Safely split sound card analog out.....?

I would like to split the analog out from two outlets on a sound card with signal going to

  • one set of computer desktop speakers - with 1/8" plug
  • rca jacks on a stereo amp to inturn power a pair of speakers

Could any of the devices or the sound card be damaged because of the change to impedance?

Will such a splitting degrade the quality of the signal going to each device?

If coming from a sound card with balanced outlets (1/4" plugs), would going to unbalanced devices cause a problem?

Would a sound card with twin rca jacks be less likely to cause a problem?

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That’s the part that has me worried. I split the Line-Out of my sound card to go to a powerful audio amplifier with speakers and also to a bass speaker with built-in amplifier.

But you can’t connect two different outputs of your sound card to each other. That will drive the system nuts.

Koz

Assuming that you mean taking a stereo out signal from your sound card and splitting it into two stereo signals to drive two stereo inputs, then it will work fine as long as you do not exceed the drive capabilities of the sound card output. If you try splitting the signal between several pairs of pairs of passive speakers or headphones, then you will probably destroy your sound card. Splitting the signal between two high impedance inputs such as the inputs of a domestic amplifier (typically around 20,000 ohms) then there should be no problem. Of course, if you make a mistake with your wiring and short out the output, then that could destroy your sound card.

Ooooo, an electrical engineering question. I just have to answer this one:

I would like to split the analog out from two outlets on a sound card with signal going to

  • one set of computer desktop speakers - with 1/8" plug
  • rca jacks on a stereo amp to inturn power a pair of speakers

It should work just fine. Outputs can generally be split amongst a few different high impedance inputs without any perceivable loss in quality. If you do more than a few though, the effective impedance might drop too low and cause the devices to draw more current than the sound card is going to like (even then there might be a limiting resistor to save the electronics). Two inputs will be just fine though, I promise.

Keep in mind that you can’t split inputs like this without putting resistors in-line with each incoming audio signal.

Will such a splitting degrade the quality of the signal going to each device?

It depends on the sound card, I’m sure. The potential problem is that It will increase the amount of current that the sound card has to supply. If your sound card doesn’t have any ‘left over’ current then you might be dropping below the threshold and the output will either gradually sag (it will sound like the volume is slowly lowering and becoming distorted) or shut off completely. However, I’ll be very surprised if you can notice a difference. Perhaps if you had some audio testing equipment you could find a difference, but even then I’m a bit skeptic.

If coming from a sound card with balanced outlets (1/4" plugs), would going to unbalanced devices cause a problem?

Not really. It’s my opinion that balanced outputs on a high impedance signal are wasted. High impedance signals are already pretty well immune to outside interference, so losing the extra conductor will probably not make a noticeable difference. On the other hand, if you’re running really long cables (more than 50 feet or so) then you might be able to notice the difference.

Would a sound card with twin rca jacks be less likely to cause a problem?

It might be easier to find cables. But other than that, no.

Hope I am not to bothersom with all these questions and details, here and other subject areas. It is great that a novice like me has a place to go to get info from people who know.

A few additional detials relating to the posted replies

    • The split will go to two devices that have their own power supply (the stereo receiver and the desktop computer speakers).
    • The sound card will have two 1/4" analog out plugs for left and right channel.
    • The cables from card to the receiver will be 6ft. The desktop computer speaker with the amp will be connected to the card with the speakers 6 ft cable and a short “Y” cable.

I was talking in future tense about the sound card for I am deciding on which one I can split with and have the performance that I want. I will be replacing the SoundBlaster Live 24bit. I want more than a Creative Labs card for my card need is only for music. I also want something better than the normal consumer card.

I have been looking at the M-Audio 192 and the E-MU 0404. I was going to go with the USB version but it does not have the needed analog in from a stereo receiver (mics and midiboard only). M-Audio FastTrackPro USB has the needed analog inputs and 4 analog outs with the 1/4" being switchable to unbalanced. The performance specs though were not high enough.

Question: Concerning the resistors that Alatham referenced.
– Are they passive devices that plug into the outlines?
– What exactly do they do?
– Where can I get them?

Question -Isn’t a balanced signal at a higher voltage than an unbalanced RCA jack is rated for? From sound card specs I read, unbalanced is -10db and balanced is +4, so a 14db difference. But would proper volume adjustment on the playback software prevent overdriving the receiver jacks?

