GemTune BL-02 Tube Amplifier Reviewed!

If you play in a band or just love music in general, getting a tube amp is a good way to improve your sound. This is thanks to the fact that tube amps can make the sound of your instrument warmer and fuller.

However, the problem is that there are a lot of tube amps out there. It can be hard to make a choice from all of them. If you’re just starting out, you might want to take a look at some GemTune products. One of their more popular starter ones is the GemTune BL-02 tube amplifier with 5Z3P*1; EL34-B*2; 6N9P*2 Tube. Let’s take a closer look at what it is packing.


Well, the first feature that you’ll notice with the BL-02 is the tubes. There are five tube slots for this tube amp. It features three different tubes for use: one for a 53ZP, two for the EL34-B, and another two for the 6N9P.

What does this mean in practical terms? The 5Z3P is the Chinese equivalent of the 5U4G power rectifier tube.  Though it is good enough, you may want to do some tweaking with it to get a smoother power output.

The main part of this tube amp is supplied by the four other vacuum tubes. EL34-B tube is a tube that musicians generally use because of its greater distortion at lower levels. The 6N9P is a Russian tube that also produces great sound. When combined, the two of them work fairly well with each other.

One of this product’s defining features thanks to its varied tube selection is its distortion. It has less than you would expect and delivers a clear sound with a minimum of fuss. This is a good thing for those who are just beginning to experiment with tube amps. All you need to do with this amp is to plug in the speakers – no need to tweak those tubes yet.

For those who want to get technical, the amp’s output power is just around 10W and has a frequency response range of 20Hz to 25kHz. That’s a pretty good spread. Testers have put its distortion levels are below 1%. At its highest, you can expect 88dB from this device.

Overall, this is a good tube amp for those who want a clear and simple sound, with not a lot of expectations.


If you’re thinking of buying this amp, there are several pros that should encourage you to purchase it.

  • Ideal for Simple Music. This amp works really well with a particular set of sounds. This includes vocals, pipes, and strings. This make it good for jazz, since that genre usually focuses on that particular mix of music.
  • Incredible Clarity. One of the definite advantages of using this tube amp is the clear sound that you get. Some amps have difficulty in the lower ranges, but this amp will ensure all of your notes are heard perfectly.
  • Easily Modifiable. Though this tube amp starts out with a factory set of vacuum tubes, you can easily replace them. All you need is to get the appropriate size of tubes for each socket. EL34 tubes have a wide variation, while the there are many 6N models out there that may be a better fit for the music that you would want to make.
  • Simple Layout. Besides having an easily modifiable tube choice, you can even open it up and see the layout yourself for troubleshooting purposes. There’s no spaghetti mess of wires and contacts inside – everything is easy to identify. This makes it easier to troubleshoot or repair when something goes wrong. You can even upgrade components this way.
  • Auto Biasing. One of this amp interesting properties is auto-biasing. Bias is how much power goes through your tubes. You normally adjust this on your own. Without adjustment, the power passing through it can damage your tubes. However, biasing can be time-consuming. Auto-biasing makes things a lot easier for you.
  • Compact. This product is very portable. You can bring it along anywhere, though you will have to be careful about the tubes. It is easy to pack and can fit in a small bag.


There are also a few problems with the product.

  • Delicate. This is a problem with a lot of tube amps. The essential part of the amp is the vacuum tube. If the tubes break or burn out, then the amp will stop functioning. Depending on how well you take of the tube amp, this may shorten its lifespan.
  • Burn-in Time. You won’t get a tube amps’ full performance until you get the tubes sufficiently broken in. This may take some time though. Expect to play it for a few hours before the sound really opens up – so you’ll need to practice for a while with it.
  • Need for Good Equipment. This amp won’t improve your sound on its own. You will need to pair it with a good pair of speakers that can work in its range.
  • Best with Some Types of Music. This amp won’t work with every genre out there. As I mentioned above, it works well with Jazz. However, some genres also don’t mesh well with it, especially those with loud sounds and a lot of distortion in them.


This tube amp is a good choice for those who want a starter amp. It gives you some optimization options and is easy enough to tweak. Tube rolling, which is the replacement of vacuum tubes until you get a good sound mix, will be essential if you really want the most out of this product. I would say that this is a great purchase if you’re not expecting much or plan to move on to something better later.

The GemTune BL-2 is well-worth the effort that you put into it. If you’re looking for a tube amp to work with your home sound system, then you should buy it. For burgeoning musicians, this is also an excellent first amp to cut their teeth on.

1 thought on “GemTune BL-02 Tube Amplifier Reviewed!”

  1. The schematic for this amp is a popular chinese design for many manufacturers amps. I own an amp by another manufacturer with an almost identical schematic for voltages and component values but, probably better OTs.

    The cathode resistor is about twice what it should be and probably biases the amp very cold at 40-50ma.

    It does not have a screen grid resistor, the screen grid supply is from the same tap as the plate supply and it is most likely higher than the actual plate voltage.

    It is a pentode SE but there is no local or global feedback.

    I corrected all of these items in my BEZ. Before correction it was very distorted at 2 watts and clipped at 3+. Afterwards it had excellent performance up to clipping which occurred at about 7 watts.


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