[HAM] Best 12AU7 now 6550

[David Anderson]

The 6189 was a "special" version of the 12AU7 optimized for shock and  
vibration resistance. If you look closely, it may have extra internal  
bracing or extra mica spacer plates compared to a typical 12AU7.

This usually means lower microphonics, which could help when you have  
a speaker only a few inches from the tube.

Otherwise, it's just a 12AU7.

I once put some RCA black plate 6L6GCs in a 32H amp and found that at  
least one of them was severely microphonic. It howled.

David A.

On Mar 9, 2008, at 12:06 PM, goffmac747 at aol.com wrote:

> The preamp tubes in one of my l22's are the 6189W versions. What was
> the reason for this? And is there a difference is the way this tube
> works and sounds compared to the 12AU7? The 6189W crossrefs to a 12AU7
> (A?) but am curious as to why the difference in tube numbers and  
> choice
> for this tube.