I would think so too - but the problem stays the same even with an entirely different tube configuration. So it seems quite impossible to me that multiple sets of tubes should show exactly the same issues.

Example:
Configuration 1: 3x 6N1P + 5U4G = strong hum in both channels, hiss & crackling in left channel.
Configuration 2: 1x EH 6922 + 2x Amperex 6922 + RCA 5Y3GT = medium hum in both channels, hiss & crackling in left channel.
Configuration 3: 3x JJ E88CC + GE 6087 = medium hum in both channels, hiss & crackling in left channel, audible distortion in medium and high listening volume (the last issue is most likely caused by the poor quality of the JJ tubes).

OK,  Indeed it would be unlikely for everything you've tried to be crackling on the left channel.

Either the left side (pins 1, 2, 3) of the input tube, or the left output tube circuit is likely at fault.  The fault is most likely to be either A) a bad solder joint on pins 1, 2, 3 of the input tube, or any of the 8 pins used on the output tube.  B) a bad plate resistor on pin 1 of the input tube.

To find out if the crackling is in the input stage or the output stage, wait until it is crackling again and then remove the input tube while the unit is still on.  If the crackling stops we know the problem is the input stage.  If it continues, we know the problem is the left output stage.

Steve

Lord Soth....The tube isn't going to be any cooler if you pull it out while its running Sorry I couldn't help it.

I use one of these jar lid removing round circular rubber pads, (stole it out of the kitchen drawer) to hot swap tubes on certain amps. Other wise I just use my bare hands. Just make sure you know where you are going to set the hot tube once you've pulled it out. You don't want to hang on to it any longer than you have to.

I hope you get this figured out, it can be frustrating, I know....

Zygi

Alright, I tried to remove the input tube and then checked again. Result: No more hissing and crackling with the input tube removed. I guess we can safely narrow it down to the input then?
I didn't know either that the tube could be removed safely while the amp is running. Also, I managed to keep the burns to a minimum - the input tube gets much less hot than the other ones. I guess with some gloves you wouldn't even feel a thing. Real men use their bare hands of course.

Anyway, how to proceed? Steve, do I have your permission to open up the amp and take a look inside? Just making sure, I don't want to void my warranty.
If it's just a bad solder joint on the tube socket I should be able to fix it - I do know how to solder and have the equipment - but if it's in any way related to the electronics I'll stay away from that. In any case I could take a few pictures of the inside and check if there's anything nasty.

Hi Mad Dude,

Glad to hear that you "survived" the  hot-swapping exercise.  ;)