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.

http://www.rig-talk.com/forum/viewtopic.php?f=26&t=56736

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).

An extremely versatile setup. I can use the extension cab for recording, the combo alone for a rehearsal amp, or both for playing LOUD!

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 🙂

  • jT

    thank you! I also bought a used Rebel 30 combo and LOVE it! But, Ive started hearing what I thought (hoped) might be bad tubes. You’ve pretty much solved my problem for me. I’m going to change the tubes now and look into an extension cab. It never occurred to me that the compact nature of a combo would effect the life of the tubes.

    Best wishes
    JT

  • admin

    Glad it could help you out! It never occurred to me that combos would have that noise and reduce tube life, but it makes a whole hell of a lot of common sense when you think about it 🙂 haha.

    Good luck with it all and thanks for posting!

  • Paul C

    Nice article. I was looking for exactly this information after one of the 6V6s on my Rebel 30 Combo blew.

  • admin

    Glad I could help you out Paul! Thanks for the comment 🙂

  • Kurt Gaetano

    Great article. I am in the process of buying a used Egnater Rebel 30 (head version). This couldn’t be more timely information for me! Excellent trouble shooting details in your article. I Love the sound of tube amps, but have used mostly modeling & solid state amps in the last few years due to the hassles involved in using tube amps (expense, weight, high volumes to get to the sweet spot of the amp).

    I tried the Rebel 30 and loved the tone! I think that the size, weight, and relatively low power of this amp will make using a tube amp again a lot more practical for me. It really helps to have some solid tube amp maintenance knowledge to keep them running optimally, and this article will really help with that!

    Thanks!

  • Gianpiero

    Excellent review!
    I have the same problem.
    Can you tell me where to buy the dampeners like yours?

    I’m teplacing the tubes with the same original ones. Do I need to bias the tubes?
    Many many thanks!

    Gianpiero

  • admin

    Hey,

    Well, it turned out that the tube dampeners didn’t solve the issue. I bought an extension cab so the tubes don’t rattle. This rattling issue is actually a common problem in combo amps in general.

    The guitar amp tech I talked to last recommended biasing every time you switch tubes.

    Hope that helps 🙂
    -Aaron

  • Joe

    I have a problem with my clean channel on my Reblel 30
    Amp. It is making crackling noise and power volume intermitting. Was told it was bad pre amp tubes. I replaced them wit tubes that finally worked, but after 20 min. of playing, problem came back. I do not know how to Bias the Pre Amp Tubes, or is it needed to? I am in the process of getting some more tubes to replace the blown ones again, The Channel two is fine, I put the guitar threw the effects loop return and there is a good clean signal, meaning it is in the Pre Amp Section of the Amp. Were is the adjustment for the Bias, and does anyone have a schedmatic or Diagram? Thanks….

  • admin

    Hey joe,

    It’s too hard for me to advise you without hearing the noise. The noise could be a dirty power source, grounding issue, RF/EMI noise, or bad tubes. Can you record it and post it? Then I might be able help advise how to fix it!

    First, check if your power is clean and isolated. It should be on an isolated audio circuit without any non audio devices on the same circuit.

    If the noise is a low hum around 50-60 cycles it is probably a ground loop. This can be fixed by putting all audio gear on the same power or using a DI with a ground lift in the signal.

    If its a high frequency noise it’s probably RF. RF comes from all sorts of devices, especially in an apartment complex, so you’ll have to treat your guitar and amp with copper tape to prevent this from getting into the gear. Sometimes it’s as simple as moving your guitar amp around…

    Tube noise is usually like glass beads being shaken. Sometimes I’m told they can add hum as well.

    Good luck tracking it down. This stuff is a huge pain in the butt!

    As far as biasing goes I recommend going back through this post for the info and links to people who walk you through the process.

    Keep in mind it’s best to let the amp stay in standby before turning it on and putting it into standby before turning it off so the tubes warm up and cool down 🙂

  • Tom Black

    Thank you. I’ve had the 30 for a few years and it is a great amp. I have played guitar and harmonica through it. My tubes are starting to get bad and I want to replace them. I was actually thinking about getting rid of the amp because of a lack o knowledge on how to set the bias. You have me motivated. I have had a lot of amps and this is my favorite. I have even used it in the silent mode to record directly in and it is very clean. Thanks again for taking the time to post and pictures are very helpful.

  • admin

    Glad it helped you out Tom!

  • Tom

    I was getting frustrated with my egnater and was about to get rid of it. I set the bias and put new tubes in and it really is a great amp. Thank you for this article. I don’t plan on ever getting rid of the egnater.

  • Simon Crosbie

    hi Aaron, I bought a shop-demo Egnater from Guitar Center in Eugene, I lined it up against a Blackstar 20 and the tone difference and build quality were dynamically different in Eganters favour. As a Brit’ and a Marshall fan, I was disappointed in the comparison, but then the retail price difference between says something. GC gave me a great deal on the Egnater, used and a couple of scratches but at $450 I was stoked.

    Thanks for this detailed guide to replacing the tubes, I am close to installing GT power tubes and this going to be invaluable info’. Friend of mine has a Mesa Rectifier in the UK and he strongly recommends biasing, as I have heard before.

  • Aaron Brown

    Right on Simon! Glad it helped you out 🙂 Let me know what you think after biasing.

  • Daniel B

    Hey man,
    I just picked up a used Rebel-30 head. This is my first non-combo amplifier, and I have been reading up on how to properly hook it up to a cab. When you say “at least 12 gauge”, does that mean that anything *above* 12 is good, or *below* 12? Wondering if it works like shotguns, in that lower numbers mean more power. I am trying to pick out some short cables to add 2 of the rebel-112x extension cabs. –Daniel

  • http://www.theconreteproject.com SB1

    Thanks so much for the write up. Very useful info!!

    Quick questions. I’ve owned by amp for about a year now bought used. A couple months ago it started cutting in and out on me and got it fixed at a guitar repair shop. I can’t really remember exactly what the repair guy said it was but then last week again it started doing the same thing.. My question is have you every experienced this with this amp? I REALLY LOVE the tones and the simplicity of the design and really don’t want to move on to a different amp..
    Any help would be greatly appreciated!!! 🙂

  • Scott V

    Can you send me the contact info for the tube dampeners? Thanks