1/4" input not working using RCA jacks?

[dinkyguitar]

Hi All,

I have a Hafler P-125 power amp with 1/4" jacks for inputs, no rca jacks.

My Harmon Kardon receiver has RCA pre-outs so I can run a separate power amp to drive rear speakers. But when I run the rca jacks to the Hafler power amp using rca to 1/4" adapters there's no sound?

Are 1/4" inputs different than rca inputs?

My mp3 players works fine...and what I did was spice an rca jack into a 1/8" stereo cable....

I just can't figure out why I can hear anything when I try to use my receiver and power amp?

dinky,

 

[Bone]

You probably find that the output from the receiver is too low to drive the Hafler. Do you know what the output of your receiver is. Your MP3 player could put out up to 2v rms. I dont think the HK receiver would do that.

 

[tinitus]

some jack plugs have shorted input
I think its called switching plugs
or could be mono to stereo issues
might result in shorted signal/ground

 

[dinkyguitar]

Thanks for the responses,

Bone, the manual I have shows a picture of rca cables running from the receiver pre-out to "Line-In" of the power amp...I think your right about the signal being too low since the diagram shows going into "line-in".

dinky

 

[tinitus]

even so, you should be able to hear something

if you hear nothing at all, theres either no connection, or its shorted

 

[Terry McGee]

What you don't know is if the receiver isn't sending, or the amplifier isn't listening, or the cable isn't carrying. So you need to devise a troubleshooting technique that will close in on the problem. For example, if you pull the RCA connector from the back of the receiver (with the other end still connected to the amp), and touch a licked finger to the centre pin, do you hear a happy brrrp from the speakers? (Make sure the volume control isn't too low!) If that works, the problem must be at the receiver end. If not, it must be cable or amp. Now, depending on your resources, determine a way to work out which one it is.

One thing to ponder is that an amplifier with jack inputs is possibly intended for professional use. It probably has a balanced input, and may require +4dBm input levels. These could be contributing to your problem.

It's possible that, if it has a balanced input, your RCA to 1/4" jack is not earthing the input return (normally the ring on a TRS jack). I've had situations where adaptors wouldn't work or were at best unreliable.

But, anyway, get past the wet finger test and come back to us.

Terry

 

[Charles Darwin]

Could depend on if your 1/4 jacks are TS (tip+sleeve) or TRS (tip, ring + sleeve).

The latter are balanced, just like XLRs, and you would have to make up a special TRS to rca lead because otherwise ring and sleeve will just short each other and you'll hear nothing.

 

[Soldermizer]

Should be pretty simple to troubleshoot. I have had good luck with 1/4 adaptors (Ebay from China) for my Behringer amp (ditto). There is always the Redneck Troubleshooting Method ("If it makes trouble, shoot it!")