replacing 1965 TRRI pre-amp tubes

darkstar73 · June 27th, 2008, 08:32 PM

Hey guys,

I’m looking to overhaul my ’65 twin reverb pre-amp tubes. Since I am only using the second channel, would this set of pre-amp tubes work well? 2 JAN GE 5751s for V2 and V4 (will this tube work here?). and a Mullard CV4024/ECC81/12AT7 in V3. the stock tubes will remain in V6, V5, and V1. I have never swapped out my tubes. All I have to do is unplug the amp, pull out one tube, and put the new one in right?

Thanks for any feedback.

teleamp · June 27th, 2008, 09:20 PM

Put the best tubes in the first position for the channel you use the most V1 for the "normal" channel and V2 for the "vibrato" channel. That will make the most noticable audible difference.

JimiBryant · June 27th, 2008, 10:40 PM

preamp tubes (the little ones) can be swapped with no problem.
you might try varying the order to see if any particular set-up
sounds better than another.. a 5751 is basically the same as a
12AX7 although it's less gain, for lack of knowing the proper term.
those GEs are nice! the Mullard CV4024 you have may or may not
be what you want in place of a 12AX7 but of course if your V3
is already a 12AT7 then no worries.

anyhoo: with preamp tubes and I believe rectifiers as well there's
no need to re-bias or anything like that.

careful! let 'em cool off before touching 'em because those little
buggers get HOT!!

6942 · June 28th, 2008, 08:06 AM

You might want to contact Mike at KCA tubes in Springfield, Va.
Not only does he sell LOTS of NOS tubes.....but he also works on LOTS of Fender amps.
He's a real good guy to deal with and about as knowledgeable a Fender tech as you will find.
Good luck!

Steve

darkstar73 · June 28th, 2008, 07:53 PM

looks like i'll contact mike and see what he thinks. thanks for the suggestions.

Scott S · June 29th, 2008, 12:26 AM

I'd suggest that at this point, the only tubes that *might* need replacing are the power tubes.

JKjr · June 29th, 2008, 11:48 AM

+1 6942. I love the old GE's in my twins. Many prefer the RCA's, and I believe they were OE in the day. Either way, Mike is the man. Think about what it is specifically that you would like to alter in your amp; ie brightness, drive, clean headroom etc... or just ask which he prefers. Either way you win.

darkstar73 · June 29th, 2008, 09:02 PM

i got the amp last November so the power tubes are fine. they are the white GTs that came stock in it. i was thinking pre-amp tubes because i heard this was one of the quick and easiest ways to change the tone of the amp. i am basically looking to take some harshness out of the highs and earlier breakup.

woodman · June 29th, 2008, 09:10 PM

i wouldn't think 5751's for earlier breakup ... seems like they would give you more clean headroom. of course, it all depends on the amp, your style, etc.

Scott S · June 29th, 2008, 10:44 PM

Hate to say it, but if you're looking for *any* breakup, you probably have the wrong amp there. Your eardrums will overdrive before the Twin does!

- Scott

marshman · June 30th, 2008, 09:29 AM

Well, there's that...if 'overdrive' is what you're after, you're gonna need to do a lot more than change your tubes with that particular amp.

Yes, 12A?7 tubes are all interchangable with no risk of damage to your amp, though 12AT7s and 12AU7s are designed to do a different job than 12AX7, 12AY7, 5751 & 7025s. A lot of these tubes have different names, as well, depending upon for whom they were sourced/packaged. But it's really all a matter of taste, so have at it.

JimiBryant is half-right--rectifiers do not require any sort of 're-bais' to change, BUUUT they can damage your amp if swapped out indiscrimantly. There are several common guitar amp rectifiers, each a bit 'more powerful' than the last, and switching a lower-scale recto (say, a 5Y3) for a higher-scale recto, like maybe a GZ34, will throw off most of the voltages throughout the amp, possibly damaging a lot of expensive little bits inside--unless you're a real knowlegable guy about that stuff, I wouldn't switch recto tube models. Switching around brands is usually not a problem.

Scott S · June 30th, 2008, 11:30 AM

Quote:

Originally Posted by marshman

JimiBryant is half-right--rectifiers do not require any sort of 're-bais' to change, BUUUT they can damage your amp if swapped out indiscrimantly. There are several common guitar amp rectifiers, each a bit 'more powerful' than the last, and switching a lower-scale recto (say, a 5Y3) for a higher-scale recto, like maybe a GZ34, will throw off most of the voltages throughout the amp, possibly damaging a lot of expensive little bits inside--unless you're a real knowlegable guy about that stuff, I wouldn't switch recto tube models. Switching around brands is usually not a problem.

Luckily for the OP, there is no rectifier tube to worry about.

