Oversample to DSD128 Into DS SR via USB?


#1

I was given advice specific for the Directstream DAC on another forum to upsampe everything to DSD 128 in the playback software, as this reduces the processing in the DS DAC. This would be going from a uRendu to the USB input. Is this correct?


#2

IMO that is silly advice and ignores what the DS is designed to do. With that logic I believe one would be better off with a much cheaper DAC if they are going to use inferior filters and algorithms upstream.

If you are upsampling in software you are going to have odd math as 44.1/88.2 etc… are not divisible equally to 2xDSD. That is one big benefit of the 20xDSD in the DS.

Also, all of these guys online doing upsampling, i’ve seen the settings and they are all over the place. Half of the people are introducing major aliasing into the equation, and the other half are randomly changing the min phase/lin phase settings until they sound right. What they are really doing is tweaking the settings until they counteract the negative effects they introduced by doing the upsampling in the first place.

I only have the SGCD and I have compared DSD from nativeDSD, PCM 44.1 from Tidal, and the PCM converted to DSD in software. Both the DSD and PCM sound great, the PCM to DSD converted sounds like something got lost in the process… life was sucked out.


#3

Whoever gave that advice knows nothing about the DS and/or FPGAs: in FPGAs (at least the ones we are using) all of the work is done all of the time, the logic just picks the answers it wants and ignores the rest.

Some prefer the sound of differing upsampling algo’s and that’s fine, they just shouldn’t try to justify their choices with faulty logic.


#4

Thanks for the replies they are very much appreciated and helpful.

I’ve been using the Bridge II and getting great sound, but last weekend tried USB with a Sonore ultraRendu powered by an Uptone Audio LPS-1. It came with a Roon trial and I see Roon allows upsampling and other tweaking. I’m more the type that just wants to listen to the music, but I’m willing to make a few adjustments if they are known to be beneficial. Are there any recommended for Roon?


#5

Before I bought the DS two or three years ago, saw a YouTube video of Ted explaining some of how it works. It was fascinating and I tried to transcribe part into a Word doc to help understand it. I just found the document which would have been useful to answer my own question. Here’s part, which could have inaccuracies since I was just typing what I thought I heard:

DirectStream takes any input, up samples it times 10 and takes it into a 55 bit word. Doesn’t matter if you input in a 16 bit word, 24 bit word or 1 bit word like DSD, it up samples everything to the same 55 bit word, 20 of those are used for the volume control and the other 30 bits are used for the music. Everything is up sampled to 50 MHz then goes through all the processing then taken back down to 2X the DSD rate of 5.6 MHz, goes through sigma delta modulator and comes out as single bit. Then goes through the output of DirectStream which is not an analog stage, instead an audio transformer that is the low pass filter that you need to clean off the high frequency stuff.


#6

Watch the LPS-1, the stock power supply used to power it is very noisy and nasty.SMPS … I would not recommend plugging it in the same strip as any of your other equipment.


#7

@jeff-s
Since you already have access to a mRendu, why don’t you try to listen for differences in sound between the two. I don’t have Roon but I do have Audirvana+ , an ultraRendu, a DS DAC with the BridgeII module. With Audirvana+ I can switch between upsampling/filters and no SRC (Sample Rate Conversion) and listen for myself. I am sure Roon has the same feature.

Try it for yourself and let us know what you think.


#8

@rodrigaj
Since you are using an ultraRendu are you ever using the BridgeII module in your DS DAC? I assume you have something like a MacMini with Audirvava+ and Ethernet out into your uRendu and USB into your DS DAC.

I will take your advice and listen using Roon with and without upsampling. Have to learn how first, I just installed it last weekend, had time to listen for a couple hours, and will have time again this weekend.


#9

@jeff-s
I am currently using the BridgeII module for only MQA / Tidal unfolding using mConnect.

You are correct. I have a mac mini which serves as my stand alone Audirvana music server attached to my network. This gets Audirvana off of my iMac.

My long term strategy is to be 100% Octave, replacing the BridgeII with the new Octave compatible Bridge and getting rid of the ultraRendu, the mac mini and the associated power supplies.


#10

@rodrigaj
I’m also very interested in the Octave compatible Bridge.

