Interference on Audio out inter-connects

dohouch

I have the audio outs from a Sat FTA receiver and a Sky box combined and feeding to the AUX-in of a mini-HIFI system. The combining is done with simple 2 into 1 cables. This used to work, with reduced volume, on my previous setup but now since changing the FTA receiver (old receiver FTA Topfield, new receiver Technomate) it doesn't.

What do I need to do so that these work without interferencece.


I use the Sky box because having the "Magic Eye" in another room is a great feature for me.

Been rooting round the interweb and now know that it is down to mixing unbalanced inputs. See here "Why Not Wye?"

A wye-connector used to split a signal into two lines is being used properly; a wye-connector used to mix two signals into one is being abused and may even damage the equipment involved.

Here is the rule: Outputs are low impedance and must only be connected to high impedance inputs -- never, never tie two outputs directly together -- never. If you do, then each output tries to drive the very low impedance of the other, forcing both outputs into current-limit and possible damage. As a minimum, severe signal loss results.

and the solution in the picture below



I've been using Wye connectors to join the 2 audio outputs.

Problem, this diagram means nothing to me, Can I buy something that will do it for me? or how should I go about it?
Thanks

dohouch

Found 2 different retail solutions:
One in the USA $44 +$9 p&p HERE

Powered by USB, the TinyMix can be plugged into a computer, a powered hub, or into a USB voltage adapter. An LED indicator lights to show that it's powered on. When powered off, the TinyMix will operate in passive mode, which draws its operating power from the audio inputs themselves, at a cost of reduced volume.

And at Maplins £10.99 + £8.99 p&p!!!!!!!!! HERE

A 4-way switch box connecting three stereo pairs of input phono sockets to one stereo output pair for connection to a stereo amplifier. The three phono inputs are labelled 1: ‘CD/MD’; 2: ‘TAPE/DAT/DCC’; 3: ‘VIDEO SOUND’. In addition an ‘AUX’ input (number 4) is provided as a stereo 3.5mm jack socket. The selector switch is in the form of a 4-way rotary knob labelled 1 to 4, on a sloping front panel.

I'm 100 miles from any Maplin, they don't half screw you on p&p!!!!

earpiece

dohouch,
Those 'jagged line' things in the drawing are just resistors...... the two 470Ω (Ω=Ohm) with a 5% tolerance (ie. + or - 5%), are in series with the 'live' output of your device, and the 10,000Ω resistor is in parallel with the combined output. The return (or neutral/neg) are all connected together.

Suitable resistors should only cost about 20cent each.
Cheap way to do it is to go find yourself an electronics student to throw one together for you.

dohouch

@earpiece: Thanks for the explanation, but I travelled to Cork and bought the Maplin unit. It's a nice unit, old fashioned solid metal box and very firm switch.

P.S Spotted a single F-Connector for sale= €3.55