2 DT25 combo questions

[jonboyuk]

Hi all, loving the amp so far but I have a couple of questions....

 

1. The piece of plastic under the control knobs on the top of the amp, certain lower frequencies make it vibrate so hard it's audible (almost like it's not stuck down correctly). Has anyone had this before?

 

2. This may not be the amp....but at around 12 o clock (not really that high volume wise when playing with a band) the thing create ear splitting feedback when I'm using the middle pickup/out of phase. If I stick my guitar into position 1/5 (humbuckers), it's okay again. I also found that the feedback happens more if I stand behind the amp?! It's really frustrating! 

 

Also there were no other devices on at the time (other microphones etc). 

 

Any ideas?

[Brad_Ames]

That feedback happens with any amp if your closemail die to the magnetic humbuckers, most of my amps do it with gain up about half or more.

 

As for number 1, are you sure it's the plastic panel vibrating and not the speaker itself? And is it just on low 5 and 6 string notes? My amp did it and turned out to be a speaker issue among other problems.

[jonboyuk]

Hey Brad,

 

It's a bit annoying because I have to mute before I play...is that normal? My previous SV 112 didn't do it at similar volumes and the feedback happens even if I move away from the amp!

 

Secondly it's definitely the plastic because if I press the area where the plastic's vibrating the noise disappears completely!

[Brad_Ames]

Hey Brad,

 

It's a bit annoying because I have to mute before I play...is that normal? My previous SV 112 didn't do it at similar volumes and the feedback happens even if I move away from the amp!

 

Secondly it's definitely the plastic because if I press the area where the plastic's vibrating the noise disappears completely!

Oh dear, it should not be doing that if you move away. Check your guitar cable and try another one or 2 to make sure it's not them, If it's still doing it, it might need to be looked at. Especially if the plastic is vibrating that loud.

Has the amp always done that since you bought it?

[spaceatl]

In terms of item 2. the uncontrollable squeal from your middle pickup...Most likely, that pickup is not potted, the potting has deteriorated.

 

When a pickup goes micro-phonic, even loose wiring in the guitar can resonate and just make things completely crazy. I have a Baker where the stock pickup rings resonated around 300 Hz....That was when the guitar was stock...The rings are gone and the pups are direct mounted to the body.

 

Sometimes the baseplate of the pickup can resonate. One trick is to put some soft foam rubber under the pickups to dampen the baseplate a bit...Good luck running that down....my guess is the guitar based on what you said, but sometimes a bad tube can squeal in a similar way.

[jonboyuk]

Thanks guys, sadly my amp is at the gig venue and I haven't got time to check it! But based on your advice, for now I'll take my second guitar and different jack cable! Fingers crossed! :)

[moogary]

You can also try to lower the middle pickup a bit and see if it makes a difference (don't forget to count the number of turns if you want to put it back to the same position)

[psarkissian]

"My previous SV-112 didn't do it at similar volumes and the feedback happens even if I move away from the amp"---

Different amps, different tubes (valves), different loop gains (aka- topology), different power levels, different sounds overall.

 

As for the loudness, there is a "Low Volume Mode" switch in the back of the unit that acts as a volume pad.

[Brad_Ames]

Good luck with your gig!

[jonboyuk]

Gig went well. No feedback? SO strange, there must have been something where we were practicing setting it off.

 

Also note to self, not to position one's self directly next to the drummer, made it impossible to hear myself without having the amp set to 7/10! Oops!