a hardware change).

Hope to hear something from Motu soon!

[Spencil_Splodge]

...now I think about it, it was leaking current onto the PCB through an unused communication line on the display driver which needed to be disconnected in the end - maybe, as you suggested, it is a similar issue here only we can actually 'hear' the problem

[Klaus]

I just set up a monitor and checked a *live* situation...
SM58, +10dB gain setting ( medium - level voice, input peaks at loud screams ),
Cuemix FX channel send at -12dB, master send full at 0 dB, 7200 Crest poweramp at x 40 gain setting, volume knob fully cw.
Everything is *just* before feedback onset, no critical EQ tuning applied...

And the 1k65Hz is clearly audible.

The oscilloscope shows it too, 24dB above noise...

This is only 1 monitor and 1 channel, and I'm sure, on stage, with multiple ( and loud ) monitors and multiple channels open, the whole stage will *whine*.
Just checked a typical mix with 4 channels open. Using compression will bring up the whining
to a *what is this* - *switch of the generator* level...

This unit needs a redesign, IMPOV

Klaus

[Spencil_Splodge]

Thanks for the update!

Geee... this is bad. I wonder how long it will take all owners of this unit to realise? And where will the fix be - likely hardware... maybe Motu will have the luck of the firmware fix, who knows... as long as they don't bodge some kind of EQ notch filter at around 1.6k in the DSP

This is sooo bad for their flagship Firewire interface (err, not cheap either), where the hell was the QA? This is my first experience with Motu which started with a Traveler Mk3 which died within an incredible 30 seconds (likely a power supply issue) which I then changed for the Motu 896mk3 Hybrid... and here we are now. My previous interface is an EMU 1616M PCI - never had a problem with this one until Windows 7 64 bit BSOD's which is purely a driver issue, other than that a superb quality unit with excellent sound.

Sort it out Motu, for what is otherwise a reliable, feature filled unit.

[Klaus]

I had to edit my post with the screenshots, the ref pic was missing...

http://www.motunation.com/forum/viewtop ... 05#p412305" onclick="window.open(this.href);return false;

Klaus

[Klaus]

And here is a screenshot of Cuemix FX FFT analyzer, 4 channels open in a realworld situation...gains set to +35db.

http://www.redmountain.ch/896mk3H-FFT-s ... 1k65hz.pdf

Hmhh....

BTW 1k65hz relates to PSU ?

edited :
Comparison of 896mk3H and 896mk3 PSU bleeding, screenshots of Cuemix FX FFT :

http://www.motunation.com/forum/viewtop ... 11#p412611" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Klaus