Now here’s a current-make tube well worth becoming acquainted with! While I have heard the excellent sound of the Sovtek and the Electro-Harmonix 6H30PI “super-tube,” I must confess that, while as excellent as they are, they paled in comparison to the JJ Electronics ECC99. And no, we are not affiliated with JJ Electronics in any way; we just really like their tubes because they have better vacuums and they have excellent sound — they have improved the sound quality of their tubes significantly over the last few years.
So what is so special about the JJ ECC99? Simply put, they have a soundstage like we’ve never heard before. The sense that the sound is not coming from the speakers at all when using these things is amazing! And not only that, but with good circuitry, vocals can sound so lifelike as to be “creepy” — according to one impressed listener we had reviewing our 300B amplifier prototype that uses them. We must confess that at $16 a tube, we are rather surprised that more people aren’t using the JJ ECC99!
One thing to keep in mind when using the JJ ECC99 is that it tends to present a high capacitive load to the driving stages, so precautions are necessary to retain all the details in the highs. A cathode follower drive tends to be beneficial here….
The main quirk of these tubes is that (for reasons unknown) two of our three samples pulled a fairly sizable grid current when first used — they seem to be trying to achieve a net gird bias of 0V. Oddly enough, when they were used in a circuit with almost no grid resistance for a few minutes, the problem went away completely. Upon the next power-up, in a circuit with a grid resistance of 470K, there was no grid current whatsoever. An annoying problem, to be sure, but easily remedied. Just put your new tubes on the input of the amplifier when the volume control is at minimum, and then put them into the rest of the amplifier — or better yet buy them pre-burned-in if possible. I have not tried the gold-pin version as yet to see if these still have the problem, by the way, so I can’t speak to what improvements the gold variant carries.
My guess as to what is going on here is that the grid is contaminated with by-products from the cathode during the manufacturing process, and these contaminants have to be “burned off“ of the grid. The good news is that once the tubes are “cured” in the way described above, I have yet to have another problem with them; there seems to be no grid leakage whatsoever. And who knows, maybe I fluked into a poorer run.
The bottom line is that, despite the slight inconvenience described above, these are arguably the best pre-amp tubes I have heard to this day, and if you want to astonish your friends with an amplifier that sounds eerily lifelike, these are well worth their small cost! With some experimentation and careful designing, you’ll have a mighty fine amplifier!