SMSL DO400 Fully Balanced Audio Decoder & Headphone Amplifier

[Roland68]

@Roland68 Did you have a chance to compare these?

According to Amir's measurements, the D40 Pro HPA starts to have some distortion for load impedance below 300 Ohms. At 12 Ohms they are still below ca. 95dB - clearly below audibility to my opinion.
Technically this surely is avoidable with more care given to the PCB artwork.

I compared the HPA of the DO400 and the SP400 with the Hifiman HE6se V2.
When switched to high gain, I couldn't turn both up all the way. But the DO400 seems to be the one with the slightly larger headroom. I also couldn't find anything in the HPA of the DO400 that bothered me, nor anything that indicated distortion. When it comes to performance, it doesn't matter that the HPA in the DO400 is "only" SE.
If that's not enough for you, you should go for an amp with at least twice the power.

 

[nanook]

HPA in the DO400 is "only" SE

Thanks a lot for this assessment. So the HPA in the DO400 not only has lots of power, but it sounds on par with a really good separate HPA if I got you right.

Once I have a 4-pin XLR connector I can measure the HP-output. I'm curious if the PCB-layout DO400 is indeed different and yields lower distortion compared to the Loxjie D40 pro at high levels and low impedance.

The HP-output is balanced - there are 4 pieces of the driver IC, so the balanced connectors are indeed wired differential.

 

[Roland68]

Thanks a lot for this assessment. So the HPA in the DO400 not only has lots of power, but it sounds on par with a really good separate HPA if I got you right.

Once I have a 4-pin XLR connector I can measure the HP-output. I'm curious if the PCB-layout DO400 is indeed different and yields lower distortion compared to the Loxjie D40 pro at high levels and low impedance.

The HP-output is balanced - there are 4 pieces of the driver IC, so the balanced connectors are indeed wired differential.

You seem to be right about the balanced output. I assumed, since SMSL did not provide any additional information on the performance and other values of balanced and SE, that 2 of the TPA6120A2 were connected in parallel.
But the SE output is quieter than the balanced one at the same volume, so it does seem to be balanced.

Since there is no switching between the individual HP outputs, you should definitely not plug in SE and balanced headphones at the same time.
I would be very happy to see measurements of the HPA.

 

[arrow0309]

You seem to be right about the balanced output. I assumed, since SMSL did not provide any additional information on the performance and other values of balanced and SE, that 2 of the TPA6120A2 were connected in parallel.
But the SE output is quieter than the balanced one at the same volume, so it does seem to be balanced.

Since there is no switching between the individual HP outputs, you should definitely not plug in SE and balanced headphones at the same time.
I would be very happy to see measurements of the HPA.

And I thought exactly the same lol.
Just like my ex DL300, only more powerful.
Good to know, nice to know!

 

[nanook]

I think the DO400 is quite well equipped given its nominal price.
So far I had a look at distortion (1kHz), Multitone spectrum and jitter with USB, Coax and Toslink (the last two with PO100-AK as source). All of this looks pretty much perfect.
(ADC is Ivan's Cosmos ADCiso with APU for THD and SINAD.)

SMSL does not advertise the CK-03 clocking circuit, but comparing the layout and chips with other SMSL DACs, it might be there is at least something similar included.
The jitter spectrum for Coax and Toslink is just perfect and with USB there are a few tiny sidebands at - 155dBc

I will post some of the measurements when I have a bit more time.

 

[arrow0309]

They've contacted me back from SMSL, I told them that I've solved with the firmware flash (for now) and I'm also away for some time.
I'll test the standby power / connection issues ASAP and we'll take it from there.
I really want to keep this one now, for good.

 

[nanook]

Did SMSL comment on the firmware being taken from their website?

 

[Longfellow78]

I have not yet emailed SMSL yet, since I was hoping someone could confirm my observations.
But of course, SMSL can check this easily, so maybe SMSL is following this thread.

@SMSL-Mandy: Can you please initiate that the design crew double-checks that the PCM filter name in the display matches the actual filter response (impulse response and frequency response)?
In case they are mixed up indeed, please provide us with a corrected firmware.

For details see: https://www.audiosciencereview.com/...ecoder-headphone-amplifier.47766/post-1981982

For the D-6s, the PCM filter description given in the manual does not match reality as well according to my measurements - since just a number is displayed, an update of the manual would do.

Hello. I am on v3. I am a noob and please could you advise. Given the "wrong" names for the filters, which corresponds to the most widely used or appropriate filter (misnamed) for general use. I will not be going in and changing it for different genres and headphones. Just want to make sure I get the best and most rounded "default" sound. Thanks.

