This is my all time favorite amp and one I had planned on never selling - that's how much I enjoyed it. I kept trying to beat it and have had a looong series of much more expensive amps but I always kept this one and with the exception of 2 (very much more expensive amps), not were immediately and significantly better (to me). But sense I have always had other amps, this amp has seen very little use - it hasn't even been plugged in or had anything connected to it for the last couple years. It literally has done nothing but be a decoration. I was planning on packing it up and putting it into long-term storage but I've sold off so much stuff lately and I'm thinking about selling this. I really haven't listened to headphones in quite some time now. From what I can see, this is still the same model and same version being sold and non of the actual internal parts have seen enough use to have any kind of heat aging. I do not have the backside input selector switch that you can get but that's because I had a custom made line router built by the designer of the amp, made to match the amp. This line router lets you select between several source inputs and even a couple out puts (to different amps) - so it's pretty awesome to help test gear. This is a lower power amp but I like it as much with my LCD-2s as I did with my grados. The front label came from the builder with some damage and it has gotten worse since I owned it but I've received 2 sets of replacement labels and haven't used either one. I think I also have 3 other input tubes that can go with it. The set of 2 power tubes are said to make no difference in tube rolling, so I never tried. Tubes for the amp for pretty cheap. I am the original owner and it was built by the designer. price is shipped with pp gift and they come in the original box's and packaging.