JE Labs 300B Deluxe
300Bs, 2x 76s, 2x 6SN7s, and 5U4
9 watts per block
Buyer: Vern in BC, Canada
" Hi Min, Just a quick note to thank you again and let you know how much I
am enjoying the amps. I had some audio friends over last weekend and asked them how much they thought the amps cost,
the lowest estimate was $4500.00. So I think you need to raise your prices. I will do my best to sell some more for you. Best Regards....Vern" - Vern in BC, Canada
I have had such a success with
JEL 2a3 deluxe that I wanted to try the design with 300Bs. I did not work this out myself, but it's JE Labs'. Here is the
schematics. The design employs type 76 direct coupled to 1/2 section of a 6sn7 driver capacitor coupled to the grid of the output tube.
I had loads of fun building these. Here is a step-wise depiction of the build process:
I use a template, on which I directly drill pilot holes
for all the surface mounting parts. No fancy equipment used here. All done by hand, including designing the template. I use
a hole punch of various sizes, a hand drill, and Dremel tools for non-round cut outs.
The layout is carefully thought out as to avoid
any magnetic coupling bewteen chokes, PT, and OPT. Also, I worked it so that all leads are kept short, especially AC wires.
This is essential for keeping the AC-induced hum and noises down.
Finished wiring. I exclusively use a combination
of bus ground and star ground for all my amps. It keeps the wiring of passive components around tubes sockets neat and well
organized. I know there are other grounding techniques out there, but I am sticking to what has worked for me the best.
Notice the magical Russian PIO coupling cap that everybody in
the DIY audio community is raving about. Also, notice that I have bypassed the cathode caps with those Solens. Apparently,
this snubber removes any ESR and ESL
issues with the electrolytic and the WW resistors, and noticeably improves the HF response.
The Japanese OPT is rated at 25W 3k:4,8 ohms. Weighs
about 7 pounds. 20 Hz - 20 + kHz frequency response. Great bass response and high top ends.
Cooking in stereo!
These are great sounding amplifiers. Sounds much like
the 2A3 version, except there seem to be more depth to the bass.
Smooth highs and mids with a plenty of high-end detail. They really groove to the music. They also run pretty quiet, even
on my 98 dB/W/m speakers. The hum pots cancel out any 60 Hz AC-induced hum. The amps have a very robust PS that effectively
filters any noise, so that all I need do is to enjoy music.