Help

throw_this_away · Post by **throw_this_away** » Mon Oct 10, 2005 1:18 pm

See if you guys can help figure out the problem…

When playing my combo (fingerstyle) I get sharp cracking noises… but only sometimes. It is more prominent when playing around the note G or when playing harder. The higher the amp volume the less it takes to cause the cracking.

- My combo is a 130W Tubeworks (200W at 4ohms, 1x15, tweeter, tube preamp, 8ohm speaker). It is almost 5 years old with moderate use. Gain around 50%, limiter 50%, master volume 30%, bass boost, low mid slightly cut, high mid boost, flat highs.

- I have been using my 72’ 4001 set to low action. (I would like to try my other basses to be sure it is the amp and not the bass… but I don’t think it is the bass as al the electronics and knobs work smooth without crackling)

- It is not my bass input jack, or the cord. Checked that out.

- In the last month I replaced the preamp tube (the tube is not the issue as switching to the solid state preamp still results in the cracking.)

- I don’t think it is an issue of the strings hitting the pickups as the problem is worse when playing notes around G.

- The night I started having issues I played it long and hard for 3 hours and for the last hour I had it's speaker slaved with a Traynor combo (1x15, 200W). The traynor turned out to be 4ohm (oops… I thought it was

… I think that is what did it. By the end of the night both were very hot to the touch.

phlemmy · Post by **phlemmy** » Mon Oct 10, 2005 1:22 pm

maybe the jack going into the rig?

throw_this_away · Post by **throw_this_away** » Mon Oct 10, 2005 1:30 pm

I am pretty sure it is not the jack... or at least not the cord. Wiggling it does not cause problems.

admin · Post by **admin** » Mon Oct 10, 2005 1:51 pm

John: What do you mean by the G note. Does this happen on all strings?

throw_this_away · Post by **throw_this_away** » Mon Oct 10, 2005 1:57 pm

Cracking can happen on any note/string if I push the amp hard enough... but when I play notes around G (G, Gflat or Gsharp) the cracking is more intense/occurs at lower volumes.

kcole4001 · Post by **kcole4001** » Mon Oct 10, 2005 2:02 pm

That's what my Traynor was doing before I decided it was time for a new amp. Turned out to be the voice coil of the EV 15, not the amp at all. It was intermittent at first, then got worse & happened more often. Try a different cab with the amp to isolate what is causing the problem.

throw_this_away · Post by **throw_this_away** » Mon Oct 10, 2005 2:32 pm

I figured it was a voice coil or speaker issue. I will try it out on a diff cab next chance I get (it is in a jam room... not at home).

kcole4001 · Post by **kcole4001** » Mon Oct 10, 2005 2:48 pm

At first it was only low notes, like below A. Then it happened more often, then all the time. The last practice with the old speaker was a waste of time. Tried the amp with a new cab, & bingo, perfect sounding again. What clued me in was when I tried the NEW amp with the old speaker I got the same ****** noise.

throw_this_away · Post by **throw_this_away** » Mon Oct 10, 2005 5:37 pm

Is there any visual tell-tale sign that the voice coil is in peril?

ozover50 · Post by **ozover50** » Mon Oct 10, 2005 9:22 pm

In my experience, the easiest way to check is to push the cone in with your fingers spread widely over the voice coil cover. Get as close as you can to the centre of the cone with your ear and push the cone straight in about 1/2" a number of times (or until you feel strong resistance) and listen closely for a slight grinding or scraping noise - you may even feel it with your fingers. It's important to have even pressure all round when doing this, but you'll know by the feel whether you're doing that.

This usually indicates a 'bump' in the voice coil windings or a flat area and is a sure sign that it's on the way out. It can be caused by overheating or sometimes exposure to damp at some stage.

Also a weak area or break in the cone surround (be it neoprene, foam or gummed paper) can allow the cone to move slightly side to side, which will cause the coil to make contact with the side of the chamber. This is the 'cracking' noise that you are hearing.

It usually occurs through heavy cone excursion caused by low notes at high input.

ken_swearingen · Post by **ken_swearingen** » Mon Oct 10, 2005 10:27 pm

Howard,its nice to see you spend some time over here for a change,we can use the help.

heinpete · Post by **heinpete** » Mon Oct 10, 2005 10:53 pm

Dear John,

some time ago I also had this on my huges and kettner bass-preamp. This is a sign of some preamp ECC83 valve problem as they have only a limited lifetime. It should be gone when you replace the valves. Maybe also the voltage of the valve anode has to be adjusted, specially if you have 2 of the ECC83 in your preamp section.
Hope this helps.

bob_the_bass · Post by **bob_the_bass** » Tue Oct 11, 2005 4:58 am

Sounds like a voice coil on the way out try what Howard suggested

ozover50 · Post by **ozover50** » Tue Oct 11, 2005 11:00 am

My pleasure, Ken. I spent over 12 years in the car audio industry and diagnosing dodgy speakers was a regular thing. However, don't discount any other suggestions here - mine's only one of many!

Forgot to mention - make sure the amp is off when you do it.

admin · Post by **admin** » Tue Oct 11, 2005 11:13 am

The tube change is an easy thing to try as well.