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Old 03 October 2012, 21:43   #1
bbond007
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Kipper2K HDMI Audio Output

My Samsung S27B750V monitor is able to sync with my Indivision AGA MK2 and looks fantastic, so I decided to switch over to my Kipper2K HDMI adapter.

Anyway, I notice that the audio output on the HDMI cable has a lot of background noise interference that I'm not getting on the RCA output.

I thought that maybe the HDMI adapter needed a more direct path to ground so exposed a little bit of the copper on the bottom left corner HDMI adapter's PCB board and used one of the legs from a resistor as a jumper to the ground on the A1200's motherboard. Should I have used something thicker than a resister leg? The Indivision itself is also grounded....

That did not seed to help. What else do you guys think I could do to improve the quality of the audio? I'm wondering if the HDMI cable itself might be the cause. Perhaps some nose is being introduced by the close proximity of the wires with the video signal?

I have included a picture of the inside of my A1200. I had not added the ground jumper on the Kipper2K HDMI prior to taking the picture, so you can't see that. I really just included the picture because I know threads with pictures get more reads

Thanks!
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Last edited by bbond007; 03 October 2012 at 21:53.
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Old 03 October 2012, 22:22   #2
johnim
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nice miggy there

sorry cant help with audio

do you have any heat issues with indy
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Old 03 October 2012, 23:07   #3
bbond007
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Quote:
Originally Posted by johnim View Post
nice miggy there

sorry cant help with audio

do you have any heat issues with indy
No issues of any kind (heat or other).

Just the standard stuff. Limited DVI, banding on VGA....
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Old 03 October 2012, 23:27   #4
kipper2k
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Hi,

thats a busy little Amiga you have there. The ground for the audio signal is common with the video ground. I have never heard any interference noise on any of the audio devices i have tried.

Do you have a picture of the soldering of the L,R channel to the motherboard? Also, unplug the HDMI cable at both ends and measure the resistance between both centre posts of the L,R RCA plugs... resistance should be infinite as they are electrically isolated from each other when not plugged into the Amiga and TV.
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Old 04 October 2012, 00:50   #5
bbond007
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Quote:
Originally Posted by kipper2k View Post
Do you have a picture of the soldering of the L,R channel to the motherboard? Also, unplug the HDMI cable at both ends and measure the resistance between both centre posts of the L,R RCA plugs... resistance should be infinite as they are electrically isolated from each other when not plugged into the Amiga and TV.
Hi Kipper2k, thanks for the response....

I don't have a picture of the soldering on the underneath side of the motherboard, but I'm pretty sure I did solder it correctly. I checked it with my meter to determine the correct pads before I started, and checked my work for continuity after I had completed the install. Like you noticed, My A1200 is pretty busy on the inside, and my work area is a bit messy, so I'm not sure I'm up for a tear-down tonight. Maybe this weekend.

I have the HDMI with audio running to a little converter that takes to the 1/8" headphone style jack. It leaves pretty easy access to the ground of the HDMI RCA cable. If I touch one of the grounds of the HDMI RCA cable to one of the RCA cables connected to the Amiga, the noise goes away...

If I touch the same RCA cable to the shielding on the HDMI port, the sound persists. That leads me to believe that the problem is with the ground in the HDMI cable...

EDIT:

Quote:
Originally Posted by kipper2k View Post
Also, unplug the HDMI cable at both ends and measure the resistance between both centre posts of the L,R RCA plugs... resistance should be infinite as they are electrically isolated from each other when not plugged into the Amiga and TV.
OK, I did that, and the resistance is infinite.

For another test, I wrapped a wire around the shielding on the HDMI portion of the of the cable and touched the other end the the ground shield portion on one of the RCA connectors (which I'm hoping is bypassing the ground in the HDMI cable). The noise in both channels stops.

I'm guessing now I should check the resistance going from the RCA ground to the HDMI shield? Humm, there is some resistance I'm just not sure if that is ok or not...

One thing I know about electricity is that electrons flow down hill, so I can definitely fix this by elevating the computer over the speakers, lets hope it does not come to that...

Thanks...

Last edited by bbond007; 04 October 2012 at 01:41.
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