- Scott

June 27th, 2008, 08:32 PM	#1 (permalink)
darkstar73 NEW MEMBER! Join Date: Jun 2008 Location: georgia Posts: 5	replacing 1965 TRRI pre-amp tubes Hey guys, I’m looking to overhaul my ’65 twin reverb pre-amp tubes. Since I am only using the second channel, would this set of pre-amp tubes work well? 2 JAN GE 5751s for V2 and V4 (will this tube work here?). and a Mullard CV4024/ECC81/12AT7 in V3. the stock tubes will remain in V6, V5, and V1. I have never swapped out my tubes. All I have to do is unplug the amp, pull out one tube, and put the new one in right? Thanks for any feedback.

June 27th, 2008, 10:40 PM	#3 (permalink)
JimiBryant Tele-Afflicted Join Date: Sep 2007 Location: Chicago Chicago that toddlin' town Age: 46 Posts: 1,543	preamp tubes (the little ones) can be swapped with no problem. you might try varying the order to see if any particular set-up sounds better than another.. a 5751 is basically the same as a 12AX7 although it's less gain, for lack of knowing the proper term. those GEs are nice! the Mullard CV4024 you have may or may not be what you want in place of a 12AX7 but of course if your V3 is already a 12AT7 then no worries. anyhoo: with preamp tubes and I believe rectifiers as well there's no need to re-bias or anything like that. careful! let 'em cool off before touching 'em because those little buggers get HOT!! __________________ I'm sick and tired of following my dreams, so I'm just gonna ask 'em where they're going and hook up with them later!

June 29th, 2008, 11:48 AM	#7 (permalink)
JKjr Tele-Meister Join Date: Aug 2007 Location: raleigh nc Posts: 158	KCA +1 6942. I love the old GE's in my twins. Many prefer the RCA's, and I believe they were OE in the day. Either way, Mike is the man. Think about what it is specifically that you would like to alter in your amp; ie brightness, drive, clean headroom etc... or just ask which he prefers. Either way you win.

June 29th, 2008, 09:10 PM	#9 (permalink)
woodman Poster Extraordinaire Join Date: Nov 2004 Location: Mint Hill, NC Age: 62 Posts: 5,628	i wouldn't think 5751's for earlier breakup ... seems like they would give you more clean headroom. of course, it all depends on the amp, your style, etc. __________________ Truth is stranger than fact ... www.myspace.com/woodymitchellmusic BAND PAGES: www.myspace.com/stragglerswing (Stragglers - Western Swing) www.myspace.com/loafersgloryband (Loafers Glory - '70s country-rock)

June 30th, 2008, 09:29 AM	#11 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 644	Well, there's that...if 'overdrive' is what you're after, you're gonna need to do a lot more than change your tubes with that particular amp. Yes, 12A?7 tubes are all interchangable with no risk of damage to your amp, though 12AT7s and 12AU7s are designed to do a different job than 12AX7, 12AY7, 5751 & 7025s. A lot of these tubes have different names, as well, depending upon for whom they were sourced/packaged. But it's really all a matter of taste, so have at it. JimiBryant is half-right--rectifiers do not require any sort of 're-bais' to change, BUUUT they can damage your amp if swapped out indiscrimantly. There are several common guitar amp rectifiers, each a bit 'more powerful' than the last, and switching a lower-scale recto (say, a 5Y3) for a higher-scale recto, like maybe a GZ34, will throw off most of the voltages throughout the amp, possibly damaging a lot of expensive little bits inside--unless you're a real knowlegable guy about that stuff, I wouldn't switch recto tube models. Switching around brands is usually not a problem. __________________ 42

June 27th, 2008, 09:20 PM	#2 (permalink)
teleamp Tele-Holic Join Date: Oct 2006 Location: Central TX Age: 49 Posts: 552	Put the best tubes in the first position for the channel you use the most V1 for the "normal" channel and V2 for the "vibrato" channel. That will make the most noticable audible difference.

June 28th, 2008, 08:06 AM	#4 (permalink)
6942 Tele-Afflicted Join Date: Apr 2006 Location: Western Maryland Posts: 1,437	You might want to contact Mike at KCA tubes in Springfield, Va. Not only does he sell LOTS of NOS tubes.....but he also works on LOTS of Fender amps. He's a real good guy to deal with and about as knowledgeable a Fender tech as you will find. Good luck! Steve

June 28th, 2008, 07:53 PM	#5 (permalink)
darkstar73 NEW MEMBER! Join Date: Jun 2008 Location: georgia Posts: 5	looks like i'll contact mike and see what he thinks. thanks for the suggestions.

June 29th, 2008, 12:26 AM	#6 (permalink)
Scott S Tele-Afflicted Join Date: Dec 2005 Location: SW CR IA US NA PE Age: 28 Posts: 1,393	I'd suggest that at this point, the only tubes that might need replacing are the power tubes.

June 29th, 2008, 10:44 PM	#10 (permalink)
Scott S Tele-Afflicted Join Date: Dec 2005 Location: SW CR IA US NA PE Age: 28 Posts: 1,393	Hate to say it, but if you're looking for any breakup, you probably have the wrong amp there. Your eardrums will overdrive before the Twin does! - Scott