[ColSaulTigh]

Hello all!

I am looking for an answer to a question that Google seems to be unable to provide (unless I'm using the wrong search terms). I just now discovered that if I shine a flashlight on my tubes, I can hear a very audible hum/buzz that goes away when I move the flashlight off them.

Details:

Amp: Woo Audio WA5-LE Gen 2 w/upgraded internals
Tubes: Power tubes - Elrog 300B-Mo, Drivers - National Union 6F8G w/Woo Audio Adapters, Elrog 5U4G rectifiers
Headphone cable: Norne Audio Solvine (copper/silver combo)
Headphones: ZMF Atrium

Details:

I'm listening in a dark room (except for the monitor and the light from the tube glow). I dropped something on the floor, so I grabbed a flashlight (Harbor Freight LED Ultra-bright "penlight" style, uses 2 AAA batteries) and found what I dropped. When I moved the light up, I happen to shine it on the tubes, and I heard a very substantial hum/buzz. When I moved the light off the tubes, it went away. Flashlight was approximately 2' from the tubes (give or take a few inches). I was able to narrow it down to the sound coming when I hit the National Union driver tubes directly with the beam. Move it off them and the hum/buzz goes away instantly. I have never noticed this phenomenon before and wondered how that flashlight could be affecting the sound so dramatically. I figured I'd turn to y'all for help on this.

So, can anyone explain why a flashlight causes my system to hum/buzz when shining a light on my driver tubes? I can try to make a video of this if y'all think it'll help.

Thanks!

 

[71 dB]

https://en.wikipedia.org/wiki/Photoelectric_effect

 

[gregorio]

When I moved the light up, I happen to shine it on the tubes, and I heard a very substantial hum/buzz.

71dB is right, although it’s probably more specifically the photovoltaic effect. The photons produced by your flashlight are absorbed by the electrons in the tube components, giving them more kinetic (motion) energy. More random motion of electrons in a circuit produces more Johnson/Nyquist noise (that sounds like hiss). Shine enough light on the right components/materials and you’ll get a full voltage differential, which is how solar cells produce electricity.

I’m guessing to a certain extent though, a physicist would be able to tell you for sure, if you know the exact metals in the tube exposed to the flash light.

G

 

[castleofargh]

Hello all!

I am looking for an answer to a question that Google seems to be unable to provide (unless I'm using the wrong search terms). I just now discovered that if I shine a flashlight on my tubes, I can hear a very audible hum/buzz that goes away when I move the flashlight off them.

Details:

Amp: Woo Audio WA5-LE Gen 2 w/upgraded internals
Tubes: Power tubes - Elrog 300B-Mo, Drivers - National Union 6F8G w/Woo Audio Adapters, Elrog 5U4G rectifiers
Headphone cable: Norne Audio Solvine (copper/silver combo)
Headphones: ZMF Atrium

Details:

I'm listening in a dark room (except for the monitor and the light from the tube glow). I dropped something on the floor, so I grabbed a flashlight (Harbor Freight LED Ultra-bright "penlight" style, uses 2 AAA batteries) and found what I dropped. When I moved the light up, I happen to shine it on the tubes, and I heard a very substantial hum/buzz. When I moved the light off the tubes, it went away. Flashlight was approximately 2' from the tubes (give or take a few inches). I was able to narrow it down to the sound coming when I hit the National Union driver tubes directly with the beam. Move it off them and the hum/buzz goes away instantly. I have never noticed this phenomenon before and wondered how that flashlight could be affecting the sound so dramatically. I figured I'd turn to y'all for help on this.

So, can anyone explain why a flashlight causes my system to hum/buzz when shining a light on my driver tubes? I can try to make a video of this if y'all think it'll help.

Thanks!

I don't know how something like that manages to end up at audible level(although being part of a literal amplifier probably helps a good deal^_^).
It's one weird and cool anecdote. Thank you for sharing, and I'd like a video but only because I think it's a fun phenomenon.

 

[gimmeheadroom]

Hello all!

I am looking for an answer to a question that Google seems to be unable to provide (unless I'm using the wrong search terms). I just now discovered that if I shine a flashlight on my tubes, I can hear a very audible hum/buzz that goes away when I move the flashlight off them.

