Valve or Tube Rolling is the process of trying out a number of valves in the same spot in an amplifier and selecting the one that sounds best to you. This can be very useful in optimizing the overall tone of the amplifier.
The appeal of valves, other than the ease with which they can be swapped out of a circuit (tube rolling), is that they often create a sound that seems more “relaxed” and “untiring” in many amplifier designs. It is hard to say why they sound so different to their solid state counterparts. Some experts claim that the distortion characteristic of audio valves (while typically higher in absolute terms than solid state) at even order harmonics vs odd order harmonics of solid state are easier on the ears (It is suggested that our ears are more sensitive to the odd order harmonic distortion which can show up in higher frequencies and can result in listener fatigue). Valves might sound better in a given circuit because of the design simplicity of the electronic circuit itself. In general valve circuits are fairly simple with relatively few components as compared to quite complex solid state circuits using a myriad of tiny components.
The same type of valve made by different manufacturers and in different variations from one manufacturer can have a definite impact on the actual sound of an amplifier. The most common and easiest audio valves to “roll” are the preamp tubes. Audio preamp valves are self-biasing and so generally no technical adjustments are required when they are installed.
On the other hand power audio valves will in most cases require resetting the bias after tube rolling. Also, you will want to change the whole set of power tubes at the same time. Some amplifiers have no bias adjustment. If you want to “roll” the tubes in these amplifiers, you order matched sets. Some amplifiers that use either 6L6 or EL34 tubes often have a switch to change the bias range between these tubes.
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 or elusive sound you have been searching for.
NOW SOME IMPORTANT WORDS OF CAUTION:
Valve equipment runs on dangerous high-voltages and the tubes get very hot during operation. Equipment should always be switched off and unplugged from the wall power outlet whenever venturing inside the cabinet or chassis. It is also a really good idea to let valves cool for a few minutes before removing them – they can get very hot and can burn you.
Obviously some technical knowledge or advice is required before contemplating changes to the configuration of any electronic equipment. Some valves have subtle differences between them and what may appear to be a straight swap can become a nightmare for the unwary. Do your homework first!
If you feel uncomfortable trying this yourself, enlist the services of a competent technician who can physically inspect the amplifier and ensure that what you are proposing is safe and within the proper design parameters of the circuit! Remember there are voltages inside that can kill you. Even when the power is disconnected there can still be dangerous voltages around as energy remains stored in electrolytic capacitors for a time.
In the picture:
NOS 1960’s WEST GERMAN E88CC/6922 with BEAUTIFUL GOLD PINS!
Some of the nicest we have are these E88CC’s / 6922 double triode audio valves with diamond bottom.
This 10,000+ hour tube is known as the HOLY-GRAIL for excellent performance, smooth highs, outstanding 3-D holographic soundstage, lots of open-air, neutral timbre, true to life un-colored sonic reproduction, magnificent inner resolution and detail, and overall perfect resolution and balanced sound. Improved dynamics, smooth frequency extension across the spectrum are immediately obvious, making the music sound much more accurate and real. A major improvement over other 6922 E88CC, these have been voted one of the “BEST” 6922’s ever made!