The 46 is a double grid power amplifier valve with a 5 pin, (UY5), base that can be wired for class A or class B operation. Triode use is required and connecting the second grid to the anode allows for class A use. Introduced at the start of the 1930s, the 46 was produced in large quantities by all the major American manufacturers until its popularity declined in the late 1940s.
RCA 46 Valve Datasheet
They were manufactured in both globe and the later shoulder type varieties. Increased reinforcement in the shoulder type, in the form of mica supports and the stronger glass envelope itself, made for a more durable product less prone to vibrations and microphonics. It's tough to hear a difference between the two types but the globes do have a certain visual appeal.
Raytheon 46 Globe and Shoulder Types
According to the datasheets, the 46 is good for 1.25W of clean power output. Not a problem for higher efficiency speakers - the Davison Audio 46 power amplifier pushes closer to 1.5W output. Certainly in the territory of high efficiency speakers, depending on how loud you listen of course, but the Klipsch Cornwall IV speakers energise the listening room here with an authority you need to hear to believe.
RCA 46 valve
The 46 is often compared to its sister the 45, the 'queen of DHTs' and one of the most linear valves ever produced. The 45 is a triode with a single grid and its outputs a slightly higher 1.5W according to the datasheet.
General Electric 46 valve
Listening to the 45 against the 46 in our power amplifier's output stage, (5k load for the 45 vs 7k load for the 46), reveals the 46 to be the more compelling valve. The 45's mid-range magic is still there with the 46, but the 46 further enhances it and lower frequencies reach deeper giving a stronger grip on the music.
Raytheon 4-Pillar 46 globe
The 46 is truly a special valve and Davison Audio is proud to be bringing it to a modern audience. Still widely available today, we hold good stock for our customers, helping to ensure this valve still has a long future in hi-fi audio.
Davison Audio 46 Power Amplifier