Here are my basic Clementine ULtra notes. I can add more commentary later. In a nutshell, I discounted an ultra-linear Clementine due to the high plate impedance thus extremely poor damping and high ampifier Z. But with 6dB of negative feedback, we gain parity with the triode configuration plus we get more output power as the mu is higher in an ultra-linear configuration. Damping factor was measured at 5.2 (UL without feedback is less than 1 and selective distortion wreaks havoc) and the distortion was mostly 2nd harmonic even at max power - key triode 'signatures'. Read more about this in RDH3 pages 16 and following. Note how beam tetrodes are superior to pentodes for this application. The only negative in the ULtra is the high input voltage needed - 1.6V for 7W - so a preamp is needed and an iPod will not drive it.
Mods from the Clementine 6L6 Build in the main thread:
- Remove R15 and R16 (no triode strap resistors)
- Connect ultra-linear taps to J3-2 and J4-2
- Use connectors at J10 and J11 or solder directly to the pads. I used CDROM audio cables since they are cheap shielded cables. The yellow output secondary (+) goes to J10-1 and J11-1 respectively. The white output secondary (-) goes to J10-2 and J11-2 respectively.
- R27 and R28 are 680 ohm resistors with 6800pF (i.e. 6.8nF or .0068uF) strapped across them. I am using cheap ceramic discs. A good temp rating or voltage rating is not important.
You are then done, and have about twice the power. It sounds pretty awesome, with the 3D 2nd harmonic is 100% there and no irritating dominant 3rd harmonic.
7W and 4W output power and distortion:
http://www.diytube.com/clementine/7wultra1640mV.pdf
http://www.diytube.com/clementine/4wultra1208mV.pdf
Shannon