Crack question regarding DAC and the Xonar DX

[CmdBrewsky]

Hi guys,

I just finished building my Crack build, however I thought that I could use my Asus Xonar DX card in my PC as a DAC, however, I guess I thought I could use a 3.5mm stereo male to dual RCA female adapter to get sound of my Xonar DX. But I do not get any sound from my Bottlehead, and now I am unsure whether I made some error with the build or whether I was mistaken that I can use a Xonar DX as a DAC. I believe that the Crack is working fine since the tube starts glowing and heats up, and there are no other problems except the no sound issue and since this is my first build I don't know if there is something wrong with the Crack or just I wrongly assumed that I can use a Xonar DX.

Could use some help finding out what the problem is.


Thanks in advance

[kgoss]

Your sound card will act as a DAC if you connect the analogue output of the card to the Crack. As far as testing goes you could use powered speakers with the sound card to make sure you have it configured properly. To test the amp you could use the headphone output of an iPod, tablet, or phone. Or use an AM/FM tuner or any other analogue source that you know works.

[ALL212]

Turn the volume all the way down on the crack and make sure the volume on the PC and any software you're using is all the way up.

Then up the crack volume slowly.

[CmdBrewsky]

Ok I will re-check everything in the morning. Currently 5AM in Europe where I live.

So the Xonar DX can be used as a DAC? I should expect it to work with a simple RCA to 3.5mm adapter (I can't link images but its a simple adapter).
When I tried to connect everything, it went PC > the adapter plugged in the 3.5mm jack that I used for my headphones > two RCA cables that went into each RCA jack on the Bottlehead Crack > the heaphones.

As I said I will check everything again then, however I thought that maybe the Xonar can't be used as a DAC since I tried everything with the volume knob and the PC volume and on top of that the big tube was glowing on the Crack and was getting hot. (The small one wasn't glowing if I remember correctly though).

[Rocketman248]

If the input tube isn't glowing, then there's something wrong in the circuit.  Have you done the resistance and voltage checks?

[Grainger49]

How did the voltage checks go?

[kgoss]

If you are plugging into the same jack that works with your headphones it should work with your amp given you are using the adapter cable. Like Grainger said do a voltage check, but not before making sure you pass the resistance test first. The resistance test can uncover problems that would damage the amp if you apply power to check voltages.  So resistance issues must be corrected first.

[Paul Birkeland]

How did the voltage checks go?

I'm also interested in the answer to this question.

If you haven't checked the voltages, you shouldn't be plugging in headphones or your DAC. 

[ALL212]

And don't worry about getting beat on by this bunch - they're only here to help.  I've never heard a discouraging word...hmmm, could make a song about that...   

[CmdBrewsky]

There was one tiny problem with the resistance on one of the wires. I think it was pushing on one of the resistors, but I rechecked everything this morning after a good night sleep and now everything works perfectly. I pruned any wires that still had some length to them after the soldering point, so maybe that helped as well. As I said after getting some sleep and doing some minor modifications everything works fine.

Except for a slight hum when there is nothing playing but from what I read that is due to the (bad?) soldering or something (the 2nd tip at the end of the manual). I presume I can try and do a better job when I decide to get the speedball upgrade.
Or maybe if any of you have an easy(er) way of checking where the hum is coming from instead of random re-soldering of wires?


Edit: Clarifying things..
Edit 2: After trying it out for a while, I tried just pushing the sound level higher without anything playing in the background and the hum gets considerably louder at levels which would be considered normal listening levels. And it is now quite noticable and annoying if nothing is playing. Or when listening to songs without too many instruments or when there are just vocals for example. Is this just the bad soldering or might something else be the problem? Maybe related to the different electricity (as I am from Europe and in my country we have 220v electricity) even though I have the 240v Crack package?
Edit 3: Seems like the buzz becomes louder only when upping the volume on the amp, managing the sound on my PC has no effect on it. Although I did connect it to my phone and there was only a tiny buzz (the same as when the input cables on the amp aren't connected to anything and this time changing the volume while plugged into a mobile phone has no effect on the buzz. Then I tried hooking it up on my mainboard sound card instead of the Xonar DX card, and again, the same buzz.
So, Edit 3 tl;dr: Loud(er) buzz is only present when connected to the PC (either onboard sound card or the Xonar DX) and when changing the volume on the amp itself. Minimal buzz that is not affected by volume change is also present on a phone.
Edit 3.5: If I start a PC game, the background hum changes. For example if I open a menu in-game, the hum becomes quieter or louder. Maybe something to do with the power the GPU takes?
Edit 4: It must have something to do with the electricity and interference with the power/noise coming from the PC itself. This is my opinion though, any ideas are of course welcome. Anyway, if this turns out to be the case, what can I do to prevent the hum? Any special shielded RCA and/or power cables that can lessen the hum? Maybe using the optical out of the Xonar DX instead of the 3.5mm jack, or any special cables that are shielded against EMI or some such?

[Paul Birkeland]

Do try the optical cable, that may solve 90% of your problems.

Also, try maxing out the output of the DAC.

-PB