The only issue I think you might run into is not getting enough current to the HG+. It’s a digital pedal, so it’s a tad power hungry…however, operating it at a lower current shouldn’t do any damage (worst-case is it just doesn’t turn on). Cheers.

To quote the manual:

However, as far as I understand it, the power supplies are rated for a maximum current draw (somone please correct me if this is not the case). At any rate, your 300mA supply isn’t putting out 300mA all the time, but it can supply up to 300mA. Seening as the HG+ should only need 200mA or less, you should be fine (again, someone please correct me if necessary). Also, to be honest, I’m using the VL Pedal Power and that beast claims it can supply up to 750mA (on the output I’m using to supply my HG+) and mine’s totally fine. I hope this helps!

That’s about what I figured…

Yes generally speaking enough current being supplied is the main issue. If you run a 300mA supply and the pedal needs 200mA it should be fine. The thing to remember is that if it’s a regulated DC power supply you will never have a problem.

Unrelated but interesting to note is that I had a Seymour Duncan Twin Tube pedal that was needing about 760mA at 12Vac or thereabouts. I used a 12Vac 2amp supply and it made the internal power supply transformer run very hot. This is because the supply was an unregulated AC supply. Sure it would run 12Vac at 2amps, but at only 1/3 the current needed it wasn’t loaded down enough to settle at 12Vac. In short the transformer was seeing higher than 12Vac.