NESRGB AV Famicom Audio

[Lamprey]

Hi,

I recently installed the NESRGB in my AV Famicom and the picture look great, but the audio has a pretty nasty humming sound and it's much worse when using 8bitdo wireless receivers.

I see that Tim Worthington doesn't even mention hooking audio through the NESRGB on the AV Famicom instructions. I was wondering if there is an "easy" way to use the NESRGBs audio amplifier to see if that helps with the humming? I was going to do the balanced audio restoration, but Console 5 is out of the capacitor kit at the moment. Would it be enough to wire up everything like the balanced audio restoration and just not modify the NESRGB?

Here is the blanced audio restoration I'm referencing:
https://www.retrorgb.com/av-famicom-hvc ... n-mod.html

Or if there some other fix for the humming I'm happy to know about that too.

For reference, I'm using the Retro-Access 75 ohm multicore coax cable. So, the signal should be well shielded.

Cheers!

[Kez]

Well the mod you linked is a non-standard implementation of the NESRGB audio circuitry. I don't think it would be a good idea to attempt without doing the requisite resistor mods! However, to wire up the standard NESRGB sound you simply need to connect A and B to pins 1 & 2 on the CPU, then the O pad becomes audio output. So you'd need to disconnect the audio output pins on the connector and then connect O to them instead. However this will remove support for expansion audio, and further mods would be required to mix that into the NESRGBs audio output. My hunch is that using the NESRGB audio circuitry as standard would be more likely to reduce the hum than doing the audio balance restoration mod, but it is a bit more destructive (in terms of traces cuts and stuff) and it does make the audio balance restoration mod more difficult to do down the line.

Trying to remove the hum as-is is probably a good starting point, first order of business would be a full cap replacement (either wait for console5 to restock or source good quality caps from elsewhere - there aren't that many caps in the AV Famicom) and also replacing the 7805 with a new one.

[Lamprey]

Thanks Kez,

I did replace the 7805 with a 2amp L78S05CV while I was doing the NESRGB just to make sure it had enough head room. I'm pretty sure I have a cap kit floating around here someplace, so I'll start with that and see if that helps while I wait for a audio cap kit.

[Lamprey]

I did a cap kit and that seeems to have reduced the hum to a pretty low/tollerable level. But, if I plug in an 8bitdo wireless receiver the hum is really loud. Not sure if that is a ground issue or an interferece issue or something else.

I don't suppose anyone has any idea as to why wireless controller receivers would cause an audio hum?

Thanks!

[jd213]

Maybe a ground loop or something due to non-standard hardware?

I used to have an AV-modded OG Famicom (done by someone else) that had a horrible ground loop hum when I plugged the audio into my receiver, but it was fine when both the audio and video were plugged into my Framemeister. So maybe try different setups.

[Kez]

Was the new voltage regulator from a legit source?

I remember I installed one I got from eBay in a PC Engine once and it had horrible hum, so that could be the culprit - if the receiver draws a lot of power for example.

[Lamprey]

Was the new voltage regulator from a legit source?

I remember I installed one I got from eBay in a PC Engine once and it had horrible hum, so that could be the culprit - if the receiver draws a lot of power for example.

Sould be legit, it was from Console5.

I just swapped the voltage regualtor just incase the combination of the NESRGB and Everdrive would draw a bit more than a stock console. But, the humming with the wireless receiver was there with the stock voltage regulator too, so I dont think that is the cause. I have a pack of 3-4 I bought so I have some others I can give a test and see how they read.

The only other mod I've done on this console was the NES Zapper "mod" to use a north american light gun on the AV Famicom. I''ll try undoing that and see if that makes any difference. Mod link for reference:
https://famicomworld.com/workshop/tech/ ... v-famicom/

[Lamprey]

Just wanted to follow up on this incase it helps anyone.

Turns out it was my power supply. I beleive I am/was using the original (japanese) power supply and had lots of audio noise.

I had read that the Sega Genesis model 1 uses the same connector type as the AV Famicom, so I tried that and the audio is totaly clear. The one that works happens to be a Triad Magentics power supply if that helps anyone.

Cheers!

[jd213]

Ah, good to know that the PSU was the issue.

A Triad that works on the Genesis 1 is nice to have since it's a pretty standard rating/barrel and can be used for a bunch of other JP systems, like FC, SFC, PCE/Core Grafx, as well as random stuff like Roland MIDI boxes.