Possible effects of inexpensive SMPS + linear power supply

[canvas]

Due to limited space, I am thinking to get a small SMPS to power my stepped attenuator (mainly relays, bjts & micro controller). In this case, the SMPS ground will be connect to my analog stage. What would be the disadvantage of this? This inexpensive SMPS takes the input from the mains and outputs 5V. The output will be dirty, full of spikes and HF harmonics...

Poting

 

[kodabmx]

I'm running a tube preamp from SMPS without issue. I'd think there would be more noise from the MC than the SMPS but I'm no expert.

 

[jan.didden]

Due to limited space, I am thinking to get a small SMPS to power my stepped attenuator (mainly relays, bjts & micro controller). In this case, the SMPS ground will be connect to my analog stage. What would be the disadvantage of this? This inexpensive SMPS takes the input from the mains and outputs 5V. The output will be dirty, full of spikes and HF harmonics...

Poting

Have you considered a SilentSwitcher for your sensitive stuff?

Jan

 

[canvas]

Hi Jan,

Yes, I know your SilentSwitcher. It looks great. However, I just need a small size 5V supply. Its performance isn't my concern. I am thinking about a $3 SMPS here. It's just that I am not sure if this will have any side effects.

Poting

 

[TNT]

Well, it's performance indeed seem to be your concern

//

 

[canvas]

Well, it's performance indeed seem to be your concern

//

To be precise, the interference is my concern.

 

[TNT]

No, because if it had splendid performance it hadn't been a problem

:-D

//

 

[jan.didden]

In that case, a wall-wart would be a great choice. You have the benefit of distance, and putting some common mode cores on the cable will get you pretty clean on interference.

Putting an SMPS in your case probably is the worst you can do....

Jan

 

[canvas]

No, because if it had splendid performance it hadn't been a problem

:-D

//

Well, I am referring to the interference of the SMPS though. I know the SilentSwitcher is already excellent.

 

[canvas]

In that case, a wall-wart would be a great choice. You have the benefit of distance, and putting some common mode cores on the cable will get you pretty clean on interference.

Putting an SMPS in your case probably is the worst you can do....

Jan

Thanks. I will just stick to linear supply then. I was hoping the SMPS could also save me a pair of winding from my trafo.

 

[kodabmx]

For $3 why not try it and see? You could even dismantle a phone charger and use the board from that.

This might do the trick since it seems to be potted. AC-DC Converter 100-240V to 5V 0.6A 3W Switching Power Supply PCB Mount #1443 | eBay

 

[canvas]

For $3 why not try it and see? You could even dismantle a phone charger and use the board from that.

Aha, you just save me 3 bucks. I got tons of USB phone charger.

 

[kodabmx]

There you go

 

[jan.didden]

And don't forget the common mode cores on the cable!

Jan

 

[canvas]

And don't forget the common mode cores on the cable!

Jan

Thanks for the tip. I do have some SMD common-mode chokes. Will try the SMPS and see what happens. I appreciate the help and comments from all of you.

Poting