Tube rolling - faq

[tomcza11]

hello all. i really would hope to create a sticky with this, because i think many newbies would benefit.

1. What is Tube Rolling?

2. How do you know what tubes you can use?

3. Are there many different basic types of tubes?

4. Where are good places to find tubes to replace or roll?

i think this would be a good start because i have all those question too and i cant find any good info on the process.

 

[heekma]

Hey there Tom,

Tube rolling is using different tube types with matching pinouts and similar operating conditions, heater current, etc.

For example, 12ax7s can be switched with 12au7s. Same pinout, similar operating condtions, slightly different gain between the two.

Deciding on which tubes to swap...there are "families" of tubes, gain stage as well as output which can be swapped.

For example:

http://tdsl.duncanamps.com/show.php?des=KT66

http://tdsl.duncanamps.com/show.php?des=6L6GC

If you look at these two tubes, they share an identical pinout, and similar operating voltages. Main difference is heater current.

KT66 heater current is 1.27amps, 6L6 is .9 amps. Other than the current considerations, these tubes can be swapped as long as your filament secondary on the power transformer can handle the extra heater current.

There are some considerations involved with tube swapping. In the case above, if an amp used KT66s, 6L6s could easily be swapped, since the heater current of the KT66 is higher and easily covers the heater current of the 6L6.

On the flip side, if an amp used 6L6s, KT66s could be swapped if the filament secondary of the power transformer can handle the extra heater current.

Now look at a tube like a 7591 vs. a 6L6 or KT66:

http://tdsl.duncanamps.com/show.php?des=7591A

http://tdsl.duncanamps.com/show.php?des=6L6GC

These tubes cannot be swapped--the pinouts are different.

Does that make some kind of sense from my rambling post...?

Best,

John

 

[tomcza11]

yeah thats what i'm sort of looking. i got a B-283 tube processor and have read a couple threads about how it can take different tubes. i just didnt know how one can determine what kind of tubes to try or if theres dangers.

so are the pin numbers a give away to? i dont want to just stick a tube in because it fits.