Re: Preamp tube substitutions

[Ray Beltran <raybeltran@xxxxxxxxxxx>]

I agree with you, Jim. Especially when you say:

> Lower powered tubes removed all the features of tone that led me to buy the
> Twin in the first place.

Yes, it seems that lowering the gain via preamp tube subs in an attempt to
control feedback sucks the tone right out of the amp and negatively alters
the character of the amp. The only "change" I make in preamp tube subs is to
go back to the original tube compliment for the particular circuit. In the
last two large amps I've owned, that means changing V1 preamp from 12AX7 to
12AY7. I don't consider that a tube substitution, but rather recognizing
what the original circuit called for, and appreciating the intent of that
circuit.

Feedback is an acoustic problem. It doesn't matter WHAT kind of gain change
you make...the output at the speaker looping back to the mic or vice versa
has nothing to do with what preamp tubes value you've chosen. Once you reach
a certain volume level, feedback will occur.

I'm not concerned that you're only at 2.5 or 3 on the clock. If you have
proper technique and resonance, you're able to have quite good tone at that
seemingly low knob position.

I have to agree with you on small amps, too. One of the nice features of my
new amp is that it has 2 separate preamp channels. Separate in that they
have their own dedicated preamp tubes. And each channel has two inputs, so
I'm covered as far as volume goes. I attended a semi-acoustic jam recently,
and played through the lower gain channel in the softer number 2 input for a
lower volume. Worked great.

This amp is unique to my experience in that it is capable of accepting
higher than originally intended preamp tube values and is still usable for
harp. So in the bright channel, I'm actually using a preamp tube that has a
higher mu factor than the one in the normal channel. I'll use the higher
gain channel whenever I need the extra volume, or possibly when playing
chromatic.

Thanks for your post, Jim.

Ray.
- -- 
www.resgraphics.com/Music






On 7/15/04 7:02 AM, "harp-l-digest" <harp-l@xxxxxxxxxx> wrote:

> ------------------------------
> 
> Date: Thu, 15 Jul 2004 10:07:33 -0400
> From: "Jordan, Jim" <JJordan@xxxxxxxxxxxxxx>
> Subject: Preamp tube substitutions
> 

> 
> 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