Modifications

Dr.Tube modifies & repairs (tube) guitar amps and other interesting music related analog electronic equipment.

Common guitar amp repairs at Dr.Tube are:

  • Bias mod:
    When the power tubes are replaced the bias current (almost always) needs to be set correctly again. This is called biassing. Correct biassing is very important for good tone and a reasonable lifetime expectancy of the power tubes. In cathode biassed amps, like the VOX AC30 etc., this isn't necessary or possible. In (almost) all Mesa Boogie, most Peavey and a lot of older Fender amps there is no bias pot where there should be one. The bias mod is installing a bias potmeter (so that the bias current can be adjusted) and one or more bias measurement resistors so that the bias current can actually be measured.
  • Master Volume mod:
    The older classic guitar amps, such as the Marshall 1987/1959 (Super)Lead type amps, are limited by the fact that they only distort/crunch at huricane sound levels; not always a viable option for small gigs or rehearsals. An added Master Volume control will enable the preamp to be ovedriven without the power amp going full blast. This subtle mod makes these amps so much more versatile.
  • Mercury Magnetics mod:
    See the Mercury Magnetics page for more information on modifying guitar amps with these excellent transfpormers and chokes.
  • 2 Channel mod:
    The older classic Marshall amps, such as the 1987/1959 (Super)Lead amps aren't exactly high gain distortion amps. The 2203/2204 Master Volume sport a lot more gain but cannot easily change from the clean to the distorted channel. The popular Dr.Tube 2 Channel Mod will turn these amps into a footswitchable clean/high gain amp, with a very good rock tone (transformers permitting).
  • Mesa Boogie power transformer (PT) mod:
    There are quite a few guitar players outside of the USofA which buy a Mesa Boogie amp through eBay or such in The USofA because this is cheaper than buying the same amp locally. The only problem with these amps is that they only function on 115V mains voltage and cannot be switched to another mains voltage, like for example, 230V, for use in Europe. Up to now the only option was to use a special converter transformer, which converts your local mains voltage to the 115V as needed by the amp. This isn't exactly handy and it also compromises your tone. Dr.Tube can now supply drop-in replacement 230V power transformers for almost all Mesa Boogie amps.
    Do you have an American Mesa Boogie and you wish it to be fitted with a 230V power transformer then let Dr.Tube know the exact model and the 6 digit number on the power transformer and Dr.Tube will tell you if your amp is suited to be converted to 230V. There are some Mesa Boogie amps that can be switched to 230V (without fitting a new power transformer), but these are just a few.