Cheap & Sane Desktop or Laptop mods and tweaks, for use with USB DAC?

turbodawg

Member
2004-02-13 12:51 am
Hey guys just decided to get serious about the sound output of my main HTPC / projector setup. Currently run a 2011 Dell XPS 8300 tower in a closet with a AMD HD6950 and SSD. Have on order a Schiit Modi 2 and a Denon DA-300USB Dac (closeout pricing), to replace my 10 year of creative labs USB soundblaster. Various 2-channel speakers and amps, mid-fi.

Did a bunch of reading about audio PC's........high end usb PCI cards, cables, power supplies etc. It seems like electrical noise reduction is a pretty huge deal - power supply ripple voltage and EMI/RFI, etc.

How much of this is actually real vs. BS? Seem like over on computeraudiophile.com they are following many of the classic pseudo-science tweaks............? Thanks!
 
Actually even an internal sound card will do fine in many cases (and gives you higher-performance components at the same price level due to no enclosure etc.). Granted, they may be a bit peeved when sitting right next to a high-power graphics card, but it looks like the XPS 8300 gives you enough slots to avoid that sort of problem.

There's only a few problems that you may run into.
1. USB-powered devices can be quite fussy about cable lengths due to the unavoidable supply voltage drop associated with them.
2. You are likely to be just fine when using an ordinary hi-fi / home theater amp that has nothing else connected to it save for speakers. People typically start running into problems when a ground loop is formed, demonstrating the brokenness of unbalanced consumer audio in all its glory. At that point only some kind of ground loop isolation will help, and if it's a Toslink (optical) connection between soundcard and DAC.
3. When using front-panel outputs, a lot of cases have a ground loop built right in, resulting in annoying interference.
4. You mess up configuring the sound device or run into some stupid bug. Even OS-level resamplers are far from as bad as they were years ago though.

Only very occasionally is there a problem that ends up being solved by stuff like another power supply without anyone really being able to tell why.

As for tweaks... Low cable shield resistance still has theoretical benefits to offer (even if PC sources tend to have low output impedance, which typically means most any non-broken cheapie cable will do), but you don't have to spend a fortune for it, just get / make a cable using half-decent coax. Many other tweaks are dubious at best, based on inaccurate reasoning (maybe it did help when they had a ground loop in there, but I'd rather do away with that then), or plain snake oil.

On the software side, there's a fair bit you can do for free.
On Windows systems, using WASAPI output in exclusive mode in your player (or ASIO by way of ASIO4All if need be, which translates things to WASAPI again) ensures that hardware sample rate and bit depth can be set automagically depending on bit rate and player settings.
If you don't want some to be used because e.g. the hardware does not support them (well), there's a very nice SoX resampler plugin for Foobar2000, for example, which comes in multiple versions including "resample everything to X", "use only X, Y, Z" and "use everything but X, Y, Z".
If your collection contains everything from early-'80s CDs to modern-day releases and you are annoyed by sound level differences, use ReplayGain. This also tends to do away with the threat of intersample-overs - you typically need no more than 1-2 dB of attenuation to steer clear of them, and RG would tend to dial down problematic releases a lot more than that anyway.

The DA-300USB seems to have its quirks. For all of the things it does, they seem to have neglected to buffer the line-out properly, instead tapping it off in front of the headphone amp. And then you wonder why your headphone audio is getting distorted when the equipment on the line-out is turned off... (Said equipment then has some kind of protection diodes going from the input to the supply rails then, which in off state tend to be zero, so that's a nice diode limiter right there. You can probably imagine what that means if said diodes need ~0.6 V to conduct and peak input signal amplitudes can be close to 3 V...)
 

turbodawg

Member
2004-02-13 12:51 am
Thanks guys! Got the Denon DA-300USB in ($220 Adorama deal) and tried it out, off my laptop. Very impressive so far. Running Foobar2000, with the software's resample DSP providing an upsampled 88.2khz output over ASIO USB. Into a Musical Fidelity A2 (late 90's small class A int. amp) and Klipsch CF-1 (mid 90's d'appolito design, cabinet mods, have Crites Ti tweeter diaphragms to install). Tried my old HD280 headphones on it, nothing special.

