A Few Good Watts
"Here's To Hoping That The Best Comes From That First Watt."
Stage 1
How Low Can You Go?
What does it take to achieve great sound? Well, how about a watt or two? I opted to piece together some parts for a cheaper alternative than the Welborne Labs 300 DRD kit. I am now buying a few parts each month to make the JE Labs 2A3 SRPP amp. This project is featured at the Angela Instruments web site along with Joseph Esmilla's web site. The idea is that costs can be minimized by using regular parts instead of boutique parts - like using Hammond trannies instead of Magnequest Output Transformers; Panasonic caps instead of Black Gate capacitors; and Solen polypropylenes instead of fancy electrolytic and oil caps.
Now that I've completed my Frankenstein Horns, I can try out a Single Ended Triode amp to see what's all the fuss about. People say the 2A3 and 300b can't be compared to each other as the sound is subjectively different, not to mention that with more wattage a 300b has an advantage in the bass department. However, what drew me in was that the 2A3 has been described as having a nicer midrange in comparison to the 300b. Now that's what I'm looking for! So I scoured the net for ideas and came back to the simple JE Labs design as parts are readily available.
Here are the schematics:
Driver schematic (linked from the JE Labs site)
Power supply schematic (linked from the JE Labs site)
Check out Arnold Cruz' 2001 Edition of a similar design
Tube data:
There are two possible rectifiers for this project, GZ37 and 5U4GB (PDFs)
The 2A3 data, page1, page2 (PDFs)
There are also two possible driver tubes, 6SL7GT or 5691 (PDFs)
5691 Pin Outs
Stage 2
Parts Selection So Far...
Hammond 272FX - 146VA, sec. 300-0-300 - Angela
Hammond 193D 8H, 150mA, 75 ohms, 600VDC - Angela
Hammond 166L2 for the 2A3 filement - Angela
Valve Art 2A3 matched pair - www.tubeman.com
5691/6SL7GT N.O.S. '80s JAN Philips tubes. - Angela
One Electron UBT-3 - Antique Electronic Supply - Some people on the Net like them. Since they cost about the same as the Hammond 1627SE I thought I would give One Electron a try.
Cardas Copper binding posts - PartsConnexion - I gave in and wanted the solid copper posts. These are also on my Muse 100 amp and they look and feel nice.
Cardas female RCA - PartsConnexion - looks like I'm spending more than I should now, but these jacks are beautiful!
Alps series stepped attenuator - PartsConnexion - had this around waiting for a project
Jensen copper foil coupling caps - PartsConnexion - this is said to be the best for the job. Other caps are Solens, a few standard series Black Gates at the cathodes, and a cheap Xicon in the powersupply.
The resistor directly in the signal path is a Riken, the others are generic metal oxide and carbon film types from Mouser.
The chassis is a 1444-series Hammond.
