Ultra-Low Noise Preamp Power Supply: +/-12 V, 650 mA

[tomchr]

Thanks for the answer and this information about the practical behavior of the Recom's. I intended to use it pretty much naked but I'll have to rethink that.

Yeah. I had the same thought ... and rethought.

Tom

 

[Johno]

Thanks Tom, look forward to more specs (and appreciate the response curve of a few posts past). At last it seems a regulator that actually regulates is on offer. Well done.

 

[tomchr]

I played around some yesterday. The line rejection is incredibly high as you'd expect from a regulated SMPS with a post-regulator. You need a 6.5-digit DMM to resolve the changes in output voltage as the input voltage is changed from 85 VAC to 150 VAC. The line rejection measures -107 and -110 dB, respectively, for the positive and negative rail.
Basically, you're looking at a ~20-30 uV change in output voltage as the input is changed from 85 VAC to 150 VAC, which is as low as the SMPS will accept and as high as my variac will go.

The load regulation is nearly -70 dB on the positive output and -60 dB on the negative output.

Recall:
Line regulation = 100 * Delta_Vout/Delta_Vin [%]
Load regulation = 100 * Delta_Vout/Nominal_Vout [%] for a min -> max load step

Tom

 

[kn0ppers]

Sadly this board is too large for my intended application, but the thread has been quite helpful as I was intending to use the same AC/DC Modules and the same LDOs with CLC filtering in between. But because the information here probably saved me the assembly of one prototype, I'll make use of the donation button on your website instead.

 

[soekris]

You might want to consider the XP Power ECL30UD02. I know they're more expensive, but they have the advantage that they support unlimited capacitive loads, meaning you can do a good CLC filter with large and low esr capacitors.... The price get better when buying volume from a distributor, for some reason Digikey is very expensive on XP Power....

In my dacs I used the 12V version, ECL30UT02-P, with 4700 uF caps and discrete 11.3V LDO post regulators....

 

[tomchr]

Unfortunately, due to the parasitics in the Ls and Cs of the filter, it's rather challenging to get good attenuation of the ripple voltage coming out of the switching supplies. Under some load conditions where the SMPS goes into pulse/hiccup mode, you can get 100 mV ripple at audio frequencies. Additional capacitance will help some, but the best solution is a regulator with good line rejection, such as the TI ones I use in the Preamp Power Supply.

Tom