There are two sets of tube sockets, one 4-pin for the 2A3 and an octal (hidden by the jarrah wood shroud in the picture) for the 6B4.
Once the output tubes were chosen, we went ahead and chose the iron. The Edcor CXSE25-8-3K is an excellent performer and gives this amp 10Hz capabilities. Each output tube had its own filament transformer.
The driver stage is a traditional mu-stage using the 6EJ7/EF184 with a power-filtered screen supply as the top follower and the bottom voltage gain tube can either be a trioded 6EJ7/EF184 as well, or a trioded EF86 (its socket covered by the metal plug).
Why the 6EJ7/EF184? Electrically, it's a superior tube. Three times the transconductance of an EF86 at the same voltage gain makes for incredibly low noise and high drive capability. Because it's operating in triode mode, it is very linear at the current we're running them at (8-10mA), as these curves show.
Sonics of the 6EJ7/EF184 vary from one manufacturer to the next, as with most tubes. The Sylvania green print we used have an authoritive bass with clear mids and neutral top end.
The EF86 is the quintessential audiophile tube in many circles. The Russian 6J32P is also a nice sounding tube in this circuit.
Our client describes the sound: "....the three sounds [are] really [in] balance (Mid,High,Low) they don't overkill one another the mid is very smooth,the sound stage is wider and deeper. you can easily pinpoint where the instruments are placed.".
More pictures of this amplifier: Front, 2A3 closeup, Rectifier closeup and Operating in our system.
The cabinet is oiled mahogany and the decorative top shrouds are oiled jarrah.
Want one of these? Single output/driver tube pair (no 6B4 or EF86 socket) and including balanced and unbalanced inputs (switchable) and 2 year limited warranty begin at $1,500.
Local clients or pickup only, we don't ship these.