 

[Roland68]

The FW update sequence that finally worked for me:

- DO400 is plugged in (mains and USB), but power switch at rear of unit is "off"
- install SMSL driver (not sure if it is really needed for FW-update)
- unpack "DO400MCUVA3.rar" (contains zipped loader directory "ISP_PC_EN2" and hex file "IAP_DO400_1V0A3.hex")
- unpack "ISP_PC_EN2.zip" to the desktop and make sure there is only one level of folder "ISP_PC_EN2"
(I moved all files one level up such that the loader "ispV2.4.exe" and all other files reside in "C:\Users\xxxxx\Desktop\DO400\ISP_PC_EN2\")
(the executable e.g. is now located here: "C:\Users\xxxxx\Desktop\DO400\ISP_PC_EN2\ispV2.4.exe")
(I copied the hex file to this location: "C:\Users\xxxxx\Desktop\DO400\IAP_DO400_1V0A3.hex" to have it near to the rest of the stuff)
- start the executable "ispV2.4.exe" (the GUI should come up)
- make sure Device is "MM32F103xx_o" (upper right corner of the GUI)
- open pull-down menu "File -> open" and search for the hex file "IAP_DO400_1V0A3.hex"
- select hex file "IAP_DO400_1V0A3.hex"file and click "open" (after a few seconds the GUI freezes for ca. 30s)
- make sure only boxes "Run_Prog" and "vefify" are checked (I did separate runs for "Run_Prog" and "Verify", i.e. only one box checked at a time)
- press volume knob and hold it pressed
- cycle rear power switch and hold volume knob pressed for at least 5s
(display of unit should stay dark)
- GUI still shows "Disconnect" in red
- open pull-down menu "Options -> Connect"
- GUI should should show "Connected" in blue now
- click large button "Start_Program"
(A green bar should signal progress; it takes about 80s to program and 80s for verification)
- open pull-down menu "Options -> Disconnect"
(GUI should now display "Disconnect" in red again
- switch off DO400
- close loader GUI by clicking the "x" in the upper right corner

Please find attached the screenshots of the GUI after the "Run_Prog" and after the "Verify" run. Doing this in two separate runs assures you that the firmware was really updated.

In case something is not clearly described here, please let me know and I will update / correct these instructions.

My DO400 apparently still had the first firmware on it. After it was in standby for a long time yesterday and I wanted to play something on YouTube, there was just a huge screech from the speakers. Luckily nothing happened. The amplifier wasn't even turned up very loud.

I had to dig out a Windows notebook to upgrade the DO400 to the 3rd firmware.
Thanks again for the effort with the instructions.

@SMSL-Mandy , you are welcome to pass the following on to the technical and management teams.
But when it comes to firmware, SMSL is an absolutely botched company. I have rarely experienced anything so terrible, and in my time in IT I have upgraded several thousand devices. When you consider that this is a consumer device....
Every buyer will probably have to live with the errors with this device, as is now the case with some SMSL, Sabaj and Loxjie devices.
The same applies to the development of the devices. How can you deliver devices that have such problems? A fault like the screeching noise on the DO400 can damage speakers, headphones and even your hearing.

 

[RedEyeNinja]

Here's a review I wrote on another forum about my testing of my SJY Audio Horizons, 25ohm magnetic planars, that some are saying are as hard to drive as Tungsten, requiring a hotter signal...

"Just to share my continuing experience with the Horizons.

I have been running them balanced with xlr from a DO400 w/ 6w@16/3w@32. Tho adequate I wanted to see what they can do with more watts. I’ve been running them now on a SP400 w/ 12w@16/6w@32 and I notice about a 10 to 20% improvement in layering, resolution, soundstage and headroom. My reference tracks for this test was the “Tropico 6 OST” With the DO400, I run the Horizons @ high gain between -10 to -5dB. With the SP400, I’m running them @ 85 to 90 out of 99 on high gain but this THX amp is a low gain design.

I will likely be trying a H400 w/ 15w@16/7.5w@32 and a high gain design."

 

[Roland68]

I think the DO400 is quite well equipped given its nominal price.
So far I had a look at distortion (1kHz), Multitone spectrum and jitter with USB, Coax and Toslink (the last two with PO100-AK as source). All of this looks pretty much perfect.
(ADC is Ivan's Cosmos ADCiso with APU for THD and SINAD.)

SMSL does not advertise the CK-03 clocking circuit, but comparing the layout and chips with other SMSL DACs, it might be there is at least something similar included.
The jitter spectrum for Coax and Toslink is just perfect and with USB there are a few tiny sidebands at - 155dBc

I will post some of the measurements when I have a bit more time.

I think that the CK-03 clocking circuit is also present in the DO400, as the same circuit can be found in the DO300EX. In other devices they put this cover on for the shielding, but strangely not over the quartz.
I suspect that this circuit is a self-written application that replaces the transceiver chips on the one hand and implements MQA for SPDIF, Toslink, etc. on the other.
I would personally prefer a combination of AK4118 and AK4137.

Would you also like to measure the DO400 with the external USB interface SMSL PO100 Pro (via i2s)?

 

[nanook]

Hello. I am on v3. I am a noob and please could you advise. Given the "wrong" names for the filters, which corresponds to the most widely used or appropriate filter (misnamed) for general use. I will not be going in and changing it for different genres and headphones. Just want to make sure I get the best and most rounded "default" sound. Thanks.

