Community: Message List - Crackling & Popping Noise coming from DT25 Combo

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Thu, 27 Dec 2012 19:13:07 GMT

This issue resurfaced for me. In the end I just needed to use a power conditioner. Turns out my house AC unfiltered was causing an issue every time my central air fan would kick in,

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Fri, 21 Sep 2012 14:32:39 GMT

Cheers.

I spoke to the same amp tech as before who suggested that if all I have done is change the poweramp tubes and am having no problems with excess hum then the bias is probably appropriate. I'll therefore probably hold off having it properly biased at present (bit of an effort lugging the combo amp to the music store!).

Interestingly, he feels strongly that valve amps should not be left for more than a few minutes at a time in standby mode as this bypasses the valves but heats them up more and causes them to expire quickly (something to do with "HT" current, can't remember exactly). I had been doing that quite a lot while using low power mode.

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Fri, 21 Sep 2012 02:52:40 GMT

Adjusting bias is a little "techie thing". You need an electrical voltmeter to do it. It is very easy if you know what you're doing but if you do not have any background in electronics then it is best left to a technician. With the DT25 amp it is about a 30 minute job only because you have to take the amp out of the enclousure, adjust the bias (about a 60 second job) and put it back in. When you change tubes it is always best to at least check the bias but I would say that if things sound ok then the bias setting is most likely within acceptable limits. I wouldn't worry about it.

This thread talks about bias adjustment.

http://line6.com/support/thread/75238?tstart=0

I think you are good to go. You obviously did the right thing to change the tubes so enjoy your amp.

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Thu, 20 Sep 2012 20:15:38 GMT

This is my first tube amp and to be honest I have no idea how to check or adjust the bias.... I just switched the tubes and it worked (no crackling).

If you mean switch between class a and a/b I tried that previously and it had no effect on the crackling.

Is there something else I should be aware of?

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Thu, 20 Sep 2012 19:18:09 GMT

Good news on the "replacement tube solution". Lesson learned. Did you check/adjust the bias? If it sounds good it is probably good to go.

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Thu, 20 Sep 2012 17:37:17 GMT

Update: Installed a matched pair of jj-tesla cryo EL84s. Left the stock 12ax7 in place.

This has completely solved the problem. No more noise. Interestingly, the new tubes seemed to fit far more solidly as if contct is better. They also light up more brightly which (possibly) is a sign that the stock EL84s were failing. Not really sure if the tone has changed much, possibly better note separation/ clarity.

Anyway I'm happy now as I don't have to arrange shipping back to Line 6 to have the amp looked at!

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Wed, 19 Sep 2012 15:56:09 GMT

It's been my experience that anything "crackling and popping" is usually related to the tubes in one way or the other. Either "reseating" or "replacement" is the key. Also check/adjust the bias. I replaced my stock EH's (DT25) with vintage Amperex all around and they really make a nice sonic difference, plus, now the EH's provide a spare set as backup. I'm big on having backup solutions. I use my SV212 as an additional 2 x 12 cab for my DT25 on gigs plus it puts a spare backup amp sitting there should I have a problem with the DT (none yet).

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Wed, 19 Sep 2012 12:01:50 GMT

I had the same issue. Simply reseating the tubes was not enough in my case. I replaced my 12AX7 with a Mesa SPAX7 and it fixed the issue. In the end I could have replaced with any 12AX7 that was of good quality as the 12AX7 is just used for phase inversion. The POS 12AX7 that it shipped with was pretty low quality.

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Mon, 17 Sep 2012 15:06:14 GMT

I've got exactly the same problem. I've had the amp about 11 months now and it probably started after 6 or 7 months.

Like you, the noise is intermittent and not affected by adjusting the master volume. The best way I can describe the noise is like a crackling, almost like wood burning or paper being scrumpled up. Most noticeable on amp models III and IV.

I re-installed the DT25 software via midi cable and no improvement. It happens whether or not I use my podHD300 with the DT25.

So, I looked at a few similar threads and some people have found that the DT25 valves needed changing early. I spoke to an old school amp tech over the phone who first started to write it off as a circuitry problem until I told him that the DT25 is a tube amp! He suggested the "tapping" method (also seen it called the chopstick method) of testing the tubes. He thought it was more likely to be a poweramp problem.

So...I took of the back panel of the amp and tapped the poweramp valves with the amp running. Sure enough, this made the sound much more noticeable and louder. I'm therefore assuming its a poweramp tube problem. To be fair the stock electro-harmonix eL84s don't seem like badly made tubes but there you go.

I've ordered a matched pair of JJ-Tesla cryo EL84's from Watford Valves. I'll let you know how I get on.

Re: Crackling & Popping Noise coming from DT25 Combo

support@line6.com — Fri, 13 Jul 2012 03:18:58 GMT

Same trouble here on a DT25 ... took out the Chinese 12ax7 and replaced it with an old Sovtek I had lying around and snap, crackle, pop was reduced 90%. Tomorrow I'm gonna pull the EL84s and reseat them and see if that gets rid of the remaining 10%.

Thanks for everyone's input on this.