Backgroung hum\interference from amp

kelbal

Hi Guys,
I have a new amp, and I'm connecting my old speakers to it. My old amp was rated 8 ohms on the back where the speakers connected, and the speakers say 8 ohms also.
Where I'm connecting the speakers to on the new amp is screw-in connections (not sure what the proper terminology is), and it says these are reate 8-16 ohms. With the speakers connected and the amp turned on I'm getting a background hum\interference. Definitely not there on the old amp, so the speakers are fine. Is it anything to do with the new amp being rated 8-16 ohms and not just 8?
There's also RCA output connections on the amp, is it worth giving these a shot? I'd have to solder RCA connections onto the speaker cable. Here's what the back of my amp looks like............

b318isp

Sounds like an amplifier problem - but may be cable problem on an input. If the hum persist when you change the input channels, it's probably the amp. If it is one one input only, disconnect the corresponding input cable - if the hum disappears, the cable is defective.

Also double check you've made the Left and Right speaker connections to the correct + and - terminals.

There is also a slight chance that something else with a strong magnetic field (e.g. speakers, laptop power supply) could cause it - ensure that anything like this is kept around a metre away.

The RCAs are not for speakers.

FYI, many amps will have some low level of hum or hiss.

kelbal

b318isp wrote: »

Sounds like an amplifier problem - but may be cable problem on an input. If the hum persist when you change the input channels, it's probably the amp. If it is one one input only, disconnect the corresponding input cable - if the hum disappears, the cable is defective.

Also double check you've made the Left and Right speaker connections to the correct + and - terminals.

There is also a slight chance that something else with a strong magnetic field (e.g. speakers, laptop power supply) could cause it - ensure that anything like this is kept around a metre away.

The RCAs are not for speakers.

FYI, many amps will have some low level of hum or hiss.

Thanks - what are the RCA outputs for then? Is it not possible to wire speakers to them?

The amp is in my TV cabinet - with the TV and a portable hardrive right beside it. There's also a CD player (bought with the amp), on top. So maybe there's some interference. I'll take the amp out, away from all this, and see what its like on its own

b318isp

Thanks - what are the RCA outputs for then? Is it not possible to wire speakers to them?

They are unamplified signals that can used to connect to other devices, e.g. power amplifiers, recorders, TVs.

The amp is in my TV cabinet - with the TV and a portable hardrive right beside it. There's also a CD player (bought with the amp), on top. So maybe there's some interference. I'll take the amp out, away from all this, and see what its like on its own

There is a slight chance the TV is causing interference, but I'd rule out the cables first.

ZENER

Do you have the TV connected to the amp inputs ? TV's are renowned for causing hums and hiss and buzz in my experience. As asked above is the hum present on all inputs ? Does the volume control have any effect ?

Start by disconnecting all input sources - CD player etc. - from the amplifier and turning off the TV and any other devices nearby. Is the hum still there ?

Ken

kelbal

I just investigated a little more. The speakers are fine, no cabling issues there, as there is no 'hum' when connected to the old amp.
I took the amp\CD player away from the TV unit to test, to rule that out.
With just the amp plugged in, and the speakers connected, there is no hum\buzz.
However, when I connect the CD player to the amp, thats when the noise comes. I'm using a Red\Black RCA analog audio cable. I've tried a few different cables.
So the amp gives this noise when you connect an input to it.

kelbal

........ interesting update! The amp\CD player came with audio cables with red\black RCA male connectors on them. The female ports on the back of the amp\CD player are red & white. I didn't pay any attention to this, I assume the colour of the connector doesn't really matter, and I do still beleive this. However, looking at my old equipment setup, the cables are red\white - so I took one of these to my new system, and hey-presto, noise gone! I don't know what the significance of the black connector is versus the white one, Id imagine there's no difference - but when I swapped over to an old cable (thats probably been in use for over 20 years), its all fine now.
Is it just faulty cables that were shipped with the new equipment, or are they cables for a different purpose?