Tube Amp Question

[halfwhit]

Hey guys,

Probably not the right place for this question, but I'm gonna take a chance that someone knows the answer.

I'm playing through a Peavey Valve King 100w head (on an Ampeg 412 guitar cab with Eminence speakers...thing moves a lot of freakin air! but I digress...)

I've been thinking about playing around and trying different tubes. Someone told me that replacing the 6l6's with KT88's would really warm up the sound. Of course, I'm playing through a fixed bias amp. So the first question. Would it be worth having somebody mod the amp so it could be rebiased for the bigger tubes? Would they even fit...

Second question. Someone said jumping on a set of NOS 6L6's would make a difference too. What I've found is that you can practically steal a set of Russian military surplus 6P3S tubes from the 60's and 70's. Allegedly, 6L6's are a direct match to 6p3s. Can anyone back up or shoot down this theory? Would the tubes still need to be "biased" or is it a plug and play kind of deal there?

Hope you're all well! Starting my next guitar project pretty soon so I'll be posting pictures

-Whit

[Ripthorn]

As for the 6l6 6p3s question, you can compare characteristics using the data sheets at frank.pocnet.net (my favorite tube resource). You will want to check the heaters (this is a common problem with Russian tubes, where they only accept parallel heaters and a lot of amps will use series) as well as plate resistances. As for the KT88's they are a lot more inefficient, much larger in size, and your power transformer may not be up to the extra load. I would suspect that a production amp would have a PT with only a small amount of leftover power, so putting something that is that much more hungry for power could cause a large draw that could potentially blow out the PT. Of course, you can take it to an amp tech to check out, but unless you are really unhappy with the sound of the amp, I would either go with real NOS 6l6's or just stick with what you've got.

[Paul Marossy]

As for the 6l6 6p3s question, you can compare characteristics using the data sheets at frank.pocnet.net (my favorite tube resource). You will want to check the heaters (this is a common problem with Russian tubes, where they only accept parallel heaters and a lot of amps will use series) as well as plate resistances. As for the KT88's they are a lot more inefficient, much larger in size, and your power transformer may not be up to the extra load. I would suspect that a production amp would have a PT with only a small amount of leftover power, so putting something that is that much more hungry for power could cause a large draw that could potentially blow out the PT. Of course, you can take it to an amp tech to check out, but unless you are really unhappy with the sound of the amp, I would either go with real NOS 6l6's or just stick with what you've got.

Yeah, I agree.

[Tim37]

i wounldnt jump on changing tube type quite yet there are too many brands of 6l6's out there all with a slightly diffent flavor. look up some reviews on diffent tube brands and see if you can find some that will get you a little warmer. also dont forget your preamp tubes you can change the way a amp sounds and responds with them. check out the JJ tesla they have a good rep i have tried them and where happy plus they wont cost you a arm and a leg.

i did a quick search and found that your amp should have soveteks in it from my experience not the best sounding tubes out there, i had a crate with them in it and changed to preamps to groove's and the power tubs to jj's and it made a world o diffence in the amp still not a great amp or any thing but not so bad.

[verhoevenc]

Slightly off topic... but I'm a complete noob when it comes to dealing with tubes. I realize he's looking to change his for tonal reasons, but since I have you all here this might be a good time to ask you guys about changing tubes for other reasons. How does one know when a tube is done, should be changed, etc. etc.? How do you know WHICH tube it is out of the XYZ number your amp may have?

Thanks,

Chris

[Tim37]

diffent ways

reduced volume is usualy the way a good tube dies

fluxuations in volume

gets progressivly muddier

microphonic starts to hum or get a feedback sound to it.

color change IE: blue changes to orange glow.

i have had two go out on me one went micro phonic the other just went got muddier until it sounded like garbage that was the hard one i though the amp was dieing. im sure there are more ways than that but these are the ones that i have read/heard about. if its a preamp tube you can replace them one at a time but on the power amp even if its cathode biased you need to buy matched pairs and change them together. be sure on a nonself biasing amp to have it rebiased or get a meter and do it yourself.