Have a desktop computer that I am going to wipe clean and dedicate it for the station. Initially planned to simply connect the airchain to the earphone jack, which appears to be the norm; but began to wonder if the audio quality coming from the earphone is a less than an ideal source for the audio to originate from?
I mean trash in, trash out - right? Not saying trash is necessarily coming out the earphone, but it's an earphone! Is that the ideal method?
Or would it be better to get some kind of special sound card or something?
The question is: What is the best method to produce the highest quality audio output from the computer, before it even hits the airchain to be processed?
Ideally, you would find another way to get that audio out of the PC. The 1/8" stereo mini jack on most sound cards have several issues that have been setbacks for me when I have tried to use them.
First is noise - the outputs aren't well shielded and while typical uses don't often suffer, I have had all kinds of problems with noise coming into the transmitter using the mini-jack.
The second is issue is mechanical connection quality - I've come home and tuned in my station only to hear nothing and after wiggling the jack plugged into the sound card the audio comes back - grrrrrr!
Last is impedance - goodness knows what the output voltage and impedance might be - some sound cards have line out jacks and other confusing options and some are jumper-settable on the card - it's always a guessing game and lots of trial and error.
I'm thinking of trying one of these - good old RCA connectors and a better path away from all the noise
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The Earphone jack should work just fine,
that's what I use and haven't had a problem with them.
If your PC soundcard has a line out jack, that may be a better choice. I've found that the soundcard amplifier for the speaker/earphone output jack can be noisy especially with inexpensive soundcards. The line out jack won't drive a low impedance load like a speaker but is usually quieter regarding the noise floor.
If your transmitter audio input is designed for line level input, it probably has a 10 K ohm impedance that would work well with a line out jack. If, however, the transmitter audio input is designed to be connected to a speaker/earphone output, it may have a low impedance that would not work well with a line output.
My PC only has a speaker output jack and is connected to a line level input at the transmitter. That works OK as the low impedance speaker jack output can drive a high impedance line level input and the audio level is high enough above the noise floor that it's not a problem.
SCWIS is correct in pointing out the various differences in impedances and output levels among PC sound cards. The devices he has shown us, will make durable audio 'in's and out's' available fo pro or semi-pro levels and impedances. There are PC cards that can do that, as well, but they do live inside the noisy PC .
However, many times you can 'luck out', and get decent results with most 1/8th" line level outputs. It's even possible to get digital SPDIF i/o s on some lower-end sound cards these days, if you like to be 'creative' with the hardware.
I'd be careful with an amplified earphone output without proper padding and matching, though. There's too much chance of overdriving your audio into distortion, especially if it's feeding a transmitter with no processing in front of it. They're usually noisy, too.
Come to think of it I have always carried a timid dis-trust of "head phone outputs," but without any certain knowledge of what they provide (aside from listening on headphones).
My un-informed impression is that headphone outputs have a higher power level than line outputs, perhaps 1-watt or more, which, as has been said, can overload many inputs.
On the other hand I also suspect, but don't know for sure, that there is no real standard for headphone outputs.
Another impression, un-founded, is that headphone outputs must be properly "matched," that is, if they are 8-ohms, then the headphones should be 8-ohms. Failure to provide a match can perhaps damage the headphone output transistors, but I am guessing.
One problem we have a lot of today is either poor or no circuit documentation with computer equipment. There was a good TWiRT (This Week in Radio Tech) program about the lack of manuals with today's equipment.
An engineer who once mentored me told me "if it rattles what do you do? You bolt it down." This was in context with an electrical noise problem we had with a circuit we were developing and what he meant is make the signal source and load low impedance. With this in mind, I chose the speaker output of my sound card and have had no problems at all. Despite the high power output capability compared to the line output it doesn't matter since it is the voltage and not the power which drives the line input to the transmitter. My experience has been that the voltage levels at the speaker output can be adjusted to be the same as the levels at the line outputs.
Be aware that some sound cards detect if a headphone is plugged in and the software switches to a lower level output and to "headphone mode" which is some sort of channel blending which reduces channel separation. On XP this can be reset and on 7 it can be turned off if necessary.-
I have had no problems with the mini phone plugs and jacks but have had many problems with the RCA phono connectors so I wouldn't convert to the RCAs.
