I’m talking about equipment documentation, in this case, computer sound card documentation.
I’m talking about equipment documentation, in this case, computer sound card documentation.
It’s not really a soundcard, it’s built onto the mother board, and I use it because it produces broadcast quality sound. If I was recording the New York Philharmonic I might get something else.
But recording the ALPB Meetings has put new demands on the sound board, and although I managed to get the job done, there was hum in the resulting signal, and it happened again when I talked to Lefty Gomez on Team Speak, which is the same system used with the ALPB.
As far as I can tell, the board is capable of outputting two distinct and separate stereo audio channels, a total of 4-channels, except it doesn’t seem that the stereo can be split for use as individual channels.
KDX programming streaming on the web and broadcasting on AM & FM ties up Audio Output No. 2, and keeps running during recording sessions over on Audio Output No. 1.
I think the normal way to employ Team Speak is to use both Audio Output Channels, one for sending voice to Team Speak and the other to play back Team Speak participants speaking into their mics.
But in manner that I do not understand, I am getting my microphone to Team Speak and hear back without interfering with KDX Streaming Audio, by simply sending on the C.Crane FM transmitter and receiving on the C.Crane radio. But the hum.
I opened the little one-sheet fold-over from the mother board company and found the most unexplained description of the input and output plugs, opened the software on the screen and saw many things that may or may not have a use, if someone knew.
Probably the documentation is so feeble because, like this blog, it gets harder and harder to describe, the more one tries.
Anyway, bottom line, I have made an improvement, but not because I tried to study the problem in a formal scientific way, but because I stumbled onto a solution by trying a bunch of stuff until something worked.
I don’t know why it works.
mram1500 says
This But Not That…
I wouldn’t be so quick to blame the mother board sound system.
From what you have stated it seems the hum occurred when speaking with Lefty. The hum you refered to could have been the source audio. Was the hum constant throughout the interview or just when Lefty was speaking?
Perhaps comparing his recorded audio to others recorded from Team Speak meetings would give a clue.
radio8z says
Sound Cards
Carl, I don’t know if this is helpful for your hum situation but I have noticed hum in my FM chain which is just audible to someone who listens for such things. Long story short it is always there on the sound card line output regardless of what is muted. The only time it is gone is when the computer is powered down which might indicate a shielding or power supply problem inside the computer but this theory is contradicted by the observation that when booting from a power down condition the hum does not appear until about half way through the startup. This is most likely when the sound card drivers are loaded and the card becomes active but I do plan to check lead dress inside the box. Since the hum is barely audible I am going to live with it for now but am a bit surprised that this sound card is touted to be one of the best. By the way, this is the one which has a “known problem with no fix” for uselessly low microphone input gain.
Unfortunately I did notice hum during the interview with Lefty (one of the best you have done by the way) in LPH 56. It did seem to change at times during the interview so maybe it is originating external to your computer. Could it be originating on Lefty’s end?
Neil
Carl Blare says
What Is Known and Unknown
Here are some details, which got left out of my original posting because they would have caused a very sleepy reaction if all said at the same time…
Since one of my soundcard audio channels is tied up with streaming KDX, there remains one channel for monitoring incoming signal from Team Speak.
Key Bit of Information: I do not use headphones nor is there a monitor speaker hooked to the computer, since I listen to everything on radios following transmission.
Switch your mind over to my microphone, used to speak to Team Speak and the recording software (Audacity). The microphone runs through a 4-channel mixer which enters the soundcard and uses an input channel, which is not one of the two output channels, but which miraculously sends to Team Speak and the Audacity input.
I once found that I could get a digital version of the Team Speak incoming audio to mix downstream with the audio mixer’s output, but that caused feedback when I keyed on my mic send to Team Speak.
So I took the soundcard output from Team Speak and sent it to the C.Crane FM transmitter, linked by 1-foot of air to the C.Crane Plus Radio, and the audio out from the radio to the input to the Mixer, so it could be isolated from the …. at this point my confusion matches yours…. but it got the Team Speak returning sound unto the recording.
And, of course, the radio allowed me to hear whoever was talking on Team Speak.
I think the hum was a ground loop caused at two points… owing to the way cheap consumer cables are grounded doubly at several points. And I noticed last night that the C.Crane transmitter has audio hum when the audio input is turned down.
The build up of hum got further emphasized because I use compression in the final recording to bring the speech forward and make it extra-present.
Rather than build custom audio cables correcting all the ground loops, I figured out that I could patch the output from Teamspeak to both the audio mixer input and over to the radio for listening, thus avoiding the hum in the FM chain.
The hum was mostly constant (with Lefty), so I don’t think it was caused by Lefty’s mic being keyed on.
However, I did notice a hum from your mic, MRAM, so I understand what you’ve said about your sound card.
By my calculation none of this equipment should work at all, and the fact that it does makes no sense.
Carl Blare says
Success As Usual
The new audio patching arrangement is a success based on a very clear and hum free recording of last night’s meeting of the ALPB (Association of Low Power Broadcasters).
Interested persons will have the opportunity to judge for themselves as the meeting is to be featured on forthcoming editions of the Low Power Hour.
I now believe the main source of hum was the C.Crane transmitter, since previously my Team Speak recordings were being linked via the FM pathway, but I have a test in mind which may find that the transmitter only hummed because of its proximity to other equipment, a common situation known to induce hums. The results of that test will be posted here.