Looking for some help on getting rid of speaker interference...

purbeast

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As some of you may know, I am in the process of converting my Rush 2049 cabinets into full on racing emulation machines using the original hardware.

I have a thread on that here if anyone is interested - https://forums.arcade-museum.com/th...to-emulation-racing-machines-work-log.554376/.

I am running into an issue right now with having some interference in the speakers however.

I have all 5 speakers hooked up and connected and it's all working, but as mentioned, it's got some interference and I'm trying to figure out how to rid of it.

I am using a 24v Mean Well power supply ( https://www.amazon.com/dp/B013ETVO12 ) to power the 2 amps( https://www.amazon.com/dp/B0DCN8472L ) for the speakers, as well as the FFB motor.

I have another ATX PSU that is powering the PC and that ATX PSU also powers the UFFB (which is the interface board between the PC and the arcade parts) via the USB plug, on 5v. I also have a 4 pin molex connector from the ATX PSU going into the UFFB to pass through the 12v to power the lamps on the cabinet.

Now I have removed a lot of this from the circuitry to try and track down the cause of the interference, but I am still getting it with minimal stuff hooked up.

Right now all I have hooked up is the PC and then the 24v PSU is ONLY powering 1 amp, and that 1 amp ONLY has the 2 front speakers connected to it.

I also have grounded the ATX PSU in the PC with the 24v PSU by running a wire from the -V on the 24v PSU to a ground pin on one of the 4 pin molex connectors.

The speaker wires are coming from the 4 speaker wire pins on the JAMMA harness that I pulled. Now to be clear I pulled the pins and wanted to keep everything stock, so what I did was extend the wire from the JAMMA harness for those 4 pins to the amp. But I did not solder them and did not want to cut the pins, so I basically stripped like 1" of wire, put it through the pin and then wrapped the rest around it, and then used heatshrink to keep it pressed hard against it. If this could be the culprit, then I'll definitely just cut and solder wire but I was trying NOT to do that and thought this would be okay.

The UFFB is not being powered at all, there USB cable is not connected between the PC and it, and the 4 pin molex connector is not connected to the UFFB. I also pulled the power from the motor, so the motor is not getting any power as well.

And even after doing all of that, with JUST the 2 front speakers hooked directly to the AMP, I am still getting the exact same static as I was getting with everything else hooked up.

So does anyone have any ideas on how I can try to fix this?

EDIT:

Oh and also, the original PSU for the cabinet is not plugged in at all or turned on. I also disconnected the 2 wire bunches from the original power supply that went all through the cabinet wiring. I wasn't sure if this information would be of any help.

EDIT 2:

Oh one more detail - there is no CRT in the cabinet either, there is an LCD that is just being plugged into it's own outlet on a power strip.
 
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A switching power supply is NOT a good choice for an audio amplifier. It's going to produce noise, especially if there is a lot of current draw.
And, it may just be a problem with the switcher that you have. Some are noisier than others.
Also, a motor of any kind should never be the same power supply as an audio amplifier.

You should use a separate analog power supply for your audio.
I don't know the inerds of Rush 2049, but if the original PSU is analog, put it to use for the audio amp.

If you can't find an analog power supply for your amp, at least get a large capacitor to stabilize (filter) the power to your amplifier.
 
A switching power supply is NOT a good choice for an audio amplifier. It's going to produce noise, especially if there is a lot of current draw.
And, it may just be a problem with the switcher that you have. Some are noisier than others.
Also, a motor of any kind should never be the same power supply as an audio amplifier.

You should use a separate analog power supply for your audio.
I don't know the inerds of Rush 2049, but if the original PSU is analog, put it to use for the audio amp.

If you can't find an analog power supply for your amp, at least get a large capacitor to stabilize (filter) the power to your amplifier.
I just tagged onto that PSU since I already had it for the motor.

But I also removed the motor completely from the picture and see the same noise as I do when it's hooked up.

When you say a problem with the switcher, what are you referring to?
 
From Gurgle:

A switching power supply works by first rectifying AC to DC, then "chopping" this DC into high-frequency pulses using a transistor. These pulses are fed to a high-frequency transformer to step the voltage up or down, which is then smoothed by filtering to produce a stable DC output. This rapid on/off switching allows for a smaller, more efficient power supply compared to linear regulators.

