In the past few month there were discussions about a tube issue accuring on the AC30HW (2010) when replacing the standard power tubes with non Ruby Tubes. In the official Vox UK forum they call it the “McAllister thread”. …
After long discussions and mailwriting they did a fix by changing the position of 4 resistors (complete fix describtion here soon). If you´re interestet in the whole story, you can read the several threads in the forum.
Some time ago Vox posted an official statement (Original thread)
Posted by the Vox Administrator “vox_max_usa”:
“I’m posting this on behalf of VOX Amplification, LTD.
Hello VOX Community,
As has already been discussed, we have identified an issue with some AC30HW amplifiers experiencing noises caused when the power tubes are replaced with certain aftermarket tubes. Please be assured that if the tubes are replaced with Ruby Tubes, as originally used in the amp, at a qualified service centre, this behaviour will never occur. And of course there are no noise problems if you use the amp as shipped.
If you wish to use non-Ruby Tubes in your power tube section and experience the aforementioned behaviour, your amplifier may need to be updated. Please note that we strongly recommend you only use a qualified service technician as there are significant risks with opening and servicing an amplifier such as the AC30HW Series and any costs associated with updating would be minimal anyway. To maintain your warranty, the update must be done at an Authorised VOX Service Centre. Your local VOX distributor will be happy to assist you in finding the nearest service location and answer any additional questions you may have.
Any comments made before our official policy was posted were made before this issue was thoroughly investigated and understood, and are therefore deemed by VOX and VOX distributors to be outside any warranty claim because the amplifier works perfectly as shipped and stays working perfectly if any component is replaced by the same component.
Finally, please rest assured that we have already taken steps to ensure that future production of the AC30HW amps will have no noise problems if used with a different set of tubes other than the Ruby Tubes shipped with the AC30HW.
Thanks again for supporting VOX and we hope you enjoy your handwired amps for many years to come!