• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Noise on Fosi audio k5 pro mini with Truthear Zero Red

Melbylaw

Member
Joined
Jul 12, 2024
Messages
22
Likes
1
Yesterday my new order arrived, a Fosi audio k5 pro mini "gamer" audio DAC, I bought it to use with my IEM Truthear zero RED, both to amplify the sound and because its cable is too short to use on my PC.

However, when I connect my Truthear to the DAC I hear white noise in the background when nothing is playing on the PC.

The DAC is connected to the PC via the USB-C to USB-A cable, I tested all the USB ports on my PC but none of them resolved the noise problem. I tried plugging the PC into a socket isolated from the other components, it didn't work either. I also tested my Logitech g335 headset, the noise is also noticeable (but it is lower)

I've been trying to find a solution all day on the internet and I ended up finding this forum, does anyone know how to help me? Preferably a solution that doesn't cost 50 dollars (I live in Brazil and the dollar is very expensive here, I need a cheaper solution)
 
What intrigues me is that I saw several people using the same IEM and the same DAC as me, but no one complained about noise.
 
The truthear is not a sensitive pair of iem so to get a constant audible hiss suggests something upstream isn't right at all.

Just out of interest, do you have any other headphones /buds just to check it's not the truthear? EDIT you already did. Try plugging the fosi into your phone and see how noisy that is.
 
The truthear is not a sensitive pair of iem so to get a constant audible hiss suggests something upstream isn't right at all.

Just out of interest, do you have any other headphones /buds just to check it's not the truthear? EDIT you already did. Try plugging the fosi into your phone and see how noisy that is.
I still don't know how to connect it to my phone (I have an iPhone 13). However, I tried to connect via USB-C to my mother's cell phone but a message appeared on the cell phone saying that the device requires external power.

My father is coming home from his trip later today, so I'm going to test the DAC on his laptop
 
I just tested it on my father's laptop, it didn't help, the same noise persists. It's not the worst noise in the world, it's practically imperceptible while I'm listening to something. But I would prefer it to be completely silent.

Any tips on what I can do to make this noise go away?
 
I just tested it on my father's laptop, it didn't help, the same noise persists. It's not the worst noise in the world, it's practically imperceptible while I'm listening to something. But I would prefer it to be completely silent.

Any tips on what I can do to make this noise go away?
It seems your DAC is making noise from your description of what you did. How old is the DAC?
 
Any tips on what I can do to make this noise go away?

You may have to get another DAC/Amp...

Headphone Output Power / Noise Floor
This device easily powers every gaming headset I own and also has no problems with headphones which require a bit more power. The lack of a gain switch makes the amp almost too powerfull for typical gaming headsets, my PC38X and Coolermaster MH751 are already really loud (about 80dB) at about 10 o´clock on the volume knob. The Noise Floor gets audible at around 15 o´clock on the volume knob (which would be way too loud for regular use, my MH752 gets about 110dB loud on that volume setting).

This is especially appearent when you use IEMs with it, they are already loud enough for me at around 8-9 o´clock, if I lower the volume a bit more, I can hear the channel imbalance of the analog volume knob. I also didnt hear any audible noise with the IEMs. I can only hear noise with IEMs when i turn up the volume to around 13 o´clock, but that volume would probably deafen me if I played any sound.

So the range of volume control is quite limited with sensitive headphones/IEMs. You can counter that problem by lowering the digital volume on Windows, however you will have to turn down the windows volume a lot (to around 10-15% to get a „good loud“ volume at 12 o´clock on the volume knob), but thats also very close to the audible noise floor for IEMs. So the device isnt really suited for IEM usage.

 
You may have to get another DAC/Amp...



Any suggestion? Under 50 dollars, because brazil taxes are like 92% above 50 dollars
 
My DAC is new, it arrived yesterday…
Hmmmz IC. As a side note my DAC a JDS Labs ATOM DAC+ is dead silent supplying signal for a Schiit MAGNI headphone amp. Have you listened to the DAC-amp without the PC connected?
 
Hmmmz IC. As a side note my DAC a JDS Labs ATOM DAC+ is dead silent supplying signal for a Schiit MAGNI headphone amp. Have you listened to the DAC-amp without the PC connected?
How do I listen to it without the PC connected if it needs power? The only power I could get was via USB.
 
Have you tried lowering the volume on Windows and raising the volume on the K5 Pro? (or the opposite) Does it make any difference?
I've already tested, if I increase the volume using the knob the noise increases, also using the threble knob, but if I decrease the volume/threble, after a moment the noise no longer decreases
 
Update, I tested the DAC on other devices, such as a TV, speaker and even directly connected to a socket. The white noise didn't go away. I don't know if it's because of the usb connection or if the Truthear Zero Red is very sensitive. What makes me curious is the fact that some people use the same setup as me and don't complain about noise…
 
Power up the dac from a usbc phone charger without any source connected and starting at 0 volume and increasing. See if you get any noise from the dac /amp. If you do, send it back.
 
@Melbylaw try plugging the Fosi into a good quality phone charger (e.g. Apple).

This will give you a baseline reference of the DAC's noise floor.

If you still hear hiss, then the Fosi is just not suitable for your IEM.

FWIW, the Apple headphone adapter is one of the cleanest and most transparent sources you can get for IEMs.

Like the Fosi, it's both a headphone output and microphone input.

I use one on my PC for IEMs, plugged in via a Steelseries USB cable for extra reach:

Currently sold out on their website, but you can find it and other cables like it in other places online.
 
Update, I tested the DAC on other devices, such as a TV, speaker and even directly connected to a socket. The white noise didn't go away. I don't know if it's because of the usb connection or if the Truthear Zero Red is very sensitive. What makes me curious is the fact that some people use the same setup as me and don't complain about noise…

I think you're hearing the noise floor of the DAC/Amp. This sort of noise, when audible, can bother some people, but not others. For example, I once bought a pair of JBL 305P MKII monitors which measure well and sound great apart from the hiss from the tweeters which I just could not stand. I had to send them back.
 
Power up the dac from a usbc phone charger without any source connected and starting at 0 volume and increasing. See if you get any noise from the dac /amp. If you do, send it back.
what do you mean? I took a cell phone cable and connected it to my apple charger, plugged the dac into the socket but the noise still continued on my IEM
 
Like this, with this setup, i still hear the noise, even when i put all knobs on minimun
 

Attachments

  • image.jpg
    image.jpg
    131.5 KB · Views: 70
Back
Top Bottom