12au7 tube?

I never thought the Sylvania GTB was anything special. Very warm midrange and extended top. I liked the Raytheon 6SN7 WGT brown base which is a really nice sounding tube. For 12au7’s, I liked Raytheon’s, RCA black plates, Valvos, Brimars, didn’t like many Siemens because in my circuits they sounding bright. 

Yeah, GTA / GTB variants aren’t as good sounding as most of the older 6SN7GT tubes. You would need a GTA / GTB for 2 reasons:

1. Your tube slot (usually preamp or phono stage) is particularly sensitive to noise and microphonics. GTA and GTB tubes tend to be a LOT less microphonic than older GTs. Especially quiet are Sylvania chrome tops with the angled plates.
2. Your amp slot specifically calls for a GTA / GTB because it’s running a higher plate voltage and/or dissipation than spec’d for GT or 5692 (this one is even lower spec’d than GT so watch out). Sometimes driver slots in amps do this - like VACs, which specifically label these slots "GTB". You can often "get away" with running a GT or 5692 past its spec’d limits, but they might not last as long. Adding to the confusion: New Sensor makes an Electro Harmonix 6SN7 without "GTB" labeling, and a Tung-Sol variant that is labeled "GTB" - but they both have the SAME datasheet specs. Fortunately, it’s the higher GTB spec, so these are both safe for use in strictly GTA/GTB slots.

If you find you really need GTA / GTB (these are the same for audio applications), you might look for older 1950’s Sylvanias with deeper chrome tops and (sometimes) tall bottles. Sylvania really started cutting corners on production costs & quality in the 1960s. Their tubes also lost their beautiful midrange, sadly. Then they became Philips ECG and at that point, they practically sound like solid state devices.

@audiojan also try some RCA 5814’s with your Sylvania’s. They are warmish but seem to go nicely with the Sylvania’s I’ve tried in my preamp.

@inna rumor is PSvane makes many of the Ray’s tubes.

@inna rumor is PSvane makes many of the Ray’s tubes.

Right, but these days who else could it possibly be? We could pretty much guess that every time, and be right :) 

• New Sensor is doing just fine with its own fleet of sub-brands, and probably doesn’t want to encourange new brands (beyond a simple re-screen of labels) to compete with those.
• JJ / Czech can do it, but you can spot their trademark spherical glass domes from a mile away, and many of us avoid them out of habit & experience.
• Western Electric is too busy trying to establish itself as a high end option, trying to expand its tube offerings (very difficult w/ necessary tooling), and pushing its amp line
• Shuguang is gone? TJ Full music has always been small scale.