Topic: Testing an USB 5V to 9/12V step-up converter

[taper420]

Got this cool little gadget from China yesterday. It's a USB step-up converter with switchable 9V or 12V output. It claims 2 Amps at 9V and 1.5A at 12V. It's the device on the right, the meter I already had and that's plugged into an EasyAcc USB power bank. It powers my 680mkii (running two mics on phantom), using about 4.4 Watts which equates to about 850mA at 5V and means the converter should be outputting about 370mA at 12v to the 680 (minus conversion losses). Cool.

But how high can we go? Testing the unit on a V3 causes the converter to fail and it defaults to outputting a 5v passthrough from the USB (as shown on the converter's built-in voltmeter). But a V3 only uses about twice the power as the 680, so we should be well below the rated 1.5A/12V output. Upon testing on some other devices, it turns out that rating is referring to the USB Amps at 5V, which means the claimed rating is hogwash marketing. However, it also demonstrates you actually get more wattage using the 9V setting instead of the 12V setting... 10W @ 9V vs. 7.5W @ 12V which means the actual rating is 1100mA @ 9V and 620mA @ 12V (which is just shy of running a V3). But something about the math was bothering me... the V3 should be able to run on the 9V setting, but it's not. I get lights for a split second and then it shuts off. So perhaps there is a spike when turning it on that puts it over the ceiling. So I tried starting it on a 9V DVD battery and running the converter in parallel with it, then unplugging the DVD battery once it is already running. It worked... it draws about 1.8A from the USB port which is pretty close to the 9V setting ceiling, but still within "spec." Doing the same thing with 12V does not work, which is in line with the "1.5A" rating on that setting.

Adding more mics to the equation on the 680 increased consumption by about 40mA @ 5V for each one, so running all 6 channels on phantom (with my mics) is still safely below the ceiling for this thing at either 12V or 9V (but I'd probably run at 9V just to be safe and have a higher ceiling). I did some readings to check what the efficiency of the converter is and at 12V it is 85% and at 9V it is just a hair better at about 86%. So when it is drawing 4.4W it is outputting 3.75W, losing about 15% in the conversion.

I doubt I'll ever use this to power my 680 or V3 in the field. I got the thing to be able to USB charge my bluetooth speaker which takes 9V. But it's cool to know you can indeed power a 680 or V3 off an USB power bank.

Currently $10.98 on Amazon
and $3.53 on AliExpress

[jerryfreak]

Are the internal jumpers on your V3 set for low-voltage operation? In other words have you used it with other 6V batteries?

[taper420]

Yes, it's 6V. When I got it, it was with those 6V ecocharge heavy bastards, and I quickly upgraded to the 9V DVD batteries. That's still what I run it on, two in parallel, still gets me like 10-11 hours on older cells. I can also run it off a switchable voltage enclosure, six new high-capacity cells gives me about the same, 10-11 hours running at 6V. But I prefer redundancy and hot-swapability to size reduction so I still go with the twin DVD batteries (which just so happen to fit perfectly in the old Eco-Charge cases).

Like I said, I can't imagine using the step-up converter in the field, especially on the V3... this was more proof-of-concept.

[jerryfreak]

i used to use a step-down converter to power my v3 of same battery as ad2k

i wonder if these regulated power supplies are inferior to straight DC solutions?

people get snobbish about exotic DC power solutions for home amps and DACS

wouldnt the same 'clean power' philosophy apply to our gear?

[taper420]

Perhaps. But like so many pieces of equipment, the only real way to know is listen. If I can sit in a quiet room with headphones on, crank my preamps and not hear any anomalous noise, I can be happy with the weight reduction from losing the lead or nickel. Granted, you could rig up an unregulated but protected lithium-ion solution which would give you a voltage discharge range from 12.6V to around 9V. But I'm happy with the easy solution, as it's worked for me for years without any indication of a problem.

[jerryfreak]

yeah i ran my AD2K for years with 3-cell li-ion solution. technically it loses headroom when the voltage rail falls below 10.5V, but per John Siau

The battery voltage is regulated down to 10V using and LM2940-10 LDO
voltage regulator.  If the voltage drops below 10.5 V the internal rail
will start to drop below 10V and you will start to lose headroom.  What
this means is that the converter may start to clip before reaching 0
dBFS.  It could start clipping at -1 or -2 dBFS.  If you must operate in
a low battery situation, avoid levels higher than -6dBFS and you should
be OK.

which was fine, as with the CMRs my levels were already really low