T2 Tubes Question

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gweb

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I just picked up a T2 and love the thing. I like to do a lot of experimenting with my sound and was wondering what changing the tubes from 12AT7 to 12AX7 would do if anything and if it's safe to do this without hurting the head. I did a search on the subject but couldn't find the full answer.

Thanks,
Greg
 
Hi Greg,

The 12AT7 in the power amp cannot be changed to a 12AX7, because the 12AT7 tube provides specific voltage needed to drive the Valve-Dynamic power amp. You can use any brand of 12AT7 or ECC81, but it has to be that type of tube.

If really doesn't matter what you use in the front 3 tubes, but any 12AX7 or ECC83 will give you the most preamp gain. Using a 12AT7 in the preamp will lower the gain amount.

Hope this helps?
Thanks!
 
Thanks, that's what I needed. I guess my next question would be, do all 3 front tubes need to be the same type, and are there any bias adjustments required. I've been using solid state amps for so long I never learned this stuff.

Thanks,
Greg
 
They are all preamp tubes, no biasing nessesary.

But if you change the Front 3 12xa7 with 12at7s, you will get less gain...; and they don't necessarily all need to be the same type.
 
These heads do work with Ax7's - ish I have actually got an ex demo T2, and it is running faulty ahem... it was loaded with a 12ax7 as the power amp valve.

Will this cause severe problems? My amp doesn't turn on any more...
 
Like Doug said:

The 12AT7 in the power amp cannot be changed to a 12AX7, because the 12AT7 tube provides specific voltage needed to drive the Valve-Dynamic power amp. You can use any brand of 12AT7 or ECC81, but it has to be that type of tube.

I mean it's physically possible to put that tube there but no real reason to. Try changing the tube to an AT7 and see if the amp works. If not, you may have to take you amp in to a tech.
 
Hi,

I fortunately had ordered a JJ 12AT7 and running it with that, it seems to be a little more stable although I am having a couple of other problems:

When turning the amp on too quickly after I turn it off, the fuse blows, I currently have a 3.15amp antisurge fuse in there, and it has gone through at least 3 of them and it seems to do the same if I turn it on too soon after being plugged into the wall.

Secondly, after playing the head for about 1hr+ at about one third volume on the gain channels, it starts cutting out then cutting back in. It seems to be an overheat circuit of some sort cutting in but I don't think it should be coming in so soon when I'm not making it work particularly hard? The cab running on it is a 4.6ohm cab, so I don't think I'm putting to heavy a load on it, my G2 100w could handle it no problem.

I am UK based, so I don't know if the mains there makes any difference to the operation of the head.

I've had a look inside the head and I can't see or smell any burned out components, still smells like new!

Could you please advise?

Cheers,

Dan
 
I would take your amp to a local tech and him check it out.

I am UK based, so I don't know if the mains there makes any difference to the operation of the head

This does actually make a difference. The T2 is setup for international use but you will have to change the mains fuse. This is located next to the IEC connection on the back of the amp. The tab pops out and you just need to change the fuse that sits in there and rotate the tab to the correct voltage for your country. We have amps already setup for shipping to other countries w/ correct voltage and fuse in place. If you purchased your amp new in the UK you should be fine. If you did purchase your amp used from another country or new from another country, you would have to change the voltage and fuse.
 
What fuse do you recommend for UK? I currently have a 3.15amp Antisurge fuse in it, set to UK.

Any thoughts on the overheating/cutting out?
 
In answer to the country issue, I bought it Ex-demo from Andertons.co.uk, so I assume it was a straight out UK head
 
You need to use a 4 amp fuse (preferably ceramic). The amp will defiantly continue blowing fuses if you have the 3.14A in there.
 
Nice one, cheers! Just to let you know, gigged it for the second time tonight and it sounded wicked! definitely a step up from the G2!!!

www.myspace.com/blackoutblack if you fancy a listen!

Cheers,

Dan
 
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