[HAM] 21H Leslie

[Scott Hawthorn]

At 06:27 AM 12/19/2007, Ricky Leonard wrote:
>I just bought a 21H Leslie that has the 32H series 3 amp in it.
>I have some questions about it if anyone can help.
>
>*The tube chart calls for four, 5881 tubes. It has two 5881's and two 
>6L6's. It does say that 6L6's can be substituted for the 5881's.
>Is it OK to have them mixed or, would it be best if they were all the same?
>
>*The Leslie seems to break up/distort a lot quicker than my 122. Is that 
>characteristic of a 21H? Could it be that it just needs new tubes or an 
>amp rebuild.

5881s are the military spec version of 6L6. I hope I'm not wrong in saying 
they can handle more power than 6L6s. Leslie amps are not nearly so 
particular as some in requiring matched tubes in the output section, but if 
any of these tubes are tired and worn-out, it could be causing the 
distortion. If you understand that an amp of this type has what amounts 
to  left and right channels, one for each side of the wave form, you will 
see that the two sides need to be relatively in balance in order to perform 
correctly. If this was my amp (BTW, the standard amp for a 21H), I would 
replace them all just on general principals. But in the meantime, I would 
put one tube of each type on each side. So, looking at the amp from the 
front, the set on the left should consist of a 5881 and a 6L6, and 
then  the same on the right side. I could also make the opposite case for 
putting both 5881s on one side and the two 6L6s on the other. What really 
matters here is how worn-out each individual tube might be. I could be 
screamingly-wrong about all this; I'm sure somebody would let me know. 
Decent Winged-C 6L6s aren't very expensive if you wanna go ahead and start 
by replacing them.