One thought on “Brimar 12AU7 Clear Top Gray Plates”
These are some beautiful, very rare tubes. The Brimar 12AU7 Clear Top with gray plates is one of those valves you almost never see come up, and when it does, most people walk right past it; because at a glance it looks just like an RCA 12AU7 Clear Top. Same clear upper glass, same gray plate structure. But they are not RCAs, and once you know what to look for, the differences are obvious.
The sound
Through my preamp it lands somewhere between American drive and British ease. Mids are the star; vocals have body and a slightly forward, textured presence without any shout. Treble is open and extended, sweeter and less glassy than the RCA clear top, with real air around cymbals. Bass is tight and well defined rather than fat; it doesn’t bloom the way a Mullard does. Soundstage is wide, layered, and surprisingly deep for a 12AU7. Low noise, quiet background, and it never got fatiguing over long sessions. Detailed but never clinical; that’s the balance I keep coming back to.
It looks like an RCA Clear Top — but it isn’t
These look like RCA 12au7 Clear Top, but they are definitely not. Here’s what I look for:
No RCA logo etched. RCA etched their logo into the glass. If there’s no etched RCA mark, you’re not holding an RCA.
Round mica. Brimar used round micas here. RCA never made their clear tops that way.
Different clamps. The plate clamps are completely different in shape and construction from anything RCA used.
Round side getter. RCA only ever fitted square getters to the clear tops. A round side getter is a red flag immediately.
Etched Brimar data codes. The dead giveaway; Brimar’s own etched codes, such as 2E3 and 1571. Once you spot those, the identification is settled.
Any one of these on its own might make you hesitate. All five together and there’s no ambiguity at all.
Final verdict
The Brimar Clear Top is not an RCA impostor; it’s a genuinely better tube than the one it gets mistaken for. More air on top, better separation, a bigger stage, and none of the slight hardness the RCA can show on brass and strings. If you want the classic clear top look with a more refined, more musical British voice underneath it, this is the one to hunt for. Strongly recommended.
These are some beautiful, very rare tubes. The Brimar 12AU7 Clear Top with gray plates is one of those valves you almost never see come up, and when it does, most people walk right past it; because at a glance it looks just like an RCA 12AU7 Clear Top. Same clear upper glass, same gray plate structure. But they are not RCAs, and once you know what to look for, the differences are obvious.
The sound
Through my preamp it lands somewhere between American drive and British ease. Mids are the star; vocals have body and a slightly forward, textured presence without any shout. Treble is open and extended, sweeter and less glassy than the RCA clear top, with real air around cymbals. Bass is tight and well defined rather than fat; it doesn’t bloom the way a Mullard does. Soundstage is wide, layered, and surprisingly deep for a 12AU7. Low noise, quiet background, and it never got fatiguing over long sessions. Detailed but never clinical; that’s the balance I keep coming back to.
It looks like an RCA Clear Top — but it isn’t
These look like RCA 12au7 Clear Top, but they are definitely not. Here’s what I look for:
Any one of these on its own might make you hesitate. All five together and there’s no ambiguity at all.
Final verdict
The Brimar Clear Top is not an RCA impostor; it’s a genuinely better tube than the one it gets mistaken for. More air on top, better separation, a bigger stage, and none of the slight hardness the RCA can show on brass and strings. If you want the classic clear top look with a more refined, more musical British voice underneath it, this is the one to hunt for. Strongly recommended.