Rossini Transport upsampling confusion

I’m getting this topic out of my other thread on using Clock.

I need to clarify/validate a few of my understandings regarding using Rossini Transport with Rossini Dac (no clock).

  1. If I use both AES1+2, there is no way I can stop Transport from upsampling the PCM 16/44.1 data from regular CD. So the DAC will always get DXD data as input.
  2. SACD data would be always sent to the DAC as DSD data. Then DAC’s level upsampling would be applied.
  3. DAC has the intelligence to change the upsampling for a specific input sources (in this case AES1+AES2). So if I set for DXD input the upsampling to be DXD it will continue to do that (or do nothing). And say if for DSD input I have set it to DSD2 then it will upsample the DSD input to DSD2.
  4. If I enable PCM (which I typically don’t do because of some suggestion in the manual), then at SPDIF level I shall always get 16/44.1 data. But in that case the DAC will read the clock information from the Transport sent over spdif.
  5. I cannot use AES3 of the transport if AES1+2 is used (because Rossini Dac does not have 3 AES inputs).
  6. Neither I can use AES1+AES3 as a pair so that for DSD the transport automatically use both AES but for CDs use AES3 (or AES1) without upsampling.

Any inputs ?


1, Yes. Unless playing an SACD the output from dual AES will be DXD or DSDx2 ( as selected) when playing CD. To play CD natively you need to use AES 3 or S/Pdif.

2 and .3 Playing SACD will output using AES1 +2. This will be DSD64 and be processed as sch by the DAC. I don’t think that native DSD can be upsampled. The instruction manual only refers to an upsampling stage to DSD for PCM as far as I understand it ( p.39 in the v.2 manual). However I if anyone wishes to correct me please do.

  1. Yes if synchronisation is set to A.With an external clock, synch would be set to W and timing will be referenced to the wordclock. The timing with S/Pdif isextracted from the source rather than the transport. So preferable without a system clock is to slave the transport to the DAC’s wordclock output with synch set to Master. The transport and DAC are then in synch.

5.Yes, you would need to swap cables to use either dual ( 1+2) or single (3) AES with Rossini. I guess dCS decided a three AES input could be sacrificed to reduce cost as it is there with Vivaldi.

  1. Correct. You would need Vivaldi to do this without cable swapping. I would use AES 1+2 for DSD and S/Pdif for native PCM. Is there a notable audible difference between dual AES and S/Pdif for native PCM ( CD)? Not that I have noticed but I guess it depends on all of the cables being of similar quality.

Thanks @PAR for validating my understanding.

I have not really tried spdif output for CD much. Kind of ok with AES1+2 with dxd upsampling for CD.

The reason for this topic is to check if I am missing any other possible optimal use of Rossini Transport with Rossini DAC which has clearly better perf benefit.

Especially if the upsampling stage in the Dac is better than upsampling at transport level as suspected by @Anupc

What frustrates me is why dcs has not provided a clean way (without the hassles of changing the wire etc) to send cd data without upsampling to the dac especially when someone wants to use the transport for both cd and sacd ( and clearly the transport is meant fot that, right ?) connected with its logical/legitimate partner Rossini dac.

It is a serious usability issues IMHO.


AS I said earlier , use the S/Pdif output to the available S/Pdif input on the Rossini DAC. I have not found any audible difference between this and AES 3 transport output using XLR or coax cables from the same range.

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Sourav, in fact, the Rossini Transport Manual tells you exactly how best to set it up when connected to the Rossini DAC (without the Rossini Clock), specifically page 12.

  • AES1+2 interconnect between them
  • DAC’s Word Clock OUT (and Master Clock setting) to Transport’s Word Clock IN
  • Additionally, as Pete suggests, connect SPDIF1 on the Transport to SPDIF1 on the DAC.

The above configuration will give you the best sound (with lowest jitter performance), and the ability to A/B compare upsampling on the Transport vs. upsampling on the DAC by just changing source inputs on the DAC back and forth. You won’t need to change anything on the transport, nor the interconnects.

Thats spot on Pete. dCS does not upsample native DSD (from SACDs or media streams).

In order to upsample DSD, one would have to apply a low-pass filter, followed by decimation, and then delta-sigma conversion.


Thanks @PAR . I’m trying this now with spdif1.

The transport is automatically syncing with the master clock of the DAC (showing M in DAC). That’s pretty neat.

I have never tried this option before because the manual says that keeping PCM output off provides a quieter electrical environment when AES1+2 is used.

Too early to say whether this route (spdif output of 16/44.1 from Transport and then DXD upsampling in DAC) is better than doing DXD upsampling at the Transport level.


After almost 2 weeks of trying both spdif (no upsampling in transport) and aes1+2 (upsampling in transport) based options I kind of settled back to aes1+2.

The sound from aes1+2 is much musical to my ears compared to the same from spdif one. Though spdif one is sometime more punchy for bass heavy songs.

The aes1+2 sounded even more interesting when in between I tried Rossini clock in my setup. I found it got more benefitted with clock than all other sources including network music from Roon.

Thanks everyone here to help me find out the way to do a/b comparison.


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