SMSL DO400 Fully Balanced Audio Decoder & Headphone Amplifier

Edit: Corrected comment for #8, Low Dispersion Dirac measurement and spectrum at Fs=44100 Updated slides for PCM filter options. According to my measurements the description of the PCM filters in the menu of the DO400 is wrong for several of the filter settings. Since people experiment with...

www.audiosciencereview.com

 

[nanook]

I think that the CK-03 clocking circuit is also present in the DO400, as the same circuit can be found in the DO300EX. In other devices they put this cover on for the shielding, but strangely not over the quartz.

I had the same impression comparing it to the DO300EX. Looking at the jitter spectra that I measured, there's no reason to worry about jitter.

Would you also like to measure the DO400 with the external USB interface SMSL PO100 Pro (via i2s)?

I don't have the I2S version PO100 Pro and thus no I2S source. I was about to order it when I came across the PO100-AK and I felt the analog output would be more useful. Regarding the PO100-AK: The performance of the analog outputs of this small USB-powered DAC is impressive.

 

[Roland68]

I had the same impression comparing it to the DO300EX. Looking at the jitter spectra that I measured, there's no reason to worry about jitter.


I don't have the I2S version PO100 Pro and thus no I2S source. I was about to order it when I came across the PO100-AK and I felt the analog output would be more useful. Regarding the PO100-AK: The performance of the analog outputs of this small USB-powered DAC is impressive.

That's why I'm asking. Since I'm also interested in these measurements, I would send you a PO100 Pro including all cables. I can do without it for 2-3 weeks.

 

[nanook]

That's why I'm asking. Since I'm also interested in these measurements, I would send you a PO100 Pro including all cables. I can do without it for 2-3 weeks.

Sure, measuring the Jitter spectrum is not a big thing and the ADCiso from Ivan is doing a really good job.
I have never used I2S, so I'm quite curious if the performance matches what we're used to on the other inputs.
It won't take long, I can return the unit within a few days.

@Roland68: I will contact you via PN when it makes sense to send the PO100-Pro.

 

[nanook]

Isn't it strange, that SMSL does not comment on the weird firmware situation (firmware files removed for several products)?

@SMSL-Mandy: Can you give us a clue what's going on and what we should expect?

 

[nanook]

Jitter Measurements on SMSL DO400:
Stimulus: REW JTEST, 48kS/s
Source for Coax and Toslink: SMSL PO100-AK
ADC: Cosmos ADCiso, 48kS/s

The spectra are pretty much clean.
- USB shows some lines at -146dBFS and a bit wider skirt
- Toslink shows a slightly broadened skirt with DPLL = 5 (default); with DPLL = 1 or 15 it looks better
- Coax shows a slightly broadened skirt with DPLL = 1; with DPLL = 5 or 15 it looks better

 

[iTuner]

When I had a problem with the firmware update for my DO-400, I contacted SMSL technical support, but I received a response from Amanda from AOSHIDA .
Devices of the DO/AO/HO series are supported by AOSHIDA.
Try contacting technical support via email at [email protected].
This way, your information will be more likely to reach the engineers quickly.

 

[Longfellow78]

SMSL DO400 Fully Balanced Audio Decoder & Headphone Amplifier

Edit: Corrected comment for #8, Low Dispersion Dirac measurement and spectrum at Fs=44100 Updated slides for PCM filter options. According to my measurements the description of the PCM filters in the menu of the DO400 is wrong for several of the filter settings. Since people experiment with...

www.audiosciencereview.com

Thanks. Forgot I asked this twice.

 

[Longfellow78]

Looking at my measurements I would choose #3 (Menu: "Apodizing") which is steep and rolls-off early, so it provides good attenuation at Fs. My guess is that this actually is the one ESS labelled "Linear phase fast roll-off" in their datasheet. It is the only steep filter that rolls-off earlier than all of the others.

In case this one rolls off too early to your taste, #4 (Menu: "Linear Fast") would be an alternative. It also rolls off steep but at a bit higher frequency.

If you prefer minimum phase filters (no pre-ringing, more post ringing) #2 (Menu: "Minimum Phase) or #7 (Menu: "Minimum Slow") would be an option. They provide a steep roll-off and similar attenuation as #4

The attenuation at Fs is not really readable in my measurements due to the large frequency span and the log scale. I was hoping to identify the filters comparing them to the frequency- and impulse- response given in the datasheet, but some of them appear to be quite similar.
What's also weird is that many of the filters they show in the datasheet have a steep roll-off down to -60dB only, whereas I measured a steep roll-off down to ca. -100dB.
(I'm referring to the datasheet version ES9039MPRO_ES9039PRO_v0.2.1.pdf)

I'm actually not optimistic they will build new firmware...

This is useful thanks. I'm also hyper treble sensitive and get ear pain for a couple days after wearing some of my too bright headphones. Would apodizing also be best for this? Thanks.