[CoFire]

I need some help guys, my laptop is not recognizing the m9xx.
I'm getting "the last USB device you connected to this computer malfunctioned........." from Windows 10

I tried reinstalling the driver and it still did not work

Any suggestions, I was working fine for months and today it stop working

Are you sure you are on U2? Sometimes I forget that detail when using the installed drivers.

 

[John Q Lin]

I need some help guys, my laptop is not recognizing the m9xx.
I'm getting "the last USB device you connected to this computer malfunctioned........." from Windows 10

I tried reinstalling the driver and it still did not work

Any suggestions, I was working fine for months and today it stop working

Are you sure you are on U2? Sometimes I forget that detail when using the installed drivers.

I restarted my pc and it fixed the problem

 

[Michgelsen]

 
Do you mind sharing your source for that info please? I've wondered why there was no discernable difference at lower volumes also.

​It has been explained a number of times in this thread, I believe also by someone from Grace.

 

[Roger Gu]

Beyond 90, it seems to work differently. What I have noticed is that when there is no input(either no sound play or no input plugged in) and turning the volume up, there is a jump on noise right on 90. I am using a sensitive IEM to test it. Below 90, it is dead silent and after 90, it has a little hiss noise, but does not increase as volume increase. It may be the high gain kicked in, causing noise.

 

[GraceDesign]

This is our hybrid digital/analog volume control. To keep noise down for sensitive IEMs, 0-90 is all digital attenuation with no analog gain added. Once you hit 90.5, an analog +10dB gain boost is applied. When you boost gain in the analog domain, the noise floor rises as well. We only apply analog gain for the last 10dB so that the noise floor is at the minimum up to 90. If you have to push your headphones beyond 90, they would be quite inefficient and would probably not notice the bump in noise floor. 

 

[Roger Gu]

  This is our hybrid digital/analog volume control. To keep noise down for sensitive IEMs, 0-90 is all digital attenuation with no analog gain added. Once you hit 90.5, an analog +10dB gain boost is applied. When you boost gain in the analog domain, the noise floor rises as well. We only apply analog gain for the last 10dB so that the noise floor is at the minimum up to 90. If you have to push your headphones beyond 90, they would be quite inefficient and would probably not notice the bump in noise floor. 

 
Make sense. It sounds like the 10dB analog boost is constant for the last 10DB volume range. If so, it lines up what I have observed.
 
Maybe it has been answered before, but does the high power mode take effect when the analog boost is needed? Or it actually applies to the entire volume range, but just because most headphones do not need the extra power, the difference is barely noticed.

 

[GraceDesign]

Right, once you hit 90.5, 10dB analog gain is applied and the digital attenuator drops -9.5dB to compensate. 90 is the optimal level for feeding external amps as it is the highest signal to noise. 
 
Someone asked me about high power today, this is what I wrote:
 
The difference between bus power and high power mode is the current driving capability. When you are in bus power mode, you are limited to 500mA from 5V. If you were trying to play power hungry headphones at a high volume in bus power mode, the current draw from the 5V bus would exceed 500mA so the m9xx protection kicks in and turns off the audio power supply. This will save your USB port from burning out by exceeding it's max current.

When you are in high power mode, there is 2A available at 5V. This will allow you to draw the max amount of current from the headphone amp without exceeding the current available on the 5V bus. Generally you only need high power for inefficient headphones. Bus power should be fine for the majority of headphones out there.

 

[Roger Gu]

Thanks for the explanation! Now I get all the magic around 90.

 

[davehutch]

Hi Alex, you and I have been emailing each other on the subject as user Michgelsen stated that High Power mode only kicks in above 90.
He clearly has that mixed up with the hybrid digital/analogue switch and as you rightly say, high power mode is available at all volume levels, should it be required.

 

[CoFire]

Hi Alex, you and I have been emailing each other on the subject as user Michgelsen stated that High Power mode only kicks in above 90.
He clearly has that mixed up with the hybrid digital/analogue switch and as you rightly say, high power mode is available at all volume levels, should it be required.

Is this correct given GraceDesign's explanation? I understood high power mode only being initiated past 90. Perhaps I'm misinterpreting something here?

 

[davehutch]

Yes, that has always been my understanding regarding high power mode.. The extra current is available at all volume levels if required to drive a demanding pair of headphones, but the analogue amplification (which I wasn't aware of until now as it isn't mentioned in the manual) kicks in at level 90. They are two different things

 

[Roger Gu]

Has anyone tried to drive Beyerdynamics T1? Would it be under power?

 

[John Q Lin]

Has anyone tried to drive Beyerdynamics T1? Would it be under power?

Your one lucky dude, I just got my T1 today. I only have the it at 80 and it's loud as f.

 

[Roger Gu]

How did you compare it with your thx00 under m9xx?

 

[John Q Lin]

How did you compare it with your thx00 under m9xx?

65 to 70 max