Tung-Sol.com:: FAQs What is tube rolling?

FAQs

Question:
What is tube rolling?
Answer:
Tube rolling is the process of trying out a number of tubes in the same spot in an amplifier and selecting the one that sounds best to you. This can be very helpful in optimizing the tone of the amplifier.

CAUTION: Tube amplifiers run on dangerous high-voltages and the tubes get very hot during operation. The amplifier should always be placed in standby when replacing tubes. Also, an oven mitt or a Tube Glove should be used when removing hot tubes to avoid painful burns. It is actually a good idea to let the tubes cool down for a few minutes before removing them. If you feel uncomfortable trying this yourself, you can always take your amplifier to your favorite technician and have him assist you in changing the tubes.

The same type of tube made by different manufacturers and in different variations from a manufacturer can have a definite impact on the actual sound of an amplifier. The most common and easiest tubes to "roll" are the preamp tubes. Preamp tubes are self-biasing and no adjustments are required when they are installed. In guitar amplifiers these tubes are almost universally 12AX7/ECC83. Actually, many technicians will try a variety of 12AX7 tubes when an amplifier is repaired to find the tubes that the amplifier "likes". If the amplifier is thin and bland sounding, a high gain version, such as the reissue Tung-Sol 12AX7, can be substituted to thicken and give definition to the sound. The reissue Mullard 12AX7/ECC83 is a large plate format, which is characterized by having a large soundstage with a lot of detail. If the amplifier has too much gain, a Sovtek 5751, which has 70% gain of a 12AX7 can be substituted. Another tube that works well for this purpose is the Electro-Harmonix 12AY7EH/6072A. This tube has a lower gain and a higher transconductance. In many cases this tube will give the amplifier the sound of a custom "boutique" amplifier and make it very touch responsive. The Sovtek 12AX7WB has a dark (or warm) character and is useful for taming an amplifier that has a harsh sound. You have probably already realized that by hand selecting the preamp tubes, you can actually change the gain structure of the preamp and create a custom sound.

Power tubes will in most cases require resetting the bias. Also, you want to change the whole set of power tubes. Some amplifiers, such as Mesa-Boogie, have no bias adjustment. If you want to "roll" the tubes in these amplifiers, you can order matched sets with middle matching numbers. The Sovtek 5881WXT will give an amplifier an aggressive sound, where a Tung-Sol 5881 will have more of a Fender Tweed character. The Tung-Sol 6L6GC-STR (depending on the amplifier) will lean toward a vintage Fender Blackface GE or RCA sound and the Svetlana SV6L6GC will sound more like the Sylvania 6L6GC tubes found in Fender Silverface amplifiers. Some amplifiers can accommodate either 6L6 or EL34 tubes. These amplifiers most often have a switch to change the bias range between these tubes. If you have an amplifier that can use either 6L6 or EL34 tubes, you will quickly notice that 6L6 tubes are more "Fender", where EL34 tubes are more "Marshall". As you can see, tube rolling can give new life to an ordinary sounding amplifier. It is also the most logical way to try to find that custom sound you have searching for.

<<back