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Topic: pre-amp tube reccomendation for '71 Twin Reverb |
Dave Zirbel
From:
Sebastopol, CA USA
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Posted 16 Mar 2001 3:44 pm |
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| What are you tube guys using in the pre-amp section to get a cleaner sound from a Fender Twin Reverb? I don't plan on doing any modifications to the amp. The sound is almost almost where I want it. I'm using a JBL E130. I've been researching the Dan Torres website but the info and advice is geared towards guitarists. Any help would be appreciated. Thanks Dave |
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Tele
From:
Andy W. - Wolfenbuettel, Germany
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Posted 16 Mar 2001 11:17 pm
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I use 5751 tubes
Andy
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1957 Sho~Bud D-8:1961 Sho~Bud D-9:1962 Sho~Bud D-10:1966 Sho~Bud D-10 : Bigsby T-8
My guitars &s
ShoBud Gallery
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Vernon Hester
From:
Cayce,SC USA, R.I.P.
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Posted 17 Mar 2001 12:41 am
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I have replaced the 2 pre-amp tubes in my Fender with Radio-Shack 12AX7A and they are great, nice and clean.Don't where they get them but they are good.I have used all types thru the years,7025,etc.
Vern |
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Ricky Littleton
From:
Steely-Eyed Missile Man from Cocoa Beach, Florida USA
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Posted 17 Mar 2001 8:08 am
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Can't go wrong with a good quality 12AX7 for sure.
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Emmons LeGrande - 8x4
Session 400 Ltd
Alesis Microverb
Dan-Echo, E-Bow
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Jay Ganz
From:
Out Behind The Barn
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Posted 17 Mar 2001 11:03 am
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Dave,
Actually, to keep your signal cleaner, you
should install preamp tubes with a slightly
lower gain. That's
so they won't overdrive the power amp
section quite as easily.
12AX7's are the highest gain of all. Next one down from there are those 5751's...
then the 12AT7's...then 12AY7's...and
the lowest would be 12AU7. The main output
tubes will also affect the amp's headroom
or how loud you can get it before you start
hearing distortion. Switching from 6L6 type
tubes to 7581A's will clean things up as well. They are interchagable with only an
adjustment of the bias (to control the
current flow thru the tube). Less current
flow = cleaner tone.
------------------
 Feelin' tense???...Pick some STEEL!!!
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 17 Mar 2001 10:18 pm
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Thanks guys!
Jay, how many different brands of 7581As are there? Also, are the preamp tubes interchangeable with each other? I don't have a clue about which tube controls the reverb, bass, etc. I guess should read up on this stuff or do some experimenting.
Dave |
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Scott Swartz
From:
St. Louis, MO
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Posted 17 Mar 2001 10:33 pm
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Dave,
The only 7581A's you are likely to find are the JAN Philips, which were sold off by the military as surplus. The military sold many thousands of these and lots of different tube dealers have them. Jay Ganz is right, they will clean up the sound, as well as using 5751s in the preamp.
Email me your phone number and I can call to discuss tubes if you want, I have had articles published in vacuum tube audio magazines and am fairly knowledgeable on the subject.
There are easy reversible mods for the Fender circuit to make it cleaner and more suitable for steel also, but they require some tube electronics knowledge to implement, and tube amps are pretty dangerous if you don't know what you're doing. |
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Jay Ganz
From:
Out Behind The Barn
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Posted 18 Mar 2001 4:31 pm
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Dave,
Scott's right there. Philips are pretty
common, but I've been using ones made in
West Germany way back when. I got 'em
as NOS (new old stock) which means they're
new...but have been sitting around unused.
The main preamp tubes to worry about
are just two really. The 2nd 12AX7 tube
in from the right (looking from the back is the one for the reverb channel. The first is for the normal channel which you probably don't use anyhow. The other is the 12AX7
right next to that little reverb transformer
that's hanging down there. That acts to
remix the reverb back in with the main signal
but is also considered a gain stage. I'd try
a 12AY7 in that 2nd tube in from the right position first. That in itself may be enough.
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 19 Mar 2001 8:09 am
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Thanks everyone. That's sounds like a good place fr me to start.
Dave |
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Bill Terry
From:
Bastrop, TX
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Posted 19 Mar 2001 11:30 am
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I just replaced one of the pre-amp driver tubes on my Twin Reverb. I bought a handful of new and used 12AX7, 12AT7, and 12AU7 tubes at a garage sale. I think I got 6 or 8 tubes for 5 bucks. These folks found the tubes stored away when they bought the home, evidently a previous owner did radio repair back in the tube era. Unfortunately, I didn't see any other tubes I could use except a GZ34 rectifier tube which I also bought.
Anyway, the first 12AX7 I picked up was a Mullard so I plugged it in and it works great, it really expanded the top end. I'm not sure if the original was that bad (it was slightly microphonic) or if this Mullard is that much better.
It says made in Great Britain I think, so I assume you can't get them anymore?
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bterry.home.netcom.com
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Hamilton Barnard
From:
Oro Valley, Arizona (deceased)
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Posted 19 Mar 2001 5:23 pm
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Bill, Mullards are my favorite preamp tubes in Fender, Marshalls and Vox's. Unfortunately I only have a handful left and at $50 for NOS 12AX7s, I hope mine last another twenty years (yea, right).
If you like the Mullard tone, Ei makes a tube that is very similar in "flat plate" design and sound. However they can go microphonic because they are built right on the edge, but their magificant tone is worth all that fuss...at least for me.
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Home page.
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Bill Terry
From:
Bastrop, TX
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Posted 20 Mar 2001 7:33 am
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Thanks for the tip Hamilton. I did a web search and in some places the Mullard 12AX7s are going for 65-75.00 a piece.... Unbelievable.
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bterry.home.netcom.com
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Rick Johnson
From:
Wheelwright, Ky USA
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Posted 20 Mar 2001 9:32 am
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Watch the Reverb Driver and Phase inverter
tubes. They should be 12AT7's. The others
can be 12AX7's. Reference the tube chart on
the inside of the amp.
My .02
Rick
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Rick Johnson
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