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Bad practice to use USB DAC and stream from USB hard drive?

ToTo Man

ToTo Man

the band not the dog
I realise part of a dying breed who still streams music from local storage, but I'll ask anyway.

When I was optimising my digital playback setup almost a decade ago, I used to frequent the ComputerAudiophile forum for advice (it's now called AudiophileStyle). There was a strong consensus that the drive on which your media is stored should NOT be connected to your computer using the same interface as your DAC, in order to avoid bottlenecks and noise being injected into the DAC. i.e. If your DAC was connected bu USB, your external hard disk should be connected by FireWire, eSATA or Ethernet.

See this thread for example:
https://audiophilestyle.com/forums/topic/14933-any-harm-using-usb-external-hdd-with-usb-dac/

I've followed this advice for almost a decade. I started off with a portable bus-powered 2TB WD MyPassport FireWire drive, then when I outgrew that I bought an OWC Mercury Elite Pro FireWire enclosure and installed a 6TB WD Blue HDD.

I'm now at a crossroads. Having filled the 6TB external drive to the brim I need more space, so I either pay over the odds for a 10TB WD Red drive and install that into the OWC enclosure, or for the same sort of money I could buy a 14TB WD Elements external USB drive. The latter of course necessitates that I connect the drive to my 2010 Mac Mini by USB instead of FireWire.

My Mac Mini has a total of 4 USB ports. I often have two DACs and a UMIK-1 microphone connected at any one time, and I can't say I've noticed any difference in the performance of the DAC I'm listening to whether or not these two other devices are connected. An external hard drive may however be another kettle of fish, as the data transfer rates involved are likely to be much higher.

Does anybody have first-hand experience of a worsening in audio performance from their USB DAC as a result of streaming music/video from an external HDD that's connected to their computer by USB instead of FireWire? Or is this a prime example of audio nervosa?
 
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My local music is on a USB drive connected to an old Mac Mini. The Mac Mini also feeds a DAC via USB (a Pro-ject Pre Box S2 Digital). The Mac is running Roon Core. Control is anything laying around - a PC laptop mostly, or a modern Ipad if the wife is not using it, or even an Iphone. The Mac Mini runs mostly headless, but there is also an HDMI lead running to a nearby TV, upon which I can display what is playing - and a simple keyboard and mouse is knocking around to restart Roon if it gets stopped for any reason.

Darned if I can hear any problem at all with the arrangement. A lot of this talk about multiple devices on USB is more theoretical than actual. If the USB Dac is properly designed why would any noise get into it? Anyway computer hardware is designed to have multiple I/O streams, all working. Handling audio, even HD, is an almost trivial task to a modern computer - and within the computer it is not audio anyway - just another bunch of data to process as instructed. There may be a bigger workload if DSP is in use - but that is about the power of the computer not the noise.
 
From a quick search it seems your OWC firewire drive also has a USB port, so you could hook it up that way and have a listen.

And 6TB? Thassalorratunes mate.
 
ToTo Man said:
I There was a strong consensus that the drive on which your media is stored should NOT be connected to your computer using the same interface as your DAC, in order to avoid bottlenecks and noise being injected into the DAC. i.e. If your DAC was connected bu USB, your external hard disk should be connected by FireWire, eSATA or Ethernet.
Click to expand...

That was the conventional wisdom, yes. The main culprit is USB, which keeps polling for attached peripherals, generating noise. Think of it as the digital equivalent of three kids on the back seat of the car constantly asking 'are we there yet?' FW was designed to cope with higher throughput in a somewhat less frenetic manner.

I confess I've always stuck to the separate bus arrangement, largely out of habit. I use Audirvana, OS is on one SSD and the music library on another via a FW drive which loads files into RAM.

Does this still matter? In truth, I don't know, I don't really use files for any 'serious' listening these days, so don't pay much attention. Audirvana will 'optimise' playback on a Mac by shutting down or minimising a lot of background processes, at one time it was necessary to roll your sleeves up in the Terminal app to do that.

I guess the best approach is suck it and see with an existing USB drive. A 2010 mini has 2 USB busses, I'd suggest have the DAC on one and external storage on the other. You can use 'System Information' to identify what's attached to which bus.

Any degradation in 'noise' will likely show up as forwardness or a false impression of 'added detail,' but to be honest I can't imagine it's going to be 'night and day.'
 
I forgot to mention I do use Audirvana+ for music playback (in iTunes integration mode, - yes I'm one of those weirdos who actually likes the iTunes GUI, plus it works seamlessly with the Remote app on my iPhone). For video playback I either use the DVD Player app for my DVD rips (I've ripped a lot of music DVDs as disc images using the now defunct RipIt app), or Elmedia Player and VLC for mp4 and high def video downloads. I presume these apps play the videos in real time and do not buffer them into RAM.
 
deebster said:
From a quick search it seems your OWC firewire drive also has a USB port, so you could hook it up that way and have a listen.

And 6TB? Thassalorratunes mate.
Click to expand...

