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W4KAZ Softrock Based CW Skimmer Station – 04) Sound Card Experiment Notes

Notes on sound card experiments for SoftRock SDR based CW skimmers.

Updated 2015-03-30, additional test results and new soundcard information:

Two things changed that provided some new information in the search to pair up cheap sound cards with softrocks for use with CW skimmer.  The shack found itself in custody of a much improved computer for testing, a Dell 960 sporting a Core 2 Quad processor.  This box was loaded with a copy of Windows 8 that had been left in limbo in favor of keeping Win7 on the daily use computer.  The Core 2 Quad has two physical threads and two virtual threads.  One of the problems running multiple skimmers on less capable CPU’s has been the lack of thread horsepower.  For multiple instances of Skimmer, multiple threads on the CPU are a big boost in capability.

A second development was the discovery of a new inexpensive sound card to try out for skimming, the Diamond Xtreme XS71HD(pci version) and Diamond Xtreme HS71HDU(Usb version).  These cards have record scan rates of 48/96/192khz, so they accommodate the ability to skimm at wider bandwiths. Nabbed one of each to do some more tests of sound card co-existence.

In summary, the XP operating system was part of the problem with the ASUS cards being unable to co-exist with other outboard sound cards.  Perhaps Windows 7 would have solved the problem, but Windows 8.1 was available.  Windows 8 allows the ASUS cards to be installed in the system along with a Soundblaster, and both of the Diamond cards.  The one remaining caveat is that the ASUS card seems to feel the need to be the default for all of them to function properly in the Win 8 system.

Begin original post.

Audio quality is a subjective thing.  The technical specs are of merit, but don’t always coincide with the listener’s experience.  Everyone’s ears hear differently.  With software defined radio derived from sound card inputs the technical specs matter a lot more.  Computer programs are more objective observers than people, aina?

Lacking either the skills or the equipment to measure any of the sound cards, one is left to either rely upon the advice of others or do some direct comparisons and roll with the “subjective”.  The subjective is about as technically reliable as shooting craps in Vegas.  Sometimes the crap-shoot has more appeal than expert opinion.  At least that’s the way it works for this subject.  ;0

So what follows is a singularly and highly subjective review of several sound cards tested, intended for use in a six-band CW skimmer system built around SoftRocks.

Roll With The Crap Shoot

Curiosity is a wondrous thing. Since several cards are required for setting up CW skimmers on six bands, a few extra sound cards are needed.  So they may as well be part of the experiments.  Round up a few and see how they play.

The first tests were done with on-board SoundMax audio that is integrated into the motherboard of the Dell platforms used for hosting the station skimmers.  These perform adequately for casual use and tinkering, but the published dynamic range attribute specs are up to 12db lower(worse) than most of the available add-in sound boards.  On one of the systems, the on-board sound scan rate is limited to 48khz.  This limits the bandwidth of the SoftRock to 24khz on either side of the center frequency.

Another problem was that add in cards needed to be half height small-form-factor to fit into the first of the available CPUs.  A major limiting factor.

So…..A-hunting we will[did] go:
General testing conditions are/were
  1. Use the K9AY RX antenna for comparisons, fixed on the NE loop
  2. scan at 96khz scan rate where it is supported
  3. comparisons done on 40m, where activity is more common
  4. computers running Win XP with latest versions of drivers installed
  5. computers are dual core CPU’s running at 2.2Ghz, most tests repeated on Dell Optioplex 360 SMT to allow comparison of Xonar cards against the full height M-Audio
  6. CW skimmer software limited to 500  300 decoders
  7. amended 2015-03-30  Soundblaster Audigy and both Diamond devices tested only on windows8/dell optiplex 960 with core 2 quad processor.

Tested sound cards include:

  1. Asus Xonar DG
  2. Asus Xonar DX
  3. Asus Xonar DS
  4. M-Audio Delta 66(a full height PCI card)
  5. SoundMax on-board integrated audio(two different Soundmax chips)
  6. Soundblaster Audigy 2
  7. Diamond Xtreme HS71HD (a half height PCI card) [20150402]
  8. Diamond Xtreme HS71HDU (the USB version of the Diamond Xtreme)[20150402]
  9. One big happy coexisting family [20150402]
1. Asus Xonar DG

The Xonar DG was the first candidate.  It has good on-paper specifications, and was available for next to nothing at the time of purchase.[$22.xxUSD less a $10.00USD rebate]  Thirteen bux for a sound card?  Must be crap right?

