Does anybody recognize this noise?
This is what I’m getting out of the Korg B1. I don’t know what kind of noise this is. The link is to an .m4a file. Works on mac/apple. Not sure if Windows uses that format. I’ll try to save it in another format if someone can tell me what the preferred format is. Thanks.
Dropbox - NuTube noise 20210614.m4a - Simplify your life
It almost sounds line an old radio stuck between stations.
Edit: here is mp3 version:
Dropbox - nutube noise 20210614.mp3 - Simplify your life
This is what I’m getting out of the Korg B1. I don’t know what kind of noise this is. The link is to an .m4a file. Works on mac/apple. Not sure if Windows uses that format. I’ll try to save it in another format if someone can tell me what the preferred format is. Thanks.
Dropbox - NuTube noise 20210614.m4a - Simplify your life
It almost sounds line an old radio stuck between stations.
Edit: here is mp3 version:
Dropbox - nutube noise 20210614.mp3 - Simplify your life
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My understanding is the board is grounded to the chassis via the screws that hold the board. As far as I remember that was part of the design I haven't checked though, but I would expect continuity from board ground to chassis via the stand offs.
I can't though tell you if that is the problem. BUT you can easily chekc that; just attach a wire to one of the stand offs and to a chassis screw, ensuring continuity, and see if your problem is gone.
Good luck
Claude
I can't though tell you if that is the problem. BUT you can easily chekc that; just attach a wire to one of the stand offs and to a chassis screw, ensuring continuity, and see if your problem is gone.
Good luck
Claude
Had a listen... defo wrong, but never had this. Sorry for the little help.
The only limited advice I can give you is:
- checking continuity point by point on the board with a multimeter, perhaps a cold joint somewhere with intermittent contact
- check voltages (see this thread) to identify any possible issues
If that doesn't help / has been already done and didn't help, then some active component might be gone.
Good luck
Claude
The only limited advice I can give you is:
- checking continuity point by point on the board with a multimeter, perhaps a cold joint somewhere with intermittent contact
- check voltages (see this thread) to identify any possible issues
If that doesn't help / has been already done and didn't help, then some active component might be gone.
Good luck
Claude
A few thoughts, perhaps you've already covered them.
If it's common to both channels then probably it's either in the grounding or in the power supply. If not, it's on the PCB or I/O wiring.
I listened -- it does sound like the kind of noise I used to hear on shortwave bands, never understood if it was a transmission or natural noise. Calling it a “hum” muddies the water – it sounds more digital square wave than sinusoidal analog. So, I wonder if it’s your SMPS wall wart.
The recording has two distinct sound signatures. Is that from the middle of a session with a Korg that has been on for a while, or is that the signature of what happens right after you turn the power switch on or plug in the power supply?
I kinda lean toward a noisy/defective power supply. For me the first step would be to try an entirely different power source -- bench supply, two 12v batteries in series, another wall wart, anything. See if the noise remains. After that, start looking at ground, but do the PS examination first. While grounding the chassis to the pcb should provide shielding from external noise sources I don’t think you need to connect to the third pin of a 110v socket. The Korg kit is designed to work with 24VDC provided from a wall wart that does not use that third pin.
You might consider installing the excellent SMPS filter that has been mentioned on this thread. The diyaudiostore sells a kit for $10, and it's money very well spent.
wapo54001: Thank you!
You prompted me to take the action that fixed the problem. I had 2x24v Meanwell PSs for mono ACA’s, so as I swapped them, I inadvertently touched a Google WiFi node that was about 3 feet away. When I did that, the noise stopped completely.
Upon further experimentation, the cause of that noise was definitely the WiFi. I would have thought 3 feet would have been enough, but that was definitely the problem.
Any ideas as to why a WiFi node 3 feet away would make so much output noise on the Korg B1? Do you think it affects the “tube” itself or is it affecting something else? Having eliminated the problem, the question is pure curiosity as the problem is gone.
Thanks again!
You prompted me to take the action that fixed the problem. I had 2x24v Meanwell PSs for mono ACA’s, so as I swapped them, I inadvertently touched a Google WiFi node that was about 3 feet away. When I did that, the noise stopped completely.
Upon further experimentation, the cause of that noise was definitely the WiFi. I would have thought 3 feet would have been enough, but that was definitely the problem.
Any ideas as to why a WiFi node 3 feet away would make so much output noise on the Korg B1? Do you think it affects the “tube” itself or is it affecting something else? Having eliminated the problem, the question is pure curiosity as the problem is gone.
Thanks again!
I also started out using the smps I got with the ACA. This made a loud hissing sound over the speakers that matched the sing/sound coming from the smps itself. I changed to a laptop smps (20V). To my surprise that was completely silent. Now have recommended smallest 24V Maxwell smps. Fortunately that is silent too.
