Dosmix Headphone Dongle Review

[Jimbob54]

If that's true, I hope they made the non-pro async instead of the original sync setting which mades the sound break up every now and then. Personally not bothersome for me but others found it quite annoying.

Assuming sales were good I presume this means a revision/ lineup change is in the works- so yes, lets hope you are right.

 

[ympo]

I bought a similar product only under a different name - CharmTek HD audio on the same Qualcomm WHS9415 chip. I can say that for some reason its volume is higher than any other DAC. I listen to it on my headphones at volume 9-15 on Windows 10. If you do more, it's very loud. Perhaps it's not the chip, but the quality of manufacturing Dosmix. My CharmTek works even louder than the Meizu HiFi dac pro that I also have.

 

[Jimster480]

I bought a similar product only under a different name - CharmTek HD audio on the same Qualcomm WHS9415 chip. I can say that for some reason its volume is higher than any other DAC. I listen to it on my headphones at volume 9-15 on Windows 10. If you do more, it's very loud. Perhaps it's not the chip, but the quality of manufacturing Dosmix. My CharmTek works even louder than the Meizu HiFi dac pro that I also have.

Alot of the time these chips have a built in gain setting. They could have simply selected a higher gain setting when they configured the chip at manufacturing.

 

[338h10]

I'm giving my incompetent 2 cents here.

Imho the name of the problem here might be: "TPR22" spec sheet is totally misleading (read wrong) vs its real features.

Inside the box there is a WHS9415 dac-amp chip and apparently nothing else. No downstream amp I mean, unlike on the Meizu.

I dug I bit around
The WHS94xx family includes 4 chips.
9420 has the same specs as 9415 with the addition of ANC circuitry. Fair enough.
This distinction is interesting insofar as online I found this : 1543460058893017551.pdf "WHS9420 USB Interface Audio Codec Device Specification"

Page 22: Single Ended Output Performance, at the bottom:
- Full Scale Output Performance (PCMI): 0,95- 0,99 Vrms
- Output power (32Ohm load) 27 - 30mW
- Supported loads 4 - 32 Ohm <----- VEEERY different from 16-600 in'i ?

Put like that, the TPR22 has simply never been what it is apparently marketed for, that is, a dac amp dongle supporting headphones (too)

I personally use it to drive my E5000 (14Ohm) on which it produces great SPL, and very resolved sound already at 28-30/100 volume scale. With no perceivable distortion artifacts noise etc.

Yes, the volume scale appears absolutely "worng".
My suspect was that the chip's volume control is exclusively linear vs logarithmic.
After reading Amir's findings, may it be a wrong wiring or sort of ? It looks like someone set a "volume endscale" of 2V onto a chip which is only able to deliver 1V - that would sound "consistent" with Amir's finding it going nuts just about after halfscale (?)

As I said, my 2 cents nothing more

Just got my Charmtek TPR22 yesterday, which should be the same as Dosmix. Agreed that anything beyond volume level 52 was heavily distorted. Also with Win 10's USB audio 2 driver and ASIO4ALL, PCM only goes up to 32-bit, 192Khz (which is fine for 95% of my collection). Below 52 though, the sound appears normal.

I am using it in a desktop setting, feeding the DAC with a 5v linear regulated supply (multi-stage, which is an overkill), and having it feed into a speaker amp with 22k ohm input impedance. TRP22's outputs have minimal DC, as after 22x voltage amplification, I am only getting 2mv at my speaker amp's outputs -- my DIY speaker amp has zero DC blocker/servo, so I have to be very careful what feeds into it. Bravo! I have not seen any indication that the QUALCOMM chip uses any output capacitors to block DC, so the chip appears to be well-designed in this regard.

My amp also has zero high-frequency noise filter (i.e., no shunt capacitors at the inputs and no compensation network). So far, it runs perfectly stable and cool, meaning that the TRP22 appears to have functional filters at its outputs. Once a filter-less PCM5102A-based DAC caused my amp to oscillate because that DAC natively outputs some out-of-band noises.

Subjectively the sound is comparable to my Tempotec HD Pro, but with thicker body (or perhaps somewhat shelved highs). This may have to do with the 22K load it is facing, as the QUALCOMM chip appears to be designed for only low-impedance loads. With the Tempotec though, I get about 14-20mv at the speaker outputs (i.e., less ideal, but still tolerable for speakers).

Tempotec HD Pro is still my benchmark for this type of DAC, but I somehow feel like enjoying the music more with this DAC. For ~$20 delivered to the US, not bad at all -- what an amazing era we live in, as this level of D/A conversion would have cost thousands just 15 years ago.