Active Output
 

 

  

 

 
The active output stage is the result of years of research and development of the ultimate line stage circuit. It is now used in both the line stage configuration as well as the active RAKK dac output. 

The amplifier is a differential class-A triode connected in a bridged parafeed arrangement. It features moderate gain, low output impedance, wide bandwidth and extraordinary sound quality. The circuit is on one hand classic, while on the other hand state-of-the-art. It uses a transformer output in a bridged parallel feed configuration that was used by Western Electric over 60 years ago. However, it uses a depletion mode MOSFET constant current source (CCS) that is more effective than anything available to the Western Electric engineers. 

The kit uses all top quality parts, among them: Cardas capacitors, Mills wire-wound resistors, Kiwame carbon film resistors and  Holco metal film resistors. The transformer employed is the LL1674, a superb amorphous core unit from Lundahl. The amplifying device is the awesome Russian 6N6P dual triode.  

This version of the Active Output includes dual mono Minimal Reactance Power Supplies for the high voltage.

For further information on the use of the active output board, refer to the Active Output Article. 

To read about the development of the Raleigh Audio line stage, see the 
Line Stage Articles.

Here is the schematic diagram of one channel of the the active output board.
 

 

Output Specifications
 
Gain 12.5dB
Output impedance 250 Ohms
Frequency response 
   6Hz to 40KHz , +0dB, -3dB  

Requirements
180-220vDC @ 32mA for two channels
6.3vAC @ 1.2A for two channels

Size
6.1 inches by 5.5 inches