Tube Audio Lab 300B Stereo
Modified version of JE Labs 300Bdx
Split rail power supply with different
cap values, 5Z3 rectified
300Bs, 2x 76s, and 2x 6sn7
watts per channel, pure class A
Single Ended Directly Heated Triode
Completed on 2/26/09
Built on 17x 10 x 3 steel chassis painted in hammertone
Notice the different layout this time - I usually group
OPTs together and have the PT on the one end of the chassis. I mostly did it for my entertainment. It turned out pretty good,
in my humble opinion. Maybe I ought to try this layout more often.
It's no fun to see your beloved 300Bs and precious
preamp tubes blow up on power up. This is why I always use a time delay circuit board to warm up the tubes first before the
HT plate volts kick in.
One of the input driver (76 tube) section, notice the
cloth lead wires. I am trying to keep things look vintage, even inside. I love those NOS Sprague Atom 'lytics, as well
as those huge Russian military PIO coupling caps.
I find those James 6123HS 20W OPTs to be a match made
in heaven for JE Lab circuits. They are an excellent cost-effective alternative for those that want Hashimoto-like performance.
Beauty is only skin deep - I have tendency to put
in more efforts to keep the inside more beautiful than the outside. Careful planning in layout keeps sound artifacts and hum
out. Notice there are more irons under the amp than the above.
I am a big fan of JE Labs' designs. The 300Bdx certainly is one
of them. I built a monoblock version of it before and it was very well received by my buyer (Vern's amps). I wanted to build it in stereo, but I wanted to use a split rail PS with a choke in each channel. I also wanted to
use the 5Z3 rectifier instead of 5U4G, so I redesigned the PS accordingly. The result of this is tighter bass and improved
channel separation. The amp sounds really good. This probably is one of the most transparent amp I've heard. This amp
certainly will please any SET fans that like all triode driven 300Bs. I have also built a linestage using the same combination
of preamp tubes (6sn7 and 76) with a great success. The linestage seems to work great with the 300B.