The Shuguang Treasure CV181-Z Vacuum Tube
Tip #90
Dick Olsher (August 2021)

My passion for 6SN7 based line preamps hasn’t diminished over the years. There are plenty of designs out there based on 9-pin miniatures such as the ubiquitous 12AX7 family of dual triodes. But after living with such designs for a while I start to miss the tonal gravitas, the lower-midrange focus of the 6SN7, and eventually make a beeline back to my Blue Velvet (BV) DIY preamp. The BV design consists of two primary design elements: a single 6SN7 per channel operated in Class A topology and tube rectification. Low gain (~3 dB) makes it ideal for digital sources. As with other simple 6SN7 designs, sound quality is strongly dependent on tube brand, which brings me to the Shuguang Treasure CV181-Z.

It’s not really a British-spec CV-181 but actually a premium 6SN7 in a fancy carbon-coated glass envelope and may be substituted in any circuit that uses a 6SN7. However, what is remarkable about it is its inherent tonal sweetness, image focus, and excellent dynamic linearity. In these respects, it proved to be superior to even my favorite 7AF7 and 7N7 near-equivalents. As of now it has assumed the mantle of my favorite 6SN7 type. And yes, I’ve listened to a host of vintage types. It’s easy to find on eBay, and buy direct from China/Hong Kong. As with most things in audio, performance is context specific, so there is no guarantee that your results will match mine. But in my opinion, you would be foolish to pass it up.