The DA-300USB seems to have its quirks. For all of the things it does, they seem to have neglected to buffer the line-out properly, instead tapping it off in front of the headphone amp. And then you wonder why your headphone audio is getting distorted when the equipment on the line-out is turned off... (Said equipment then has some kind of protection diodes going from the input to the supply rails then, which in off state tend to be zero, so that's a nice diode limiter right there. You can probably imagine what that means if said diodes need ~0.6 V to conduct and peak input signal amplitudes can be close to 3 V...)

I noticed that when I turned on the DAC, with the A2 amp's source selector still set to my desktop's old sound card and playing TV sound, the level actually dropped by at least a few db's. Very odd, maybe it has something to do with what you said...?
 
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turbodawg

Member
2004-02-13 12:51 am
A lot of it is scare mongering to create sales for all the new add-ons, Jitterbug, regen etc. none of which are really designed to combat noise or isolate the downstream devices from noise....

Right. Denon seems to have fully addressed this in their design of the DA-300USB, isolating the usb board, copper shielding, etc. I think it has like 7 separate boards in it. I'm going to try lifting the usb power pin at some point, maybe a better usb cable ($7 belden gold series, or 24g/20g, lol). I do have the USB cable coiled through a choke about 8 or 9 times, btw.

There's also an plug in to upsample PCM to DSD in Foobar2000, then send it direct out over USB ASIO, that I'll try out. I think there was a very slight improvement upsampling 44.1khz to 88.2khz in Foobar, then sending via USB ASIO.
 
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turbodawg

Member
2004-02-13 12:51 am
Hooked up the closet PC/projector system to the Denon DAC. OTA TV from a tuner card sounds much better, sharper and more defined/punchy, if a bit harsh and sibilant on poorly recorded commercials. I set the upsampling in windows to 192khz, which seemed to help a bit, and configured the ASIO out on foobar with a 88.2khz upsample as with the laptop.

Trying to figure the out the best cabling setup, as far as USB vs. RCA cable length.

1. Position the DAC in the PC closet a few shelves below the computer, with a 1.5m USB, then reach the amp in the equipment rack with a thick shielded 3m RCA.

2. Put the Dac in the equipment rack, reach it with a 5m USB, then connect to the amp with a 1m RCA.

3. Lower the computer in the closet from a shelf to the floor and possibly punch a hole through the wall from the closet to near the equipment rack, which would probably reduce the cabling needed by 2-3m overall, so maybe a 2m or 3m USB needed to reach the rack. Just measured - going from the floor through the wall, could use a 2m USB and the rack would be in an optimal position.

Considering picking up a $100 24" monitor to mount near the couch, with a hdmi splitter, for pure music listening off the closet PC with the projector off. Or I run the DAC off a laptop, or build a hush box for the projector. Eh?
 
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turbodawg

Member
2004-02-13 12:51 am
So, compared OTA TV with the Windows audio output set to 48khz, 96khz, and 192 khz. The native 48khz is just too sibilant and harsh, while the 192khz is smooth and clear, but lacks a bit of punch. 96khz seems to split the difference, with less harshness while still having some punch, which I'll probably end up using.
 
Right. Denon seems to have fully addressed this in their design of the DA-300USB, isolating the usb board, copper shielding, etc. I think it has like 7 separate boards in it. I'm going to try lifting the usb power pin at some point, maybe a better usb cable ($7 belden gold series, or 24g/20g, lol). I do have the USB cable coiled through a choke about 8 or 9 times, btw.

There's also an plug in to upsample PCM to DSD in Foobar2000, then send it direct out over USB ASIO, that I'll try out. I think there was a very slight improvement upsampling 44.1khz to 88.2khz in Foobar, then sending via USB ASIO.

