General Question

pikipupiba's avatar

Where is the noise coming from when I hook several amps together and how do I fix it?

Asked by pikipupiba (1629points) May 20th, 2010

Please read everything!!! I have already tried many fixes. I appreciate any help, but I don’t want to be showered with things I have already tried!! Thanks!!

I have 3 Pyle Pro 3000 Watt Hybrid Amplifiers BIG PIC. They all have 2 inputs, 3 signal outputs, and 4 powered speaker outputs.

Inputs: Same stuff under different labels- DVD/CD and AUX

Outputs: Rec- Outputs original signal as it is recieved
PreOut- Outputs original signal leveled by main voume control
SubOut- Outputs only frequencies below 200 Hz with volume leveled by amps main volume control and separate SubVol nob

Whenever I try to rig them together lots of noise is created. For example, when I plug the PreOut to the AUX input of another. In this situation, noise is created in the amp that is OUTPUTTING the signal. Like just having it plugged in, not even playing anything. Changing the master volume of an amp DOES NOT change the volume of the noise, so even turning the volume to zero doesn’t get rid of it (WHY????????). Oh, and the noise fluctuates slightly. Its not a constant tone, it clicks occasionally and gets higher or lower.

Now for the observations!!!

I will describe a connection and then describe the noise. All the noise is generated in the amp OUTPUTTING the sound. So speakers connected to the amp outputting the signal to the other amp are affected. This noisy signal is then also sent to via the output to the other amp.

Rec to AUX- Least amount of noise, more high pitched. Stops if amp receiving signal is shut off.
PreOut to AUX- Lot more noise than Rec, stretches into lower frequencies. Stops if amp receiving signal is shut off.
Sub to AUX- Worst noise level. Same as PreOut, just louder. PERSISTS WHEN RECEIVING AMP IS SHUT OFF!

Ok, now some fixes I have tried and their results.

Thought: Their grounds aren’t synced up.
Action: Connect the grounds on the powered output channels.
Result: no change

Thought: Maybe the lights on the front are interfering???
Action: Dim the LED’s on the front panel.
Result: Noise quiets down and loses the lower frequencies. (WHY????)

Thought: I give up, I’ll try anything.
Action: Connect the signals on the powered output channels.
Result: Very weird. One amp shorts (don’t worry, built in protection), then noise changes. The noise persists, but its tone changes. (WHY???????)

Ok, just two questions: Why is this happening and how do I fix it?

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7 Answers

Buttonstc's avatar

Feedback. They are too close to each other. Experiment with different configurations separated in various ways.

jazmina88's avatar

I have a peavey amp that has a rumble…...too close to my keyboard, I think.

new cords?

john65pennington's avatar

Could be feedback, because of the closeness of each amp to the other. also, could be polarization. if there is more than one amp plugged into the wall, try turning the plugs in different directions, before inserting into the wall outlet.

IchtheosaurusRex's avatar

Ground loops. Try tying all signal grounds to earth ground.

njnyjobs's avatar

If you’re diasy chaining the amplifiers then you will not get the desired results. If Amp1 is connected to Amp2 which has the speaker connections, the signal you’re trying to output from Amp1 will be overly/excessively amplified as it passes thru Amp2 thereby creating the noise. Adding the 3rd Amp to the equation would probably make it worse.

The typical signal chain et-up would be a Pre-Amp connecting to a Noise Gate and then to a Power Amp that outputs to the Speakers. . . . you’re equipment may possibly lack the features to truly process the signals as a Pre-Amp (Pre-Out) or a Noise Gate. (Sub-Out).

pikipupiba's avatar

@Buttonstc I kinda want them to be really close so they are not taking up a bunch of room. Is there any other way to get rid of the feedback?

@jazmina88 I am looking for some new cords, yes. Do I need shielded or something?

@john65pennington The plugs all have ground prongs on them.

@IchtheosaurusRex How do I tie them all to Earth ground???

@njnyjobs The original signal is only AMPLIFIED through the PreOut connection at volumes above 50 (main volume stretches from 0 to 64), otherwise it is reduced. The noise even happens at 0 volume (WHY???). Seeing as these are pretty cheap amps with lots of features, I wouldn’t doubt that they lack the ability to truly do all the things they say they can do effectively.

IchtheosaurusRex's avatar

@pikipupiba , run a wire to the grounding tap of a 3-pronged outlet, or just to the screw that holds the wall plate to the junction box.

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