I have been using the 30A switch mode brick type chinese made PSU’s for some time now and found them to be clean, cheap and reliable. Lightning took one out but the rest have done well. Like all things there is an upside and a downside. The upside is the price. There are cheap. The downside is that they don’t come with leads! You have to supply the power cable and the DC you just screw into the front. The AC connection on most is quite open and needs to be covered unless you are putting it into its own box. In fact they are designed to be incorporated into some piece of equipment. No meters. no fuses.
The linear supplies at the back are astron 70A units and I think the little 74A switcher could probably hold its own against it, but I do like to use linear supplies with my solid state amps. However the 74A unit drives a DX500 amp just fine. Save messing with batteries when we go on a d-x-pedition! The fan is loud when it kicks in…
Major downside of the switchers is that they do not go well on fluctuating voltages like what you get with a generator when it starts up or shuts down or goes under load. If you are going to turn off the gen set, disconnect the switcher first…they do a mighty fine job of holding output against varying voltages especially under 220v but they do not like dynamic fluctuations of the input AC supply (especially the hertz) as they try to compensate and adjust for them on the fly. A linear PSU will just show decreasing voltage when the AC supply drops off. Best is NOT to run it on a small genset.
The intention is to provide these for sale with our solid state amps to keep the overall cost down. High amp PSU’s still command a hefty price in the west but this is fixing to change as these bricks find their way into various boxes.
They also come in voltages up to 48V for that mosfet amp project we all want to build. Higher voltages mean better IMD and a smoother sounding AMP…and all the new RF mosfets are 48V DC.
The 600w supply like the 400w supply has multiple connections (3) to hook up your DC wires to. None of them have meters or on/off switches.
THE TEST. 21st of May 2012.
It was time to try out the 74 A PSU. Hooked up the AC and covered the terminals with insulating tape but something more solid would have been preferable if this was going to be an exposed installation. The power up voltage was 15.0 VDC so I had to reduce the output voltage by turning the little screw set back in a hole next to the black negative DC terminal. It needed quite a few turns to the right to bring the volts down to 14.2 which is a good voltage for a solid state amp. I had to test a Texas Star DX500 prior to shipping so hooked it up and turned it on. No problems at all even with the amp sitting on the power supply which is as bad as things can get RF wize for a switch mode PSU. Didn’t seem to bother it. Did not notice any pick up in hash either. It easily pegged the Amp to 600w without any dimming of the meter light noticeable. If there was any drop it was not noticeable. All audio reports on SSB were fine. She certainly is stout and easily up to the task of driving the DX500.
Is there a downside? Maybe. It does not have an on off switch. If you want to turn it off you need to pull the AC plug. The fan, when it comes on is pretty loud. It blows some air. You would not want this close to your microphone! But for 74Amps, a kilo and a bit of weight and a good price you can’t go far wrong.
This one gets the thumbs up so far.
I will see how the 44A one goes next.