As I mentioned in the 1st year post, I recently picked up a Proton AM-300 for $60 on eBay. I chose this integrated amplifier as I wanted something relatively low power with 4 Ohm output capabilities, as well as a moving coil phono preamp for potential future upgrades. I was originally looking at Yamaha models, such as the R-9 receiver, A-420, A-520, or A-500. However, none of them had the ability to do 4 Ohms and all of them were over $100, as Yamaha gear is sought after and integrated amps are generally more expensive. Then I saw this funky thing with no knobs and "Dynamic Power On Demand" on the front for sale with a dead display for a pretty resonable price.
I had heard great things about Proton gear, and I thought DPD was like Yamaha's "Auto Class A", so I decided to see if the display was a common issue, and sure enough it used incandescent bulbs for an LCD backlight, which often go out, and LED replacements were very cheap. So I did more research and found out that it had 0.02% harmonic distortion, or about 0.005-0.015% worse than the Yamaha options I was considering, but it had a dampening factor of 90 as opposed to 50, so the specs were quite a bit better especially considering I don't blast my music all that loud, plus I learned that "Dynamic Power On Demand" actually refered to the class of amplification. This 30 watt Proton has a toroidal transformer in a Class H setup, meaning it has variable power input based on the volume level as opposed to a constant output, with a high quality transformer for amplification. That means it is more effecient than Class AB, while being closer in performance to Class A. It's the best of both worlds. So I decided to snag it.
But, of course, that meant I had to repair the display. And well, the only things I knew were that it had green filters and that the polarity was completely random and had to be tested for each of the bulbs before soldering. So when my bulbs arrived, I opened up the Proton and figured out how to remove the front panel so I could access the bulbs.
And this is where I made a realization. Only one of the color filters stayed intact, the two in the backlight were badly singed and disintegrated. Kinda dissapointed, I stripped the wires, taped them down, turned on the amplifier and measured the polarity with my multimeter. Sure enough, one was reversed polarity and I had to solder the LED the opposite way around. I then tried finding some things I could use to tint the color, but I had no good options, so I just stuck the whte bulbs into some cardstock and taped them in.
When I expected it on, I expected it to be orange, like what JVC has on a lot of gear from this time, based on what I've read online, but no, it is actually white. If I would've known that, I would've tried getting green LEDs rather than trying to get the neon green color I expected by filtering out green from white into orange (green LEDs wouldn't work for that as they're only one frequency of light so it would only appear dark green)
In addition, it appears as though the power light isn't working, and that's the only one I had the color filter on. But, that one appears to be always on anyway as I tested the polarity with the amplifier off and it had a reading. So I'm probably happier without it anyway.
Though we aren't here to stare at the pretty lights, how does thing sound? Well, simply put, it sounds amzing. My Yamaha RX-500 sounds nowhere near as detailed, which I feel is largely down to the dampening factor and lack of places for corrosion to affect the controls due to it being digital. I was able to hear a few more treble details in one cassette album I have, plus the soundstage appears to be a tad wider, though that may just be placebo. It honestly surprises me though, as I didn't think an amplifier could make much of a difference aside from the distortion department. It also feels like it warms up my electrostatics faster than the Yamaha, only taking about half a song to reach volume, though I am still getting the hang of what volume level I should have it at for different sources, so that may be why.
My concerns with the digital controls were also answered, as despite only having 10 level markers, it has steps in between, allowing me to get my Stax more or less perfectly balanced and get the volume just right.