It uses "cathode bias".
There is one resistor connected between the cathode of all 4 output tubes and ground.
Nothing to adjust!
Ron
The SCA-35 is a nice EL84 push-pull amp; not at the top of the heap, but very musical and live-with-able
There's one in my living room even as I type this.
It was a low-low-end kit/product, though, which is good and bad. On the bright side, as with all (AFAIK) Hafler/Dynaco designs, the output transformers are very good (best part of the amp). The preamp section (except for the MM phono preamp, of course) is entirely passive; the two 12AX7s in the phono preamp may be removed if you're not going to use the phono preamp (it's not very good sounding); this saves a little stress on the power transformer and doesn't seem to raise voltages in the amp unacceptably.
The problem with Dynaco's economy lies mostly in that
über-cheap cathode bias scheme (one cathode resistor and electrolytic capn for all four output tubes): the four output tubes must be very closely matched or the bias on the tubes will be all mucked up. One surprisingly inexpensive solution (or ameloriation) is to add an aftermarket power supply board that uses pairs of cathode resistors and electrolytics. Under this condition, one need only match pairs of outputs (a bit more achievable, 'specially if one wants to run vintage tubes). I used the board from
http://www.audioregenesis.com/ It is inexpensive, easy to install, very well documented, and the support of the proprietor was excellent. No affiliation, just a satisfied customer (and just sayin').
There are also output boards that are designed to use more readily available tubes than the 7199s used in the original design. I have no experience with these (yet).
Tom's advice, of course, is also good if yo want to stick with the single cathode resistor topology.
Hope these ramblings are helpful.