Preamp tube substitutions

["Jordan, Jim" <JJordan@xxxxxxxxxxxxxx>]

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Hi everyone,
I am a long time lurker of Harp-l and have posted once in a while but
generally just read posts through the archives.  I want to share my opinion
that preamp tubes substitutions are not as useful to me as numerous others
have expressed.  Let me first tell you that I've been a working in the New
England area as a harmonica player for over 20 years.  I love Fender amps
and have played through a 66 Fender Super Reverb for many years.  This amp
has never given me problems with feedback (until reaching ungodly volume).
A year or so ago, I purchased a 67 Fender Twin Reverb (85 watts, no master
volume).  I fell in love with the tone I get from this amp..
However, the Twin, being 85 watts,  is slightly more prone to feedback than
the Super.   I always have room on the Super for a little extra volume when
the situation arises.
This is the point where the Twin would start feeding back.  The point of
feedback is at a high volume.  So I experimented with lower powered preamp
tube substitutions in the Twin.  With the stock tubes, I can get my volume
knob to about 2.5 to 3 max.  This gives a loud output with powerful tone.
After substituting the preamp tubes, I realized I could turn my volume knob
to about 6.  I was happy.  I gigged with it but my tone was changed (not for
the better).   The tubes substitutions gave me more room on the volume knob
but not more volume and less overdriven tone.   
In my experience, tube substitutions were not the cure all for feedback.  My
volume knob was at six but the output of the amp was the same as at 3 with
stock tubes.  Lower powered tubes removed all the features of tone that led
me to buy the Twin in the first place.
So I put the stock tubes back in the Twin.   I use the Twin in most gig
situations.  If I play a very large venue where extra volume is needed, I
use the Super (or both amps).
I have a Kinder Anti-feedback device.  It certainly works great and I keep
it handy if I'm using the Twin and feedback becomes an issue  (a rare
occurrence).
Low powered small amps, although wonderful in a studio or small club,  makes
you reliant on the soundman to fill the room.  I like big amps so I have
control over my sound and my stage volume.  
I just wanted to share my experience with tube subs.  I'm know others have
different opinions and I hope this post doesn't cause me to be attacked by
the harp amp experts out there.
Thanks,
Jim