[szore]

As per the manual, when you switch it to Standard, the Gain is about 2.47; when you switch it to Low, the Gain is almost 1.1.

So it could be set to Low when using very sensitive sensitive iems for instance.
There are 2 switches for left channel and 2 switches for right channel.

Right. But why are there 2 switches for each channel? That's the question. Thanks in advance!

 

[Eylrik]

One for +, one for -, for each channel (the 400i is fully balanced).

 

[szore]

One for +, one for -, for each channel (the 400i is fully balanced).

hmmm Ok, so would there be a situation where you want R+standard R-low or vice versa? I still don't understand the implementation... Would you ALWAYS put all switches to standard or all switches to low, or would you mix them up?? I don't understand!

 

[Eylrik]

No, all switches have to be set either to low or standard at the time.
This follows the way the 400i is designed, as you can see on this picture.

 

[szore]

No, all switches have to be set either to low or standard at the time.
This follows the way the 400i is designed, as you can see on this picture.

OK, Thank you so much!

 

[szore]

Hello,

could anyone please help me with my problem with DAC Questyle CMA 400i? My dac making "electric" buzzing/noise/brum/hum (I do not know right word for this noise). I think it could be toroidal transformer or something in powering the dac.
Have anyone noticed this? I can hear it pretty much in the night whwn everything is quite only my studio monitors and pc going. I have the dac om my desk about 40 cm from my head. When i put my ear close to dac, then it is very "loud" sound. For example it is 5-10 times more loud and more anoing then standard noise from studio monitors.

I found some threads where someone says it could be low grade power cable. I have low end basic power cable (it was bundle for dac). Someone else says it can be removed by some filters (but they cost a lot).

I am finding any "not expensive" solution.

Until now I tried 2 different power cables in all my rooms and even without usb cable and without signal cables to monitors. Everything was turn off. Still the same "brum".

Thanks wery much for every help and information on this my problem.

I'm having the same thing happen to me about every 20 minutes.

 

[szore]

I think with the support questyle has created a lot of enemies here in the forum, so that less people are interested in Questyle.

So nobody can answer my question above?!

To the possible solution of my problem (post 916):

i connected my 400i with a toslink optical cable to the pc for testing.
With this toslink cable the crackling noises are no longer present.

Was it possibly because of the USB cable? Bad quality of the cable?
I will order another USB cable and test it......

If this toslink cable has any advantages or disadvantages compared to the USB cable, I don't know.



@plachta
Your problem is unknown to me, so I can't help you there.

Either optical or usb I get the same BRRP noise every 20 minutes or so.

 

[plachta]

I'm having the same thing happen to me about every 20 minutes.

Hello, I have this "noise" all the time (when DAC is ON). Now I have for some time Supra USB and power cable and "noise" is still the same.

 

[Eylrik]

Hello, I have this "noise" all the time (when DAC is ON). Now I have for some time Supra USB and power cable and "noise" is still the same.

Have you tried plugging the cma400i, alone, to a different electric socket ?

 

[szore]

I'm still getting the BRRR artifact every 20 minutes or so....

 

[Reactcore]

So i figured the cause for the usb dropouts.. after it happened more often i went searching and found the voltage of the digital part was unstable and falling below 7v. (Normally above 8v) one of the rectifier diodes was running hot so i replaced all 4 for higher current rating. No issues for weeks now It seems its a design flaw so others might benefit too if they have them replaced.

 

[DreamMan]

So i figured the cause for the usb dropouts.. after it happened more often i went searching and found the voltage of the digital part was unstable and falling below 7v. (Normally above 8v) one of the rectifier diodes was running hot so i replaced all 4 for higher current rating. No issues for weeks now It seems its a design flaw so others might benefit too if they have them replaced.

Could you please elaborate on that and maybe put in some pictures of the new parts? That would be really great!

 

[plachta]

Have you tried plugging the cma400i, alone, to a different electric socket ?

Yes i tried this too. In about 4 different rooms. Even without any other cable (only power cable in). It's really annoying and it looks like I am only one who have this problem.

 

[Reactcore]

Could you please elaborate on that and maybe put in some pictures of the new parts? That would be really great!

Sure its the 4 diodes in the circle in picture

On the place of the wires u need to measure about 8v, also while the unit is in use(playing)

The wire is for a relay of a modification i made (analog input) see link for that. The relay draws only some mA and is switched off while using internal dac. The usb drops i had before the mod too.

https://www.head-fi.org/threads/add...mp-which-doesnt-have-one.912647/post-15410320

 

[Reactcore]

Yes i tried this too. In about 4 different rooms. Even without any other cable (only power cable in). It's really annoying and it looks like I am only one who have this problem.

If you hear this coming out of the unit (not headphones) its most certainly the transformer.
A 50Hz (or 60Hz in USA) net humming is caused by loose vibrating wires in it.