6CB5A DIY Thomas Mayer 2 Chassis AmplifierThis is an amplifier I built based on the design of Thomas at his VinylSavor site. The modifications include a choke loaded solid state B+ supply and a 2 chassis build. Thomas has championed the 6CB5A as a reasonable and less expensive alternative to the 300b tube as a single ended triode amplifier. Power output was measured just under 8 watts, frequency response was -3DB <10hz to 46khz. I find the sound is really satisfying. One of the 4 or 5 best single ended amps I have built. Good extension, solid bass, and a quiet background even on my 96dB sensitive speakers. It is most quiet with the power chassis a foot or 2 from the Signal chassis. It has a 3 foot set of power umbilicals. The power supply chassis is 8 x 16 Hammond. It uses an Antek torroidal for B+ and 6N7 filament supplies. Two Hammond filament transformers supply the 6CB5A filaments. The B+ supply is solid state, with a Linear Audio Delay Board for slow application of power. One filament regulator board supplies the pair of 6N7 driver tubes and each power tube has it’s own DC filament supply, as the tubes each draw 2.5 A. There are 2 Hammond chokes in the B+ and the capacitors are all DC Link 700v caps. Only DC is carried over the umbilicals to the signal chassis. The 8 x 12 inch Hammond signal chassis houses 2 shielded Lundahl LL1660A interstage transformers and 2 shielded Lundahl LL 1663 5 kOhm 8 ohm output transformers. Dropping resistors are all 25W chassis mount resistors. Ultrapath and decoupling caps are 700v DC Link film caps. This was a proof of concept build, so the chassis are not pretty but quite functional. Heavy duty connectors are used on the umbilicals. The only adjustments ever needed would be checking the DC filament supplies, but they have been quite stable as is and should be fine as is even with tube changes. The signal chain tube sockets are teflon based. Overall, a very nice amp, which runs hot like any high filament current tube amp. The supply chassis only gets warm. I will ship in a 20 x 20 x 12 inch box, well protected. One pair of 6n7 tubes and 1 pair of 6CB5A tubes supplied. I will ship to the Continental USA only. Schematics will be provided.
| 
