Blackstar cab-wrongly put 16ohm head into stereo cab input-help!

[witeter]

Hey guys i wonder if you could help-ive done something really stupid and only realised today. Two weeks ago I tried out a Peavey jsx and chose the 16ohm output and connected it to the 16ohm input of my blackstar cab. However i had moved the switch at the back of the cab to the stereo option. Later on during that session the amp started dying and i thought it was the tubes,etc-i played it about 1/2 an hour or so before it died.

Anyways, I had band practice today and i was using my mesa rectifier...and i notice that my cab is making slight noises after i stop playing-nothing huge but just like a small crackle. Now im getting worried that since i messed up the connection that something has gone wrong-the sound is fine but i have a suspicion that something is not quite right (ive only done that wrong connection that one time btw as i normally use the 4ohm connection for my mesa). I wont have a chance to open it up until tomorrow or day after. Any ideas of what could be causing the crackle? anything i should look for when opening it up? thanks!

[Twinfan]

Speakers could be blown if you play loud?  If you were using the stereo input, you were only using 2 of the 4 speakers...

[witeter]

Thanks twinfan- at practice yesterday the sound seemed fine, it was just that one crackle the speakers would emit when i would stop playing-is this normally a sign that speakers have blown? are there any tell tale signs? thanks

[Twinfan]

They crackle when you're not playing?  Sounds like a valve issue to me?

[witeter]

Yeah so for example after playing a chord,etc there will be a gap then a crackle (almost like interference, wires,etc) and then back to normal. So you think it may be an amp issue? i could swap tubes and see if it makes a difference. Its just that when i tried that peavey some weeks ago (which admitedly was damn old and prone to issues anyways) it went mental and starting making high pitched weird harmonic noises-so when i realised yesterday my connection mistake i assumed it was the cab and never assumed it could be my head...cheers man will look into it.
And when you said that by putting it in stereo i would've been using only 2 speakers from my cab, in theory it shouldn't have affected it then as it would've been like playing through a 2x12? also- the ohmage was still matched correctly. So i assume that this setting though wrong shouldn't have allowed the cab to go weird...right?

[Twinfan]

Try swapping valves around, particularly preamp v1 - that may well be your crackle issue.

When you ran your cab in stereo, the ohmage will have been different but only one step out (in stereo it runs at 8ohm, not 4 or 16).  That's usually OK and won't do any damage  :)

[witeter]

Ahhh i gotcha-well i really hope its not the cab as i love that blackstar cab.
yeah will try the powertubes first and if not will aim for the preamp ones. Thanks man!

[Frank]

Try swapping valves around, particularly preamp v1 - that may well be your crackle issue.

Connecting the wrong speaker load won't affect the preamp tubes. It may stress the output tubes and the transformer but the preamp tubes won't be affected. I'd check to see if the amp crackles with the volume turned right off, watch for any signs of red plating or arcing in the output tubes, check the output transformer isn't getting too hot. Any problems, replace the output tubes and rebias. If there's still a crackle then ditch the preamp tubes.

[Frank]

Actually, I'm not clear on whether you've used the wrong speaker load - what is the impedance when your cab's set to stereo? And where did you have the impedance selector set?

[witeter]

Hiya Frank, the blackstar cab at the back has 2 inputs and a toggle switch in the middle that goes from mono to stereo.
So i plugged in a Peavey head with an output of 16ohm into the blackstar cab 16ohm input BUT the toggle switch on the blackstar was switched to stereo instead of mono.

Ive changed powertubes on my mesa and the issue is still there. So i uncovered the preamp tubes and tapped them when having the amp at a reasonable volume and it seemed to me that the preamp tube at V1 was omitting a different sound than the others. Its hard to tell because its the first time i have done this. Ive so far ordered a new V1 preamp tube which hopefully should be with me in the next couple of days. Im assuming that if i swap v1 and the issue is still there i can try the new preamp tube in each of the other positions until i find the faulty location?

[JacksonRR]

IME, tapping V1 always sounds a touch louder. It's first in the chain after all. It's signal is amplified the most. I'd be looking inside the amplifier if swapping the power valves didn't work. Not saying a preamp valve can't be at fault, but I'd be sticking my nose in there to see if damage can be spotted. No sense blowing through sets of valves, not even JJs.

You'd be surprised what valve amps can and can't withstand though... I was swapping out 3 heads to use with one cab at one point and one time I ended up plugging the outputs of two heads together, turning one on(not standby, ON), leaving the room for a cig and a beer and it didn't do anything to either even though I strummed out a few puzzled chords before I turned it off.

[witeter]

Yeah thanks for that-the mesa i bought second hand a couple of years ago and i havent touched the preamp tubes but have upgraded the powertubes twice. So it could be that it simply needs a change of preamp tubes-remember that it wasnt this amp which i switched onto the wrong input, so it may just be a coincidence. Yeah its tricky to know about the v1 sound, but i guess its a good place to start with preamp replacement.

[JacksonRR]

oh.... Didn't sink in about which amp it was...  :oops: Always forgetting which amp is plugged in..

[witeter]

Yeah so even though the peavey died on me, i have never plugged the mesa into the wrong input and its this amp which is playing up-well im pretty sure its the amp and not the blackstar cab. Ive just tried it again basically theres a lot of humming and hissing which before was non existent, almost like when you get that crackling noise on old radios when scrolling through stations.

[witeter]

Actually the sound is more noticeable on the gain channel, so when i increase the channel volume to max and turn the master vol to 0 the noise is still there (yet reduced in volume) BUT when i turn the channel vol down to zero and turn the master vol all the way up i don't get any of the swishing sound. This tells me its the preamp tubes right?