Neil
No one mentioned the many Pro sound cards which have 24 bit sampling and balanced XLR in and out plugs. They also have better than -100db noise floor. These are the proper output cards to use for broadcasting. Also the cables should be 100% shielded,low oxygen type,low loss cables. Ground the PC like any other gear in your chain.
ENJOY!
That one looks fairly reliable, mainly because it has industry standard 1/4" jacks, much hardier than consumer grade RCA or mini jacks, although that's what I use on my STL computer on the boat ... it never gets touched, so it gets no wear plugging-unplugging, etc. On that old iBook, there doesn't appear to be much noise ... probably because it's a laptop.
OTOH, in my studio I use a mixing board, with a recording snake and a Presonus Firewire interface ... all balanced stuff. But I still hook up unbalanced stuff to board channels (tape, turntable, CD players, instruments, etc.) in addition to balanced lowZ mics.
No real problems since I can run the audio through SoundSoap once it's digital in the computer. If there is some noise, I can usually get rid of it.
Being a Mac user I also use GarageBand in static mode (live tracks without recording) which gives me access to all of my AU's and VST's in the computer. I can use all sorts of compression, instrument effects, noise suppressors, etc.
After doing a search for the subject and considering sound cards - if it be an usb or an internal card, I still haven't determined for sure which route to take.
But did find some pros and cons to each.. which I'll try to briefly summarize (I wish I bookmarked some of those pages now)
For example, consensus is, when it comes to laptops, they generally have a lower quality of audio output than most desktop units. And there are several references that using the earphone jack of a laptop in particular as a sound source is sub-par -- not so much the jack itself, but more so the guts of laptop sound circuits themself, with further degradation of the sound quality occurring from electrical interference caused due to the tight construction of components in a laptop.
Suggested also is that desktop computers almost always have better sound cards than a laptop, but they are also hindered by interference from the computers inter-workings such as video card interference and other noise.. and advises to always move your audio card as far down from your video card as possible.
And almost exclusively, everyone from forum posters on music forums, to product reviewers, as well as more technically inclined articles all seem to say that the best sound from any computer can be achieved by using an external usb sound card as opposed to internal, because it is isolated from the interference going on inside the cabinet.
But one drawback to an external usb soundcard is that it tends to use more of your processing power. Seems there was also another disadvantage mentioned , but I can't recall what it was.
By the way.. I use a usb mouse on my desktop, and I don't know if this ever happens to anyone else, but occasionally all of the sudden my mouse will just quit working - and it's always a quick easy fix.. I just pull the mouse usb out and put it back in again and that takes care of it.. but I would hate something like that to happen if I was using the usb for my sound output, and it just quit! especially if I wasn't there! Dead air!
But the bottom line, if you do some googling yourself, I think you will find that the evidence point to that fact that the best sound output of any computer is almost exclusively achieved by using an external sound device.
Speaking for myself, I don't know, I don't have the technical know how to realistically debate about it, my comments just reflect what I searched out.
Oh, there's something I've noticed while looking at several external soundcards.. they almost all boast special features like "surround sound" and extended channels, etc...
We as part15 broadcasters don't need or want that - right? I mean we already have to convert 2 channel stereo to mono for broadcast.. what do we want with 7 channels!
There are some simple stereo externals though.
Just saying.
The bottom line answer is yes, the earphone jack is just as good as a line-out jack.
Unless you own a high end "multi-media" computer, you likely don't have a "sound card". Your audio is handled by an audio chip on the motherboard, which is compliant with the INTEL AC'97 or HD Audio standards. My 5 year old computer has a Realtek AC'97-compliant audio chip.
There are a dozen or more manufacturers of audio chips that may be in your computer. In Windows XP, you can find your chip manufacturer by clicking Programs -> Accessories -> System Tools -> System Information -> Components -> Sound Device. Then search the web for a datasheet that matches what you see.
Your chip will most likely be compliant with the AC'7 spec http://download.intel.com/support/motherboards/desktop/sb/ac97_r23.pdf spec, but if it is new, it may comply with the INTEL HD Audio spec. For AC'97, here is the pertinent information:
AC'97 specs:
- Headphone output:
- Full scale output = 1.41 Vrms.
- Load impedance = 32 ohms
- Level controlled by master volume control
- Line output:
- Full scale output = 1.0 Vrms.
