I don't know that I'd use the word "must". As you can read in Section 5.3.2, the common-mode noise is only an issue if the load is asymmetrical. That said, as we don't have to worry about isolation (the supply providing the incoming DC takes care of that), it looks like three capacitors will alleviate the concerns regarding common-mode noise. Seems worthwhile to spend $0.30 (plus a little bit of PCB area) to make that problem go away.
Tom
I wouldn't go with an AC/DC module. That would defeat the "don't mess with the mains voltage" purpose. If I was going AC/DC, I might as well use a pair of IRM-15-15 and be done.
I'm thinking to use a DC/DC converter powered by a wall wart (or rather a desktop supply as it needs to be a bit beefy). This will leave all the mains wiring to the manufacturer of the wall wart (or desktop supply), which is attractive from a DIY point of view.
Tom
Got it. Selecting an IRM series +/-15V unit, the following four models are available that are in excess of the UB stated draw:
IRM-03-15: 0.20A
IRM-05-15: 0.33A
IRM-10-15: 0.67A
IRM-15-15: 1.00A
All of them have 200 mV p-to-p ripple, only the physical footprints and price are different as far as I can see. Those two variables aside, what is the minimum model of the 4 based upon output current would you select for building a Universal buffer; 1 pair balanced in/1 pair balanced out, 6dB of gain and a small front panel mounted LED. No other inputs, volume control, etc.
If you run the Universal Buffer to clipping, you should expect about 100 mA current draw per board. For powering just one board, a 3W or 5W switcher would be fine. So IRM-03-15 or IRM-05-15. I don't have a strong preference between the two.
Note that the medical MPM-series offers lower ripple.
Tom
Note that the medical MPM-series offers lower ripple.
Tom
Nice!
These Recom ac/dc converters and mounting pcb will make for a super easy and convenient psu to have in any Diy’ers toolbox. Thanks fellas
Putting together a relay attenuator with virtually immeasurable distortion is trivial, it boils down to resistor distortion and very simple choices. Benchmark may have spent some time scratching their heads how to make the steps silent and smooth but certainly not fighting distortions.
The practically complete lack of distortion in most resistor based switching attenuators does not in any way mean they sound the same or even similar, but this is of course not a topic for this thread.
Looks good!
I'm planning to use the buffer as a laboratory buffer/pre-amp for various measurements, including PSU noise. For the latter I will need to AC couple the inputs. I see in the specs that the input impedance is 48k so I was thinking that a series 1uF cap could do the job (fc = 3.3Hz). Do you have any advise in this respect?
Thanks!
I'm planning to use the buffer as a laboratory buffer/pre-amp for various measurements, including PSU noise. For the latter I will need to AC couple the inputs. I see in the specs that the input impedance is 48k so I was thinking that a series 1uF cap could do the job (fc = 3.3Hz). Do you have any advise in this respect?
Thanks!