I've been subscribing to a bug related to my soundcards of choice, namely M-Audio Delta cards (chipset: envy 1712).
There has been a problem getting these cards to work with Pulseaudio for years now.

https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/178442?comments=all

I've been reading about envy 1712 all over the web, more so last year, when I was trying my best to solve the problem on my own machine.
One of the things I picked up was that there seemed to be a discussion on whether this is an Alsa bug, or a Pulseaudio bug.
The bug itself makes it impossible to use audio inputs and outputs with Pulseaudio, only digital ins and outs are detected. Alsa, OSS and jack all work well with these cards but not Pulseaudio.

So, is it Alsa or Pulseaudio that causes this?
Who would one want to contact to fix this bug?

(pretty soon there will be no computers left that supports these cards, so perhaps the problem will eventually solve itself).

I have two machines with 1712 cards. The first one I use for everything, the second only for music production.

On my Ubuntu Lucid machine, the Pulseaudio problem has caused a really nice side effect:
I found that I can use Pulseaudio and jack at the same time, side by side (less reliable perhaps, but reliable enough for my needs).
For this I need two soundcards.
I use the built-in card for Desktop audio/Pulseaudio.
The M-audio card I use only with jack, which I start from the terminal (Qjackctl suspends pulseaudio, but jack itself does not).
This requires a physical mixer so that both soundcards can be fed to the same amplifier.
This is the machine I use at home and I use it for everything. That is why I'd rather have a distro like Ubuntu installed on it. I do not require low latency at home, so performance is not my main criteria in this case.
Even though Pulseaudio could be made to work with my M-audio card, I actually prefer this solution, because it enables me to run both Pulseaudio and jack at the same time, which otherwise would be impossible, to my knowledge.

My Puredyne (based on Ubuntu, but comes without pulseaudio) machine is only used for music, and there are no problems getting M-audio cards working with that machine, for any intended purpose. Desktop audio is Alsa-based. Low latency and high performance is my first priority on this machine. For this purpose I don't use a distro like Ubuntu and I don't need pulseaudio.

In the end, the pulseaudio related bug does note affect me anymore, but it does seem a little strange that the problem still persists.
These chipsets must be some of the most popular, if not THE most popular among pro-audio users. They are cheap and perform well. The second hand market is huge.
Surely there must be a way to fix the problem with getting pulseaudio to detect all channels of envy 17xx chipset based audio cards.