Because the device lacks an input RC filter. Maybe also stray in via power wiring. The device is best built in a metal casing.
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As I was building mine recently there was a discussion about the SMPS filter that is now available for $10 from the diyaudiostore. I expressed interest and a generous member sent me the parts for one and it now resides in my Korg. It's very well regarded and fits in the Korg chassis (see attached image) and I feel more secure that powerline noise is not entering the audio path through the Korg's SMPS.
Attachments
I'm a belt-and-suspenders kind of guy.
I didn't install it to solve a problem, I installed it to avoid problems.The 'scope images I saw showed it eliminating even small levels of PS noise, and for very inexpensive and dead simple install, well worth it.
Possible causes and solutions for wifi RFI pickup
Several possibilities:
* You did not use a metal case.
* You did not twist the internal signal wires pairs (signal and ground) to the signal input and output jacks wires, or did not twist them tightly together.
* If the RCA jacks were insulated from the chassis with isolation washers, then you did not solder a small ceramic capacitor from the shield lug of the capacitor to chassis right at the entry point.
Some additional steps you could take:
* insert a ferrite bead or core on each of the twisted signal wire pairs, to dampen RFI. You can find these surplus at All Electronics and similar establishments.
* use shielded wire instead of twisted wire pairs.
Several possibilities:
* You did not use a metal case.
* You did not twist the internal signal wires pairs (signal and ground) to the signal input and output jacks wires, or did not twist them tightly together.
* If the RCA jacks were insulated from the chassis with isolation washers, then you did not solder a small ceramic capacitor from the shield lug of the capacitor to chassis right at the entry point.
Some additional steps you could take:
* insert a ferrite bead or core on each of the twisted signal wire pairs, to dampen RFI. You can find these surplus at All Electronics and similar establishments.
* use shielded wire instead of twisted wire pairs.
I thought I was a belt-and-suspenders guy but obviously I'm a minor leaguer . . .
If the noise stopped when the offending wifi device was simply touched, I suggest that the device itself was somehow defective and needed to be dealt with. Don't defend against a defective device that can be removed -- just remove the device.
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That is a strange approach to troubleshooting/prevention. There will be HF/RF in the air from many other devices (it is not a defect but a main part of their function...) and it is up to the builder to make the audio device being able to cope with that. A metal casing is an absolute must and several other suggestions were given. IMHO opinion the input RC filter that is omitted is also a must to avoid trouble.
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Well, WiFi operates at 2.4GHz and 5.8GHz so unless there is some unintended consequence going on that will be a much less likely problem than a misbehaving or poorly designed SMPS dumping noise back into the 110.
Come to think of it, WiFi draws a lot of power to transmit so the SMPS in that Google device must be delivering something between 6 and 10 watts to the WiFi alone plus whatever the active function requires. If touching the device made it quiet I'll bet it has something to do with the SMPS in the Google device, not the WiFi. But we'll never know and I'm good with that, the happy thing is that someone is out there enjoying 2nd harmonic in his music!
thanks for the great suggestions, guys! A few questions/comments:
1. I used the metal chassis that came with the kit. BUT, I don’t see a clean path to chassis ground from the board. The closest is the stand-off screws for the board, but they clamp down on anodized aluminum (?). Do I need a real ground strap to the chassis?
2. I don’t recall anything in the kit or instructions about a small ceramic capacitor between shield lug of capacitor and chassis. If I should have that, can somebody provide more details? I don’t know what “small ceramic” means.
3. I have some ferrite snap-on “chokes”. Are you saying I should put one on each input wires inside the chassis?
Thanks for your help. I’d be lost without you guys’ advice.
1. I used the metal chassis that came with the kit. BUT, I don’t see a clean path to chassis ground from the board. The closest is the stand-off screws for the board, but they clamp down on anodized aluminum (?). Do I need a real ground strap to the chassis?
2. I don’t recall anything in the kit or instructions about a small ceramic capacitor between shield lug of capacitor and chassis. If I should have that, can somebody provide more details? I don’t know what “small ceramic” means.
3. I have some ferrite snap-on “chokes”. Are you saying I should put one on each input wires inside the chassis?
Thanks for your help. I’d be lost without you guys’ advice.
You should scrape some of the anodizing off so that a good connection is made, that is essential.
There is disagreement here about the caps. My vote is to not do anything like that, ditto the ferrite chokes. Those could be essential in harsh environments like technical facilities or live stage performances where wires are long and signal is everywhere. In a home environment don't overcomplicate and you should be fine (my opinion, there will be others).
