Up for sale is a rare matched quad (4 Pcs) of vintage NOS Sylvania Gold Brand (GB) 5751 high-mu dual triode audio tubes, packed in white boxes. Manufactured in the USA, these premium Gold Brand series tubes feature heavy-duty black plate construction, a disc getter, and non-corrosive gold pins. Universally praised by audiophiles for their exceptional detail retrieval, silky highs, ultra-low noise, and balanced warmth when replacing standard 12AX7 tubes in preamplifiers and phono stages.

All four tubes have been tested on an Amplitrex AT1000 automated valve tester at nominal reference settings. Plate Current (Ip) and Transconductance (uMhos) measurements alongside percentage performance ratings relative to standard factory specs are detailed in the table below.