Fw: [Harp-L] Fender pre amp tubes

[MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>]

If this is a BF/SF Fender, or a brownface, you must keep the 12A#7 tube that sits next to the power tubes, as this tube takes the preamp signal and delivers it to the power tubes, removing it will kill ALL the preamp signal that the power tubes see.
 
The only other tubes that must be kept are V1 (farthest from the power tubes and rightermost when looking at the back of the amp - this is the preamp tube for the Normal channel) and/or V2 (to the left of V1 - this is the preamp tube for the Vibrato channel). On BF/SF amps & Brown Vibroverb/Tremolux you can use either V1 or V2. On early brownface amps (#G, with no "A", or "B" suffix) you need both V1 & V2 for either channel to work. Oon late brownface (#G-A/B) disabling the vibrato function may also kill signal from the Vibrato channel preamp.
 
Removing V3, V4, V5 will disable any reverb or vibrato functions.
 
The main thing to be aware of is, if you can live without vibrato/reverb and you have enough tubes in the amp to still get a signal from the channel that you use, you are good to go. You cannot damage the amp by running it with missing preamp tubes. Rod Piazza is well known for running brown Fenders with just the very outer 2x 12AX7s fitted (V1 & V6).


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From: hazcon <hazcon@xxxxxxxxxx>
To: harp-l@xxxxxxxxxx 
Sent: Monday, 13 February 2012, 2:28
Subject: [Harp-L] Fender pre amp tubes

Just wondering if (say) a Fender Amp has 6 preamp tubes can you remove the two first ones and then still safely use the Amp running on 4 only?
I just want to do a bit of experimenting.
Thanks for any advise on this