Please ensure Javascript is enabled for purposes of website accessibility Jump to content

Screeching/popping Noises From Dt25 Head/amp


Recommended Posts

Hi guys,


I've had a DT25 head and DT25 extension amp for almost 6 months now, and was lucky enough to get the pod hd500x for christmas. I've been loving it. But a couple of days ago all of a sudden I started to hear a sort of popping noise. 


The popping noise gradually got worse and now there's regular screeching noises too. It's like nails down a chalkboard. I'm not even touching the guitar when this happens sometimes. After talking to some people it sounds like it's the valve or valve stage in the head(?)


Anyway, I've been checking out the Line 6 warranty, and I've been trying to get written proof from the retailer of my date of purchase. The retailer has offered to help, and have told me to get the head bundled up and they'll arrange a courier. (and yes, all they said was "help", they didn't actually say "try to fix" or "replace")


I'm just pretty sceptical about doing this when it's still under Line 6 warranty....albeit I can't actually prove that at the moment.


I would just love some advice!

Link to comment
Share on other sites

Tubes are consumable. I think some websites warranty 30 days or something, but if they are stock tubes, it's time to throw some new ones in.



Most likely...does Line6 warranty the tubes themselves, or are they considered a "consumable"? Eventually they'll all crap out, especially if it's well-used.

Link to comment
Share on other sites

  • 2 weeks later...

I'm not sure, if 6 months is enough to finish the tubes. Althou i've had tubes broken after one days use, it is not very common. Before using money to tubes (even when one should always have a set of spares for every amp he/she/it owns), i'd check few things.


There may be several explanations for them strange sounds. One my old JTM popped an hissed when it needed resoldering of a tube socket. Resonance works in mysterious ways and tube amps tend to dismantle themselves occasionally.  A tube may be also loose in its socket. Yanking a tube soflty tells you if something like that is happening. Do not roast your fingers with hot tube!! Knocking tube softly with handheld of a screwdriver may also tell you about tubes condition.


However if you do not have slightest clue what to do, leave the inestines of your amp to a pro. Even if Wylie E Coyote survives when electrocuted to black and smoking pile of ashes, humans tend to start their travel to the paradise of their chosen religion in same circumstances.


If you have your POD connected to a computer via usb cable , you may've created a ground loop. That will give some noises. For this try to disconnect usb and see if noise goes away. However dunno if it is possible with DT. I had ground loop hissing when using POD with my boutique thingy, but it is silent with DT.

Link to comment
Share on other sites

I'm not sure, if 6 months is enough to finish the tubes. Althou i've had tubes broken after one days use, it is not very common.


I started to experience screeching and poping with my DT25 after 10 weeks of moderate use (approx. 50 - 60 hours total).


I didn't have time to wait for new tubes via mail order, so I went to my local GC and picked up a matched pair of Groove Tubes (model = GT-EL84-S "medium", part # = 555-0113-580, performance rating = 5).  The bias readings for both tubes were 23.5mV and 23.7mV respectively.  Both of those readings were within the recommended range (25mV +/-3mV), but I adjusted the bias so that both tubes read exactly 25.0mv.


Here is a link to a thread in the old Line6 forums with details on how to check and adjust the bias on a DT25 head.



One of the things you might consider is to buy a set of 4 matched power tubes .... this way you have 2 tubes for the next change over and/or a set of spares you can swap in any time. 


Great suggestion!

Link to comment
Share on other sites

Hi guys, just wanted to thank you for all your help and advice. Tubes have been changed, and the offending noise seems to have disappeared. Hurrah.


I did run into a couple of issues whilst biasing the tubes;

The meter I used only had settings for 250m or 100m. The guide said I should be using 200m.

I couldn't get any reading at all whilst in A/B mode.

In A mode I got a reading of 9.0 for both valves (I tested it twice, once in 250m and once in 100m. Same reading both times)


So I decided not to adjust the bias at all, considering I wasn't in the right mode etc, and it did seem to be balanced.

I've just been playing for a good half hour and everything seems fine....maybe a slightly louder hum, but that could be my imagination, or the new tubes.

Link to comment
Share on other sites



In most (?, at least many) meters, options are something like 200m, 2V,  200V and 600V or so. From those options you choose 1st one big enough to fit your wanted range (in this case 25mV-ish). So if you have 100m option, use that.


Of course making sure that you're in Voltage sector of your tool (how can it be 9?).

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...