New DSL100H loud hum on high gain settings

[Duffy]

I have a new DSL100h and it produces a lot of hum on both Lead 1 and Lead 2, as well as on the "clean crunch" settings. This happens when the gain is turned up even moderately and also at relatively low volumes. I have one guitar that is very quiet at these settings though, a Fender FMT HH tele mahogany with mahogany neck and dual Seymour Duncan full sized humbuckers. My other humbuckers equipped guitars produce the pronounced hum, noticeable even when playing. The hum slightly goes away when I mute the strings on these guitars, but not completely.

The amp head does not hum when the guitar cable is unplugged. It is completely silent. I have switched cables and have had the exact same problem.

Anyone have an idea as to what might be going on?

I'm using a four by twelve Epiphone Southern Cal. cabinet and never turn the amp up high. The hum is noticeable at low volume as well.

I know any tube amp will hum, especially at high gain, but this seems like too much hum. It does not hum on the clean channel unless the "clean crunch" button is engaged.

I can still send it back for a replacement because it is only a couple weeks old. Also there is a good warranty repair guy not far from here. I don't want to send it back unless this is the best route to take. I don't mind having the warranty guy work on it. Then again maybe I should try changing the V1 preamp tube. However, tubes would be covered under the warranty if I take it to the warranty repair guy. Plus I would get it biased and have the power tubes replaced with JJ's.

Any ideas?

[surlybastard]

You need to identify what kind of hum this is, if it's just the hiss/hum from the high gain section of the amp that's just the way it is. If it's some kind of other hum (like a 60 cycle hum, ground loop) then there's something up. Could be a bad tube, but if one guitar doesn't give you the problem I'd say it's not the amp that's the problem.

[Duffy]

More info.

I plugged the head into the "wall socket" and tried it again.

Now I can play my Gibson SG Standard thru it on the clean channel with the "clean crunch" engaged and not get any significant hum until it is turned up way loud.

The same guitar on the "Ultra Gain" channel, the red channel, on Lead 1 can be turned up quite loud - to number 2 on the volume and number 5 on the gain and not get any significant hum, beyond what I would consider normal; only a faint hum. When I engage Lead 2 at these same settings I get slightly more hum, as I would expect to be normal. So I am thinking that this amp may be performing correctly now that it is plugged directly into the wall instead of the power strip.

However, on any channel at any of the settings described above, if I turn up the volume and the gain all the way the amp immediately tries to loudly feedback with the typical feedback sound. I immediately turn down the volume, and stop it from happening. I could also stop it by turning down the guitar volume. I am about 8 to 10 feet from the four by twelve cabinet and the cabinet is not facing back at me but to the side. I am probably still getting feedback from the cabinet because I'm so close and the sound is bouncing around in the room.

With these observations in mind I think I'm correct in thinking that the amp is working properly and that I'm just trying to turn it up too loud when testing it, for the size of the room I'm in. But I'm not really sure. Any ideas.

Along the same lines my 6505+ combo also had a lot of feedback when I turned it up loud in this same environment. I was able to tame the feedback by replacing the V1 pre-amp tube with another tube after testing a few. The stock one was most noisy.

Feedback, no pun intended, is appreciated. I'm going to try using my one by twelve cabinet next and see how that works.