Single Ended power amplifier with type '45 triode (3)
The mains connection and loudspeaker terminals are mounted
on a copper subchassis behind a milled hole at the rear end of the oak chassis.
This seems to me a right choice due to the reasonable amount of strength put
on the mains connector when plugging in and out. The fuseholder is mounted inside
the amplifier (lack of space at the rear side).
At the front side the hum pot for the '45 is mounted as close to the pins of
the tubesocket as possible - the solderlugs are soldered directly to the tubesocket.
Adjustment on the hum pot is done from the bottom to provide a "fixed look".
The 4606 needs an UV4 socket which is hard to find (for reasonable
money), so I made them myself using wood (Bubinga). Wood has a remarkable good
value in isolation, when dry ofcourse... I drilled holes about .1mm less in
diameter than the tubes' pins and the tube clenches perfectly. In doing this,
wiring has to be soldered directly to the pins which is an advantage but not
when replacing the tube...
The filament voltage of the 4606 is 4.5 Volts at 1 Ampere and will give an inevitable
hum when AC is used. The idea was designing an amplifier using Super E-cap as
much as possible, so the filament voltage is rectified and BlackGate Nx in Super
E-cap are used as capacitors. A hum pot is used since a reasonable amount of
AC is still present because I don't want to use a too high value resistor in
the pi-filter to avoid too much dissipation. Schottky diodes are used as rectifiers
and the whole circuit is mounted on a piece of experimenting PCB which is located
between filament transformer and tubesocket and screwed at the innerside of
the chassis.
The supply capacitors are "hot-glued" to the chassis:
removable but sufficient anchored for normal use. The grounding wire connects
the mains receptacle to the metal housings of the transformers where star-grounding
is used. The "0" of the high voltage winding of the powertransformer
has a separate connection via the first capacitor, the only paper-in-oil, to
the star-ground. Each pair BlackGate NH's have also a separate connection to
this star-ground. Wire used for grounding is 2.5mm solid core copperwire.
A RikenOhm gridresistor is used and a Mills wirewound as kathoderesistor and
(again) Super E-cap as kathodebypass. The '45 is coupled using an interstage
which is mounted under beneath, between driver and powertube. Both tubes have
their own (floating) star-ground which are connected to the minus of each circuits
last powersupply capacitor. A Quantum Purifier "purifies" the mains
voltage....
On the next page several enlarged pictures are displayed, each about 90Kb...
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