hi!
I´ve just made a compilation of my tube and audio amplifier project videos over the past 12 years. There are preamps, power amps, vacuum and gas rectifiers, some scientific vacuum stuff - but each video 100% comes with at least one tube, with glowing filaments or an ionized plasma
It´s all compacted in a youtube playlist, otherwise the tube stuff would go down in my other videos.
YouTube
I´ve just made a compilation of my tube and audio amplifier project videos over the past 12 years. There are preamps, power amps, vacuum and gas rectifiers, some scientific vacuum stuff - but each video 100% comes with at least one tube, with glowing filaments or an ionized plasma
It´s all compacted in a youtube playlist, otherwise the tube stuff would go down in my other videos.
YouTube
so I finally got to a spot I'm happy with this stereo amp. Been working on it for a few years off and on, and finally got there. This is a 1625PP amp, with Edcor cxpp60-ms-4.2k iron. Uses 6SN7's as cathode followers to drive the grids of the 1625s into AB2. 1625 biased at 50mA quiescent. Got a 6SN7 long tail pair as a phase splitter with a 2N2222A CCS. Input gain is done with a 5687, biased at around 3.5mA/channel. Beast needed some serious power supply mojo, so I split it up into two chassis. The HV supply ended up being a whole project on its own. Now it doubles as a lab bench supply for fooling around with tubes for other stuff. Very similar to the STC 807 app note amplifier, but better phase splitter section. Flat to 40kHz, nice looking square waves up to 10kHz. Will post some scopeshots later on, and do a side-by-side with matched Raytheon 6SN7's and red base 5692's in the phase splitter section. Put parasitic blockers on the plates, but didn't seem to need them. Cage on the 5687 helped reject cell phone noise - it chirped some when my iPhone's radio checked in with the local tower.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The text on the top panel is laser engraving. Transformer covers are fast rotation with abrasive treatment.387A_WE, Tube 387A_WE; Rohre 387A_WE ID35019, Vacuum Pentode
387A as well as 717A wonderful pentodes. The 387A of 1935 has an incomparable sound .717A uses Yamamoto in its amplifiers. which cost 8500 dollars. probably not casual. I made this amplifier in the image of "darling" only the 1626 triode I replaced with 45. in order to increase power. acoustics I have an open box on a 12" broadband. With a sensitivity of 98 dB. 1 watt is enough for it for a good return
I have finally stashed away enough iron that I'd like to do something similar. Have you found that a 6SN7 wired as a cathode follower is working well to deal with the grid current on those AB2 peaks?
I have been staring at that 80W operating point in the 807 datasheet for a while wondering if it's actually possible...
Nice work lads. I'd be interested in seeing a schematic of your OP section cyclotronboyI presume the 1625's are fixed bias, if so where did you bias them.
Andy.
Andy.
KT88 SE amp, the Abdellah/Gendrano/Kegger/Blueglow (phew!) circuit. Power supply is a little different, with a 5U4GB and CLCRC filter. The chassis is an old handmade mahogany drawer that I reinforced with aluminum angle bar and freshened up with a bit of shellac, the top is 3 mm aluminum diamond plate.
Telefunken ECC85 driver, James OTs, 440V B+ and 78mA on the KT88s. Sounds fantastic!
Telefunken ECC85 driver, James OTs, 440V B+ and 78mA on the KT88s. Sounds fantastic!
Attachments
Not the first time a draw has been used as a base. Mahogany, now that’s classy. Amp looks good. A KT88 SE UL is on my list probably as a wine box amp.
Wowww that's a beauty congrats, I built too recently amp in a bamboo drawer but yours is really posh, you also been lucky to find a James OTs if I remember they out of business since 2018....anyway enjoy the music
Wowww that's a beauty congrats, I built too recently amp in a bamboo drawer but yours is really posh, you also been lucky to find a James OTs if I remember they out of business since 2018....anyway enjoy the music
Thanks! I got the James OTs some 10-12 years ago when they were still in business, and breadboarded the amp from Mikael Abdellah's original schematics. Then the whole project got boxed up and largely forgotten due to moving and family and lack of time. Now I had the time to finish it finally