SOtM SRC (Sample Rate Converter)

SOtM SRC (Sample Rate Converter)
In my review of the SOtM sDP-1000 DAC/Preamp, I neglected to cover an important feature, the SRC options. There are a total of four settings; off, SRC1, SRC2, and SRC4 which you select using the supplied remote. You press "Set" and "Mute" simultaneously to engage or disengage the SRC and then the "Set" and "Up" buttons are used to cycle through the different options. An unusual aspect of the SOtM SRC is its just that, a sample rate converter and not an upsampler. Well it is, sometimes.

Common to all of the settings, except "off", is the incoming data being converted to a bit depth of 32. The USB input differs from the S/PDIF inputs in terms of the sample rate conversion. For the USB input, incoming PCM data at 44.1Khz, 88.2kHz, and 176.4kHz is converted to 44.1kHz for SRC1. These same incoming rates are resampled to 88.2kHz for SRC2 and to 176.4 for SRC4. Incoming 48kHz, 96kHz, and 192kHz data is converted to 48kHz for SRC 1, 96kHz for SRC2, and 192kHz for SRC4. For the S/PDIF inputs, all incoming data is re-sampled to 48kHz for SRC 1, 96kHz for SRC2, and 192kHz for SRC4. DSD data is not affected by these settings.

That's right, unusual but right. For example, if you send 16/44.1 data to the SOtM sDP-1000 via USB and have SRC1 selected, it will be converted to 32/44.1. If you then send 24/96 data using the same setting, it will also be converted to 32/44.1. If you then select SRC2 and send the same 16/44.1 data, it will be upsampled to 32/88.2 where a 24/96 file will be converted to 32/96. Confusing? So the sDP-1000 upsamples, downsamples, or leaves the sample rate alone depending on the source file and the SRC setting selected.

I used the USB input of the sDM-1000 connected to the SOTM sMS-1000U server to take these filter settings for a test run. The differences noted were on the very subtle side or very difficult to differentiate between depending on the source file. Differences were also most notable on 44.1kHz data and due to the behavior of the SRC, I'd say it makes the most sense to use it as an upsampler but seeing as its simple to change settings with the remote, you are free to experiment.

My preference was for SRC2 with 16/44.1 data which seemed to fill out the overall sound picture with more body and presence. Music simply sounded a bit richer and more full-bodied, something I felt the sDM-100 lacked without any filter applied. SRC1 did not change the sound to a noticeable degree while SRC4 sounded a bit incisive and a touch on the tipped up side.

I did try a few higher sample rate files through the lower sample rate conversion settings and I preferred playing back higher resolutions in their native format. While the difference with downsampling were again subtle, I felt the sound was more restricted and less natural-sounding. On a practical note, while the SRC selection shows up on the sDP-1000's display, it is too small for me to see from my listening seat. So unless I remembered which setting was which, I was flying blind. When this occurred, I would simply switch settings until I found the one I preferred most and this nearly always turned out to be SRC2 with 16/44.1 files.

A Useful CD Tool
The takeaway on the SOtM Sample Rate Converter from my perspective is it a useful tool for CD-quality files where upsampling to 32/88.2 using SRC2 offered a more full-bodied and richer presentation, more akin to the sound of native high resolution playback.

COMMENTS
sauerball's picture

Now I can like mine better.  

Kidding, of course.

Other than some difficulty getting DSD to work with my Mac mini (although no problems with a Windows 7 machine) and the writing on the remote flaking off, I have been very happy with the sDP-1000.

Audreal's picture

Hi "sauerball",

I am not sure what country you are in but I would be glad to help you with your remote control issue.

You can send me a personal message with the contact button at http://audreal.us/

Eric Hudgens

Tailored Technology

OU812's picture

I auditioned oppo bd-105. mytek 192-DSD and the much hyped Auralic Vega. I heard very little difference between them. The SOTM was easy to distinguish and my loudspeakers "disappered" when playimg back music. Ony con is the np dsd128 support and batteries.....overall much better than Vega..much more transparent, playback with cd's were oustanding! the remoet control was much better than the Auralic

Archimago's picture

Is the upsampling using a minimal phase filter vs. tranditional linear phase filter for example such that the sound may be affected?

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