Angela Instruments: JE LABS 300B SE AMP

VOLTAGES FOUND INSIDE TUBE AMPLFIERS CAN KILL YOU! IF YOU DON'T UNDERSTAND PROPER ELECTRICAL SAFETY PRACTICE, DON'T BUILD THIS AMP!

Realizing that I have exploited all the possibilities out of my push-pull 2A3 amp, for my next
project, I decided to go single-ended. I have serviced and built quite a few Kit Is for Steve while
he was busy building his WE 91 clone. Although sonically quite different from each other, they
are both fine sounding amps. My instinct sensed that I can combine the virtues I admired from
those two amps using my favorite octal based twin triode, the venerable 6SN7. Since I need at -
least 7-8 watts of clean power to enjoy my music, 300Bs were a natural choice.

Off I went, borrowing back-issues of MJ from the Angela archives, searching the internet and
talking to friends. Funds are a bit tight this year but sourcing transformers and parts that are
beyond the realm of my "junk box" is not a problem; they are available from Steve (many thanks
and also to the gentleman in Japan who bought my PP2A3, you actually helped fund this project)
along with his liberal terms policy. Only to me folks, I am privileged!

My circuit choice narrowed down to the Reichert, Fi Primer 3008, and the Audio Note Conquest
series. All these amps use the 6SN7 as an input/driver tube so no drastic alterations were
necessary to try these circuits on my pair of chassis.

For two weeks, I listened in mono; one side Reichert, on the other, Fi Primer/AN Conquest (thus called because my choice of values for load resistors are somewhere between the two). I
treasure my Acro 20/20 amp because it has that dark and austere sound quality that I find
haunting. The Fi Primer/AN Conquest circuit had these qualities but added a hint of glare or
sheen in the upper midrange which bothered me. Herb's amp was very smooth and full bodied in
the mids but comparatively lacking the impact and dynamics of the latter. At this point I was
itching to listen in stereo, so a decision had to be made...... DC coupling won by a narrow
margin! This circuit was also a bit too sensitive for my system so I removed the cathode bypass
cap on the first stage. The glare was gone and I got the sensitivity needed.

Nothing is unique about this design; I am merely a "triode chef' mixing a "concoction of
ingredients" learned from trying the aforementioned circuits. The first two triodes are direct-
coupled in cascade, then, capacitor coupled to the grid of a 3008. 1 prefer the "taste" of 300Bs
running at or close to 80 ma. with approximately 425 volts on the plates. This may elicit some
controversy in some circles...... it is sufficient to say that I tried and listened both ways and voted with my "earbuds", so no arguments please. Anyway the AN 3K OPTs are rated at 140 ma. If you are worried about burning up NOS WE300Bs, be a cheapskate like me and use Chinese tubes. Believe me, they do not sound 10 times worse considering the insane prices being asked for NOS WE, that is.... if you can find them. Chinese 300Bs are rugged and take it with a smile while playing the gig.

To the more seasoned and discerning palette, may I suggest, going all the way with Black Gates
sprinkled with Rikens and/or Tantalums served through copper foil caps.......

