F50 problems following retube

[eazilyled]

I just retubed my F50 with 2 x Mesa 5881 STR425 power tubes, 1 x Mesa SPAX7A in V1 position, and 3 x Mesa 12AX7A in the other preamp positions. All tubes are brand new, but I have noticed the following problems:

1) The clean channel has some considerable background hiss, whereas the dirty channel seems a lot quieter in comparison.

2) When switching channels with the footswitch, the reverb cuts out for a couple of seconds and comes back on again.

Are these problems considered normal, or is there something wrong with one or more of the new tubes?

 

[CudBucket]

Sounds like you've got a wacky preamp tube in v1 and/or v2.

 

[jbird]

Did'nt 6L6's come out of the power section? And can you replace with 5881's?

 

[eazilyled]

Did'nt 6L6's come out of the power section? And can you replace with 5881's?

The 5881s are a type of 6L6 which can be used as a substitute for regular 6L6s to darken the tone a bit.

 

[Surfcaster]

I think the reverb does cut out when switching channels and then kind of swells back in...to avoid an unpleasant "SPROING". I don't really notice it on mine unless I have the reverb set high.

I remember thinking the clean channel had more background hiss than the dirty channel when I first got my amp, but I don't really think about it now...it could have something to do with how the master volumes are set on each channel in respect to each other.

Of course, you could always try swapping out V1 and V2 one at a time to see if that makes any difference.

 

[stokes]

Not sure about the Mesa 5881's,but a true 5881 should not be used in an amp designed for 6L6GC's.A 5881 is only rated for about 360 volts on the plates.Most modern 6l6 amps have over 400 volts on the plates.A 5881 is rated for about 19watts plate disipation,a 6l6GC is 30watts.If the Mesa 5881 is rated for these higher numbers it is not a true 5881,probably a relabeled 6L6.