Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on April 05, 2024, 03:24:44 pm

Title: diodes noise?
Post by: joesatch on April 05, 2024, 03:24:44 pm

do led diodes cause noise?. i use these indicators for channel switching. i have one close to the master and gain pot. they are dc powered so i assume they could cause noise?  use coax shield on them? move them?

Title: Re: diodes noise?
Post by: sluckey on April 05, 2024, 03:32:54 pm

I don't hear any noise. Do you?

Title: Re: diodes noise?
Post by: shooter on April 05, 2024, 03:37:00 pm

"noise" is typically AC, in the air, riding on a DC potential, even through "ground"
the only noise I would expect from an LED is at switch on/off and that would be measured in micro-seconds, way way outside audio.

Title: Re: diodes noise?
Post by: joesatch on April 05, 2024, 03:47:31 pm

ok so no noise should be expected. this sits well with me  :l2:

Title: Re: diodes noise?
Post by: acheld on April 05, 2024, 03:54:16 pm

Any diode will show a small transient when switched on or off.  These are really really short (microsecond) transients, far beyond the bandwidth of a tube amp.   

For channel switching, they would usually not be in the signal path, and would not be a factor.   Theoretically, the transient could produce EMF, but IMO it would be so small that you could never detect it.

Some folks use LEDs to bias pre-amp tubes, and when I tried it got good results with no noise.

Too much blabbing.  It's more of a theoretical issue than a practical problem.

Title: Re: diodes noise?
Post by: sluckey on April 05, 2024, 03:56:13 pm

It's kinda like that tree thing. A tree falls in the forest, but you didn't hear it. So, did it really fall?   :l2: