Goals
– K.I.S.S. for first new project (c’mon Jim, you can do it!)
– drive headphones at 22-35R
– volume control
– line-level input from DAC
– re-use components from old projects
– prepare for external PSU in future
07/04/2025
So I’m not reinventing the wheel on this one. My free time is limited so I want to just enjoy the music and not be busy building the ultimate amp for the next 5 years. All I want is to enjoy the parts I am looking at and the music I am hearing. It’s doubtful I will ever make a big system with speakers again, so I am just focusing on a headphone amp. It’s gotta be good, but within reason.
I have a bunch of tubes to chose from, as I have always hoarded good deals on tubes back in the 90s and 00s. Resulting in a stash of DHTs that I can never burn up in two lifetimes. Despite having a ton of NOS U.S. tubes at my disposal, I kind of feel bad burning those up on a headphone amp next to my PC. The lovely 801A/10Y/UX210 is still my favorite, but it is getting expensive and rare. I’d rather keep those for my pension fund someday.
Back in 2018 I found the 6E6P tube on ebay that looked like a REALLY nice spud/driver tube. It was cheap as dirt then, about $4 each, ordered a couple to test and play around with. While searching for more info on this tube (mainly the 6E5P/6E6P and E/DR/DRY differences) I ran into Ale’s site, Bartola Valves. This site has a wealth of information and was very inspirational. Ale’s 4P1L adventures were a joy to read and he put me onto this particular russian tube. Just like the 6E6P, this tube was easy to get and really cheap as well.
Around that time I had so many ideas of stuff I wanted to make, that I just burned out with almost nothing to show for it. Haven’t looked back to the site/hobby since 2018, but I now really want to finish at least the headphone amps. So might as well put those rusky tubes to good use.
Chassis
– power chassis for raw DC power supplies (transformer, rectifiers, caps)
– signal chassis will only have regulator PCBs, no power transformers
Driver section (option 1)
– 6E6P-DR
– Ua=200V, Ia=35mA, Ug=-3.3V, rp=1245, µ=34
– interstage LL2763AM-50mA
– auto bias
Driver section (option 2)
– 2P29L
– Ua=?V, Ia=?mA, Ug=?, rp=2300, µ=8
– interstage LL2763AM-50mA
– auto bias
Output section
– 4P1L in triode
– single-ended
– Ua=200V, Ia=30mA, Ug=-15V around here???
– opt LL9202AM-50mA with 6K/11K/23K configurations (801A in future?)
– filament bias?
B+ Supply
– I really don’t want another 100kg with my old chokes and huge oil caps
– SiC rectifier diodes
– eChokes
– MKP caps
– passive supply PCB from this project
– reuse Bartolucci power transformer (230-200-0-200-230V/0.2A, 2.5-2-0-2-2.5V/4A, 6.3V/1A, 6.3V/1A)
Filament supply, driver
– use 6.3Vac windings for 6.3Vdc
– rectifier with low V drop diodes
– low drop-out regulator
Filament supply, output
– passive DC pcb
– SiC rectifier diodes
– coleman regulator
20/04/2025
I was still contemplating going the 801A/4P1L route because of the lovely tungsten glow of the 801A. But the fact that this amp will be on several hours a day just listening to spotify, just kept giving me a bad feeling on wasting the VT62/801A tubes. Seeing as I bought a box of 50 for the 4P1L and 2P29L at dirt cheap prices, I would have no issue “burning up” these tubes.
Ordered some teflon Loctal sockets from Ali to seal the deal. Schematics for the PCBs are nearly done, will start work on making the PCB routing designs next. All the parts going onto the PCBs are here as well, so I can make templates for all parts.
TO220 diodes, eChoke and 50µF MKP part templates ready.