JE LABS SE171A
This amp supports the concept of it is the first watt that counts!
Output = .800mw!
I loaned my SE171A amp to my buddy Sherwin for over a year. He loved the amp so much driving Goodmans speakers in large bass reflex cabinets that the only way I could get it back was if I built another one according to his specifications. After finding free time from gigs I told Sherwin to start collecting parts for his dream SE171A amp.
He commissioned the fine crafted curly maple wooden base with aluminum top plate from George Brkich in Florida and ordered Tango M757 Opts [7K or 5K pri. Z and 4, 8, and 16 ohm secondaries] from Koji at EIFL. The power transformer is a Hammond 370BX from the classic series, tube rectified by a type 80 [5Y3 is an octal equivalent] filtered by Sprague TVA "Atom" and a surplus Mil-Spec 20H/60ma potted choke. This main reservoir is split into 2 rails provided by Dave Slagle's custom wound 80% Nickel 5H/35ma. chokes, this time using Cerafine caps for filtering. The output DHTs are AC heated by Hammond 166L5 5V/2A filament transformers with about 2mV maximum hum/noise.
The input/driver circuit is derived from my tried and tested JEL SE300Bdx. In this particular amp, he requested that I use a sexier 6J5 driver triode from his growing tube collection. As usual I used matched carbon composition resistors from Allen Bradley and/or Riken in the signal path with Jensen "copper foils" for coupling. Black Gate FK series for cathode bypasses wired with Kimber TCSS and 99% solid core silver wire complimented by Cardas input and output jacks.
I am well aware that type 76s are getting scarce and finding quiet and non-microphonic samples can be quite challenging. Likewise glass ST shaped 6J5s are not easy to find, so your favorite 6SN7 can be substituted for the input/driver circuit as indicated in the schematic. Slightly less refinement, but you will not hear it unless you do a direct A/B comparison.
Here is an example of a JEL budget SE71A built using parts scrounged from junk accumulated in the basement. This pair of mini mono-blocks uses 6SN7s for the input/driver circuit, power transformers and chokes gutted from a Roberts/Akai reel-reel tape deck and Hammond 125ESE OPTs. The 500VCT/60ma. power transformer had enough filament taps [5.7V/.3A, 6.3V/1.2A and 6.3V/.6A] adaptable to accomodate the 71A DHT, 6X5 rectifier and 6SN7 tubes.
If you have 95 dB/1W/1M or greater sensitivity speakers, try this flea powered DHT, you will be surprised how much SPLs one can get from high quality millwatts. If you do not get good sound before 1W, why should you need more? Sherwin is now having fun tube rolling different 5V power triodes like 183s, 182As, TJ205D, 71As, thoriated 171s and even 300Bs at a mighty 800 mW!
For other applications of the 76/6SN7 dx topology, please go to the SE300B page where I recently uploaded a schematic of the JEL SE245dx.
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