I’m building a headphone amplifier to use at my desk at work. A headphone amplifier with honest-to-goodness vacuum tubes.
This of course is the side project I began while the family was out of town for a week. I wanted to build something satisfyingly quickly while I took a break from planning that preamp. I’m pretty sure at the time I figured it would take a month total. Heh. Nine and counting.
It’s what they call a “class A” tube headphone amplifier, which means it runs hot. And it’s an OTL design, which stands for “output transformerless” (or something), which means the tubes do the job of pushing the music into your headphones, instead of using a transformer to convert some of that voltage into the current your headphones need. So naturally it now has a pair of audio transformers in there, custom wound for me by an industry legend, and a knob that lets you select the output impedance that best matches your headphones — OTL (600 ohms), 32 ohms or 60 ohms.
Oh, and a very, very fancy volume control: a collection of six separate circuit boards (eleven, if you count the ones piggy-backing on the main board) that combine to use light to vary the voltage (LDR, light-dependent resistor). And provide a dual panel LED (light-emitting diode) to show what the volume for each ear is set to. And relay-based input selection. And a 12 volt trigger, which means there’s a big power switch in the back that you leave on all the time, and push the volume control knob to switch the tubes off and on. And of course a remote control. Every headphone amp needs a remote control, I’m pretty sure of that.
Almost forgot the built-in DAC.
I’ve decided to try something new here. Several new things, actually.
I’ll be telling a story that is frankly unbelievable. I don’t expect anybody to buy it, and I have no way to prove that what’s been happening to me is real. But it’s time I tried.
Part of this story begins when I started getting very sick for days at a time, weeks apart. Vomiting, sweating, hypic jerks, no sleep and an average of 10-12 lbs lost over four days. Diagnosis: cyclical vomiting syndrome, which translates to “for some reason, patient gets very sick for days at a time.”
Something happens during those days. Something strange, and frightening. Just how strange, I’m still coming to terms with. I’m not ready to revisit those times just yet, so I’ll start somewhere else and loop back around when it makes sense. Maybe after the next one has left me.
So. Audio equipment—