#1
when should i change the tubes in my ashdown fallen angel? and also, do i have to swap them for the same make (exactly the same tube) at the moment there is 2 EL34s in there
GEAR

ESP LTD Viper 400 with EMG 81s
Jackson Dinky DXMG with EMG 81/85
Ashdown Fallen Angel 60 DSP
Ashdown Fallen Angel Cab 120W 4X12
Keeley Modded SD-1 Overdrive
Korg DT-10 Tuner
Noise gate (cheap)
EQ (cheap)
#2
tubes on average last a year or 2 with normal use, depending how much you play. You should be able to hear the difference when they start getting old. A lot of times it will start sounding dull, and seem to lose some volume. You can use any brand, as long as you get the amp biased, and you get a matched set of tubes. Different brands will have different characteristics to their tone. If you swap them for the exact same kind, you might be able to avoid biasing, but it's still a good idea to have it done. It balances the amp to run the tubes at the best tone with longest tube life, depending on the values of the matched set of tubes. When they match them, they test a bunch to find a group with the same values.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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#3
does it cost alot to have them biased, also, wot would it sound like if i changed the tubes to 6L6s
GEAR

ESP LTD Viper 400 with EMG 81s
Jackson Dinky DXMG with EMG 81/85
Ashdown Fallen Angel 60 DSP
Ashdown Fallen Angel Cab 120W 4X12
Keeley Modded SD-1 Overdrive
Korg DT-10 Tuner
Noise gate (cheap)
EQ (cheap)
#4
it shouldn't cost a lot, it's simple process with the right tools. I'm not sure how it will sound, that depends on the amp. Eurotubes has a little description of the different tubes, and The Tube Store has some reviews.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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#5
all bias is is making both tubes read the same voltage so they run the same power wise.

its simple...one of the power tubes runs direct...and the other has a pot you can turn...read the first power tube's plate current...then match the second to the same voltage by turning the pot.

(i'm sure my terminology is all wrong..thats my ghetto way of telling you how)...its really simple though.
Quote by deg0ey
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1996 Les Paul Classic w/ Alnico II's
Marshall Jubilee 2550
Avatar 2x12..V30 and G12H
Vox V847 Wah
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#6
Eurotubes as a good description of biasing and the difference in EL34 and 6L6

Quote by Eurotubes
There are several different ways to bias a tube amp. The two main methods of biasing an amp are what I?ll call the old school methods. The first is using an oscilloscope to monitor the sine wave output of the amp while the amp is being driven with a signal generator. A fair degree of technical know how and experience is necessary when using this method. The second is the transformer shunt method which involves working very closely with extremely high voltages and I do not recommend using this method.

The newest and by far the easiest method of adjusting bias is by using a bias probe. This is a device that looks like the base of a 6L6 type tube which is installed in one (or two if it?s a dual probe) of your sockets. Your tube then goes in the socket in the top of the probe. Some probes need to be used with a multimeter and some come with built-in milliamp meters.

Some old schoolers don?t think much of the bias probe method but I can tell you from experience that it not only works but it works very well. I?ve compared the two methods extensively and I very much prefer the probe over the scope method, especially for guitar amps. All you need to know to bias your amp using a probe is what the plate voltage is which is measured from pin#3 to ground. Once you know this then the formula is simple. Divide the plate dissipation of your type of power tube into the plate voltage. This will give you the maximum plate current which should never be exceeded.

We will use the plate dissipation for a standard 6L6 for this example which is 22 watts. Example: 22 watts divided by 500 plate volts equals .044 or 44 milliamps of plate current draw at idle. The 44mA should never be exceeded! Then multiply the .044 by .75 or 75% which equals .033 or 33mA. This is where your power tubes will be out of crossover distortion and will perform very well. There is an acceptable window of correct bias and if you want a warmer tone or what some players refer to as a "brown sound" you can use up to 90% of the maximum current formula which would be 40mA rounded off. Your tube life will be a little shorter at this setting but only by about 20%. However, I would NOT recommend this for Chinese tubes or tubes that are sold by the Big guys that have been remarked unless you know for sure what tubes they really are. The JJ Electronic 6L6 is a very stout tube and JJ claims that it will dissipate 30 watts. Since I like to run my gear pretty hot I will routinely bias them at 50mA in an amp that has 485 plate volts. The tone is very warm and the tubes stand up very well. I tortured a quad in my Fender twin for a year, set at 50mA at 480 plate volts and they were still going strong until I swapped them out for a quad of KT88?s but that?s another story....

#5. How will changing from 6L6's to EL34's affect my tone?

This is a very frequent question and although there is no perfect answer that fits all amps I can give you a pretty good idea what to expect. I've swapped EL34's and 6L6's around in Marshall's, Fender's, Mesa's and Peavey's to name a few and the results are basically the same. EL34's in general don't have a low end that is as deep as a 6L6 so EL34's tend to sound hotter in the mids. EL34's breakup a little earlier then 6L6's and the harmonic content of the mids and highs are more prominent. These differences become more noticeable as volumes increase. You have probably heard the term "Marshall crunch" used before. This term is used to describe the sound of EL34 type tubes when they are being driven into distortion. So if your looking for a great Classic rock tone with lots of complex mids you might want to try some EL34's. The JJ E34L's will crunch up real nice but they do have a deeper tighter low end than a standard EL34. If you like a big low end thump then I would stick with a good 6L6 unless you have room for the JJ KT88's which have a BIG low end but sound more like EL34's in the mids and highs.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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