Yep, you can see definite moats, minimising capacitive coupling the main mechanism for the HF noise coupling from one stage to another.
 

turbodawg

Member
2004-02-13 12:51 am
So, I moved the PC in the closet, definitely helps with the cabling. Had a 5ft usb plus a 6ft extension, swapped to another usb I had wrapped through a ferrite choke (like 8 or 9 times), keeping the extension. cable Didn't notice a difference on TV immediately, but it did sound a little less punchy. Then I went to listen to some music......something was different! Less punchy, more smooth, recessed. Swapped back to the cable without the choke, same exact type of 5ft, 28/28g shielded basic USB2 cable......it's more punchy and hotter in the upper end without the choke. Had to swap back and forth a dozen times, to convince myself I wasn't imagining things. What is going on!?
 
Is it a choke or a ferrite bead, not that it matters.... either would attenuate the top end if it was an ANALOGUE signal, as it is a digital signal being passed through a choke it is not going to have the same effect, the higher harmonics of the square wave will be attenuated giving a slight rounding to the wave... this should have no effect on the sound... and if the digital data's integrity becomes a problem then you would know, as the difference will be very obvious, drop outs, glitches etc.
 

turbodawg

Member
2004-02-13 12:51 am
It's possible you're imagining things. I'd run some experiments to see if that's the case or not before going any farther.

Nah, I really don't think so. I've been using the cable with the choke for a couple years with another USB audio interface, in my PA system. I wanted to believe that it should reduce RF noise, and sound better overall. It sounds subtly different, but not better, and I prefer it without the choke.

I've been able to tell the difference with upsampling pretty readily, with both TV audio (48k to 96k and 192k) and music (44.1k to 88.2k).

With this DAC I'm able to tell if a file is FLAC, or 320k MP3 or lower, without any sort of A-B comparison. MP3's lack a certain depth of detail that the FLAC's have. I've never been able to clearly make the distinction before, using other sources.
 
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turbodawg

Member
2004-02-13 12:51 am
Is it a choke or a ferrite bead, not that it matters.... either would attenuate the top end if it was an ANALOGUE signal, as it is a digital signal being passed through a choke it is not going to have the same effect, the higher harmonics of the square wave will be attenuated giving a slight rounding to the wave... this should have no effect on the sound... and if the digital data's integrity becomes a problem then you would know, as the difference will be very obvious, drop outs, glitches etc.

It's this thing:

https://www.radioshack.com/products/radioshack-snap-together-toroid-choke-core-2-pack

The USB is wound through it about 8-10 times. The cables are otherwise identical.

Trust me, it's a subtle but notable difference. If anything, I'm guessing the USB without the choke is getting more RF noise, which adds a bit of zip/heat to the sound when processed by the DAC, and maybe a fraction of a db louder overall.
 
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turbodawg

Member
2004-02-13 12:51 am
Nonetheless, it's worth doing the experiment just to cut the problem in half.

OK, what do you recommend for an experiment? At home I have a basic DVM, a radio shack db meter and some other USB cables. I could run tones at a fixed level and see if I measure a difference in db?

I could possibly have the DAC bench tested by a qualified EE, if I asked around a bit.
 

SY

diyAudio Moderator Emeritus
2002-10-24 10:19 pm
Chicagoland
www.SYclotron.com
What I would do is have someone (out of sight for you) changing out the ferrite and USB, using a coin-flip or randomizer to determine "in or out." Do replicate trials, maybe 8-10. See if you can still hear a difference if you don't know whether or not it's there. If you consistently identify a difference, then the electronic fun begins. If you don't, then you know that the explanation is psychological (part of the baggage we have as humans!) and you've saved yourself a lot of time and effort.
 

turbodawg

Member
2004-02-13 12:51 am
What I would do is have someone (out of sight for you) changing out the ferrite and USB, using a coin-flip or randomizer to determine "in or out." Do replicate trials, maybe 8-10. See if you can still hear a difference if you don't know whether or not it's there. If you consistently identify a difference, then the electronic fun begins. If you don't, then you know that the explanation is psychological (part of the baggage we have as humans!) and you've saved yourself a lot of time and effort.

Yeah, that's going to be tough to get someone to do a manual ABX test for me on this, but I'll see what I can do.