Nov 14, 2012 2:22 PM
There are a bunch of threads that mention issues related to this one, so I was thinking if we can try to make one that can provide ideas on how to fix/workaround the issue.
I have an open support ticket with Line6 at the moment regarding this issue and will keep you updated on any solutions that might be coming from them.
Here is the transcript of the ticket so far: (This also details the issue that me and a lot of others are complaining about...)
Hi guys, Just bought a DT50 (to add to my collection of POD plus variax) and unfortunately is suffers from excessive "crackling" noise (sometimes refered as white noise, or waterfall sound). This is not my first tube amp, so I am guessing from experience that this is probably an issue with one of the tubes. I know I could get a ticket and get in touch with the nearest support center, but unfortunately the closest one is +1500kms away from where I live. (Welcome to Australia). So as you can imagine I really don't want to ship the amp there just to replace the valves. So if you guys can help me to narrow down the problem to a valve issue, I would be more than happy to replace them. I will try to give you as much info as possible on the issue: Amp is working fine (except for the noise...) in both channels, all the modes/voicings, both in low and normal power modes. With the power on and in standby mode there is no noise whatsoever. Turning the standby mode on, voicing 1, pentode, class A/B, there is no hum (just the normal from a tube amp) and a low crackling noise (sounds almost like static from an old radio). Changing to voicing II, the noise increases every so slightly. Voicing III is the worst one. Not acceptable. Voicing IV is on pair with Level I or II. Changing the mode from pentode to triode attenuates the noise somewhat. Changing class makes almost no difference. Changing Volume/Master level has zero impact on the noise. Running the amp with nothing plugged in, direct guitar or POD has zero impact. I have tried to remove the tubes and reinsert them (maybe they would have gotten loose during transportation...). This had a very minor impact on the noise, reducing it very slightly. Leaving the amp running for long periods also makes the noise reduce slightly but remains stable after 5 minutes or so. Ok I hope that is enough information so you guys can help me out to diagnose the source of the issue. Thanks in advance for your help. Cheers. Hugo Fonseca
After some more troubleshooting (and head scratching) here is some more info:
Removing either of the preamp tubes and turning the amp on makes the noise go away.
There is a slight difference in the noise volume between channels one and two with two being lower than one.
I have swapped the preamp tubes positions with a slight change in the volume of the noise.
I have tried electric contact cleaner with no success.
Found that moving the presence knob to a value higher than around 90% increases the noise even further. Decreasing pass that mark gets it back to the "normal" level. This variation is not linear. Constant up to ~90%, higher above it.
Please disregard the differences between channel one (A) and two (B). I forgot the fact that they save the tipology and so when I was switching between the two the tipology was changing also and that accounted for the noise volume difference.
How loud is the noise when using the amp? It is normal to hear hum/noise differences when switching topology and class on the DT Amps.
Can you hear the noise while you are playing the guitar?
The reason that you do not notice this on other tube amps is that the power class and rating is not changeable so you get used to the hiss or hum over time.
I.e. in class A on and setting III or IV you are going to hear hiss because your preamp and power tubes are juiced.
On Class AB with setting I is going to be relatively quiet.
Ultimately, there is no dead quiet tube amplifier. the DT amp just might be drawing your attention to the difference in noise floor because of the gain staging implications of changing the class and topology settings.
Can you post a sound clip of the issue?
As I mentioned I had several other tube amps including a twin reverb, a TSL 100 and an AC-30 (which have different levels of noise and/or hum), so I am aware of the typical noise floor on tube amps.
The hum level on my DT50 is fine and as you say changes with the different settings on the amp as expected.
What is not normal is high "waterfall style" constant sound, even with all the knobs turned to 0.
The noise is noticeable even when playing at low levels. When playing at higher levels the guitar sound drowns out the noise.
I will post a sound clip of the issue tonight so you can judge for yourself.
(File is attached)
<EDITED TO ADD LINK TO FILE>
As requested here is an audio of it. It was recorded with my phone from about 0,5m distance.
Sorry for the late reply. I don't hear anything out of the ordinary depending on your topology and gain settings. Can you hear the noise while you are playing?
You can hear hiss even with the knobs turned to 0 with the DT. This is the noise floor of the power amp.
Do you hear any pops, clicks, monophonic feedback, doubling sounds?
You can definitely hear the hiss while playing at low to mid volumes. It gets drowned out while playing at gig level, but it is still unusable since even muting the strings/using a noise suppressor on the effects loop won't silence it, so if for instance there is a quiet part on a song and you are playing live with a mic'd cab it becomes impossible to stop the hiss. Plus again makes it unusable for studio recording with a mic'd cab.
I have used some very noisy amps (ac30 comes to mind) and none was anywhere close to this.
Can you give any ideas on how to reduce the noise as in replacing valves with another brand or biasing the power amp ones lower? Maybe some other minor mods/tweaks?
I honestly think that the amp sounds great and am very happy with it, but the very high noise floor makes it unusable. from reading in the support forums there seems to be a bunch of other users complaining from the same thing. Also on general amp forums, every time someone is asking for advice if they should buy it or not, there is always someone advising against it because of the noise.
This are all customers you are losing because of something you are calling a "feature".
If you can somehow find a solution to reduce the noise (again no one is expecting it to be silent. some hiss IS expected), this may all be customers you are gaining back.
I would even be ok with some noise suppressor solution post power amp, so at least the hiss wouldn't be audible when not playing...
Ok, that is all the conversation so far. When i have some time I will round up the other threads regarding the same issue and provide links for them.
I also have a set of 12AX7's (TungSol) coming and will let you know it it made any difference.
Any other ideas?