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[SOLVED] Vewlix Amp picking up JVS data noise

harih

harih

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I have a Vewlix FC with the following setup for the controls:
  1. Taito JVS IO (v2)
  2. JVS-PAC2
  3. Thinkpad T430
With this setup, I'm running into significant data noise entering the amp once the JVS IO is active. It appears to be matching up with the hz reported on the JVS-PAC2 (~400Hz).

To try to isolate where it's coming from, I've tried the following:
  1. JVS-PAC2 connected to laptop and IO, laptop connected to amp: Noise (standard setup)
  2. JVS-PAC2 connected to laptop and IO, laptop not connected to amp: No Noise (retested, I was wrong)
  3. JVS-PAC2 connected to laptop and IO, a different laptop connected to amp: No noise
  4. JVS-PAC2 connected to laptop and IO, headphones connected to laptop: No noise
  5. JVS-PAC2 connected to laptop but not IO, laptop connected to amp: No noise (sound from laptop works fine)
  6. JVS-PAC2 connected to IO but not laptop, laptop connected to amp: No noise (JVS-PAC2 had no power)
  7. JVS-PAC2 connected to laptop and IO, laptop connected to amp, testing with headphones dangling nearby: No noise in headphones
This seems to isolate it to being something with the amp / IO / laptop combination, as the issue only occurs within the amp itself once the IO is on and doesn't appear in nearby sound systems. I'm not really sure where to go from here to resolve it, so any ideas would be appreciated!

EDIT 2020-08-07:
Solution found!

The part is just an audio ground loop noise isolator. By adding it in-line between my laptop and the amp, the JVS data noise is no longer picked up and the speakers stay silent even when the amp is all the way up.

It also works in your car if you have a line-in and get noise from having your phone/DAP charging at the same time :smile:
 
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If this was an arcade board and not a Thinkpad computer I'd be telling you to bridge/join your DC grounds (ie PC powersupply DC ground to cab powersupply DC ground, NOT earth ground).
I'm not sure this is the proper approach in your case however.
 
jassin000 said:
If this was an arcade board and not a Thinkpad computer I'd be telling you to bridge/join your DC grounds (ie PC powersupply DC ground to cab powersupply DC ground, NOT earth ground).
I'm not sure this is the proper approach in your case however.
Click to expand...
Ah you know, this did point me in one direction: I just realized I'm using the ungrounded charger for that laptop. I should have one with a ground plug somewhere, I'll see if I can dig it out and if it makes a difference.

EDIT: Just tested, this does seem to be an issue with the laptop's (lack of) ground when connected to the amp. My second scenario above does not generate noise, the noise is only introduced once the laptop is connected. Connecting the amp to a separate device doesn't introduce noise, and listening to the laptop with headphones doesn't have the noise.

I was wrong about having a grounded charger so I'm going to need to test with a separate device before I order one, just to make sure it really is something about the laptop and not a general issue
 
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harih said:
and listening to the laptop with headphones doesn't have the noise
Click to expand...
right, its the joining of the laptop to the cab that produces noise... and again in the arcade world this is common and solved by the bridging of DC grounds.
NOT earth grounds (ie 3rd prong on a AC outlet).
 
jassin000 said:
harih said:
and listening to the laptop with headphones doesn't have the noise
Click to expand...
right, its the joining of the laptop to the cab that produces noise... and again in the arcade world this is common and solved by the bridging of DC grounds.NOT earth grounds (ie 3rd prong on a AC outlet).
Click to expand...
Got it, that makes sense to me. Theoretically, if I were to tap into the ground wire after the power supply brick (so once it's coverted to DC) and connect that to the ground wire of the amp's power connector, would that be sufficient? The power adapter is barrel-style so the ground isn't too far out of reach (and is slightly visible when plugged in)
 
Solution found!

The part is just an audio ground loop noise isolator. By adding it in-line between my laptop and the amp, the JVS data noise is no longer picked up and the speakers stay silent even when the amp is all the way up.

It also works in your car if you have a line-in and get noise from having your phone/DAP charging at the same time :)
 
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