Some Suggested Parts For The JE Labs 300B Project
See the appropriate Angela Instruments web site pages (transformers, sockets, tubes, capacitors, etc.) for current prices. Parts listed below are for ONE mono chassis.
1. Angela Universal Power Transformer.
2. Hammond 159P choke, 10H/125mA.
3. Hammond 1627SE output transformer. If you use something else make sure it's a hefty piece of iron or you won't get the bass this circuit is possible of putting out.
4. Hammond 10"X17"X3" STEEL chassis is preferred over aluminum due to the weight of the transformers. You can also build on a thick aluminum, brass, copper, etc. top plate and mount that on the Hammond box or on a wooden frame. The chassis depicted below was designed by me and fabricated by a local metal shop.
5. 15uF/600VDC Angela Polypropylene In Oil capacitor. You can also use Black Gates, Angela Fast Caps, ELNA CERAFINE or even ordinary electrolytics in place of any of the Angela Polypropylene In Oil capacitors.
6. 30uF/600VDC Angela Polypropylene In Oil capacitor.
7. 50uF/515VDC Angela Polypropylene In Oil capacitor.
8. Two 1.75" capacitor mounting clamps with hardware.
9. One 2.50" capacitor mounting clamp with hardware.
10. Angela/Jensen Copper Foil Paper In Oil .22/630VDC coupling capacitor. This is MY favorite; any good quality signal capaicitor (e.g. SBE Orange Drop, etc.) will also work.
11. Black Gate 100uF/100VDC cathode bypass capacitor for 300B.
12. Black Gate 47uF/160VDC cathode bypass for 6SN7.
13. Riken Ohm 470 ohm 1W resistor.
14. Riken Ohm 100K 1W resistor, two pieces.
15. Riken Ohm 220K 1W resistor, two pieces.
16. Riken Ohm 47K 1W resistor, four pieces.
17. Riken Ohm 1K 1W resistor, two pieces.
18. Angela 880 ohm non-inductive 50W cathode resistor. A 50W rating is really overkill.
19. 1.5K 5W metal oxide power supply dropping resistor.
20. GZ37/CV378 Mullard rectifier tube. You can also use other 5V rectifiers like 5U4G/GB, 5R4, GZ34 etc. but watch your voltages.
21. 6SN7WGTA JAN Philips or any other high quality 6SN7GT. I've tried RCA, Tung-Sol, Raytheon, various Sylvania '40s-'80s, GE and even the latest China production and all of 'em work fine. The JAN Philips 6SN7WGTA is my favorite because of it's high reliability and very low noise.
22. Current production Western Electric 300B is the best power tube I've heard in this amp. Other good choice include ANY of the Valve Art 300B 'family' tubes I've heard. The Full Music 'mesh plate' globe shaped 300B is another winner. In my experience, Tesla 300Bs from Slovaka sound nice but are just too unreliable due to poor quality control. No, I don't recommend any Russian 300Bs, or any other tubes they make for that matter.
23. Angela Ceramic/Silver octal sockets are my favorite for the 6SN7 and GZ37 tubers used in this circuit. Any of the other good quality chassis mount octals we offer, including Yamamoto, QQQ, Cinch, China wafer, etc. will also work just fine.
24. China Ceramic/Silver Johnson sytle wafer sockets for 300B have worked great for me over the past ten years. We offer a number of other good four pin socket choices including the Angela Ceramic/Silver Johnson wafer style, Angela Ceramic/Silver round bottom mount type, Yamamoto, even a few N.O.S. examples. The China socket is a true bargain but you should also consider the other choices.
25. Kimber RCA Ultraplate input jacks. See our CONNECTORS pages.
26. Speaker binding posts. We don't sell 'em but any sturdy 'audiophile' style dual banana jack posts will work just fine. Make sure that they have a big enough hole for your speaker wire. Avoid the crappy banana jacks sold by Radio Shack.
27. IEC AC inlet port. See our CONNECTORS pages. Don't be a sucker and waste your money on some stupid audionut' magic' AC cord; any good quality (e.g. Belden, Carol, etc.) 16g grounded cord will work fine.
28. On-Off switch. See our CONNECTORS pages.
29. Fuse Assembly. I like the old Fender style. See our FENDER AMP PARTS pages. You'll also need some 2A Slo Blo fuses; we don't sell 'em but any good industrial electronics supplier will be able to help you out with those.
30. Hum Balance Pot. Any high quality 50-100 ohm 2 watt pot, wirewound or carbon, will work. See our POTENTIOMETERS pages.
31. ALPS Blue Velvet 100K Audio/Log. Taper volume control pot. This part is optional; if you use the 100K ALPS pots you'll need one less of the 100K Riken Ohm resistors listed above.
32. Four lug terminal strip for the cathode bypass cap and some other circuit elements. Each mono chassis just needs one. See our CONNECTORS pages.
33. Ground Lugs Du Jour. You really only need one for each chassis, used as a 'star ground' near the input jack. See our CONNECTORS pages.
34. Wire nuts. It helps to have some of these on hand to cap off the unused taps on the Angela Power Transformer. Wire nuts are available at any decent hardware store.
35. Kimber 19g Teflon coated copper hookup wire. Buy two feet of each color. See our WIRE pages.
Remember, this is a FREE PROJECT, NOT A KIT. We don't offer a "package" of parts; YOU choose which parts you want to use, depending on your budget and personal parts preferences. Listed above you'll find MY choices; fee; free to follow me or make your own choices. You can build a great version of this project with relatively inexpensive parts or maybe something just a bit better if you use the most expensive parts. The quality of your craftsmanship is probably more important than your parts choices.

Derek Walton of Ireland has an excellent website devoted to this project with some very detailed and specific pointers and tips. We recommend you check it out. http://www.iol.ie/~waltonaudio/mk1300bindex.html

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