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Username: vlad335

Post Number: 1
Registered: 1-2007
Posted on Monday, January 01, 2007 - 3:49 pm:   Edit Post


I have owned this preamp for about 3 years and lately had noticed the sound getting thinner. This was happening gradually so I figured it was time for a tube replacement. After some research, I bought a Tung Sol 12AX7 mail order to try but much to my disappointment, it wouldn't fit in the sleeve!

We played New Years last night and with no way to get another tube on short notice, I went with the preamp as is. We were rebuilding the band and this was the first time in 3 months I had my whole biamped rig together. I am using the F-1X, a QSC 1202 amp in stereo with lows in one side feeding a a SWR Big Ben 18" and highs in the other to a 2-12 and 2-10" cab. Lets just say that this usually awesome rig sounded like I was playing thru a 50 watt guitar amp!

I have been trouble shooting the rest of my rig today and I am pretty sure that the problem is the preamp and I am hoping it is the tube.

Now the reason I posted this... Can I get rid of the tube sleeve without problems? I ordered some more tubes today but what if they don't fit as well? I was thinking of using a dremel to cut 3/4 or so of the sleeve off. Is there a way to just remove it?

Also, is there a certain brand/model of 12AX7 that works well with this preamp?

I tried searching this forum today but searches are taking like 20 minutes then I am getting results that have nothing to do with my issue. I read the FAQ's as well. I apologize if this is frequently asked but I think the search function on this forum is borked today.

Thanks to all that suffer through this post. I would appreciate any help I could get with this awesome piece of gear.
Senior Member
Username: bob

Post Number: 793
Registered: 11-2002
Posted on Monday, January 01, 2007 - 4:45 pm:   Edit Post

Welcome. I'm not qualified to advise you on the sleeve, though my guess is that you really don't want to remove it, or cut it down. However, I had better luck with search and found a couple of threads where tubes are discussed, including some that didn't fit.

This one, which is also referenced by this one.
Advanced Member
Username: 2400wattman

Post Number: 273
Registered: 11-2005
Posted on Monday, January 01, 2007 - 5:00 pm:   Edit Post

From my experiences, tubes are, have been and always will be unreliable. But nothing sounds like them. All tubes are manufactured in China, Russia and I believe the Ukraine as well. I would try Groove Tubes first because I hear that they do more stringent testing of the tubes they buy from their supplier than anyone else.
I'm not sure what you mean by the "tube sleeve" but I would think any mod. to a tube would not be good.
You might want to check your cords that are hooked up between your pre amp/ power amp. Bad cords can always cause unbelievable problems.
I hope this helps and good luck
Senior Member
Username: lbpesq

Post Number: 1947
Registered: 7-2004
Posted on Monday, January 01, 2007 - 5:38 pm:   Edit Post

FWIW, Alembic uses Sovtek 12AX7 tubes in the F-2B. I wouldn't be surprised if they use the same ones in the F-1X.

Bill, tgo
Senior Member
Username: bsee

Post Number: 1430
Registered: 3-2004
Posted on Monday, January 01, 2007 - 7:29 pm:   Edit Post

Getting rid of the sleeve is a bad idea as it prevents the tube from vibrating out. There are plenty of tubes that fit, though. As far as the Tung Sol goes, the word is that the F-1X doesn't change as much with the properties of different tubes as some other tube preamps. As such, you probably wouldn't be getting the full benefit of the Tung Sol anyway.
Username: vlad335

Post Number: 2
Registered: 1-2007
Posted on Tuesday, January 02, 2007 - 4:29 am:   Edit Post

Thanks for the replies.

I don't really want to cut the sleeve off anyway. I was hoping someone would talk me out of it. LOL.

I checked all my cables and they are OK. I also used the jack cleaning method mentioned in the FAQ. Waiting for the tubes to arrive now...

