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Little Dot MKIV SE buzzing left channel

post #1 of 5
Thread Starter 

Hey all,

 

I just yesterday took ownership of a LD MKIV SE, bought direct from David@little-tube.

 

Unpacked it and noticed the volume knob was very loose, but have learnt a 1.5mm allen will fix that.

 

But sadly I am having an issue where the left channel starts buzzing.  It usually happens when the volume is lower then average, or during quiet sections of music.  The buzzing goes away if I turn up the volume by about 20-30 percent, then back down.  I can also rid the buzzing by tapping the top of the unit.  I can also start buzzing by tapping the top.  Unplugging the input cable does not stop it, when it's doing it no music can be heard through that channel.

 

First I thought it could be one of the tubes, so I swapped round both sets of tubes, the buzzing remains on the left side.  I have had a play with the DIP switches, moving them all back and forth, before settling on 5x gain.

 

I have contacted David who has suggested I clean the tube pins with deoxidiser...but the buzzing occurs on the same channel even when I swap the tubes.

 

I can't think of anything else I can do to make the buzzing go away.

 

Anyone have any ideas? :)

 

Thank you for any advice!

post #2 of 5

well.. the stock tubes are known to have some problems,  but i had none with my LD MKIII. 

 

try the deoxit kit, and see if that helps. tube rolling is another option. It could also be a ground loop. Look into RadioShack to purchase a Ground Loop Isolator.


Edited by David.M - 7/23/10 at 1:11pm
post #3 of 5
Thread Starter 

Have since noticed that if I press down on the left driver tube, the buzzing goes away.

Tapping the unit while music is playing effects the left channel at all volumes, but it only continually buzzes with a low or no volume.  It is possible to set a volume where the music is just loud enough to make the buzzing stop momentarily.  Bit quieter, buzz is constant, bit louder, buzz goes away.  But, tapping the unit can cause the left channel audio to disappear briefly.

 

I expected to run into some problems when trying a tube amp for the first time, but it should be working out of the box and it isn't :(  I'm suspecting its a dry solder or similar problem with the tube board as pressing the tube downwards makes the buzz go away until released.

 

EDIT:  Let it cool down and removed and reseated the power tubes a few times.  Seems to have made touching the tube less likely to cause or correct buzzing.

 

Right, so gonna try some new tubes.  Any suggestions for both power and driver tubes I can get hold of pretty quickly in the UK.  I know there's a tonne of 'what tube' threads!

 

Thank you :)

 

EDIT:  It keeps randomly buzzing the left channel during quiet sections of music, winding me up!


Edited by LadFromWales85 - 7/23/10 at 2:32pm
post #4 of 5

Just swap the sides of the tubes...if the buzz follows the swap then you know that a tube is bad. Sometimes tubes will be noisy in there first 24-48 hours of use and will settle down after being burned in a little...as the other member has pointed out corroded pins could also be a factor.Cleaning the pins with Caig Deoxit or emery cloth is always a good idea for any tubes with corroded pins. Also remember to check the pins of the power tubes and also make sure they are seated fully in the sockets. It's not unusual for a new production tube to go bad in it's first few hours of use (although it's not an often occurrence with 6H30's).

 

Peete.

post #5 of 5
Thread Starter 

Sorry, I should have said.  The first thing I tried was swapping the sides of both sets of tubes.  The buzzing remains on the left channel.  The buzz doesn't change volume with the volume dial but turning up the volume can make it go away.

The pins don't look corroded but that doesn't seem to be the issue as swapping tube channels doesn't swap the buzz! :(

 

Going to reseat the driver a tubes a few times.  Powered the unit off while music was still playing, the left channel went dead quite a bit before the right channel, that continued playing for at least 15 seconds longer.


Edited by LadFromWales85 - 7/23/10 at 3:16pm
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