jonboyuk

Some strange things are happening now. They might be perfectly normal, but as I bought it second hand I'm unsure of the intended manufacturer behaviour. 1. The thing is loud. I mean really really loud. In a gig practise situation, I would have the HD500X output set to max, the channel volume set to high on the amp, then the master volume at around half way. Now, if I have that I get serious volume/feedback from the amp. I've had to reduce everything quite a lot. So much so it's messed up a lot of my presets!! Sounds like a stupid comment, but I'm wondering if it's supposed to be quite that powerful (subjective I know). 2. If I roll my guitar volume down to 0% I get a quiet weird clicking/hum sound. That's even if I plug directly into the amp. It's not so much of an issue, but highlights something that might not be right. Any ideas? Thanks :)

I've FINALLY had the tubes installed and biased. Apparently one of my tubes was massively underperforming and the other was taking all the load. The loaded one was giving a reading of 68mV whereas the other wasn't providing any voltage whatsoever. 2 new tubes biased at 25 mV +/- 3 mV and it's works BEAUTIFULLY. The amp sounds so much nicer - even better than when I bought it second hand. I suspect the guy who changed them was a bit clueless. Anyway, over the moon, so thanks for all your help earlier this year.

Thanks Oscar. I got them from Watford Valves (UK)!

Thank you for all that - very useful indeed. Therefore I've bought some paired EH EL84 (medium) and a 12AX7EH as suggested. So my next question is about changing them. I'm fully aware it's a risky process and don't particularly want to die! To change the tubes alone, is that something I can do without too much fuss/risk on the DT25? I appreciate biasing them is a little more tricky and needs more disassembly (and therefore more risk). Can I change them and have someone else bias them? Or can I change them and just see if it's any better off the bat and not bother biasing? Thanks!

In the UK, all the valve shops I've looked at (6+) stock them, but they don't offer soft, medium, or hard. The only place I can see that is on musiciansfriend online. If they don't specify, is it therefore likely to be medium by default, or just potluck? EDIT*** Don't worry I spoke to the store and they said they can provide medium (something to do with Groove tube - I'm a bit clueless obviously!)

That's really useful thank you - I don't doubt you one bit! Why does the official L6 guide suggest China 12AX7's for the DT25 and 12AX7EH for the DT50? I wonder what the logic is behind that - any idea? Also, do you think this is likely to sort the issue I've described above? And if I replaced them, would I need to bias them (or get them biased)? Bit of a newbie in that sense!

Thanks and I'd agree - except that the Line 6 official knowledgebase says to specifically to use a Chinese-branded 12AX7 preamp tube on the DT25. EH are Russian! In fact the one in my amp at the moment is an EH (Russian) 12AX7, so should I be replacing it anyway?

Just an update - I found these tubes. Would they be okay? I'm having most difficulty finding a Chinese branded 12AX7, but Tube Amp Doctor have them. Is it okay that they're not Electro Harmonix tubes? It's all so confusing! 1No. 12AX7 2No. EH EL84s Cheers, J

Hi all, I bought my DT25 second hand on eBay a couple of years back. The seller said he'd replaced a couple of the tubes himself (I got the feeling he was a little clueless). Anyway, since having it it's been getting a bit - well - weird on me. Around 6 months ago, flipping the pentode -> triode switch causes notable hum. Knocking back to pentode resolved it so I've just used it in this mode. Around 1 month ago, flipping pentode -> triode makes the amp scream out with what sounds like feedback squeal (loudly). The volume control has no impact on the volume of said squeal. Pentode still works fine however. Is this likely to be a tube thing? I should also say that I'm clueless about tubes but have spent hours on these forums reading multiple old posts. I'm thinking if it is, I'll get them replaced. But, since I don't have the originals I'm not sure *exactly* what to replace them with. The knowledgebase says "Chinese-branded 12AX7 preamp tube (1) and Electro-Harmonix EL84 power tubes (2)." but which ones? ie EH 12AX7's? Or what? So confused. Can anyone point out which ones from say here or perhaps another UK based shop? Finally - on a separate note, I just upgraded my DT25 to the 2.0 firmware. I can't find any instructions on how to use the update! The only link on the L6 web site is now dead :( Thanks everyone :)

Gig went well. No feedback? SO strange, there must have been something where we were practicing setting it off. Also note to self, not to position one's self directly next to the drummer, made it impossible to hear myself without having the amp set to 7/10! Oops!

Thanks guys, sadly my amp is at the gig venue and I haven't got time to check it! But based on your advice, for now I'll take my second guitar and different jack cable! Fingers crossed! :)

Hey Brad, It's a bit annoying because I have to mute before I play...is that normal? My previous SV 112 didn't do it at similar volumes and the feedback happens even if I move away from the amp! Secondly it's definitely the plastic because if I press the area where the plastic's vibrating the noise disappears completely!

Hi all, loving the amp so far but I have a couple of questions.... 1. The piece of plastic under the control knobs on the top of the amp, certain lower frequencies make it vibrate so hard it's audible (almost like it's not stuck down correctly). Has anyone had this before? 2. This may not be the amp....but at around 12 o clock (not really that high volume wise when playing with a band) the thing create ear splitting feedback when I'm using the middle pickup/out of phase. If I stick my guitar into position 1/5 (humbuckers), it's okay again. I also found that the feedback happens more if I stand behind the amp?! It's really frustrating! Also there were no other devices on at the time (other microphones etc). Any ideas?

I gave Mark a call, VERY nice guy indeed. He said he'd be happy to do the work but thought (without looking) that it was most likely to be valve related and that I should just get someone local to deal with it. But if they can't, I'll just ship it up to him. Thanks for the contact, he's a top guy!

I live in Bristol! Any recommendations? London's still a bit far for me :/ (And thanks for your help!)