DC/DC converter to go from 12VDC to say ~250V. How to avoid switching noise?

[777funk]

I've done this twice now and it seems difficult to avoid the very high frequency noise. It's much different than the usual 50/60 Hz problem we face with traditional transformers and FWBR diodes with caps, resistors, and chokes.

How can I use a DC/DC without this high frequency noise?

 

[ccaudle]

Buying a pre-made DC-DC converter, or designing and building your own?

 

[Khron]

How can I use a DC/DC without this high frequency noise?

Additional (LC / RC) filtering. Especially since, presumably, it won't be a particularly high-current supply..?

That, and proper ground connections.

 

[Matador]

This is hard to answer with a blanket recommendation, since each system is different based on topology.

"High frequency noise" implies "noise I can hear"...is that true? When you power equipment with that SMPS you hear an audible whine?

 

[777funk]

This is going to be 12ax7s in between a THAT1510 chip preamp and AKM converters in an interface. I did it as a TRS insert on my M Audio 610 and will be doing the same on my 2626 on 2 or 4 channels.

The first thing I tried is sharing the 12VDC supply (also switch mode) by splitting off to two 2.1mm connectors. One for the interface and one for the tube (heater and DC/DC for high voltage). This was very noisy due to ground issues. The THAT chip has a dual rail power supply. Maybe that was part of the issue. I ran a separate 12VDC supply for just the tube and that helped considerably. But... I'm still getting some almost white noise plus some whine. My RC filtering has helped but it's still there. I can especially hear it (loud) if I use any compressors or distortion on the tracks (i.e. electric bass or guitar).

 

[Khron]

Interference can also be radiated, not only conducted...

 

[Matador]

If you FFT the whine, what is the frequency?

 

[ruffrecords]

This is going to be 12ax7s in between a THAT1510 chip preamp and AKM converters in an interface. I did it as a TRS insert on my M Audio 610 and will be doing the same on my 2626 on 2 or 4 channels.

The first thing I tried is sharing the 12VDC supply (also switch mode) by splitting off to two 2.1mm connectors. One for the interface and one for the tube (heater and DC/DC for high voltage). This was very noisy due to ground issues. The THAT chip has a dual rail power supply. Maybe that was part of the issue. I ran a separate 12VDC supply for just the tube and that helped considerably. But... I'm still getting some almost white noise plus some whine. My RC filtering has helped but it's still there. I can especially hear it (loud) if I use any compressors or distortion on the tracks (i.e. electric bass or guitar).

You need to be very careful when running a SMPS from a dc supply. The SMPS will draw significant pules of current at high frequency, which is something the preceding dc supply is probably not designed to cope with. So you need to help it out by providing a local energy store in the form of an adequately sized capacitor fitted very close to the input of the SMPS.

Cheers

Ian

 

[777funk]

If you FFT the whine, what is the frequency?

I'm sure I have a track with the noise. I'll have to take a look.