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DT50 Noise
by aniden on 2010-11-17 06:53:05.2800

First off, THANKS to all you guys that responded to my threads regarding "Running Two DT50's with HD500".  For some reason, it wasn't readily clear on how to respond to you. I'll have to work on my "posting chops".

The main problem is that my DT50 amps have a HUGE hissing noise, even when not connected to anything at all.  I have a ton of other amps (even with tubes), from Gibson to Fender to Johnson to Blackstar to Marshall.  None of them even come close to the noise the DT50 makes at rest.  When I plug in the HD500, it gets even worse.

Some suggestions from you guys were 1) update firmware on the DT50 (maybe using MIDI to update through Monkey), 2) checking the Presence control and 3) keeping DT50's and HD500 on same power circuit (both already are on my Monster clean power unit).  Solution 1 might help, will find out today.

I also understand that certain amp settings in the HD500 will cause the DT50 to hiss even more.

Bottom line - If I can't get "my dream amp scenario" to work (HD and DTs in stereo, yet still able to direct record), I might have to return my two new DT50's.  That would be sad.

Anyone else having such hissing issues on the new DT50?

Thanks in advance to all!

Re: DT50 Noise
by bbenham on 2010-11-17 10:52:38.9770

Just as another troubleshooting measure, are you able to completely remove the hiss with a Noise Gate?  Not suggesting this as a normal fix, but I ran into a lot of noise hooking up a Fender amp with nothing connected as well.   I hooked up the 500 and tried with the Noise Gate and was able to filter all but one part of the hum out with threshold set to 25-30%.  The other hum ended up being line noise that had never showed up in studio monitors but was clearly evident in the tube amp.  After narrowing it down with the gate it was much easier to find the source of hum.  Mine ended up being a small amplifier the cable company put in to boost my video signal.  The amplifier was plugged into the same circuit (not outlet) as my amp.  Hope you find a fix soon because that sounds like one dream of a setup.

Re: DT50 Noise
by Rowbi on 2010-11-19 01:03:26.2960

i have occasionally seen a lot of his, but nothing louder than the amp's tone, so I couldn't hear it when I played.  some settings that I found more prone to it were using maximum presence, whereas using only 90% pres would cut it down a lot.  also some NFL topologies were better or worse.

it was something I noticed, but because it's totally drowned out by the amp tone, and because it's only certain settings I just ignored it.... remember Line6's theory behind modelling is usually 'warts and all' so if their real amp hisses, then that's a feature of the amp... and all their amps were aparently fully serviced by one of the best amp techs in California..

I'm not suggesting your amp doesn't have a fault.  I'm just letting you know that it may be what I've noticed, which I don't think is a fault.

does it happen with all NFL topologies, on the amp and also with all amps on the HD500 when it's connected to the DT50?

Re: DT50 Noise
by Rowbi on 2010-11-19 01:07:17.3240

another thought.. could it be a tube is not seated, or has gone microphonic?  turn the amp off, and let it stand for a while.  then tuen on the standby switch to ensure the caps are drained (while leaving mains power off).  then standby off after a few mins and pull all the tubes and push them back in their sockets... DO NOT touch the tube sockets!

turn the amp on again as per a normal startup... and using a pencil tap the 2 preamp tubes.  if you get noise at all through the speakers, then that tube is bad (microphonis)

you could test for other tube issues if you have any spare 12AX7 tubes, try popping them in the preamp sockets and test with them.  note that one is a balanced phase inverter... it wont matter for the test, but make a note of where the original tubes went and put them back in the same socket they came from after the test.

Re: DT50 Noise
by Nick_Mattocks on 2010-11-19 13:18:40.1240

+1 to both Rowbi's replies here.

Re: DT50 Noise
by gtrman100 on 2010-11-20 13:29:01.0720

I haven't gotten my DT50 yet, it arrives Monday, but I can tell you from experience with tube amps that the amount of hiss in an amp is inversely proportional to the amount of negative feedback in the output stage. In other words, Voicing 3, with no negative feedback, will have more hiss than the other voicings. This is typical of low or no negative feedback amps, like the Fender Custom Vibrolux Reverb and the VibroKing. Once you're playing it isn't an issue, but for recording it can be annoying.

Re: DT50 Noise
by Crusty_Old_Rocker on 2010-11-27 19:28:40.4780

You're absolutely right Gtrman100.  The amount of noise from the amp is very much influence by the negative feedback.

I build cathode biased EL84 valve amps with no negative feedback and they can be a bit noisy but they really sing.  The DT50 even when using NFL III in class A Pentode mode is actually quieter than the average valve amp with a similar topology/design.



Re: DT50 Noise
by agalusha on 2010-11-28 08:03:09.4520

I had a similar experience with different amps, even with a clean power unit. This might seem obvious, but if you have any florescent lights (even compact florescent) or computer monitors in the room with the amps, try turning them off to see if effects the hiss you are hearing.   Also have you tried the ground lift switch?  Hope this helps, that sounds like a great setup.

Re: DT50 Noise
by aniden on 2010-11-28 09:08:25.3920

Hi All.  THANKS for trying to give me a solution to my DT50 noise problem.

Sadly, no matter where I plug in, or what I do (from all suggestions), the noise persists in both amps. Even when NOTHING is plugged in.  I have a good friend that is a pro kbd player (played with Larry Coryell and many others) and also owns a studio.  He's never heard such noise from an amp.

The amps are now boxed up and ready to go back to Musician's Friend.

I have now resorted to running my Flextone III with (2) 2x12 Celestion cabs on either side for a nice stereo amp sound, and no noise.  Will still use the HD500 for some direct recording and am totally impressed with the Mesa Recto Recording Preamp I recently got.  It's stereo, has an effects loop and is completely valve driven - and QUIET.

The DT50 dream will be gone for now.  I still have a Fender Twin Reverb, Gibson GA-42 and Blackstar HT Stage 60 - all pretty quiet at rest.

Oh well...

Thanks again for trying, everyone!!!


Re: DT50 Noise
by rockstardvnt on 2013-04-22 01:24:53.8760

I have been attempting all I can to avoid having to wait 2-3 weeks while my new amp gets looked at.( 8 months old out of box, but has only been used for last 3-4 months). Issues were noticed right away and have been searching regularly through this site and others to find the quick fix. As well as bugging guys at local repair co and store purchased from.

Issues are... 1. crackling popping sounds are/were the main issues. have updated firmware and reinstalled again to resolve it. swapped tubes out with new ones which had no affect. put the originals back in.. (smaller tubes only).. 2. sudden jumps in volume usually when playing in my room at lower volume then gets real loud.. 3. And sometimes it cuts out all together.. no output at all, just goes silent. amp off for a sec and back on, I have sound again.. Sort of a showstopper though.. I see many related posts with no real anwers revealed.. So, I keep looking and asking..

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