Prior to getting the uRendu I was using the BridgeII module for MQA / Tidal as well. In addition to streaming my ripped CDs with JRiver to the BridgeII. Can I leave an Ethernet cable going from switch to BridgeII at the same time switch > Ethernet > uRendu > USB > DS DAC? Probably. Then I could easily compare Tidal via BridgeII vs. Tidal via USB / uRendu.


#11

@jeff-s
You can leave everything connected. Your switch would have two CAT5/6 cables going to your music room. One to the BridgeII and the other to the ultraRendu.

If you are a purest you would then use something like OpenHome emulation with BubbleUPnP Server and Lumin App and you could switch easily between renderers (BridgeII vs ultraRendu) via the Lumin App preferences (little gear icon) on your iPad. That would be the best way because then the only variable is the renderer.

Otherwise, just try them whichever way is convenient (i.e., mConnect on the BridgeII and your favorite MPD/UPnP Tidal App for the ultraRendu).

There are probably other ways to make the comparisons but the point is that you can leave everything connected.

BTW, there are folks that would argue the BridgeII is producing noise, etc. If that sort of thing bothers you just disconnect the BridgeII ethernet cable when testing the ultraRendu. Disconnecting at the switch is probably the easier way to do that (no fiddling at the back of the DS DAC).


#12

I’ve also read, and a friend tried it and claims it’s true, that if you are using USB input, just having the Bridge module installed creates noise and should be removed. The claim is that the bridge module makes a fair amount of RF noise inside the DAC chassis, even when not in use, and you will get better sound quality with it removed.


#13

Put another way: the biggest sources of noise with many audio boxes (including the DS) is thru ground loops. To give a connection the best chance of sounding like it would if you had all unused cables disconnected, you should disconnect all unused cables (preferably at both ends, but the destination end is often a close second.) The obvious example is that when testing an optical link you need to disconnect all of the other cables or you’re not really getting the isolation that optical offers.


#14

Pulling the BridgeII out of the chasis has to be done properly. ESD station, ground strap, ESD storage bag for the BridgeII. It is not a trivial card swap. Much safer to just leave the BridgeII and disconnect the cable. It is certainly not something to do multiple times to see if you can hear a difference. Gate arrays are notoriously ESD sensitive.


#15

Good point, thanks for the reminder. I’m not in a hurry to do it anyway.


#16

Why?

When used with the LPS-1 (grounding the Mean Well’s DC plug) most leakage is blocked.


#17

Yes you block stuff coming in one way but how about the back end?

Two main reasons

(1) it’s generally not good practice to have an smps like that plugged in to a strip that would contaminate your other components.

(2) the stock supply has been shown to backwash noise into the mains line. This has been conducted on the original meanwell so it’s not conclusive for the new supply with the 1.2 version.


#18

Current travels in loops though, no?

Who has said this? I’ve seen this comment thrown around a lot but never seen it explained. I ask politely and respectfully of course.

Same as above, I’ve seen this thrown around a lot but never seen any audio gear designers confirm this - RF and ground loops and leakage currents yes, but backwash noise I haven’t seen any audio gear designers say this is an issue but it gets thrown around a lot by people. Did you watch the video I linked above?

Again, I ask politely and respectfully of course, for learning purposes, not to challenge anyone’s beliefs.


#19

Switch mode power supplies come in various versions with differing noise generation.
More detail than you want: https://origin-www.maximintegrated.com/en/app-notes/index.mvp/id/986

In general the inductor in a switch mode power supply is the energy storage and it can’t instantaneously change current. But the switch is where there are sharp discontinuities in current. The problem with quick current changes is that they radiate RF and are also hard to filter.

Step down (buck) switch mode power supplies (can) have the continuous current at the output and further the output is filtered somewhat. But they send gobs of spikes back to the source since they that’s where the current is switched on and off to regulate the output.
image

Step up (boost) switch mode power supplies are sort of the opposite, they are politer to the input and generate the spikes mostly to the output:
image

There are ways to mitigate these things, but in general with cheap (wallwart) SMPS you get a lot of hash.


#20

Cheers Ted.

When you say back to the source, what is the source ? The SMPS itself (a loop path back to itself)? Or even further upstream?

If the source is the SMPS itself and you break the loop path (at the SMPS output) then nothing gets ‘put back’ into mains power? In theory anyway?