The first test of any card once installed was just to play some of the MP3 library and listen.  The one word impression: Fabulous.  This card exceeded my expectations in its audio quality and low levels of hiss/white noise.  It is easily the best sound card audio I had ever experienced up to that point.  But prior to that point only on-board sound or SoundBlaster cards had ever been used here.  The Xonar DG sounds great, and is so far superior to any SoundBlaster that it is worth ripping them out and replacing them if you have them.

The DG’s only limitation in its SoftRock SDR application is its scan rate is limited to 96khz.  But it does a very fine job with the 96khz it is able to scan.  A/B comparisons of the 40m SoftRock and the Elecraft K2/Yaesu FT-920 showed the K2 and 920 winning out in sensitivity.  But not by a huge margin.   Not equipped for rigorous testing, so that opinion is entirely subjective.  But this subject says that the Xonar DG “works”.  The DG wins out on sensitivity compared to the Soundmax integrated audio.  The DG is a PCI card, but is also available as PCI-Express(as the Xonar DGX).  Both versions are small form factor (half-height) cards.

2. Asus Xonar DX

The Xonar DX was scoured off of e-bay, another bargain acquisition.  It is every bit as good as its little brother Xonar DG. It’s major attribute is that it also boasts a 192khz scan rate.  In a SoftRock application, that might be useful for scanning 20m from 1400-14150, or 40m from 7.00-7.15.  The upper end of 20m often has activity during major DX contests, and it would be nice to get a heads-up when that happens.  Also true on 15m and 10m, if and when I add those bands and there is actually another really good opening on those bands.  The latter are both are iffy propositions…..:o

In comparison over a few weeks of operation, the Xonar DX seems to be better at copying weak signals than the DG, but the margin is slim.  One definite advantage held by the DX is in CPU usage.  It’s CPU usage at 96khz is the lowest of all of these cards tested.  It idles along at 3% CPU when the band is slow, and peaks out at about 20-23% when the band is busy.  It consumes more CPU horsepower at 192khz, but even that doesn’t push the cpu utilization over 50%.  On a system with a quad core processor it should cruise along as a background task.

This card is the best performer of the group tested in every way.

3. Asus Xonar DS

This card was another scavenged off e-bay.  It was purchased while under the mistaken impression it supported 192khz scan rates.  NOT!  Big disappointment there.  Otherwise it seems to be equivalent to the Xonar DG.  Its only distinguishing attribute is that it has a user replaceable audio op-amp.  So this card may ultimately become the card of choice for the daily use computer to play the MP3 library.

It is otherwise the equivalent of the Xonar DG for SoftRock applications.  Good, but not better.

4. M-Audio Delta 66

Probably the biggest disappointment of the group tested.

It is the most recent arrival, and the most expensive of the group by a factor of two, despite it being acquired used at bargain price.  All three of the Xonar cards seem to do a better job with the 40m SoftRock.

There is one major advantage held by the M-Audio over the Xonar line.  Because the M-Audio is intended for use by audio geeks, it supports multiple inputs, and its driver appears to be smart enough to be able to manage multiple cards.  So with this series(Delta 44 & Delta 66) it is feasible to install multiple cards into the same CPU case and have them coexist.   I have been unable to do this with the Xonar cards, and area that begs for more experimentation.

Using multiple M-Audio cards may be a mixed blessing, because the Delta-66 seems to be a real CPU pig compared to the Xonar cards.  Granted, that is less likely to be a big problem with a latest-n-greatest 3rd generation Quad core i7 CPU.  So a kilobuck can fix the CPU pig situation, if you happen to have spare kilobucks($1000.00USD).  NOT….

On the clunky and junky dual core processor CPU’s available for free(or easily under $100USD), the M-audio idles at around 30% CPU usage, and maxed out during 2012 august NAQP CW at around 75% CPU.  Ugh.  Not ideal since this station is stuck with the dual core processors for the foreseeable future..  If that amount of CPU usage were significantly better than the SoundMax integrated audio, maybe.  But while it is noticeably better than the integrated audio at decoding weaker signals, it seems to be midway between the integrated audio and the xonar line at best.

5. SoundMax Integrated Motherboard Audio

Two flavors of this.  One of the CPU’s has SoundMax audio supporting only 48khz, the others support 96khz.  The ability to decode CW by the 48khz box is less than either of the 96khz motherboards.   Both of the 96khz on-board sound cards seem to be roughly equal to the M-Audio card.  Again, the only M-audio advantage lies in its ability to support two SoftRock inputs.   That M-Audio advantage is mitigated by the inefficiency of its driver software(i.e., “CPU pig”).   That’s a big disadvantage on the feeble minded dual core  systems used in the KazShack.  Unfortunately, the 48khz box has some unrelated practical advantages, so may be pressed into use despite its low performance.  “Engineer the possible”.

6. Soundblaster Audigy 2

This was gathered in as a low-ball bid on ebay for $8USD.  The card supports a 96khz scan rate.  As a used pull from and older box, the bad news was that neither the line-in nor aux line in inputs were functional.  Wired up a header to input the audio via the card’s CD port, and it is able to function as a skimmer.  No knocks on the original, this card had seen some abuse.  In its roll as a Softrock input for CW skimmer, it functions at least as well as an onboard input.  Not great, but serviceable.

7. Diamond Xtreme 7.1 XS71HD  (Pci half height/small form factor card)[added 20150402]

The first caveat here is to note that this is the “HD”, newer version of this product.  It supports scan rates of 24 bit 192khz.  The prior version has a similar name but is limited to 16 bit 92khz scan rates.

The HD card has decent reviews, and the 24 bit 192 khz scan rate give the option of a wider bandwidth in use with the softrocks.  The fact that it is also a small form factor is useful since several of the shack boxes are small form boxes.  It seems to do an excellent job as an input for the SDR and CW Skimmer.  Sounds pretty good with music too.  The only item of note for skimmer use is that the input level settings for the best perceived skimmer performance were  very low (5%), set via windows controls in the sound settings.

8. Diamond Xtreme 7.1 XS71HDU (USB version)[added 20150402]

This is the USB version of the card.  It has a different set of drivers, and seems to coexist just fine with its PCI brother.  All the same specs as the PCI XS71HD.  Can also be pressed into service if I need to take it portable.

 9. Co3x15T [added 20150402]

Previously, getting the cards to function when installed in pairs within an XP machine was a large unresolved issue.  With the Windows 8.1 box it was possible to install the following:  Asus DS, Soundblaster Audigy 2,  Diamond XS71HD, Diamond XS71HDU, and the built in on-board Soundmax crab.  The single minor caveat to full function is still the ASUS device.  All five devices function properly as long as the ASUS device is designated the default.  As of 20150220, the W4KAZ skimmer system has been running five CW skimmers simultaneously on the Core 2 Quad processor under windows 8.1, 160m,80m,40m,20m, and 15m.  The 40m skimmer at 24 bit/192khz, all others at 96khz.  The CW skimmer for each band was set at 250 decoders on each band.   Under that condition the CPU load was hovering at approximately 50%.  The real test of the system will come during the 2015 May CQ WPX CW.

Another minor caveat to usage is determining which control in the windows sound controls corresponds to which physical device.  The visible names under the windows control are in a couple of instances quite vague.

General Random Musings and Worthless Opinionated Observations…..

All of the add-in sound cards prior to 2015 were run through the same system, a Dell Optiplex 360 mini-tower.  It is the only one of the available systems that supports full-sized add-in cards, so it was used to get comps.  All of the tested Xonar cards are half-height/small form factor cards that will fit in both small form factor cases or in full sized cases(adapter bracket for full size is default, SFF adapter included in box).

The Xonar cards all seem to be able to co-habit any given computer along side of the integrated sound, but all attempts so far to install the Xonars with another sound card have failed(see #9 above, 20150330)(Combinations tested….Xonar with Xonar, Xonar with Soundblaster…M-Audio not yet tested).  That is a big limit on the usefulness of the Xonars cards in an SDR application relying on a single CPU strategy.  Not a problem here since the install is going to be 2 bands per physical box and 3 dual core boxes total.   That seems to be the only advantage held by the M-Audio cards, but it is significant.

The method intended here is still to use multiple physical CPUs.  That is driven mainly by the CPUs being available for zero cost, but also allows for load balancing the skimmers and built in redundancy.  Losing one CPU will not completely take the station off the air.  So in this type of environment, the ASUS cards are just fine.  The Diamond Xtreme HD cards seem to do the job well also, and both of those have the 192khz scan rates.

Better than fine.  Damn good for use with a sound card based SDR.

Additional notes……

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