Errr...does that actually produce good sound on the HE-6? What's the output on the headphone tap?
side note: I don't own a Leben but am fascinated by this congregation of what I'd call 'the golden sound masochists'. It must be really special for you guys to put up with the deficiencies such as the noise floor on the speaker out (obviously mainly an issue with headphones), low power, technical issues.... I could purchase a used 300 model for 1500 EUR (been on sale for a long time on a Belgian site) and admit to being curious but it's just a bit too risky for me as I listen exclusively with headphones and love my HE-6.
I have noissues with noise or hum on the leven ezcept when using high impedance phones. Low impedance phones, even the 110dB Sennheiser Momerntum are quiet.
I tried it with the Klipsch RF8 rated at 98dB @ 2.83V / 1m and had no hum there either.
I think the hum from the Leben varies a lot with mains and tubes, since others report otherwise. But I think that is a minority. .