These forums are read only, please use our new forums here.

Main :: DT50/DT25

DT50 crackling noise question?
by BMoe on 2011-05-17 16:59:06.3060

Thru the forums, I am aware of the " white noise issue. But I have that and also there is a sort of crackling

noise, more like a lightning/storm interference on an am radio noise, or a continued "dirty pot" noise?

It doesn't happen when the amp is first turned on but after a couple of minutes is appears.

This seems to be only when the A/B is selected.

My question is, could this be a faulty preamp tube, and can I change them if still under warrenty?

I know you can't use "long plated" tubes. I was thinking of the Tung_Sol 12AX7.

Just received it last week, and I love the tones on this amp and with the POD HD500, Sweet, Sweet , Sweet!!

Thanks for your answer in advance.



Re: DT50 crackling noise question?
by TheRealZap on 2011-05-17 17:03:03.6480

there really isnt any pre-amp tubes... the pre-amps are modeled.

i'm certain that changing any tubes won't hurt the warranty as long as the tubes are within spec.

Re: DT50 crackling noise question?
by BMoe on 2011-05-17 17:51:00.0490

No preamps, why does the DT50 FAQ specifications say they are shipped with 2 EH 12AX7 preamp tubes and

2 EH Power tubes? I also read somewhere that one of the 12AX7's is an inverter and the other a preamp?

Just curious.

I will try replacing the 12AX7's.Thank you for answering my main question.



Re: DT50 crackling noise question?
by spaceatl on 2011-05-17 18:57:29.3250

This is not an official recomendation but, generally you want to avoid the long plate in a combo if you like to play loud...They go micro faster...the plate is long...doh...In a head I think you have more leeway...I recently put in a Mesa SPAX7 in the buffer and a GT SAGAX7 balanced inverter...very nice improvement over the EH vibe...I swear SPAX7s are one louder... They are very quiet too...

Re: DT50 crackling noise question?
by TheRealZap on 2011-05-17 19:33:38.5000

they do use tubes that are typically preamp tubes but here they are: One tube is an input buffer, the other is the phase inverter for the power amp.

Re: DT50 crackling noise question?
by TheRealZap on 2011-05-17 19:34:53.1700

actually it is an official recomendation:


12AX7 Preamp Tube  Swapping: If you decide to swap out different 12AX7 preamp tubes, do NOT  use anything labeled “LP” (Long Plate) for the first preamp tube stage  (labeled as V3), as “LP” labeled tubes are extremely microphonic.


Re: DT50 crackling noise question?
by SStiv on 2011-05-18 12:32:24.0160

I used Tung_Sol 12AX7's to correct my white noise problem.

Re: DT50 crackling noise question?
by jdolby on 2011-05-18 13:19:17.8030


Your problem sounds the same as mine.  I changed the two 12AX7's in mine and the white noise got quieter did but not entirely go away.  Around that time I started to use the HD500 with the L6 link.  I do not get the crackling when using the L6 link.   It does crackle when I plug directly to the amp guitar input (high).  It's like a "dirty pot" as you say.

If I honk on a chord it is more pronounced.  It gets loud for a split second then goes away.

I wonder if any of the Line 6 guys could chime in here.

When I get home from work I'm going to call Line 6 for some help and see if I can get this sucker repaired.

Re: DT50 crackling noise question?
by arcticman on 2011-05-18 17:33:21.6090


Please let us know what you learn from L6.

I have had the same "crackling" on my DT50 112... but it's very intermittent.


Re: DT50 crackling noise question?
by jdolby on 2011-05-26 14:22:34.3630

I've been busy with work and life in general.  Today, I finally took my DT50 Head to the point of purchase.  It will be repaired by the local Line 6 repair guy.  So your guess is as good as mine right now.  Hopefully it won't take very long and comes back silent or near enough.

I'll keep you posted.


Re: DT50 crackling noise question?
by BMoe on 2011-05-27 15:23:24.5790


I too have been busy, but I did a test consisting of when the "diry pot noise" was most present.. On my amp it seems to

be more pronounced on the  Class A/B but is softer on the Class A.. I also did a test without the L6 link and it was there also.

So from what others are say and you, this has nothing to do with the 12AX7's, I was going to try that first. I looks like I probably

will have to bring the amp in to a service center (which is 60 miles from where I live.)

Anyway, thanks for the update and would love to hear your results.

Re: RE: DT50 crackling noise question?
by darealagentp on 2011-06-02 09:15:26.9430

This may be moot by now, but I just came across this thread this morning... all the info that Space, Zap and SStiv provided is correct.

However, with any of our digital modelling amps (with or without tubes), a big portion of the amp's sonic "performance" is also driven by firmware (system software code). While ultimately, the root cause of this issue you guys are having could be hardware (tube-section) related, I need to remind you guys that you should consider a firmware re-install as one of the first steps when troubleshooting audio-related issues.

To do this, you'll need a MIDI-to-USB hardware interface to link the amp to a host computer. We've had the best luck with M-Audio's MIDIsport UNO and other customers have chimed in that the Yamaha UX16 (similar to the UNO) work great.

Line 6 Monkey is the free software application that enables you to "look" inside your DT50's system software via USB-to-MIDI connectivity.

You then click on the "Flash Memory" component in the Monkey software program and click "Update Selection" or "Reinstall Latest" (whichever appears... this will vary from amp to amp, depending on the user's history with doing Flash Memory update/reinstalls).

If you try this and are up to the most current DT50 system software and the issue STILL persists, then a trip to an authorized service center tech would be in order.

Re: RE: DT50 crackling noise question?
by BMoe on 2011-06-14 16:39:09.5390

Finally, got around to testing out the "crackling noise issue". IT IS SOLVED!!!  I'm a

happy camper (camping in front of the DT50)..

I first bought some 12AX7's (Tung_Sol), Much thanks to SStiv.

Tried the amp after the tube replacement and the "crackling" was still there.

At that time, I wasn't concerned or paid attention to the white noise as I was

very busy with other stuff that day. Tried it in a hurry, always a bad thing.

Then had to purchase a Midisport Uno, Mucho Thanks to Line6Perry

I had some trouble with one of the computers, updating the DT50( with Line6Monkey,

was still getting the 80000A error. but after loading the latest driver for the uno and

hooking up, USB and both ends, Midi In and Midi Out,to the DT50, still a 800000A

error, I tried updating by unplugging the USB port (yes, I know it wouldn't work), just to

run the update process, then I got a different error, Then plugged the USB back in

and the damn update finally started and TOOK!!!

Then the final test was the "crackling noise" TOTALLY GONE and the "white noise"

GONE, just typical tube hiss. Again I am just "punked"

So, Thanks to all, for your suggestions.

JDolby: did you have to send yours in and was it fixed?

Now it's legit, My question was "answered"



Re: RE: DT50 crackling noise question?
by jdolby on 2011-06-14 17:44:56.9550


I'm glad you're enjoying your amp!

Mine is still in the shop.  Two plus weeks, now :-(

I'm hoping for the best.  Will keep you posted.

The information above may not be current, and you should direct questions to the current forum or review the manual.