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My subwoofer is making a thundering noise, can anyone help?

sergeantsam

Sep 17, 2023
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I bought a Fusion cs-at1100 subwoofer at a Carboot sale, but because I do not have a functioning car, I wanted to have it in my room. I bought an old Xbox 360 power supply because it has the right specs but when I spliced the wires it worked but it started making a thundering noise when I turned it on, even without plugging in any aux. is this an internal issue or something I can fix? any help would be appreciated :) how I got it to power on is below.
 

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Delta Prime

Jul 29, 2020
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Here you go kiddo.
Screenshot_20230917_121957.jpg
 

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Delta Prime

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yeah no ive already basicly studied this but i still can make sense of why it makes this rumbling noise even before i plug in my aux cables.

I can explain it but it can't make you understand it.
Because amplifiers always want to oscillate and oscillators always want to amplify.
The input to your amplifier is the auxiliary connection. With nothing on the input and the amplifier powered then the input becomes an antenna.
Your input Nearfield capacitivity coupled(Farfield would be Inductively coupled) RFI (Radio Frequency Interference )along with EMI (Electro Magnetic Interference). There is electromagnetic radiation all around you ,if you get close to the auxiliary input it will amplify the oscillating 60 or 50 HZ signal coming from the mains power connection, where you plug in your power supply.
The result being what you have just described. You're going to blow your amp. But you will learn. Incidentally it's more apparent with your setup because you're power supply output is not isolated from the mains.
 

kellys_eye

Jun 25, 2010
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What did you do with the red/blue wires from the power pack? If they are shorted you'll get 'issues'.

Similarly, to get the full amperage from the Power Pack you must use ALL the yellow wires into the 12V feed of the amp - fit a shorting link between the +12V input and the centre pin. By not using ONE of the yellow wires you limit the current deliverable by a factor of 1/4.

Although the XBox PSU isn't rated to supply the maximum the amplifier needs it WILL power it although you'll get issues at higher volume levels - it should work just fine at lower levels.
 

Martaine2005

May 12, 2015
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Isn’t this PSU a SMPS?.
Which isn’t good for audio due to the inherent noise they produce.

Martin
 

Delta Prime

Jul 29, 2020
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Isn’t this PSU a SMPS?.
Which isn’t good for audio due to the inherent noise they produce.

Martin
High-end switch mode power supplies are well filtered.
EMI (electromagnetic interference)
Is an electromagnetic disturbance from source to your equipment, which is the victim.
So it propagates from source to victim by means of conductive interference (power cables) radiated interference capacitive & inductive interference. A ferrite bead with a conductor through it is used forming a low pass filter to attenuate EMI.
photo_1695018713390.png


Now( EMC ) comes into play Electromagnetic Compatibility. Which is defined by (IEC) Electrotechnical Commission; The ability of an equipment or system to function
satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic
disturbances to anything in that environment.
When a piece of electronic equipment is supplied with an under voltage and or undercurrent source, it is more susceptible to EMI. . As the under current switch mode power supply source of the OP just demonstrated.
 

kellys_eye

Jun 25, 2010
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I suspect he's shorted the 5VStby supply (red/blue wires) causing the SMPS to cycle a fault status.
 

sergeantsam

Sep 17, 2023
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I can explain it but it can't make you understand it.
Because amplifiers always want to oscillate and oscillators always want to amplify.
The input to your amplifier is the auxiliary connection. With nothing on the input and the amplifier powered then the input becomes an antenna.
Your input Nearfield capacitivity coupled(Farfield would be Inductively coupled) RFI (Radio Frequency Interference )along with EMI (Electro Magnetic Interference). There is electromagnetic radiation all around you ,if you get close to the auxiliary input it will amplify the oscillating 60 or 50 HZ signal coming from the mains power connection, where you plug in your power supply.
The result being what you have just described. You're going to blow your amp. But you will learn. Incidentally it's more apparent with your setup because you're power supply output is not isolated from the mains.
so is it a problem of insulating my power supply wires more to limit the interference from them into the aux input? or is it goint to be always present because i am splicing wires.
 

bertus

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Nov 8, 2019
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Hello,

What happens when you short the aux inputs?

Bertus
 

Martaine2005

May 12, 2015
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my electronics knowledge has been gained from gcse DT and Alevel physics, so i do not know what this means. how would i check that i have shorted the 5VStby supply?
In your photo, the blue and red wires are ‘together’ under insulating tape.
Are they tied, twisted or soldered together?.

Martin
 

sergeantsam

Sep 17, 2023
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In your photo, the blue and red wires are ‘together’ under insulating tape.
Are they tied, twisted or soldered together?.

Martin
Twisted, I was going to solder them but I wanted to make sure it worked before I do anything more permanent.
 

kellys_eye

Jun 25, 2010
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Twisted, I was going to solder them but I wanted to make sure it worked before I do anything more permanent.
Separate them. Insulate them individually. The fact that they are shorted is causing the 'wooping' issue.
 
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