Details:

Amp: Woo Audio WA5-LE Gen 2 w/upgraded internals
Tubes: Power tubes - Elrog 300B-Mo, Drivers - National Union 6F8G w/Woo Audio Adapters, Elrog 5U4G rectifiers
Headphone cable: Norne Audio Solvine (copper/silver combo)
Headphones: ZMF Atrium

Details:

I'm listening in a dark room (except for the monitor and the light from the tube glow). I dropped something on the floor, so I grabbed a flashlight (Harbor Freight LED Ultra-bright "penlight" style, uses 2 AAA batteries) and found what I dropped. When I moved the light up, I happen to shine it on the tubes, and I heard a very substantial hum/buzz. When I moved the light off the tubes, it went away. Flashlight was approximately 2' from the tubes (give or take a few inches). I was able to narrow it down to the sound coming when I hit the National Union driver tubes directly with the beam. Move it off them and the hum/buzz goes away instantly. I have never noticed this phenomenon before and wondered how that flashlight could be affecting the sound so dramatically. I figured I'd turn to y'all for help on this.

So, can anyone explain why a flashlight causes my system to hum/buzz when shining a light on my driver tubes? I can try to make a video of this if y'all think it'll help.

Thanks!

Easy answer if the light is an LED light. Most of the cheap ones use PWM modulation to get the brightness with a crappy power supply. It's basically like a switching PSU. If they get the frequency high enough it is not directly visible. So could be just electrical noise. But if it happens at a distance then it becomes a real butt-scratcher.

@bcowen

 

[gregorio]

I don't know how something like that manages to end up at audible level(although being part of a literal amplifier probably helps a good deal^_^).

Yep, I was counting on the fact the effect would be amplified.

Easy answer if the light is an LED light. Most of the cheap ones use PCM modulation to get the brightness with a crappy power supply. It's basically like a switching PSU. If they get the frequency high enough it is not directly visible. So could be just electrical noise.

Could be, but then wouldn’t you expect the interference to occur regardless of which part of the amp the torch is pointing at and only reduce when it was moved further away?

G

 

[ColSaulTigh]

I don't know how something like that manages to end up at audible level(although being part of a literal amplifier probably helps a good deal^_^).
It's one weird and cool anecdote. Thank you for sharing, and I'd like a video but only because I think it's a fun phenomenon.

So I tried shooting a video but the mic on the phone isn't able to pick up the sound, but here are a few more details:

1) The flashlight is this one: https://www.harborfreight.com/lighting/flashlights/65-lumen-pocket-led-flashlight-63936.html

2) The buzz/hum changes in intensity the closer the flashlight is to the tube. It's effects are undetectable when distance is >2' from the tubes

3) The effect appears to be more intense when the beam is aimed from the center to the lower-half of the glass of the tube:

4) These tubes are otherwise clean with no SCP (Snap, Crackle, Pop) going on. FWIW, they are nice, clean, wide-open sounding 6F8G's and sound great with 6SN7 adapters in my Woo. I bought them about 2 months ago from eBay, and they're in otherwise fine shape (boxes are a bit age-worn).

5) The buzz/hum ONLY occurs when the light is pointed at these driver tubes (which I guess makes sense since they're the last tubes in the chain). Pointing the light at the 300B or the 5U4G's has no effect (that I can perceive).

@L0rdGwyn @Paladin79 any thoughts?

If anyone would like me to conduct any further experiments, please feel free to ask.

Thanks for the feedback, all!

 

[Hudson]

As noted above it’s most likely photoelectric effect related. High fields in those tubes with bright LEDs next to them dont go well together.

 

[Paladin79]

So I tried shooting a video but the mic on the phone isn't able to pick up the sound, but here are a few more details:

1) The flashlight is this one: https://www.harborfreight.com/lighting/flashlights/65-lumen-pocket-led-flashlight-63936.html

2) The buzz/hum changes in intensity the closer the flashlight is to the tube. It's effects are undetectable when distance is >2' from the tubes

3) The effect appears to be more intense when the beam is aimed from the center to the lower-half of the glass of the tube:



4) These tubes are otherwise clean with no SCP (Snap, Crackle, Pop) going on. FWIW, they are nice, clean, wide-open sounding 6F8G's and sound great with 6SN7 adapters in my Woo. I bought them about 2 months ago from eBay, and they're in otherwise fine shape (boxes are a bit age-worn).

5) The buzz/hum ONLY occurs when the light is pointed at these driver tubes (which I guess makes sense since they're the last tubes in the chain). Pointing the light at the 300B or the 5U4G's has no effect (that I can perceive).

@L0rdGwyn @Paladin79 any thoughts?

If anyone would like me to conduct any further experiments, please feel free to ask.

Thanks for the feedback, all!

LED’s transmit electromagnetic radiation, the more of them in a concentrated area, the worse the effect.

 

[rivonlol]

This is interesting. I wonder if PC monitors will have an effect on tubes based on how close they are?