"Phil Allison" wrote in message
...
, Arfa Daily wrote:

"Phil Allison"



Thanks for the tip, Phil. Noted. I'm guessing that this fender is
supposed
to keep the bias balance just so as well, as it has low value resistors
in
the output cathodes, with the voltage across them fed back to A-D inputs
on
the micro as far as I can see. Except of course that there is no feedback
volts a the moment because with - 89v on the grids, the valves are into
really hard cut-off.

I'm at a bit of a loss to see what the supposed advantage is on this
particular design, which uses a perfectly conventional EI cored output
tranny. Unless the valves have gone really badly out of balance - in
which
case they probably need replacing anyway - I would defy most users to be
able to hear any difference ... :-)


** Is your Fender a " Super Sonic Twin " by any chance ?

It's actually a Supersonic 100 head, but same chassis in a small
speaker-free cab, I believe Phil



Real dog apparently.

http://www.ultimate-guitar.com/revie...win/index.html

Sounds like their auto bias board is near identical to the one in the H&K.

Haven't come across the HK one so can't comment, but might well be. This one
actually says Fender on it, but they might be trading the design around
amongst themselves. It also has three preset 'settings' for soft, normal and
hard bias, accessed via a foil switchpad, and a toggle switch for 'club' and
'arena' modes. Personally, if they must have user bias settings, I would
prefer three preset pots inside, and a three way switch. I really don't
believe that output valve balancing is enough of an issue to warrant this
kind of complexity. On amps that have a bias balance preset, you have to set
it a long way off before you can hear much effect, and even then, it's
usually only a slight increase in background hum level ...

Arfa



.... Phil