How do I connect 2 outputs to 1 input without a mixer?

Peter · Post by **Peter** » 24 Nov 2002 12:40 pm

I need to connect the output of my guitar effects procesessor and the output of a cd player to one input.

The output of the cd player is a headphone socket, so it may be low impedance.
I dont know the impedance of the effects. The input is a normal line input for an
amplifier- not a guitar amp.

I dont want to use a mixer, just a couple of stopper resistors to create a passive mixer. How would I connect those and what are the values?

My first attempt :<fontsize=0>
<pre>
GUITAR FX >------------------+
+
+
CD PLAYER >---[RESISTOR A]---+-----------------> OUTPUT to AMP INPUT
47k? +
|-|
| | RESISTOR B
|_| 500k?
+
+
GROUND >------------------+-----------------> GROUND</pre>
<fontsize=2>
If this is correct, what would the value of resistor A and B be?
Ignore stereo for the moment.
Thanks!

------------------
Peter den Hartogh-Fender Artist S10-Remington U12-Hilton Volume Pedal-Gibson BR4 lapsteel-Guya "Stringmaster" Copy-MusicMan112RP-Peavy Rage158- - My Animation College in South Africa

[This message was edited by Peter on 24 November 2002 at 01:03 PM.]

Ole Dantoft · Post by **Ole Dantoft** » 24 Nov 2002 2:02 pm

Peter,

I would omit resistor "B" and instead add another resistor "A" in series with the FX-unit since both are bound to have fairly low output impedances which would "eat up" each others signals otherwise. You will get a fairly large signal-loss with a passive circuit whatever you do, but start out with 47k in the CD-player line and experiment with the FX-line - it WILL work, but it won't be the optimal solution !

Ole[This message was edited by Ole Dantoft on 24 November 2002 at 02:04 PM.]

Peter · Post by **Peter** » 25 Nov 2002 12:23 am

Thanks, Ole. I dont mind signal loss on the CD player, as it has an output control. But I would like to minimise the loss in the FX line. Can you make a suggestion for the minimum value for the FX-line resistor? And does it help the FX line resistor if I increase the value of CD line resistor?
What would be a good starting point for both values? Maybe 33k for FX and 470k for CD?
Thanks
Peter

------------------
Peter den Hartogh-Fender Artist S10-Remington U12-Hilton Volume Pedal-Gibson BR4 lapsteel-Guya "Stringmaster" Copy-MusicMan112RP-Peavy Rage158- - My Animation College in South Africa

Bill Crook · Post by **Bill Crook** » 25 Nov 2002 4:01 am

Peter............

Resistor B need to be on the CD player side of Resistor A. As it is now(in your drawing,) it will load down the guitar fx signal. Now, mind you that both signals will be about 0 db in strenght,meaning,you will need some manner of controling the output of each device.

The porportional value of Resistor B should be 5 times lower than the value of Resistor A. (Be sure to place resistor B in front of resistor A) This lower value will present a load to the CD player output to keep from damageing the device.

If you swaped the values of A and B, I think that would work just fine.

Louie Hallford · Post by **Louie Hallford** » 30 Nov 2002 5:58 pm

This sounds like a common Radio Shack item to me. Do you have Radio Shack store in your country.
If not email me. I think I can easily find what you need.