F-50 Preamp tubes

[JMAN60]

My F-50's gain channel to my ears is a bit too harsh and buzzy
sounding and wanted some suggestions as to what preamp tubes
to try to help relieve the harshness. Currently running stock Mesa
preamp tubes. Also should I replace just V1 or V1 and V2 preamp
tubes to smooth things out.

Any suggestions would be greatly appreciated.
Jman

 

[estring]

I put some Tung sols in V1 and V2. it did smooth it out a bit. However I am dealing with a brand new 2x12 with a V30 in it. So until that puppy is broke in I cant tell if I need more tube tweaking.

 

[JMAN60]

I have heard a lot of good things about the Tung Sols. I was thinking
about trying JJ's too.

Thanx for the suggestion, hopefully others here will chime in with some
suggestions.

 

[HipKitty]

You could try adding another Tung Sol, this one in the v4 position, which is the phase inverter tube. You might find that going to a 12AT7 in that position as an option. Doing so would drop the gain (overall...keep that in mind) and take out some of the buzziness.

The JJ's are certainly an option, however, these can add to the problem as they seem to exhibit high treble tendencies and don't slur the notes (which is where the perceived smoothness comes from in the Tung Sols).

Another tweak consideration is the output tubes. the F-50 has a pair of 6L6's in there. You could go with Boogie's STR-440 6L6...these are Chinese made tubes which are the same as a Ruby 6L6GMTR...very smooth, fat-like sounds. Yet again another option is the 5881 tube. The 5881 can be exhibit a softer distortion character than the 6L6.

Also, here's a easy/cheap tip to break in the new speakers...plug in any standard Cd player via phone out (of the CD player) into 1/4" mono plug (into the amp) and run any CD on repeat at low levels for several days. Some techs will do this for 5 - 7 days to achieve the desired "wear in" point of the speakers.

 

[JMAN60]

Thanx HipKitty for your input. Seems the TS is the way to go for
the preamp tube. I never considered the V4 position but since I
don't use much gain that could be something to try.

I am planning on swapping the power tubes. I have the stock 430's
in there now which I feel does contribute to the harshness. I'm considering
the Mesa 440's, 5881, JJ's and SED's winged "C" power tubes.

Thanx again,
JMAN

 

[HipKitty]

For what it's worth, I have SED's (winged C) in my Mark IV....with the amp biased to the tubes, these just Kill!

 

[JMAN60]

Did you have a bias adjustment mod done to your amp??
I do want to find out how hot/cold my F50 is set before
I buy any power tubes.

I know someone who just replaced his Mark 4's tubes with
440's and he said there was a huge difference.

 

[HipKitty]

Yes, I installed a variable bias pot in my Mark IV.

I recommend that you beware of Mesa's warranty if you are considering adding one. You can drop the STR-440's in, but they'll most likely be biased cold....that doesn't mean that they won't sound good, they can sound "best" when the amp is properly biased.

Check with a dependable tech if you are considering a bias pot install. Any good tech worth their salt should be able to install one at a reasonable cost. They would be able to tell you exactly how"off" bias your amp is with new or current tubes.

 

[JMAN60]

I do realize Mesa amps have a "fixed" bias in there amps
and wasn't considering modifying my amp. I usually use a
MB Studio Pre with my amps, which is in for a cap job. I love
the cleans the F50 has and was the main reason I bought the
amp, not to mention it's a decent backup amp.

HipKitty, I really do appreciate your input to my questions!!!
Jman