Well…I feel foolish right now for the E-MU USB version of 0202 and 0404 both have two 1/4 line analog line ins. I went back to the E-MU web site and read over the user manuals for both. I got mixed up previously over the inlets use also for mic and hi-z.

The inlets will take unbalanced 1/4" as well as balanced.

On the output side

  • One 1/8" stereo plug…so perfect for the desktop computer speakers
  • Two 1/4" using unbalance or balance plugs…again perfect for connecting to the stereo receiver.

The 0202 specs are the same as M-Audio 192 for recording and better then 192 for playback. Depending where you buy, the 0202 is cheaper than the 192.

The 0202 and 0404 both have the same Analog- to - Digital specs (with 0202 having a slightly higher cross talk number. On the playback side the 0404 has much higher S/N ratio 117 to 112 and dynamic range 117 to 111.

It is now a matter of do I want to spend $70 more for better playback

Not necessarily. There are different “standards” used for “Line level”. Generally, -10 dBV is used for domestic equipment, and +4 dBu is used for professional equipment (note the different terminology as well as the different numbers). There are also regional variations, and some professional equipment is switchable between these two.

If you connect two pieces of equipment together that use different standards, then it will generally work fine, though meter levels will not agree. For example, if you connect a mixing desk that is designed to run at +4 dBu into an amplifier that is designed with line level at -10 dBV, then the amplifier will be driven well into the red while the mixing desk is still in the green.

So to answer that particular question, yes you can do it, but you will have to be very careful about your levels.

It is very easy for the unwary to be misled by number - they are like statistics in that they can be made to say whatever you want them to say. The difference between 117 and 112 S/N is likely to be very small, but when comparing sound quality there are very many factors involved - there are also many different ways to measure S/N ratio. Even if we assume that these figures are representative and measured in the same way, is the difference going to be noticeable? Will the difference just mean that we can hear next doors television more clearly on our recording? Will we just get a more exact reproduction of the microphone self noise?

I still have an old SoundBlaster AWE32 in one of my machines, and it is still capable of producing excellent recordings for certain kinds of work.

Question: Concerning the resistors that Alatham referenced.
– Are they passive devices that plug into the outlines?
– What exactly do they do?
– Where can I get them?

You don’t need them for what you’re doing. They’re only needed when connecting two or more outputs to a single input. You’re connecting one output to two inputs.

The 0202 specs are the same as M-Audio 192 for recording and better then 192 for playback. Depending where you buy, the 0202 is cheaper than the 192.

The 0202 and 0404 both have the same Analog- to - Digital specs (with 0202 having a slightly higher cross talk number. On the playback side the 0404 has much higher S/N ratio 117 to 112 and dynamic range 117 to 111.

It is now a matter of do I want to spend $70 more for better playback

I’m going to mirror what Steve just said. Those are just numbers provided by the company selling the equipment. It’s true that they’re probably not lying about them, but there is a lot we don’t know about how each company runs these tests. So it’s difficult for us to know how to compare the two sets of numbers.

Even further, the difference between an S/N ratio (aka SNR) of 117 to 112 is really really small. In order for your ears to theoretically hear the difference you’ll have to have the volume level turned up to at least 112 dB in the real world and have a very quiet listening environment. Even then, in all likelihood your receiver and your computer speakers will be acting as the bottleneck when you finally get around to listening to music. Unless you’re living in a recording studio, that extra money that you spent to get an extra 5dB of SNR will be wasted.

It boils down to this: The theoretical limit for human hearing is 120dB of dynamic range. The closer you get to this, the harder it becomes to hear the difference. With a little bit of training and some nice headphones you can hear the difference between an SNR of 40dB vs. 50dB. But it’s many times harder to hear the difference between 90dB and 100dB. The difference between 112dB and 117dB is negligible for all practical purposes.

The ambient noise from the refrigerator in the house next door will probably mask the difference.
If you are playing CD’s the noise floor of the CD is way above either of these figures (even if the amplification electronics are perfect with zero noise, which they are not). To put it another way, the manufacturer may be able to produce these noise figures in lab tests, but in a practical recording situation, you won’t.