XXX Tubes

I have a tube question. I have a Peavey triple XXX head and would like to know how much the sound will differ by changing to EL84's instead of the stock 6L6's. Also changing the stock 12AX7's. What brand tubes would be the best, and are there different tonal qualities between the brands? I guess you could say I'm looking for somewhat of a marshall crunch but with the extra edge the XXX adds. I would also love to be able to achieve a bluesy marshall crunch as well. One more question....the distortion channels don't respond to the volume knob of my guitar (PRS custom 22) very well (as in going from moderate gain to slight crunch/bluesy to clean). Would changing the tubes out help this out? Any help will be greately appreciated!

Thanks

[Edited by PRSplaya on 09-02-2003 at 02:48 PM]

Hey Playa, first off I'd just like to say that I'm not very familar with the XXX, and also that anyone with enough time and money can make something work if they have too, having said that let's take a look at your situation, First off the swap to EL 84's would probaly be more expensive than you would be willing to pay, the EL 84's have a 9 pin base, 6L6's have a 8 pin base, so the tube sockets would have to be replaced and rewired to accomadate EL 84's, which leads to the next problem, the XXX being a modern high gain amp built to use 6L6's, it probably is running about 500 volts to the power tubes, way too much for EL 84's, so the power transformer, power supply, bias circuit and probably the output transformer would have to be replaced and redesigned, basically you would have to rebuild the amp, replace all the most costly components and pay someone to do it, I don't really believe you want to go that route, but their are some alternatives we can look at, but I think it is best to warn you now that you are probably not going to be able to get everything you want, first off, yes, different tube brands normally sound a bit different, and alot of manufacturers offer several different variations of the same tube with somewhat varied sound, also some tubes types can be swapped around to change tone, 6L6's, 5881's and KT 66's all fit the same base and wiring, the bias would have to be adjusted but they all work, probably your best bet is to try different pre-amp tubes, 12AX7's can sound very different, some cleaner, some alot dirtier, also pre-amp tubes can be swapped for diferent tubes, see 12AX 7's have a gain factor of 100, you can substitute a lower gain tube, 5751's (SRV favorite) have a gain factor of 70, 12AY7's a factor of 44, swapping in any of those would give a more bluesy tone, and if it was me I would give them a try but no matter what you do I think you are going to be wrestling with a major obstacle, Design, the XXX probably has a very high gain pre-amp design and the master volume circuit design is probably more suited to Metal than blues, you can work around this to a certain degree, try turning the master volume up and the channel volume down, that way you aren't driving the pre-amp so hard, if you drive the pre-amp hard you won't be able to control the crunch to milder distortion with the guitar volume like you want to be able to do and some pre-amp designs are so high gain that it's hard to get anything less than crunch out of them, I think the best advice would be to take the amp to a good shop that is familar with the XXX, tell them what you are trying to do, that you are willing to try different tubes, pre-amp tubes,etc, and see what they recommend, they may even let you try some different tube types to see what gets you closest to what you want, I would look for some one that runs a small shop, loves what they are doing and is good good at it, the larger "Guitar Mega-Store" type places don't usally want to give you the personalized service that you'll want for something like this, I hope I have given you enough information so that you be able to see the possibilities and choices that you have, if you need anything else just ask....................

[Edited by pstring on 09-03-2003 at 01:07 AM]

I'm sorry, I had the EL84 and the EL34 mixed up. I was actually talking about the EL34's. The amp had a bias switch that lets you switch between 6L6's and EL34's. What are the different tone characteristics of the EL34's as aposed to the 6L6's? I'm glad you mentioned the bit about the master volume and channel volume. I will defanately try turning the channel vol. down and the master up. If nothing else, I have a PODxt that I might try putting in front of the amp and setting it to bypass any amp modeling and just use the effects. Possibly using the tube screamer setting to get that bluesy sound I'm looking for and the classic dist.(rat) setting for the more rock crunch. btw...which pre-amp tubes will give me a warmer and and not so crisp high gain sound? On the ultra(higher gain channel) I only have the gain at 10 or 11 o'clock. So I still have alot of gain to play with if I choose lower gain tubes (if that's how it works). This is the first all tube amp I've owned, besides a '65? gibson GA-5 Skylark that doesn't work...lol. I really need to have it overhauled. I've heard it's got some great tones. So, I'm pretty new to all the tube stuff. Also, does anybody have any experience with a Peavey classic 30? I want to get a 1x12" combo amp, and want all tube. The 3 amps I'm looking at are the peavey classic 30, a fender hot rod delux, and a traynor ycv40. Thanks for all the great help!

I was just getting ready to ask if you meant EL34, I just got off from the Peavey website and saw that the XXX was switchable from 6L6 to EL34, the EL34 is probably what you want to use if you are trying to Marshallize your sound, the EL34 was used in the classic Marshall amps and it's been a pretty common swap in tube amps to try to capture more of that type of sound, the EL34 distorts a little sooner than the 6L6 but has a softer, warmer type of sound, anytime you are changing power tubes the bias should be checked/adjusted, I don't know if the XXX has an adjustable bias since I can't find a schematic for it, but a good tech will know how to set the bias if it needs it, as far as pre-amp tubes go I like EH and Groove Tubes, they both seem to be cleaner sounding than say Sovteks or alot of the china tubes that alot of manufacturers put in their amps, I don't know what came in your amp, but Peavey is very China friendly and if the tubes are marked with the Peavey brand name lets just say that they probably weren't made in Mississippi. Being new to tube amps it's easy to get carried away with cranking up the channel volume and turning down the master, when you do that you are driving the pre amp to distort and thats mostly what you are hearing, power tube distortion is softer, warmer and doesn't have that grainy, grinding type of fuzz box sound that pre amp distortion has, if you have a place where you can really crank it up, set your master on about 8 or 9 and then start turning up the channel volume, you'll hear alot smoother distortion, well keep playing with the knobs and have fun!.....................

Thanks for the help pstrings. Eventhough the amp has a bias switch to switch between the tubes, will it still need to be checked or will it be as simple as plugging the new tubes in and flipping the switch? Also where would the best place be to get new tubes? Would it be safe to buy them over the internet or better to buy them from a dealer? I actually live in Mississippi about 150(give or take)miles from meridian where the peavey plant is(just a little FYI).

The bias switch is only to increase the bias to a preset level when switching to the EL34's, basically it's switching between resistiors to increase or decrease the bias , the question is how much? too much? not enough? Can't normally tell unless someone checks it, if it's not set right it can drastically reduce tube life ( Remember you are buying 4 EL34's, not cool if they only last a month), weak sounding amp, hum, dirty sounding, weird distortion, it's just good sense to get it checked, you are protecting your investment and making sure the tubes are all good and the amp will function like you want it to. Buying Tubes off the internet will probably save you some money, but if you have any guitar dealers around that carry tubes it might not be a bad idea to talk to them see if they have any reccomendations, compare their prices, just be aware they will probably only reccomend the brand they carry, the best of the best is to find someone that really is a tube amp specialist, that has some years in the business and a good rep. Hey ever been to Yazoo City?...

I was there a little while back with an ex girlfriend to see her mom. Besides that, it's been a while. Any particular reason you ask?

Just always thought that was a cool name for a city, and I'm a Jerry Clower fan, spent alot of time in the south but never been to Mississippi.........