Zzzzapp! This week I got shocked pretty good. Looking forward to talking about that. But first, let's wrap up this little tube series we've been on for the last several weeks.
Tube amplifiers, and most general equipment carrying tubes these days (microphone preamps, phono preamps and "line" preamplifiers included), use tubes to amplify sound. Big tubes generally do the heavy lifting as "output tubes," and little tubes more often than not are used in a stage on the input.
As I started discussing last week, there are many of types of each size of tube for each job. There are also many brands (and even vintages) to choose from among the same types of tubes. Most of these brands are now defunct, but literally tons of their old unsold and unused products remain available as NOS, or New Old Stock.
There could be serious sonic goodness left on the table if you're using the stock tubes shipped with a tube amp. Here's a local example: Boulder-based high-end audio manufacturer PS Audio produces a tube hybrid (that means it has input tubes, but instead of big output tubes it uses transistors) preamplifier that ships with modern 12AU7 tubes that are very good.
The designers of the preamplifier discovered that it sounds better with higher-quality tubes in place. Higher-quality input tubes nowadays often means NOS tubes. Modern tube factories are few and far between, and while there are good modern tubes being made, there are better, older tubes somewhere (in Europe, probably) that have been sitting unused for a long time.
A manufacturer needs to deliver a consistent product, and that's why the brand ships their preamp with excellent modern tubes with a good reputation. But even PS Audio agrees the NOS options out there should be explored to reach the highest fidelity experience.
If you've been following along with this series and are just beginning to check out what a tube amp could do for your stereo, keep this in mind. While the frenzied resale world of these NOS tubes can be dizzying, most of the reputable outfits selling them— like the Tube Depot and Upscale Audio— have thoroughly tested and graded them, and you can buy confidently.
Now, if you've been stoked by this series but don't have the cash to buy a new tube amp, let me offer a caution. Tubes and tube amps have been around for a long time, and there can be some attractive-looking deals out there for very old tube amps. If you don't know how to fix ancient tube amps, and that includes most of you, my advice is to keep saving and take a pass on the rust buckets.
This week, a pair of amps from the '60s zapped me because the previous owner had inserted the tubes incorrectly. It was a really rare situation, and unless you've got your hands in the guts of tube amps from the 1960s, I wouldn't get too worried about it. But all kinds of stuff can go wrong with the old designs, and if my columns the last few weeks have done anything, I hope they've illustrated that the modern tube approach is the safest, easiest and best-sounding way to experience tubes, ever.