Replacing and Biasing Tubes – Used Egnater Rebel 30 tube combo amp
Tube amp combos have many pros and cons. It is a pain when you have to troubleshoot bad tubes, rattling in the amp, or other issues. However, when a tube amp is of high quality it can simply sound amazing and blow every hardware and software tube emulator out of the water. I, and most pro guitarist, think the quality of the sound is worth the minor troubles and costs tube amps can bring.
I recently purchased my very own used Egnater Rebel 30 Tube Combo amp to get that elusive tube amp sound. I’m in love! First, let me say that the tone it gets is of boutique quality. It’s tones are easy to dial in. Both the clean channel and drive channel are everything I’ve ever wanted out of an amp. The effects loop is very useful with my M13 and the amp takes distortion pedals VERY well. I wish I had this thing when working with bands in the past.
I bought it used at only $600,but it had a few small issues. This post is for anyone buying a used tube amp. It can be hard to find good information on these things.
First, I noticed that handle on the Egnater combo was rattling and not very secure. I saw the same problem on a different Egnater amp so it may be an issue with some of these amps. This was an easy fix. I just cut out a small piece of foam, removed the piece that was rattling by popping it off, put the foam in there, and replaced the handle piece. Now it is snug and doesn’t move at all.
After fixing that rattle I noticed that there was another noise coming from the amp. Whenever I played a low A,Bb, or B there was a light glassy-like rattling. After lots of research I found out that this sound is from a tube. It’s easy to figure out which tube is rattling because the rattling stops when touched.
BE CAREFUL OF TOUCHING THE TUBES WHEN ON!!! They get VERY hot!
Always use gloves when handling tubes to prevent oils from getting on the tubes.
I have since learned that combo amps often cause tubes to rattle after time because the sound waves cause the tubes to rattle a lot. To prevent this you can use an extension cab so the amp doesn’t rattle the tubes at loud volumes. The only fix, if you want to use it as a combo and be rid of the tube noise, is to buy new tubes.
I initially bought some tube dampeners in hopes it would hold the tube and dampen the tube rattling. Unfortunately, they didn’t have any effect on this type of tube rattle. I did end up using them later…. Read on to see how.
Everyone under the sun seems to like different tubes for different reasons. After LOTS of research I found that JJ tubes are reliable and not very prone to rattling. Using matched tubes is said to be of high importance, but no one could point me to solid proof of this. I bought matched tubes anyway since it isn’t that much more expensive.
Installing new tubes is very easy. Put on gloves, remove the tube retainers, hold them at the base, lie it up with the open connections and gently push them in.
After putting in the new tubes you have to Bias them. This involves removing the back panel, adjusting a potentiometer (one for EL84 and one for 6V6) to 40 mv. This requires you to have a multimeter. I bought the RadioShack pocket multimeter which is cheap, small, and fine for these purposes. Follow this link to get better details on how to bias your tubes.
Eventually I had the new JJ tubes installed, biased, and ready to go. I re-attached the tube retainers and added the tube dampeners to them. This prevented sympathetic ringing from the tube retainers at low recording volumes. If you want some tube dampeners leave a post and I’ll respond with a link to buy them CHEAP from a dealer.
FINAL SET UP: JJ 6V6, JJ EL84 tubes and tube dampeners around the tube retainers.
After a big of work and research I got this amp sounding and working better than new! Instead of paying $900 plus tax I paid $650 and learned how to take care of my tube amp in the future. Tube amps like this still sound amazing and are well worth the work. If you are looking for an amp you owe it to yourself to hear the Egnater Rebel 30. You simply CAN’T beat it for the price. It has a boutique sound to my ears. It actually sounded better than the amps I heard around $1500.
I’ve learned a lot recently about tube rattling. Tube rattle often sounds like small BBs rattling in a glass tube. It turns out that a bit of tube noise is expected in combo amps due to the sheer dB level in such a small space. If you plan on recording your amps it is recommended by many professionals to get a separate cabinet from your amp head. This means either buying an Amp head and Cabinet separately OR buying a combo that allows you to hook up to another cabinet. This way the speaker that’s moving isn’t rattling the tubes.
Keep in mind that tube dampeners don’t accomplish much if anything if the rattling is within the tube. I learned that for my issue it didn’t make a difference.
I ended up buying a second Egnater Rebel 1X12 cabinet for versatility. Now I can play through just the combo at rehearsals (16ohm), play through just the extension (16ohm) OR play through both for a lot more volume at bigger places (8ohm).
When using more than one cabinet make sure you set the ohms to the right setting. THIS IS VERY IMPORTANT! It’s easiest if your cabinets have matching ohms. In this case you just set the ohms to half of each cabinets ohm setting. Since both are 16 ohm cabinets I set the output to 8 ohms when using two of them. Here is the formula.
(impedance of cab 1 X impedance of cab 2) / (impedance of cab 1 + impedance of cab 2)
Hans at Egnater recommended I avoid using multiple cabinets that don’t match ohms since the math gets complicated and the output ohm settings don’t perfectly match these types of set ups. I should also add that Egnater has been VERY quick to respond to all of my questions. Their support is one of the best I’ve ever worked with!
If you hook up multiple cabinets MAKE SURE you use speaker cables of at LEAST 12 gauge. These cables are much thicker and made specifically for this type of output.
DO NOT USE INSTRUMENT CABLES TO HOOK UP AMPS TO CABINETS!!!
Buying used amps can be risky with all the things that can go wrong. In this case it was well worth the savings. Always be sure to put the amp through it’s paces when you try them out so you find issues right away. If you have issues like I mentioned you’ll probably be fine with these fixes. If something is fizzy, cutting out, or smoking then you’ll need to talk to a tube amp repair guy which can take a month and cost quite a bit.
I hope this clears up some questions you all may have had about tube dampeners, tube biasing, and the Rebel 30 Egnater combo. I LOVE this amp and so does EVERYONE that hears it!!! I couldn’t recommend it enough!
Post any questions you have below and I’ll answer them if I can. Thanks for stopping by