By nature, switching supplies are "noisy" compared to a linear supply. The original 2049 supply is also a Switcher, but may have better filtering on the output(this is why Sean suggested placing a large filter cap across the PS output feeding your amps)

Idk if the OG supply has 24V out... I would try it powering the amp if it does. You could try powering the amp w/12v as a test if thats all the OG supply has to see if the amp quiets down.

Does the other amp behave the same way? Maybe the front amp is more sensitive to the switching frequency of your Switcher.

D
 
From Gurgle:

A switching power supply works by first rectifying AC to DC, then "chopping" this DC into high-frequency pulses using a transistor. These pulses are fed to a high-frequency transformer to step the voltage up or down, which is then smoothed by filtering to produce a stable DC output. This rapid on/off switching allows for a smaller, more efficient power supply compared to linear regulators.

By nature, switching supplies are "noisy" compared to a linear supply. The original 2049 supply is also a Switcher, but may have better filtering on the output(this is why Sean suggested placing a large filter cap across the PS output feeding your amps)

Idk if the OG supply has 24V out... I would try it powering the amp if it does. You could try powering the amp w/12v as a test if thats all the OG supply has to see if the amp quiets down.

Does the other amp behave the same way? Maybe the front amp is more sensitive to the switching frequency of your Switcher.

D
The other amp does have the same type of interference.

I am wondering if I could cut into the 12v coming off of the PC ATX PSU and see if I get any interference with that.

EDIT:

I just tried 12v from the PC ATX PSU and it had the same kind of interference and may have been worse. But a quick google search also reveals PC ATX PSU's are also switching supplies.

I wish I had just a random AC adapter to plug in the wall just to compare, but unfortunately I do not. I looked all over. I had a 19v one but the plug size doesn't fit.

EDIT 2:

I just realized the arcade PSU has a 4 pin molex connector coming out of it, so I just tried powering the amp with that, and it's doing the same thing still.
 
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I also notice that the amps you are using sell for $20
Do you really expect great sound from a $20 part?

It's also possible that the noise is coming from the original signal from the PC and is not your amps at all. You need to test that.
Find an old stereo amplifier and feed the sound source into the AUX input to hear if it's clean.
If it is, get a better, "linear" power supply. Amazon has a few good ones made by "Pyramid"

Or better yet, just use that old 1990 era Stereo you picked up at the Good Will. It will have better sound than those cheep Chinese amplifiers.
 
I'm using even cheaper 5v amps to power two other cabinet speakers running a JPAC and I know people who use this same amp to power virtual pins.

I'm also not looking for audiophile quality lol I just want normal arcade quality with no interference.
 
Understood.
The test is still important though. You need to know if the noise is from the source signal (the PC), the amplifier, or the power supply.
If you feed the source signal into a different amplifier, you can determine if the noise is from the source or from your new amps.

Is this noise a constant hum/buzz, or a distortion on the sound?
 
Understood.
The test is still important though. You need to know if the noise is from the source signal (the PC), the amplifier, or the power supply.
If you feed the source signal into a different amplifier, you can determine if the noise is from the source or from your new amps.

Is this noise a constant hum/buzz, or a distortion on the sound?
It is like a hum/buzz, and it seems when the PC is "doing stuff" sometimes I hear it more. When the PC isn't "doing stuff" sometimes I also hear this little pulse.

I was playing around with it right now and just had some strange findings...

I am using a better quality 3.5mm cable as well now which seemed to make a difference.

I had 1 amp powered with 2 speakers and the sub going to the PC. I have the PC connected to the UFFB with a USB cable, which also powers the UFFB with 5v. I have the motor powered and that is all connected as well.

When I do that, I get VERY minimal noise in the speakers. Like I have to put my ears right next to it to hear anything, and it's the same kind of noise as before, but again, can barely hear it.

I then tried grounding the PC to the 24v PSU and when I did this, I get the bad noise back. So I removed that.

I then tried putting the 4 pin molex into the UFFB to get the 12v to the board to pass to the lamps, and again, the same exact noise that is bad.

I then remembered there is a 12v screw terminal, so I tried running just 1 wire from the ATX PSU to the 12v screw terminal.

When I do that, bam there is hardly any noise, only if I put my ear RIGHT next to it.

The difference between the 4 pin molex to get the 12v and the 12v screw terminal is that with the terminal, there is 2 less ground wires going to the UFFB.

