Tuesday, May 18, 2010
To increase the volume level of the Bread Board amp (Be Bamp), else where on this bLog, a driver stage was built. This is the original cct. used in the Merlot amps with some components upgraded. The is no volume control or input cap and pure silver wire used in the signal path.
The Be Bamp can deliver full volume to the point of clipping. Well short of clipping a high volume level can be obtained with large 91db sensitive 3-way tower speakers. The over-all sound of the system, which also combines a two stage valve preamp, is extremely musical. The sound is very transparent with good bass extension and weight, broad well imaged sound stage and natural tones of voice and instruments.
With the driver stage being remote other driver stages can be matched to the power stage and share the power supply. This provides another level of experimentation and flexibility with the over-all system.
Because the Bread Board amplifier (Be Bamp) performed so well, though at low volumes, a driver stage was built for it. This stage is remote from the rest of the amplifier and is joined to the amp by interconnects. A multi-pin, high grade, plug and socket connect the 400V HT+ and the 6.3V filament voltage to the driver stage. This single stage front-end has been constructed in a Twinings Tea Box to match the two stage valve preamp else where on this bLog. Having the driver stage remote allows the trial of different driver stages while sharing the power stage and the and a common power supply.
The same drive stage as in the Merlot amp was used. This employs a 6N1P Russian tube. Parts of the original schematic were upgraded and Russian military paper, foil and oil caps were used for inter-stage connection. There is no volume pot or input capacitor. Low ESR grade caps were used where possible and pure silver wire used in the signal path. Construction is all component-2-component with no PCB or any other cct. brd. The timber Tea box is bitumanised Al foil lined.