hi guys, here is my situation, last band practice my amp was putting out horrible feedback and fizz when the gain got even close to half way on the crunch or super crunch modes, my first though was valves, however i have looked at the valves, the all look exactly the same as in i cant distinguish which one if any has gone, i tapped them with a pencil as advised, one of the power valves makes a slightly different sound to the other, but this is very light, im not even sure if its enough to warrant a verdict on the valves situation, it just sounds slightly more hollow but there is no out put from the speakers when i tap either....so first of all any more advice on how to check if this is a valve problem or something else?

secondly i was wondering, the amp in question is a blackstar s1-45 combo and the multi fx i use is a pod hd 500x, normally i run the pod through the fx loop on the amp which works fine when i have a fully functioning amp, so i was wondering if anybody knows if there is a way to completely cut off the pre amp from the blackstar and literally use it as if it was a 2x12 cab and connect the pod that way so i literally just use the speakers from the amp and take everything else out the equation/chain??

any thought or advice please guys?
You should be able to plug the POD straight into the FX return on your amp.
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Disconnecting the preamp doesn't make it literally a cab. Do what Gary suggested and it's literally a cab and power amp. A Pod can't adequately drive a cab.
If you problem is in the power amp side of Blackstar the only thing to do is get it fixed, there would be no bypassing it unless you got another amp and ran it directly into the Blackstar speaker/cab
You could buy a single preamp 12ax7 tube and power tubes(power tubes are usually sold in sets of 2 or 4), and swap the tubes out one at a time to see if you come up with a bad one. Tubes will go bad so having extras is a smart move anyway.
Last edited by mcamp12302 at Oct 22, 2014,
A POD like you have is basically a digital preamp with no power amp so it cant drive a speaker without help.
Send into FX return. I do it with my HD500, sounds great.

Remember to hold down VIEW> Page 4> Mode: Stack Pwr Amp (or Combo if you're using a small combo amp)
If you don't do this, you're basically putting a guitar cabinet into another guitar cabinet and it'll kill the frequencies really bad.

You can also turn off the cabinet in the chain if you don't want the cabinet emulation to play any part in your chain. It's nice if you want to give your cabinet a different voice, but if you just want your cab, then turn it off.

You can also use an amp pre instead of a full amp. This will turn off the power amp simulation.

Choose which one you think sounds best.
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