Vox AC30: Tube Roll

By Matt Preston
on January 12, 2014

Vox AC30 Tubes


I recently retubed our Vox AC30 and happened to tube roll a few different preamp and power tubes.  Find our test results below:


Power Tubes Tested:


-JJ EL84

-Sovtek EL84

-Ei EL84

Preamp Tubes Tested:


-Ei ECC83

-Penta 12AX7

-Tung-Sol 12AX7


A few caveats:

Since the Vox AC30 runs power tubes extremely hot, we were only able to test EL84’s that consistently have a lower idle current draw.  Given our current inventory, your two choices would be Sovtek and JJ EL84’s, as we are not able to consistently provide Vox Amps with other brands of EL84’s.

We only tested three types of preamp tubes because tube rolling is a lengthy process in this amp.  It weighs 72 pounds and has a chassis that is time consuming to remove.


Set Up:


’06 Fender Telecaster (pickup switch all the way to the right)

Celestion Blue 12” Speakers


History & Baseline:


We’ve used this amp in our rehearsal space for about 2 years and finally it was time to change tubes.  A few issues we were having:

1)      It lacked the stereotypical bright, chimey clean that Vox’s are known for. 

2)      We also had some microphonic squealing in the Bright Channel.

3)      It took more to dial in the volume on the normal channel. 

4)      The EQ’s could be more pronounced and articulate.





Winner Combination: Ei EL84’s + Ei ECC83’s

This amp comes fully loaded with Ei EL84’s and Ei ECC83’s are a reason.  It’s simply the best combination out there and delivers full bodied, three dimensional, bright cleans.  Unfortunately, Ei EL84’s that fit the Vox specs are hard to come by and Ei ECC83’s are not in production anymore.  We’ve got some left, but ensure that we deliver you extra low noise, low microphonic tubes, as you’ll need them.


The JJ EL84’s are your next best choice for power tubes.  They might not produce such a wide wall of cleans as the Ei EL84’s, but they’ll produce the Vox chime that we’re all accustomed to.  It’s the next best thing and your best choice that’s out there.


The Sovtek EL84’s still had a great attack and nice cleans, with a little bit of grit and less chime.  They complimented the Tung-Sol’s well, but sounded too harsh with the Penta 12AX7’s.


For the preamp section, if you can’t land any Ei ECC83’s, your best bet is to run Penta 12AX7’s in the first 5 preamp spots and finish with a Sovtek 12AX7(from left to right).  The Tung-Sol 12AX7 provided some bluesy creamy breakup that the Vox AC30 doesn’t really tend to have, but the tube was still dull and provided no real bright clean tones. 


Our final recommendation:


4 x JJ EL84

4 x Penta 12AX7’s

1 x Penta 12AU7

1 x Sovtek LPS 12AX7

Can a Bad Tube Ever Blow a Fuse?

By Matt Preston
on January 12, 2014



It sure can. I had this happen to our Fender 400 PA system (used 4 Svetlana 6L6GC's) and Vox AC30 (used Ei EL84's). 

In both cases, there was a bad power tube. We've talked to our amp techs, and coupled with our own experiences, 80%-90% of the time a fuse is blown, its a tube.

Tube roll to find the bad seed. It's good to have extra tubes and fuses lying around.







Top 10: Signs You Have a Bad Tube

By Matt Preston
on January 12, 2014




Well, my ears have certainly had enough. Aside from my less than mediocre playing, I have decided its time to change the tubes. How do I know? Here are some signs that your tubes have crapped out:

1. The amp is way too harsh on the ears
2. The bass is no where to be found
3. It's all mids, all the time
4. The clean sounds like the dirty channel, and the dirty sounds like rubbish
5. The reverb does not work
6. Your amps' levels are down significantly
7. Any EQ adjustment shows little improvement in the sound
8. You hear a hissing noise (usually a preamp tube)
9. You hear a rattling sound (could be a loose component in a power or rectifier tube)
10. Humming (unmatched power tubes).

When you start to notice a few things that go sour, keep playing around with your amp for another week or two. Switch preamp tubes around to see if you can find the bad tube. I noticed that my cleans became dirty about a month ago, however I played around with different guitars (Gibson SG, strat, tele), and played with different pedals. I was getting a better sound out of the SG, while the amp sounded way to bright and sharp for the strat and the tele. Finally, about a week ago, the amp just sounds like arse.

I beat the hell out of this thing.
I have easily put 10 hours a week on this baby for almost a year and a half straight.

Remember, the first step to the road of tube recovery is recognizing you have a problem :) 




Tube Recommendations

By Matt Preston
on January 12, 2014

Many times, people will ask us to give them tube recommendations.

We usually ask the following series of questions:

1)What kind of guitar/amp set up do you have?
2)What kind of music do you play?
3)What do you like about your sound?
4)What would you like to change?
5)What tubes are in there now?

Once we cover this information, we usually give you the run down on the voicings of all the tubes you have questions about.

This is meant to be considered as a rough estimation. We do not consider our opinions or recommendations as final or absolute.

Our recommendations are meant to be a starting point of your quest for the right tone. However, you play the most important role in this journey! Our suggestions are a mere conglomerate of opinions and reactions from our own ears, and the thousands of customers we've had over the past five years.

Installing Tubes In Your Amplifier

By Doug Preston
on December 29, 2013

Changing preamp tubes is easy and can be done by the newest of newbies.


Changing Tubes


Power Tubes

1) Grip the base of the power tube with your finger tips, and cup the glass top with the palm of your hand.
2) Gently start removing the tube in a circular (clockwise) motion.
3) Do it carefully as to not to damage or break the tube.

Preamp Tubes

1) Carefully twist off the preamp covers.  It's common to break a preamp during this step.
2) Gently start removing the tube in a circular (clockwise) motion.
3) Do it carefully as to not to damage or break the tube.

Simple as a pentatonic scale!  Fight the urge to use an amp tech, a common misconception about changing tubes.




Doug's Tubes, Inc.

188 Tally Lane

Wantagh, NY 11793


Mon-Fri 11am-5pm EST


Call to place an order:



Email for tube recommendations:


From the Blog

Vox AC30: Tube Roll

January 12, 2014

  I recently retubed our Vox AC30 and happened to tube roll a few different preamp and power tubes.  Find our test results below:...

Read more →

Can a Bad Tube Ever Blow a Fuse?

January 12, 2014

  It sure can. I had this happen to our Fender 400 PA system (used 4 Svetlana 6L6GC's) and Vox...

Read more →