Good shout, deebster. I did try the USB port on the OWC briefly a few years back and couldn't hear any difference, but I didn't really know what I should be listening out for.

FYI - My iTunes library is around 3TB, the rest is DVD rips of music concerts. It's just as well ripping BluRays isn't an easy process on a Mac otherwise I may have jumped on the BR bandwagon and be in need of an 18TB HDD by now! :D
 
Like most wring on audiophile style it's total bollocks.

If you dac can hear your usb attached HD its a piece of 5hit not fit for purpose.

Audivarna on mbp with Internal ssd with music and os on same drive. Nothing I do on the computer is audible via the dac.
 
Simply, no, it's not a problem.

If it was a problem, it would have been limited to a given dodgy motherboard, or slow USB links back in the day, or machines without enough memory. These days, what will happen is what DV has pointed out, the file will be cached into memory by the operating system, and your playback software will just stream this to the DAC from RAM.

Let's do the maths. Assuming you are replaying CD quality uncompressed audio, this is 44100 * 2 * 2 bytes per second, so 44100 * 2 * 2 * 60 bytes per minute. This is roughly 10mb. Disk drives read data at around 100mb/second, so this means that there is 0.1 seconds worth of disk activity required for every minute of audio playback, and modern OSes just optimise this sort of sequential file access and cache ahead of use, so it basically will come in in one chunk.

So i'd not worry about it, and buy whatever disk tech you want, and let the OS worry about scheduling disk and audio interface stuff.

BTW, i've been in many studios, and they all use external USB interfaces and disk drives without any problems, and have done for years...
 
It really should not be any sort of issue. I have had the odd issue with basic USB DACs (that Maplins one everyone raved about was one culprit) that draw their power from the USB picking up some noise. Solution, butcher two USB cables and split the power off to a quiet USB plug in supply (Apple iPad one IME, Amazon one has a high pitched whine also evident if anywhere near a phono stage.) If the USB DAC is picking up extraneous noise on the data line it is, not to put too fine a point on it, hot garbage!
 
ToTo Man said:
I realise part of a dying breed who still streams music from local storage, but I'll ask anyway.

When I was optimising my digital playback setup almost a decade ago, I used to frequent the ComputerAudiophile forum for advice (it's now called AudiophileStyle). There was a strong consensus that the drive on which your media is stored should NOT be connected to your computer using the same interface as your DAC, in order to avoid bottlenecks and noise being injected into the DAC. i.e. If your DAC was connected bu USB, your external hard disk should be connected by FireWire, eSATA or Ethernet.

See this thread for example:
https://audiophilestyle.com/forums/topic/14933-any-harm-using-usb-external-hdd-with-usb-dac/

I've followed this advice for almost a decade. I started off with a portable bus-powered 2TB WD MyPassport FireWire drive, then when I outgrew that I bought an OWC Mercury Elite Pro FireWire enclosure and installed a 6TB WD Blue HDD.

I'm now at a crossroads. Having filled the 6TB external drive to the brim I need more space, so I either pay over the odds for a 10TB WD Red drive and install that into the OWC enclosure, or for the same sort of money I could buy a 14TB WD Elements external USB drive. The latter of course necessitates that I connect the drive to my 2010 Mac Mini by USB instead of FireWire.

My Mac Mini has a total of 4 USB ports. I often have two DACs and a UMIK-1 microphone connected at any one time, and I can't say I've noticed any difference in the performance of the DAC I'm listening to whether or not these two other devices are connected. An external hard drive may however be another kettle of fish, as the data transfer rates involved are likely to be much higher.

Does anybody have first-hand experience of a worsening in audio performance from their USB DAC as a result of streaming music/video from an external HDD that's connected to their computer by USB instead of FireWire? Or is this a prime example of audio nervosa?
Click to expand...

Archimago has a couple of entries on USB noise:
https://archimago.blogspot.com/2018/05/measurements-computer-usb-5v-power.html
https://archimago.blogspot.com/2015/05/measurements-usb-hubs-and-8khz-phy.html

If your DAC's USB input doesn't filter noise:
Can you connect you HDD to your router and access its contents?
Alternatively you can get a NAS (I bought a New Old Stock discontinued Synology for half price).

Another option is not to worry.
 
One (mostly theoretical) potential problem arises from multiple devices being attached to the same USB root hub, thus sharing the bandwidth. In realistic situations, this isn't much of a concern, however. Firstly, audio uses only a small fraction of the available bandwidth (unless you're streaming 32-channels at 192 kHz or something). Secondly, isochronous transfers (used by audio) have priority over bulk transfers (used by storage devices). The OS and playback software should buffer enough data that timing of disk reads won't be critical.

Then there's noise of various kinds. So-called packet noise often shows up as a low-level 8 kHz tone plus harmonics. This is caused by the USB interface drawing more power and/or producing more noise while processing a packet. If a DAC suffers from such noise to an unacceptable extent, it is unavoidable. It is caused within the DAC regardless of what else is connected to the same hub. Another possibility is noise generated by one USB device and carried by ground and power wires into another. Now all the parts of a PC and its attached peripherals share a common ground. Noise travelling there will have no trouble passing from one type of interface to another. Using Firewire or SATA will not help.

