I finally finished my Nuhybrid build!
The amp has been in service for just over a month, and it's been great step up in my listening experience. Having proper power behind my headphones makes the music sound full, and it's been nice to have something to boost my phone so I can properly listen in places other than at my computer. I now understand what the comments meant by the Nutube being microphonic. It makes a high pitch ringing sound in response to some contact and sharp movement. I mostly notice it when the relay activates or when I brush the volume dial. However, I don't pick it up when I move the amp around or if I bang on my desk. It's significantly damped when using my high impedance headphones, and I can't really notice it while music is playing.
It was a good beginners build. Very straight forward, especially with Pete's instructions. It took a bit of extra planning the assembly order to account for some of my selected over-sized components, but it all came together with a bit of patience. I can confirm that the 10uF WIMA capacitors fit in the stock Serpac base with a couple small washers as spacers. The difficult part with those was their very short leads that barely had the length to go through the board after bending to fit the spacing. Other than the visible differences in capacitor selection, I increased C2 to 22uF to lengthen the muting circuit timing as some had mentioned a decaying noise. It makes the timing ~12sec, which I find to be a reasonable waiting period. I can't say if I would have noticed the difference had I not mixed up the BOM, but it feels good to have made it my own in a small way.
I made the base from 1/2in oak for the perimeter, craft ply for the bottom, and square dowel for the standoffs, all held together with glue and finished with a dye stain and poly. I recessed some EAR feet so that it only sits a couple mm off the table. The top uses machine screws, washers, and spacers to hold up a piece of acrylic. It doesn't offer much for isolation, but it shows off the Nutube and other components while providing good protection. I felt like this was one I wanted to be able to look at all the time.
While building, I had the thought that you could mount the Nutube to the bottom of the board to make it the tallest thing on that side and mount the whole thing upside down in order to display it through an opening in a custom enclosure. I'm not sure if that would harm anything, but it doesn't seem like it would to me unless the regulator heat collecting upward is too much. The power switch going the other way would bug me until I got used to it, but it seemed like a way to be able to present just the Nutube through an enclosure without mounting it off-board and messing with jumper wires you need to keep short.
I've stated working on building Pete's Butte amplifier, with a couple add-ons planned. This one has impressed me, and I will be be building more of his designs to keep the fun going. Thanks Pete for these designs and thanks to all in the thread for your contributions to my experience.
Happy listening!