Advanced Member
Username: dfung60

Post Number: 221
Registered: 5-2002
Posted on Tuesday, January 02, 2007 - 9:50 am:   Edit Post

While you're waiting for the new tubes, check out the rest of your rig first. If you have any alternate preamp that you can use, that would be the first thing to try. If you've got another amp with a preamp out jack, try hooking that up, or try this out with your PA board (you can use an effects out or line out if you have gain controls on your amp). Use your normal cables if you can. If things sound weak now, then the problem is more likely your power amp.

If that's working properly (reasonable clean output level), then you can dig in deeper with your preamp. Preamps tubes should last a long time (unlike power tubes) but are subject to damage from impact or vibration. The most common failure mode is that the output gets wimpy over time, so this may well be your problem, however, if you put another tube in and it's still bad, then perhaps not. The 12AX7 is the most common preamp tube out there, so you should be able to mooch one from your guitarist to test.

There's a spring-loaded metal shield that covers the tube. Is this the "sleeve" you're talking about? It serves 3 purposes - first, it is an electrical shield that helps keep the preamp quiet, especially from the EM field from the power supply in your preamp; second, it helps keep the tube seated in it's socket; third, it provides some physical protection, not that there's much that going to hit it inside the case. Tubes vary in diameter, so if the new one is too big, you can go without it, but it would be better for you to find a tube that does fit in the shield.

Good luck,

David Fung
Advanced Member
Username: lothartu

Post Number: 201
Registered: 8-2003
Posted on Thursday, January 04, 2007 - 12:13 pm:   Edit Post

Hi and welcome.

I've done a fair amount of reading about preamp tubes and from what I can tell there really is no reliable way to get an exact size. Apparently there is a lot of variation in the diameter of the tubes and lots of people find themselves in the possession of tubes that "almost" fit perfectly into the shield.

I believe I remember reading a post here where Mica said that over time Alembic has amassed a little pile of preamp tubes that were just a hair too big to fit. I guess it's really just pot luck unless you can find a supplier who is willing to do an exact diameter measurement for you (and I imagine that there may be a few out there).

Best of luck.
- Jim

(Message edited by lothartu on January 04, 2007)
Username: vlad335

Post Number: 3
Registered: 1-2007
Posted on Wednesday, January 10, 2007 - 2:59 pm:   Edit Post

Thanks for the replies.

Turns out its something in my bass, the last thing I checked BTW. I borrowed a cheap bass our soundman has and everythings great. Somethings wrong in the 18v EMG system in my Warwick. I have taken the opportunity to purchase a Seymour Duncun setup to try. Also, I need to buy a backup bass for sure.

An interesting note about the tubes I ordered. I received 3 and 2 of them do not fit. A Fender and a Sovtek. However, the Electro-Harmonex goes right in.
Username: vlad335

Post Number: 4
Registered: 1-2007
Posted on Tuesday, January 16, 2007 - 11:06 am:   Edit Post

A further note on preamp tubes for this unit. I recently ordered a Svetlana 12AX7 and it doesn't fit as well.

Sorry but... WTF!

Am I just unlucky or is it that most tubes don't fit in this preamp? One out of 4!
Senior Member
Username: bsee

Post Number: 1457
Registered: 3-2004
Posted on Tuesday, January 16, 2007 - 2:18 pm:   Edit Post

You must be unlucky, or just selecting more exotic tubes. I have used a variety of JJ Tesla and GT tubes without issues.
Intermediate Member
Username: paulman

Post Number: 182
Registered: 2-2005
Posted on Sunday, January 28, 2007 - 7:22 am:   Edit Post

I just recieved a Groove Tubes 12ax7a and fitting in the sleeve is a no go. :-(

Instead I am trying out a Fender tube from my Twin. The interesting thing about that is the Fender tube is smaller than the Sovtek tube the F1-X came with (from an Ebay seller). So there is now a space gap between the tube and sleeve. I guess the tube Saga continues.
Username: vlad335

Post Number: 5
Registered: 1-2007
Posted on Thursday, March 01, 2007 - 11:00 am:   Edit Post

FWIW... I purchased a JJ Tesla, High Gain 12ax7 from Tubedepot.com and it fits right in. Not only that, it sounds freakin great!

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