The good news is that these kinds of issues rarely occur in practice. A simple test is to play a silent test file and turn the volume up to max. If there's no audible noise then, there is no problem.
 
If you cannot hear a difference then do not worry about it. I think I understand the rationale behind this advice, but I am not sure it translates to real audible issues.
 
mansr said:
... Then there's noise of various kinds. So-called packet noise often shows up as a low-level 8 kHz tone plus harmonics. ...

The good news is that these kinds of issues rarely occur in practice. A simple test is to play a silent test file and turn the volume up to max. If there's no audible noise then, there is no problem.
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Exactly. And if someone has the tools and/or knowledge, a variant on this test (which I have done) is to write a WAVE file of USB "signature" noise at various low levels and listen to that at full volume (with suitable care!).

Learn first to recognize the signature noise at -100 dB FS and then go down in level, so that you can be sure of its absence at some point (-130 dB FS in my case, so there's no chance at all of it being audible at normal volume levels).

And this is with a humble and supposedly noisy Raspberry Pi into a USB DAC, with locally attached (solid-state) USB storage. I am not saying that local USB storage is never a problem, but it's clear that it can be perfectly OK.
 
I've routinely used a USB DAC to play files from USB conected SSDs as well as from an internal SSD and from a NAS. Never noticed any difference caused by the choice of storage or use of USB. Just works.

And FWIW using a 2i2 ADC via USB-powered link, I get a noise floor in the region of -120dB when doing FFTs to see the spectrum, with no sign of USB effects.
 
I've never seen 8k packet noise on the output of a measured usb dac, has anyone else?

Just because it goes in, doesn't mean it comes out.
 
ToTo Man said:
Does anybody have first-hand experience of a worsening in audio performance from their USB DAC as a result of streaming music/video from an external HDD that's connected to their computer by USB instead of FireWire? Or is this a prime example of audio nervosa?
Click to expand...

I've never tried this experiment, but doubt I'd be able to hear a difference. I have however used various Macs over the years.

The current M1 Mac Mini is in a different class, SQ wise, than the 2011 Mini. So I reckon it's worth upgrading the machine itself. And then you may eventually find yourself upgrading storage drives to faster USB or Thunderbolt 3. These are generally more efficient but it's not something I'd expect to be individually audible!
 
tuga said:
Archimago has a couple of entries on USB noise:
https://archimago.blogspot.com/2018/05/measurements-computer-usb-5v-power.html
https://archimago.blogspot.com/2015/05/measurements-usb-hubs-and-8khz-phy.html

If your DAC's USB input doesn't filter noise:
Can you connect you HDD to your router and access its contents?
Alternatively you can get a NAS (I bought a New Old Stock discontinued Synology for half price).

Another option is not to worry.
Click to expand...
Reading those Archimago articles makes me wish I hadn't asked. If my audio nervosa hadn't been triggered before it has now!

With regards to the 8kHz noise, if this is present on the DAC's USB input then will it be output to the amp even when there's no music signal, or would I need to create an audio file of silence in Audacity and play that back to see if I could hear it?

My ears are pretty sensitive to 8kHz (it's the main reason I don't get on very well with Beyerdynamic headphones!) so I hope I'd be able to identify it if it was at a level above the noise floor of my system/room, especially with my Yamaha A-S3000 which is one of the quietest amps I've thus far heard in its generation of background hiss (you really have to put your ear against the tweeter and strain to hear it!).
 
ToTo Man said:
With regards to the 8kHz noise, if this is present on the DAC's USB input then will it be output to the amp even when there's no music signal, or would I need to create an audio file of silence in Audacity and play that back to see if I could hear it?
Click to expand...
There is only a little USB activity when the DAC is idle, so you'd want to play a silence track to be sure. Make it at the highest sample rate the DAC supports to maximise the USB packet sizes.
 
I don't think I'd get obsessive about it, because it could prove to be a very deep rabbit hole.

There is a school of thought which considers that one issue with noise in file-replay systems is that in can 'modulate' the music signal, which manifests as an 'edge' or 'glare.' In effect, if there's no signal present, there's no degradation, but... see, now you've got something else to lie awake worrying about. ;-)

If you want to have a file-based system with a substantially improved performance over your Mac mini, then buy a music server. You can tweak the former to buggery all you like — and I've done it, up to and including an external PSU which cost more than the Mac — but it'll still fall short in comparison.

I bought a first generation Melco a few years back. There was a clear difference across the board, but most noticeably in terms of noise floor. I've said here before, on the very first album I played on the Melco, it was clear from the hall ambience and audience applause it was a substantial improvement, before a single note of music had been played.

Of course, if you want to improve on that in turn, then you need a really good CD player, but that, as they say, is another story...
 
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