PSU1 versions

I've currently got two PSU1 units and they were purchased with about a year between them. During that time I think some small improvement was made to the design and so they're not exactly identical. Now I seem to have mixed them up and don't know which PSU1 came with which unit. It might be a stupid question but is it as simple as lower serial number equals older PSU1 unit?

Yes they both work excellent but I believe Graham did a small tweaking of the PSU1 design between my purchases in early 2011 and 2012 making them slightly different editions. I'm just interested to learn if there's a way of telling which PSU1 came with which unit as I've now got them mixed up. It's no problem or anything, I'm just curious.

Thanks Graham. I have 013 and 015, but the older unit (Solo UL) was purchased from an ebay vendor so I'm assuming I got a 2010 stock unit then.

Richard, I'd not noticed the cooler running myself. The PSU1 will run hot if called upon to deliver a lot more current - for example, used with the Majestic DAC it gets much warmer than when used with a Gram Amp. If anything it may be due to the latest "auto-fused" transformer. It may be a better batch of transformer steel: we specify a certain quality for reduced magnetisation current, and if a batch is even better than that, the magnetisation current will reduce further, and that would reduce idling current consumption and hence heat output.

Graham