How much on average does it cost to replace tubes (having a trained tech doing it)?
The cost of replacing and biasing power tubes depends on many factors. A good tech will generally make sure that your tubes match by measuring the current in each and will check the signal with an oscilloscope to see if there is any crossover distortion. You must leave the amp on for a while to stabilize the current and switch it on and off several times to see if the tubes are reliable. Amps that do not have an adjustable bias (Boogies, Hiwatts, Vox AC30) take longer to bias because you must change components to obtain the correct current. In some cases the available bias voltage is too low and the bias supply circuit must be redesigned. The Blackface Twin Reverb reissue is quick to bias because it has an easily accessible potentiometer with sufficient range to accommodate most tubes. Since your amp is new, retubing should be very straightforward. A lot depends on the quality of the tubes that you buy. Lower quality tubes can cause all kinds of problems from crackling noises to low fr
