The Master is just a basic EL34 push-pull amp with a Stax socket/bias supply bolted to it. The signal is taken off the OPT primaries and fed through some caps/resistors before reaching the Stax socket. This is a great solution if you are looking for an EL34 speaker amp and just happen to have some Stax sets hanging about but if that isn't the case, you'd be better off with a dedicated amp.