Absolutely fascinating for a a-technical mind trying to follow the TW amp discussions that lead indeed to a purchase of TW express clone. However, being highly motivated by the topics, I would like to change the all the tubes according to the given recommendations here. As the pre-amp 12AX7 are self-biasing, but the two output EL34 are not, are there any recommendations that are essential to be followed in any case when the current EH EL34 are changed into VOS Siemens resp. VOS Mullard?
Thanks for the help!!!!
Biasing tubes for TW express clone
Moderators: pompeiisneaks, Colossal
Re: Biasing tubes for TW express clone
Ken recommended to bias at -30V on the grid pins (pin 5) of the EL34s.
This has always worked out at about 70% dissipation for me on my builds, and ties in with the recommendation from pretty much everyone to bias your EL34s really hot in an Express.
It runs a lot plate voltage (around 400V) so the tubes take it well.
So I'd shoot for a 70% dissipation figure rather than a specific voltage.
This has always worked out at about 70% dissipation for me on my builds, and ties in with the recommendation from pretty much everyone to bias your EL34s really hot in an Express.
It runs a lot plate voltage (around 400V) so the tubes take it well.
So I'd shoot for a 70% dissipation figure rather than a specific voltage.