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Crackling & Popping Noise coming from DT25 Combo
by MikeTicehurst on 2012-05-31 10:03:32

Hi

I have had my DT25 now for about 3 months and I use it in conjunction with my HD500.

I am using it for recording at home and have mainly been using the DT25 in Low Power Mode with the speaker on the Combo off & with just the Stand By on (as it states you can do in the manual) & taking a direct out to an audio interface to record into Logic.

I noticed about a month ago that when I use the DT25 normal using the Combos Speaker in either Low Power mode or Normal I got, intermittently but very annoyingly, crackling & popping noises from the amp.

This crackling & popping does not rise & fall in level as the Master Volume is raised or lowered its just there in the background. This noise is not present when using the direct out when recording. It is only there when the combos speaker is on.

I changed cables re sited the amp everything I could think of but still the noise was there.

I then took it to the dealer I bought it from and the guys there confirmed that this crackling & popping was definately present.

Off it went for repair leaving me without the amp for a week & a half.

I have just got it back from Line6 where there had re-installed the software on the combo.

I've just plugged it in and guess what. The bloody noise is still there.

I'm waiting for my dealer to get back to me tomorrow as I believe I should have a new replacement. It's been off for repair & the problem's still present.

I was wondering if anyone else has experienced a similar problem at all and if they have has it been resolved?

Mike Ticehurst



Re: Crackling & Popping Noise coming from DT25 Combo
by spaceatl on 2012-05-31 13:16:19

Is it an intermittent "fly in the bug zapper" sort of sound...just sorta in the background? That could be a tube, dirty tube socket...even a volume pot...Most often for me that has turned out to be a tube or dirty socket...usually reseating the tube will clear that up for a bit, but if there is oxidation or a pin socket is actually loose, it might need to be cleaned, tightened or replaced...anyway, jsut a couple of thoughts...



Re: Crackling & Popping Noise coming from DT25 Combo
by MikeTicehurst on 2012-06-01 12:00:13

Thaks for your reply.

I've recorded the noise on my iPhone and you can hear it if you click on the link below

http://www.youtube.com/watch?v=1ddwldvoqe0&feature=plcp

Ithas gone off for repair, been away for a week & a half, returned yesterday & same problem!!!!!!

Surely if it was a dirty socket or tube it would have been picked up when Line 6 had it for repair.

Also if it was interference from my leads etc surely it would still be present when using the Direct Out when recording. Which it isn't.

The sound only manifests itself when I turn it on completely & use the speaker built into the combo?

When I use the amp in "Standby" to utilise the Direct Out I do not get this problem. Only when using the combos speaker.



Re: Crackling & Popping Noise coming from DT25 Combo
by spaceatl on 2012-06-01 16:11:20

I have had tubes that did that near near the end...But it does have an "interference" kinda vibe to it...sorta like a bad lead cable being gragged around on the floor...

If you are using the direct out with the amplifier on standby, then the direct out signal is NOT passing from the output tranny...So basically, this means that the issue is NOT in the modeler preamp section. To test the direct out fed from the power amp switch the amp to full power...see if you care getting this at full power...direct will not work in standby in this case...

I suppose something to narrow down if this is happening in FULL power vs HALF power (LVM switch on the back)...

One simple test you can do for the tubes is the pencil test...With the amp at full power and the master up tap each tube lightly with a pencil...If you hear it in the speaker, that might be the culprit...

However, this could be some sort of interference too...Have you tried some different power circuits/locations?

Also, does this happen with the guitar removed from the amp?



Re: Crackling & Popping Noise coming from DT25 Combo
by MikeTicehurst on 2012-06-02 04:42:27

Thanks for your help & advice.

Whilst I agree that it does have an interference kinda vibe, again surely this would manifest itself even when using the Amp in standby & the direct outs?

I have this mornign taken the combo back to my dealers (who I have to add have been brilliant over this!!!!)

I took all the same leads, power leads, guitar, everything & the problem was still present.

As I said I am blown away by the quality of the amp itself & when used in conjunction with the HD500 I have to say it is superb!!!!

My gripe is that this problem was, IMHO, to do with this Combo in particular, & that Line 6 having had it for over a week in order to identify & repair the problem returned it stating they had reinstalled the software. And I still had the same problem.

I have to make mention of the guys at "Academy of Sound" in Stoke on Trent, UK. They have been extremely helpful. This morning they offered to take the Combo back and give me a brand new combo, leaving me satisfied whilst they dealt with Line 6.

Unfortunately they didn't have a combo in stock - but they did have a DT25 Head & 112 Cab which they offerred me on loan until a new combo arrived. I have however agreed to pay the difference & keep the Head & Cab, which I now have back in my little studio & guess what - THE NOISE HAS GONE!!!!!

I do feel that sometimes, probably due to constraints of time etc that not enough time is given over to tracing these intermittant type faults. But this isn't a cheap piece of kit & although it isn't mega expensive either I do expect it to do what it says it will do & sadly the unit I had didn't.

Anyway as I said that problem aside I really cannot praise this amp highly enough!!!! 



