I've been running 3 of these ballasts for nearly a year now and I must say I am well impressed. As every other products there is a huge variety to choose from when selecting a cdm ballast. I was recommended Maxbright and here we come. These ballasts are recommended to be used with 315 Watt Philips CDM Lamps which I also highly recommend but that would be another review.
I'd say these ballasts run very quiet and at very reasonable temperature. I'd rate them better than my 600w Digital Lumatek ballast for sure. Here is some information from the manufacturer:
You get all of this, from a ballast that’s compact, light and silent – just what you need.
• No power surges (soft start technology)
• Prolong lamp life
• Low energy, to help prevent hot spots and lower running costs
• Incredible frequency control!
• Maximises beam pattern & light output of 315 Watt Philips CDM Lamp
• Silent to run
• Auto reset + short circuit protection
• Lightweight, compact & space saving – 230mm x 108mm x 68mm – (L x W x H)
Something very important with these ballasts is that they have protection. Once turned off, you won't be able to turn it back on for at least 15-20 minutes. The reason behind that - to protect the bulb ( And you will want to protect the bulb as they cost about 100£ ).
When connected, these lamps emit a smooth beam pattern, thanks to your ballast’s excellent frequency control! They’ll also kick out up to 1.9 micromoles (µmol) per Watt! That's crazy for a 315W supplemental lamp.
Now to get to the point - yield. I'd say that's very relative depending on your style of growing. 1 GPW can be easily achieved if you're using the most of the area covered by the light.
I had one problem with one of my ballasts recently. I noticed that 1 hour after the light come on, one of the bulbs goes off. If I unplug the ballast manually and plug it back in in 20 minutes It starts and runs without a problem, but if I leave it as it is, it would possibly turn itself back on in 40-60 minutes. I've contacted the Hydro Shop I bought the ballast from and they instantly replaced it!