2 x 3.5mm audio sources to 1 amplifier?

Question

One audio source is coming from a desktop computer via 3.5mm aux cable and the other audio source is coming from a DVR via RCA to 3.5mm cable. I have checked and the sound works from both sources when I individually connect them to the amplifier but I want both to be connected and playing simultaneously to the amplifier which then plays the audio to the ceiling speakers.

If I would use just a simple y splitter to merge the two audio sources to the amplifier, would one source short out the other when either is off and the other is still running? From what I know I think that would happen. Therefore I need an audio mixer which I bought for cheap online. I tried this one out by connecting it to AC power then using 3.5mm to 1/4 inch converters to connect the audio two sources to the mixer then used a 1/4 inch to 3.5mm converter to connect the audio out from the mixer to the amplifier using a 3.5mm cable since that s what the amplifier input requires.

Now the problem is that I hear so much noise from the mixer that I can t even make out the audio sources clearly whether I connect both sources or just one. Probably because it s cheap but why is this mixer creating so much noise that I can t even hear the audio sources. The volume controls on the mixer don t help at all so is there something I did wrong or that I am missing?
Thanks

Answer 1

If leads are screened and the mixer is of reasonable quality it should work ok.

I personally wouldn't use headphone Y-splitter as they tend to be cheap and poor quality. nor would I put anything in the signal path, in fact a strong signal into the LINE IN input of a mixer is likely to have less noise on it. Amps and Mixers tend to work better if a used gain control is not near the top or bottom of its range. If the sound is good with just one audio source it should be good using even a relatively cheap mixer.

You CAN short out audio level signals without harming the equipment but if the sources are not well matched, one signal source can pull the other down volume-wise. I think it's worth it to invest in a small audio mixer.

Since you will have 2 audio devices AND a mixer before the amp you will need to experiment with gain & volume controls to get the best sound.

Answer 2

Hi as a mixer desk is the best isolation between there two and when using a microphone best to use the phantom power as it cuts down on crosstalk between some sources.

Answer 3

MIXER INPUT CONTAINS PRE-AMP THAT PICKS UP 60C/S ELECTRIC HAM OR NOISE VERY EASY BECAUSE IT HAS HIGHER IMPEDANCE.

THEREFORE , ALL THE WIRING FROM BOTH AF OUTPUT SOURCE MUST BE WIRED WITH GROUNDED SHIELD COAXIAL CABLE TO BLOCK OUTSIDE ELECTRICAL 60C/S HAM NOISE.

THIS IS THE BASIC KNOWLEDGE TO DEAL WITH HIGH GAIN AF AMPLIFIER.

Answer 4

I'd guess the mixer is intended for different audio levels or impedances.



I have used a basic mixer to do a virtually identical thing and it did work well.

That one was a "Soundlab" brand, with four stereo channels.







Or, the problem could be that you are linking the grounds between different items - the computer, DVR and amplifier, That can cause a "hum loop" which adds some level of "buzz" to the audio.

With a PC that can also include various hisses, clicks and squeaks which vary as you do things on the computer...



I got around that by using the S/PDIF optical output on the PC and a little DAC box working on the same supply as the rest of the audio gear. You could theoretically use a ground isolator as sold for use with car audio gear.





If you know someone who can solder, you could get a passive mixer made up - just two 3.5mm cables to connect to the PC and DVR, with a 100 Ohm resistor connected in line with each channel (left and right) to a common point that connects to the amplifier output cable. Link the grounds on all three cables.



That will half the level from each source but provide a safe load and prevent possible damage if either is turned off.



This is the circuit, not counting the joined grounds [ yahoo has included the image, below]:

https://i.stack.imgur.com/7KfSR.png



Use 100 Ohm rather than 10K for your application, if they are both headphone/speaker outputs. The 10K as shown would be ok for "line level" audio that's not intended to drive low impedance loads.



These are typical ground loop isolators, if you need one for the PC:

http://www.ebay.co.uk/itm/PRO-DJ-3-5MM-JACK-GROUND-LOOP-ISOLATOR-TO-PREVENT-UNWANTED-HUM-OR-NOISE/291588896170



http://www.hallresearch.com/page/GLI-35mm

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Answer 5

Headphone jacks are very low power so you actually CAN use a stereo (not mono) "Y" adapter to mix the two signals together.



Your problem will be that one source will probably be louder than the other.



(Why do you want both playing at the same time? You are doing something really strange...)



They do not seem to make audio mixers that take 3.5 mm jacks. All those adapters - I suspect these are what is causing problems. You also should make sure your wires are shielded coax, not the skinny "headphone wires" as these will let in a lot of noise.



I have a small "Hopewell" switch box that takes 3.5 mm inputs to a single output. I have 2 desktops and a macbook that I feed a single pair of computer speakers. It is similar to this:



http://electronicsusa.com/mk1and2.html

Answer 6

not sure