Practically all tubes in Gold Brand series have earned legendary status among audiophiles. In this article I will go into details of the brand and what makes it so special.
Sylvania introduced Gold Brand in the middle of the 1950s to compete with GE 5 Star, RCA Command, etc. Practically all companies that produced vacuum tubes had their own “Gold Brand”. For example, Mullard introduced 10M series. Philips had PQ (Premium Quality). Gold Brand tubes have been designed to work in critical industrial, military and commercial applications. The tubes assured dependability under mechanical (500g) and thermal shock conditions (330 F and 165 C). The tubes were tested under crazy conditions to maintain electrical characteristics and reliability. As a result, tubes in Gold Brand were guaranteed to have an average life of 10,000 hours (5,000 for regular tubes)
So is this brand just a regular tube that passed strict quality control? It doesn’t appear to be so and here is why. Sylvania claimed that they redesigned tubes from the ground up to meet these strict reliability criteria.
- Rhenium-Tungsten Heater instead of pure Tungsten. The heater wire has also been thickened for added physical strength.
- Heater Over-Coat to isolate the heater from cathode electrically.
- Powdered Metal Cathode to minimize the introduction of contaminants
- Duplex Emissive Coating to maintain gain or power output as tubes age. The emissive materials progressively activated as the tube ages and reduces GM slump.
- High Thermal Conductivity Plates up to 5 layers have been used in plate construction (Aluminum, Copper, 2 layers of Steal, Nickel), this allows efficient and uniform heat dissipation to eliminate “hot spots” and “gassing”
- Gold Plated Grids to prevent grid emissions
- Gold Plated Pins to resist corrosion and for low contact resistance.
- Thick Double Micas or Triple Micas for structural rigidity and reduction in microphonics.
- U-Bold between the top and bottom micas to further increase rigidity
- Controlled Atmosphere Welding to reduce weld splash, increase weld rigidity and minimize dangling metallic particles
Looking at this list, call me impressed, it’s no wonder that all tubes in Gold Brand are hunted down to extinction. Compared to Genalex from UK for example, which practically in all cases just rebranded carefully screened Mullard tubes, Sylvania actually created a new tube from scratch.
This is a list of tubes included in the Gold Brand, all of them started with GB-. Note that the list is not exhaustive.
- GB-6DJ8 (there is no GB-6922)
- GB-5654 (6ak5)
- GB-5751 (note that there is not GB-12ax7), this tube was suggested replacement for 12ax7 tubes.
- GB-5814A (also no GB-12au7)
- GB-5931 (5U4G)
- GB-5932 (6L6G, GA, GB, GC)
- GB-6189 (12au7)
- GB-6201 (12at7)