From these tests, it seems like adding MORE ground wires is what is causing the noise, and that the more I can remove, the less noise I am getting.

But I am just not knowledgable enough or smart enough in this area to have a clue why or how that is causing it.
 
Some detail on the "interference" would help. Is the interference there with ONLY the speakers powered, or do you have the audio input connected to the PC as well? I know you said you don't have a separate power supply, but I'd try to track one down (maybe borrow from your Wi-Fi router or some other consumer device?) and make sure the amp just isn't garbage.

And we went through a lot of the same stuff in your thread a few months ago: https://forums.arcade-museum.com/th...esolving-a-bit-of-screen-interference.551238/ . If you also have the audio cable connected to the PC, a ground loop isolator may help. That's the thing you used in the last thread that mostly fixed the interference, but sounds like you returned it after switching to AB mode also fixed it. So, I'd buy another one of those and try that.

DogP
 
Some detail on the "interference" would help. Is the interference there with ONLY the speakers powered, or do you have the audio input connected to the PC as well? I know you said you don't have a separate power supply, but I'd try to track one down (maybe borrow from your Wi-Fi router or some other consumer device?) and make sure the amp just isn't garbage.

And we went through a lot of the same stuff in your thread a few months ago: https://forums.arcade-museum.com/th...esolving-a-bit-of-screen-interference.551238/ . If you also have the audio cable connected to the PC, a ground loop isolator may help. That's the thing you used in the last thread that mostly fixed the interference, but sounds like you returned it after switching to AB mode also fixed it. So, I'd buy another one of those and try that.

DogP
The interference starts like half way into Windows booting up. Like when the logo comes up and you see the spinner, a couple seconds after that it starts. If it's not connected to the PC there is no speaker interference.

It's hard to explain the sound but I don't know if I'd call it a buzz. It's more of like a scratchy sound. And it does seem once Windows is loaded up more, that scratchy noise goes away and then it's more of like a bit of a buzz possibly, but then I hear something that is like pulsating every 1/2 second or so maybe? When I am actually playing games too, I don't hear it at all since the game sound just overpowers it completely.

I actually also found that old thread when I was googling this subject lol. And I did order one of those ground loop isolators, and it's arriving by 12:30pm today, so I'll be able to test that out.

I also have some higher quality audio cables that I ordered so I'll try both of those once I get the isolator.

EDIT:

One thing to note too is the interference is there whether the Windows speaker volume is turned up or is completely off. The Windows volume has no effect on the loudness of it.
 
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Okay I got the ground loop isolator, and it appears to work, BUT there are some very odd side effects, like certain ranges of sound don't play now...

Like when I boot up HyperSpin I hear the sonic coin sound no problem. But then some of the various games, the sound is all muffled or just missing parts of it. Also when you change volume in Windows, it makes this "ding" noise, and that is completely not there with the isolator plugged in.

I also got some new cables as mentioned, and those 3.5mm cables appear to make the interference even MORE lower, so if I hook up the other amp and can only very barely hear it with my ear next to the speaker, then I'm probably going to say it's fine and good enough. If I could get full sound to work with the isolator plugged in though, I'd go that route.

But like the speaker interference without it, with my new cables, is kind of drowned out when I put my ear next to the speaker, from the damn light in the marquee buzzing lol.
 
A ground loop isolator is a transformer, so it won't have a perfect frequency response... but if you're completely missing sounds, something's probably messed up in how it's wired, or it's only mono (not stereo), or something. Which isolator did you buy?

In my experience, when you get sounds that "disappear", it's because the audio is hooked up across the L and R channels. So when something plays out of either the left or right channel only, it sounds fine... but if it's playing out of both, there's no sound.

As a test, try playing some audio out of just one side or the other, then both. Something like video may be useful:
.

You could also try the isolator on something else, like a radio's headphone output with headphones, and see if it also sounds wrong.

DogP
 
Well I don't know wtf is going on but when I plugged both amps in with the new cables I hardly hear ANYTHING interference wise.

I started doing some cleaner wiring and isolating the power cables tuning away from speaker and so far I've only done the fronts but there is absolutely no interference.

So maybe it was the other cables and also running a little too close to power wires.

Here a pic I took before running the speaker wires to fronts but they aren't even overlapping the power wires anywhere now.
 

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