The JOYO Bantamp range use a single 12ax7 tube in the preamp, it is likely at some point you might need to change the tube in your amp.
Unfortunately a tube is not covered in any guitar amp warranty, it is regarded as a consumable as they do not have a definite life span and can burn out, but generally preamp tubes or valves they will last a long time. Preamp tubes do not need to work as hard as a power amp tube, but they can fail at any time.
So how do you know if you need to change your preamp tube your JOYO Bantamp ?
Some of the most common signs that tubes need replacement are a change in the tone:
- Excessive noise (hiss, hum) including squealing or microphonic tubes. This is the culprit that causes that high end squealing even without a guitar plugged in.
- Loss of high end, a drop in the treble.
- A muddy bottom end, too much bass and note clarity is lost.
- Erratic changes in the overall volume, normally down.
- The amp doesn't work L
How to replace your JOYO bantamp tube
Unlike a lightbulb, if your tube is glowing it doesn’t necessarily mean it’s working well, the lights can be on, but nobody is at home, so it’s time to take a closer look at your JOYO Bantamp tube amp.
I do always wear gloves or a cloth to handle new tubes. There is some debate going on about the influence of oils in human skin on a tube, so there is no harm in wearing gloves to change tubes so it may be a good exercise in caution.
- Remove the hex bolts 2 on the front left and right corner, 4 on top and 2 on the back left and right corner. (remember lefty loosy, righty tighty) Thes hex bolts are holding the top of the amp onto the case. When you have removed these you can hold the handle and lift it up and off.
- Make a visual inspection of the valve, looking out for any discolouration of the screen printing indicates that the valve has been running hot and may need replacing.
- Look at the getter – that’s the metallic top bit of the tube. If you spot any discolouration or see that the top of the tube is stained with a milky coating, than air has entered the tube. It is defective and must be replaced.
- With the amplifier turned on you can also use a pencil to lightly tap each valve listening for and pings, zings, or crackles that’ll usually indicate it’s time for a replacement. Swap in a known good valve into that position and repeat the test to confirm.
JOYO Preamp tubes are plug-and-play types, so no rebias is required when replacing.
TURN OFF THE AMP & UNPLUG IT FROM THE WALL.
- Take out the tube, gently rock the tube back and forth while lightly pulling upwards. Remove the valve from its socket, pull it straight up, note the position of the pins.
- Lift it out and give it a little shake. Can you hear a rattle? This too might indicate a worn valve.
Replace the tube
- Get your new 12ax7 tube/valve (with your gloves on!), line up the pins and gently push down and into the socket on the JOYO Bantamp.
- The pins will have a prominent gap between two pins. Match this gap up with the corresponding gap in the preamp tube socket and gently place it in.
At this point it is okay to test the amp again before you replace the casing and tighten it back up.
How does it sound?