- Load impedance = 10k ohms
- Level NOT controlled by master volume control
The outputs are fed by op amps inside the chip. Op amps have an ideal output impedance of 0 ohms, but real implementations have a little higher output impedance. A series resistor is usually added at the output mainly to prevent destruction if the output is shorted to ground. The Realtek ALC201 datasheet shows the output impedances as follows:
- Headphone output: 10 ohms
- Line output: 200 ohms
The difference is insignificant for feeding typical AM transmitters which have an input impedance of 10k ohms minimum.
Searching the web for computer audio "static" returns a ton of hits. The consensus seems to be that the software drivers are to blame, not the computer analog audio output scheme.
Here is a VERY important thing to consider if you are using a mono transmitter. Don't select any advanced audio functions like stereo-wide or surround sound or whatever in your sound setup. These modes add phase shifting between the two stereo channels. When you mix the two channels to mono, the phase shifting will cause weird and undesirable reinforcements and cancellations.
Another important thing to watch out for when using a headphone output. The level is controlled by the Master Volume Control. Be absolutely sure the master volume is set to MAXIMUM. This will give you the highest audio level and the highest margin above the noise floor of the computer audio circuit.
Hi Phil,
The bottom line answer is yes, the earphone jack is just as good as a line-out jack.
I agree, the line out jack is as good as the ear jack, I don't believe I said otherwise.
Unless you own a high end "multi-media" computer, you likely don't have a "sound card". Your audio is handled by an audio chip on the motherboard,..
I assume you're referring to laptops, since all desktops have sound cards. I think when I was referring to the laptops I called them 'audio circuits' -- but I may have said cards.. my bad.
Searching the web for computer audio "static" returns a ton of hits.
I see where you're coming from, but for the record; my searches were: "usb sound card", "internal sound card vs external sound card" sound card reviews", and "pc audio quality". I didn't go searching for problems, I searched for improvements, and my post reflected what I found.
The outputs are fed by op amps inside the chip.... ....datasheet shows the output impedances as follows:
- Headphone output: 10 ohms
- Line output: 200 ohms
The difference is insignificant for feeding typical AM transmitters which have an input impedance of 10k ohms minimum.
Again I was not making comparisons between the ear and out jacks. But as for the 'difference being insignificant'.. perhaps, or perhaps not, I'll tell you now that my knowledge is minimal about how much difference there is between a 10ohm output and a 200ohm output; I know there's a 190ohm span there, but haven't a clue as to the significance of it.
I don't possess such technical knowledge. What little I do know is from vaque comprehensions I gather from listening to you guys.
I'm just utilizing the technics and methods made evident by people like you and the rest on this forum, and other forums...
Ok... Let me convey it this way;
I started this topic off questioning the quality of the output coming from the earphone jack .. or, if you will, the line out jack - and I did have laptop in my mind, thus opted to setting up a desktop...
My view is coming from the fact that for the last couple weeks I've been spending money on an air chain, and then it occurred to me that this costly processing equipment is all intended to push that audio coming out of that little earphone! -- So naturally, I think, wait a minute, how good is that sound quality to start with?
Which brings us back to where it started... "Is the earphone jack sufficient?"
I'm just saying that if we're going to be spending money and time on getting the sound right, shouldn't the originating audio source be looked at a little closer.
The ICONNIX shown earlier in this post that swcis is considering, is available from this seller for $31.95 w/ free shipping.. best price I found.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350430725483
I went ahead and bought one, it seemed a good idea.
PhilB is completely correct in everything he supplied. A print-out of his comments will be added to my documentation, because it covers a few points I haven't seen in my previous docs.
Every desktop computer I have known has a sound circuit on the motherboard, and ours is a Gigabyte board, which serves our needs with very clean quality, except that there were some limitations we needed to solve.
The audio circuit, while of high quality, seems like an unfinished piece of work. Mainly, the line input has the same wide open gain as the mic input, so I think the manufacturer skimped and simply used the mic input for both.
In the software mixer, and there are two versions, one by XP and the other by Gigabyte with better colors, both have the Line Input gain control ghosted, so that it cannot be changed in software.
What we ended up doing was building a T-pad with 3-resistors in a small black box to reduce the line level coming from our Radio Shack mixer down to mic level, to avoid over-load distortion.
All audio ins and outs are mini-plug, which I dislike, but it's holding together so I leave it alone.
There are two entirely separated stereo-pair audio channels, so we're able to send our streaming and broadcast audio over audio 2 and use audio 1 for editing and auditioning of other material.