1/4" - XLR using an isolated transformer

[drew4663]

I am new to doing things on my own. I usually would just buy it from the store but I am trying to venture out and have some fun. I have a 1/4" - XLR that is unbalanced. Playing a bass or guitar through the wiring does just fine but when I hook up a TD-20 (roland drums) I get a nasty buzz/hum.

I have one wire going from (1/4" - T) to (XLR - pin 2)
The second wire going from (1/4" - S) to (XLR - pin 3)
and then a jumper from (XLR - pin 1 to 3)


I bought a radio shack isolated transformer 1:1 and it has four wires on it. I am wondering where I would hook these wires into the mix of the above configuration to reduce/kill the buzz/hum.

I also bought a 100ohm/1watt resistor. I heard I could do this configuration and it work just the same.

I have one wire going from (1/4" - T) to (XLR - pin 2+)
The second wire going from (1/4" - S) to (XLR - pin 3G)
and then the resistor from (XLR - pin 1- wire to pin 3G)


I would like for both options to work and to know how. I have searched a lot and haven't found anything or I am just too simple minded and can't see it staring me in the face. Any help would be so helpful because the band using the equipment is needing it tomorrow.

[imix500]

If the transformer has no center tap, I would just connect it like you had it before- Tip and Sleeve to one side, Pin 2 and Pin 1&3 tied together to the other side. That will break the ground connection.
Keep in mind the bass response probably won't be great in such a small transformer.
There is a pretty big impedance mismatch here, you really should be using a matching transformer or direct box. Most modern well designed preamps can handle a pretty large mismatch, so it should work.

[drew4663]

Sorry if I am misunderstanding what you are saying.....

If the transformer has no center tap, I would just connect it like you had it before

By the above are you saying I shouldn't need the transformer based on the below config?

I have one wire going from (1/4" - T) to (XLR - pin 2)
The second wire going from (1/4" - S) to (XLR - pin 3)
and then a jumper from (XLR - pin 1 to 3)

If so, I am needing the buzz/hum isolated thus the need for the isolated transformer.

[imix500]

Sorry,
Without a center tap you won't be able to get a true balanced output easily, but it not absolutely necessary for a quick fix.
Wire the transformer in-line, with the 1/4" on one side and the xlr on the other. The packaging should have come with a diagram of the transformer.

[Speedskater]

XLR pin 1 has nothing to do with the audio signal. XLR pin 1 should be connected only to chassis and cable shield. But your 1/4in plug is mono (T/S not T/R/S) so don't connect the 1/4in shield to the XLR shield.