My amp did something weird

[Dreig]

Now, I am not exactly sure where to put this thread, so if a mod disagrees with my choice of forum feel free to move it, but honestly I am pretty stumped here, because I am unsure of what even caused the issue in question. My bet is on the amp but could be pedal or cable or maybe even my bass itself, but I have no exact idea honestly.

Ok, so we were practicing during the weekend. I run my bass into a Warwick Tubepath 10.1 with a Warwick WCA 411 Pro cab. I have a pedalboard connected to FX loop, that contains BOSS pedal tuner, a compressor, MXR Octaver, EHX Bass Soul Food, OKKO Motorbass and a tremolo pedal. We were going too loud so I made some adjustments, I turned down drive and volume on the head and also a little bit on OKKO Motorbass pedal. I pluck a string to test it and lo and behold, is too silent now, with barely any distortion, so I turn it up a little... and the volume and distortion stays the same. I start turning it up and up and it get only slightly louder. I do the same on pedal, same results. I shrug it off, thinking I am maybe going deaf at last and we start playing. Then, about a minute into the song, the volume suddenly just kicks up, along with the distortion in full blast. I had to pause and bring it down.

I was not moving much, just standing there no sudden movements, I did not touch any knob, button or pedal. I just came on it's own. What could have caused it? Now my guess is that it has to do something with the heat in our practice room was the cause because it makes my amp's fan go crazy. We even have to take frequent breaks to go cool off in the hall (that is due to the fact we cannot open the soundproofed windows, since some butt from an apartment block a mile away keeps complaining of loud music coming from our room... sometimes even when there is nobody there) but that still sounds weird. I mean if anyone has any idea what could have caused the unexplained muffle that suddenly just went away, that would be AAA++ thanks

 

[Nighttrain1127]

It could be a thermal issue if the amp got too hot it may have a protection that drops the output until it cools back down. Also if you could put a fan somewhere blowing on the amp to move more air over it that could help things not overheat as much

 

[dbase]

Bass getting loud? .. I see nothing wrong.

 

[LKTraz]

I'm inclined to agree with it being some form of overheating protection.
As Nighttrain1127 suggested, a fan to get more volume of air moving is a good idea.
It might still happen but it will probably take longer or a much higher air temperature.

 

[Jim Bergantino]

I would unplug everything from the amp and just go straight into the amp and see what happens. If all is well add one pedal at a time and retest. Given your signal chain it would be virtually impossible to diagnose without going thru a process of elimination testing scenario. I suppose you could do it in the reverse order too. Have everything hooked up and get it to act up and then remove one pedal at a time. There’s so many things it could be in addition to a thermal condition. Bad component, cold solder joint, cable, even a potential oxidized connections. At the very least you should try to get it down to one of the pedals or amp and then go from there.

 

[Dreig]

Thanks for all the suggestions,

Next rehearsal is Saturday so I will try the additional fan first. Should it happen again, I will try fully disconnecting the pedalboard, then reconnecting pedals one by one.

 

[BassmanPaul]

Most Effects Loops work a line levels for rack mounted effects. Regular pedals should be wired in front of the amp as they are instrument level.

 

[beans-on-toast]

A pedal might be getting overwhelmed and thermally shutting down. A bad pot can cause a problem with non-sensical volume changes.

As was mentioned, break the setup down and add one thing at a time to isolate the issue.

 

[abarson]

+1 to what @BassmanPaul . Don't send your pedals through the effects loop.

 

[Dreig]

Ok that part for no pedals in FX loop is a new one to me since there are lots of videos like "these pedals sound better in FX loop durr"

Also I seem to have discovered the issue. The pot for drive is faulty and it drops drive level to zero for no reason,with occasionally knocking it up to max during this state. It would go like this - the amp goes silent and mumbling (like when you drop drive to zero) and once in a while it goes into loud overdrive (again, as with drive turned up to max) for a short half a second burst. Turning the knob up and down from max to min a few times remedies the issue. So it is not heat, because I just started it up (letting tubes warm up of course) and also it is not an effects issue as they were all disconnected during the time.

 

[LKTraz]

The pot is either worn or has dirt in it.

Try opening the case to get access to the back of the pot and there should be a small slot in the casing. Spray contact cleaner in it and work it quickly to both extremes. Repeat after about 40 seconds. If the problem persists then you need to replace it.

It wouldn't be a bad idea to clean all of your control pots while you have access to them.

 

[BassmanPaul]

Many a fine amplifier has met it's demise through the indiscriminate application of 'Contact Cleaner' that 'cure all' spray. You should only use Deoxit D5 spray and then just the tiniest amount. This is a case of less is more kinda thing.

 

[BassmanPaul]

As you were using the Effects Loop incorrectly it could still be giving you problems. Use a short signal cable between the Send and Return and see if it helps.

 

[Dreig]

As you were using the Effects Loop incorrectly it could still be giving you problems. Use a short signal cable between the Send and Return and see if it helps.

Is it really bad to run pedals through loop though? I hate having having them after instrument, because I often need to lower volume on my bass and that neuters them if they are on instrument level. It does not happen in loop

 

[BassmanPaul]

I doubt you'll cause any damage per se but you could overdrive the pedal's input stages. The output from the pedals might not be able to drive the Return properly.