Re: Crackling & Popping Noise coming from DT25 Combo
by bartpuglise on 2012-06-02 07:12:24

When I purchased my DT50 Head I had a white noise that was resolved when I replaced the Pre-amp 12AX7's. Then a few months later I started getting that "crackling" noise as well. I then replaced the power tubes and since then my amp head has been perfect. There have been plenty of posts on this problem which I believe stem from the STOCK Electro Harmonics Tubes. Replacing the tubes resolved my issues! Love the Amp not crazy about Line6's Tube selection.



Re: Crackling & Popping Noise coming from DT25 Combo
by Necator on 2012-06-28 07:45:04

I had this just last week. Same noise, but it was really noticible in voicing "iii". I removed and reseated the two power tubes and the noise vanished.



Re: Crackling & Popping Noise coming from DT25 Combo
by mikej555 on 2012-06-28 12:09:00

I have a brand new (2 weeks old) DT25 and I am getting the exact sound that MikeTicehurst recorded. What do you folks recommeded as best course of action, return for exchange, or try to have dealer fix it, or attempt to reseat tubes myself? Does the upper part of the back panel (part with screen) just unscrew and pop off for access to tubes. I did try unscrewing the upper back panel piece but it would not come off and I did not want to pry on it.



Re: Crackling & Popping Noise coming from DT25 Combo
by Necator on 2012-06-29 02:58:15

The top back panel piece is just a bit tight, but it pulls off once the four screws are out.



Re: Crackling & Popping Noise coming from DT25 Combo
by rchibnik on 2012-06-29 17:31:39

I have been getting a popping noise on my DT25 combo when I (the HD500, actually) switch between feedback loops - switching between I, II, III and IV, or between Class A / AB. It doesnt happen when I play - only when switching voicings.



Re: Crackling & Popping Noise coming from DT25 Combo
by greghall on 2012-07-03 01:44:08

Switching between topologies does create a bit of a 'pop', and it's more pronounced on some configurations than others. This is normal. Line 6 have confirmed this somewhere, but I can't locate the link at the moment.

Regards



Re: Crackling & Popping Noise coming from DT25 Combo
by edstar1960 on 2012-07-03 05:30:39

MikeTicehurst wrote:

....

I am using it for recording at home and have mainly been using the DT25 in Low Power Mode with the speaker on the Combo off & with just the Stand By on (as it states you can do in the manual) & taking a direct out to an audio interface to record into Logic.

......

Hi Mike,

I tried using my DT25 for a recording session using the direct out while it was in Standby mode and did not get any signal - I had to take it out of standby and engage the speaker to get a signal via the direct out.  So is my DT25 faulty or did I do something wrong?  Which manual states how to get a direct signal without havving speaker engaged?  And where abouts in manual does it say so?

Thanks.

Ed



Re: Crackling & Popping Noise coming from DT25 Combo
by spaceatl on 2012-07-03 06:19:04

Turn on LVM (Low Volume Mode)...The switch is on the back of the amp...

Keep in mind that this is NOT an line level signal...It is mic level...Generally best to hit a mic pre...usually means turning off line pads...



Re: Crackling & Popping Noise coming from DT25 Combo
by edstar1960 on 2012-07-03 06:21:17

Ah! Thanks Spaceatl!  Do you know which manual describes this?  Its not in my DT25 Pilots Guide.



Re: Crackling & Popping Noise coming from DT25 Combo
by spaceatl on 2012-07-03 14:07:55

It's not in the original manual...It's in the connectivity guide that came out with the HD 2.0 firmware...

http://line6.com/data/6/0a06434d107f14f7b82d58d962/application/pdf/L6%20LINK%20Connectivity%20Guide%20for%20POD%20HD%20&%20DT%20Amplifiers%20v2.0%20-%20English%20(%20Rev%20E%20).pdf



Re: Crackling & Popping Noise coming from DT25 Combo
by edstar1960 on 2012-07-04 03:53:10

Thanks!  



Re: Crackling & Popping Noise coming from DT25 Combo
by UncleFestis on 2012-07-05 16:31:15

FYI I had the exact same issue.  My brand new just out of box DT25 was crakling and poping like a bowl of Rice Krispies.  Just removed and reset the tubes and the the noise vanished.



Re: Crackling & Popping Noise coming from DT25 Combo
by BrianRowland on 2012-07-12 20:18:59

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.



Re: Crackling & Popping Noise coming from DT25 Combo
by Stratman82 on 2012-09-17 08:06:15

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
by Krontab on 2012-09-19 05:01:50

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
by geppert on 2012-09-19 08:56:09

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
by Stratman82 on 2012-09-20 10:37:18

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
by geppert on 2012-09-20 12:18:09

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
by Stratman82 on 2012-09-20 13:15:38

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
by geppert on 2012-09-20 19:52:40

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">style="color: #3366ff;">http://line6.com/support/thread/75238?tstart=0

style="color: #3366ff;">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
by Stratman82 on 2012-09-21 07:32:40

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
by Krontab on 2012-12-27 11:13:08

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,




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