LED hum on toroidal trannie

[saf]

This forum has been quiet. Too quiet.
Hugh whats up with the news flash ? How is Aspen Business ? What are you selling now ?

Let me just post something make chit chat.
I have been lurking on my LifeForce55 this week, finishing the casework and handles, plus i wanted to install a new LED light connected to DC output from the PSupply.

Problem is, when i connect the LED the transformer (toroid from AVelLindberg) they start generating a pretty considerable hum/rattle. Typically oscillating. I know there are better toroids but i am trying to keep costs low and use these i already have.
This is not too strong, but enough to notice the difference with LED vs without it.

Strange for a LED light to induce the transformer rattle...no ?
Anyway, i just wanted an excuse to shake up the forum !
Cheers
Filipe

[AKSA]

Hi Filipe,
Thanks for your post, sorry for your issue with the LED.
Try putting 10uF 10VW (or higher) across the LED.
Should stop the noise.........
Still selling Mayas! I will give you more information privately.

Cheers,
Hugh

[saf]

Hi High,
Film cap non polarized right?

[AKSA]

Hmm, Filipe, an electro preferably but a film cap would work though quite large........

Hugh

[saf]

Solved it with a 20UF 50V Eletro Alu cap.
Thank you Hugh

[AKSA]

Aha, a wonderful happy ending!
We don't have many of them in audio!
Thank you very much for giving me a response Filipe, this tells me that any blue LED should have a small electro around it to remove noise where it might enter the signal path.........
I owe you a long email today, give me a couple of hours.
Cheers,
Hugh

[andyr]

Originally Posted by AKSA

this tells me that any blue LED should have a small electro around it to remove noise where it might enter the signal path.........

Very interesting, Hugh. Is this only for blue LEDs ... or also the red & yellow ones that I use?

Andy

[AKSA]

This does not happen with green LED, Andy, but it begs the question: do other LEDs create noise? We know blue does, but I would expect orange and white. I'm not convinced red is an issue however.

Hugh

[andyr]

Originally Posted by AKSA

This does not happen with green LED, Andy, but it begs the question: do other LEDs create noise? We know blue does, but I would expect orange and white. I'm not convinced red is an issue however.

Hugh

Thanks, Hugh. I've certainly never noticed any transformer noise in all the amps I've built, using red & yellow LEDs to show DC rail power 'on'.

Strange that Felipe found that the (blue) LED caused his power traffo to make a noise. I could understand that a LED might cause HF hash in the signal you hear from the speakers (by, say, causing oscillations on the DC rail) but a power traffo!

Andy

[suresh]

i have used 3mm blue led in my maya modules . i never had this problem. my amp is dead silent.