Currently on my Slackware64 14.2 system I cannot get my USB DAC working at all unless I set the sample rate to 48000Hz in daemon.conf using 'default-sample-rate = 48000'. the output of iecset on my system shows

control "IEC958 Playback Default" (index -1) not found

however if I run this on Ubuntu Live I actually output except the rate is 44100 Hz. I've tried looking on the Ubuntu Live system and do not see anything changed with daemon.conf and the sample rate still seems to be set to 44100Hz. any idea what I might be missing so that the system matches that of Ubuntu's configuration?

It would be interesting to know what kernel & alsa & pulseaudio versions you are running in Ubuntu Live, I guess they're newer (latest) than what you get in the stable Slackware64 14.2.
You could try running Slackware Live and test your desired configuration:
https://docs.slackware.com/slackware:liveslak
https://slackware.nl/slackware-live/latest/
If it works, maybe you should use Slackware -current instead of Slackware64 14.2

These are some relevant links I found looking after your reported issue (basically, you can try the advice you find there on your Slackware system ):
https://askubuntu.com/questions/8688...match-hardware
https://askubuntu.com/questions/1386.../245240#245240
https://ubuntuforums.org/showthread.php?t=1939711

1 members found this post helpful.

@abga thank you for your response! it's been a while that I totally forgot about Slackware Live and after your suggestion I was able to test and confirm that this seems to be an issue with 14.2 and not inherent on Slackware Live. that said I made the plunge to upgrade to -current and to my dismay this did not fix this issue! I've even installed -current from liveslak, but that also did not work... there seems to be something in liveslak that's been tweaked or added that's causing this, but I'll have to look further

Sorry for the late reply, really busy lately, actually started already in mid January and now ... hell just broke loose with this Chinese bat-shit virus

I was suggesting to try the Live version because it has an actual kernel (drivers) + pulseaudio + alsa.
Don't know why the Live works and -current doesn't, both should use the same latest code (the above packages). - @Alien Bob (Eric) could help here.
I would investigate (compare) if there are different/additional kernel boot parameters, the pulseaudio conf (/etc/pulse/) files and maybe how udev is launched in /etc/rc.d/rc.udev together with the rules in /lib/udev/rules.d/

P.S. Wait, I believe I went too far with the above recommendations and haven't focused on the actual kernel you were booting with the Live Slackware.
I don't have too much experience with the Live image and also too lazy to parse the build script(s). This help page isn't really helpful in identifying which kernel is used by the Live image by default:
https://docs.slackware.com/slackware:liveslak
But I believe Live uses the generic kernel and -current is using the huge one by default. There could be some differences in Sound HW support between the two. Never used the generic kernel on my own, can't tell the difference.
You should boot Live, check what kernel you're running generic/huge and use it also in your -current installation. Also, run a dmesg and paste the section where your Sound HW is identified in the Live Slackware. That will help in identifying if there are some kernel drivers/modules missing in one of the kernels and can be supported (enabled) in the next -current kernel release.