JP's Gear Review v2.0 - Ep. 3.5 - Little Bear G3 tube upgrade!

 

(Editor's note: due to a ridiculously dumb ribcage injury that occurred at the gym a few days ago preventing me to hold an instrument for more than 2 minutes, there will not be any audio demo of the upgraded tube just yet. There will be a separate post with them later on, once the pain level is tolerable.)

In the previous episode, I mentioned wanting to get a replacement 6N2 tube to get the maximum amount of overdrive possible and retain the intended design of the pedal. I ended up doing just that over the weekend, and I received it yesterday! The good people at The Tube Store have some Voskhod 6N2P-EB tubes for about 21$CAD a piece, and I ordered one along with some 7189 power tubes for the Bassbreaker.

What's a 6N2P-EB?

The 6N2P (Russian: 6H2П) is miniature, 9-pin, dual triodes tube which is compatible to the 6AX7 tubes used outside of the Soviet bloc. It uses a filament voltage of 6.3V at 0.3 amperes, and is very similar to its cousin, the 12AX7, however the latter uses a 12.6V filament voltage, and the pinout is slightly different, so they are NOT compatible with each other unless you rewire the socket.
The EB variant is a ruggedized, military, long-life version of the standard 6N2 tube. It was designed to withstand vibration and shock, and has a lifespan of 5000 hours.
The most common source for these tubes would be the Voskhod factory in Russia. Also known as the Voskhod Rockets, tubes coming out of that factory are usually very reliable. The tube I received was packed in a nice plain-white box, and the tube itself was in perfect condition. Pin corrosion was practically non-existant all the pins were straight, but the markings on the glass were a bit faint (which is to be expected for a tube this old). The date code is, I believe 09-81, making this tube 41 years old. The Voskhod "rocket" logo is still visible above the tube designation.

Changing the tube

As I mentioned in the previous episode, changing the tube is a pain in the rear-end. However, it seems that messing around with it when swapping the stock 6N2 for a 12AX7 loosened the overly tight grip the socket has on the pins, and removing the 12AX7 was a lot easier. No pins were bent this time. Also important is to move the switch back to the 6N2 position because otherwise the Magic Smoke™ might be released.

How does it sound?

It sounds great. The overdrive it produces is a lot rougher than both the other tubes I tried (the stock 6N2 and the JJ 12AX7). With the drive maxed out, it's very square wave-ish, almost like a fuzz. It's not as warm as the 12AX7, but it has a bit more depth than the stock tube the pedal came with. The bass test was successful, and it sounds pretty good. Comparing it with an Ampeg SVT would not be fair, but I'd say it's along those lines of grind. The 6N2P-EB is always overdriving the signal, i.e. you cannot easily get a clean, non overdriven tone. You need to roll the volume knob on the instrument way back down to get it to not overdrive (or at least not as much). I know, technically it's an overdrive pedal, but perhaps using a 5751 or 12AT7, both with lower gain factors than 12AX7 and 6N2 tubes, it would be more easily achievable.

The important question: is it noisy? The answer is, surprisingly, no! There is still something, but the noise floor is a bit lower than the 12AX7. At this point in my tests, I am quite convinced it is the hybrid nature of the thing that causes the noise floor to be higher than what I'd prefer for only 2 tube-based gain stages (I believe it uses both triodes of the 6N2 tube).

One thing I noticed that I'm not too thrilled about is that the Voskhod tube is microphonic. Bumping the pedal too hard or simply tapping on the tube when in operation will translate in something being audible in the output. It is a 41 years old, NOS tube though, and I don't think it has seen any use in the last 4 decades, so I'll use it here and there to get it to burn-in for at least 50 hours. I'll reassess it after that and see how the sound will change. Hopefully, the microphonics will be less noticeable. I'm not going to use this on stage or near very loud amps, so I don't think the tube being microphonic will be that much of a problem in my situation.

Summary

It's a pretty good upgrade to get rid of the noisy, unbranded, most likely Chinese tube that was bundled with the pedal. It sounds very differently than the other tubes I tried, but that may be because the tube has no burn-in time yet, so it will need to be reassessed in a few months. For 21$CAD (35$CAD with shipping), it's an interesting upgrade. Since the pedal supports both 6AX7-type and 12AX7-types tube, the possibilities are (almost) endless to craft the tone and overdrive you want!

The All-Important Rating™

Durability: 9/10. It did survive for 41 years being thrown around everywhere and it still works. It's microphonic, though, so -1 point for that.

Sound quality: 7/10. Tube has literally no use on it and needs to burn-in for some time. The 7 is subject to change in the future.

Ease of use: It's literally plug-and-play.

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