Playing this afternoon with the SiC C3D02060F, which can happily run +20mA with very low dynamic resistance. Ideal for the 6e5p/6e6p driver I had in mind for the 300B amp:
At 20mA of cathode current the forward voltage is 0.85V and dynamic resistance 1.5Ω. If cathode current is 40mA instead the resistance drops down to 1Ω:
The 6e5P/6e6P will run comfortably around 30-40mA and bias tends to be around 3.5-3.7V to swing nice volts as needed. Therefore, we will need 4 SiC in series. 4Ω resistance is good enough and not adding much when reflected to the anode…
Hi Ale,
I’m very interested in these things for my 801A preamp currently in the final stages.
Would it be suitable to use these diodes?
What do I need to know to calculate how many to use?
Kind regards,
Bas
Hi Bas, sure. What is the operating point of your preamp? I think for 10Y/801a you may need too many diodes. Let’s see
Hi Bas, I looked at my notes and the 10Y could be biased at 30mA/245V for Vgk=-6.4V. Using filament bias If=1.25A then a 5R resistor and a transformer load could give THD < 0.03% at 10Vpp output. For same bias using the SiC diodes the Vf=0.87V @30mA so you will need about 7 diodes in series to achieve the same voltage drop (6.4V). The total resistance will be about 7R which is slightly higher than the filament bias option but will consume less power! The challenge is to have good Lp in the OT to ensure you have a good bass given the high anode impedance of the 10Y/801a. Hope this helps? Cheers Ale
Thanks Ale! Only read this now…completely forgot about it.