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> Swapping Tubes In Tubeamp, How to do it?
Xuestor
post Jun 22 2008, 03:00 PM
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Hey! A couple of months ago I got myself an Switchblade 100w head, and it's everything I would ever dream of, so nothings wrong there.

I'm just curious about if I would be able to change tubes by myself. What I've heard is that if you just gonna replace old tubes with the same type, rebiasing and that won't be necessary, this is only if the tubes are different from the old ones, correct?

I would basically like to know a little bit more around this topic, cause i've read different things on different sites, and I don't really know what is right and what is not. Also, if anyone can describe different characteristics on the different tubes, that would be really helpful. The stock one's are 4 x EL34's.

Oh, just curious again, I know some people that have removed 2 powertubes to get lower output out of the amp, can this really be done in a safe way???

Cheers!

/Xuestor


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Ivan Milenkovic
post Jun 22 2008, 05:22 PM
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Don't know myself really, been hearing on different sites that putting out 2 tubes is a bad thing, and on other sites it is a good thing when it comes to diminishing power. Anyway, what I would suggest is that you really dig in the Internet in search for data about this topic. I would probably take the amp to amp tech first time and learned how to do it then.


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kjutte
post Jun 22 2008, 09:23 PM
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QUOTE (Xuestor @ Jun 22 2008, 04:00 PM) *
Hey! A couple of months ago I got myself an Switchblade 100w head, and it's everything I would ever dream of, so nothings wrong there.

I'm just curious about if I would be able to change tubes by myself. What I've heard is that if you just gonna replace old tubes with the same type, rebiasing and that won't be necessary, this is only if the tubes are different from the old ones, correct?

I would basically like to know a little bit more around this topic, cause i've read different things on different sites, and I don't really know what is right and what is not. Also, if anyone can describe different characteristics on the different tubes, that would be really helpful. The stock one's are 4 x EL34's.

Oh, just curious again, I know some people that have removed 2 powertubes to get lower output out of the amp, can this really be done in a safe way???

Cheers!

/Xuestor


Easy to change valves (just pull em out and insert new ones (remember to clean off the fat from fingers, or they break faster)) But if you change to another type of vavle, you guessed it, you have to reconfigure the 'standby current'.

These vary from each tube type.
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Andrew Cockburn
post Jun 23 2008, 12:30 PM
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Hi There!

FIrstly, if you stick to the same brand and same type of tube, you can probably get away without re-biasing although strictly speaking you should always re-bias for optimum operation.

Secondly - don;t take the tubes out to reduce the power! If you do that you also need to change the impedance of the Output Transformer to compensate (which means a re-design of the amp!), otherwise you risk an impedance mismatch whoch in the extreme could blow up parts of your amp, although you would probably get away with it ...

The bast way to keep the tubes working but lower the volume is to use a power soak - better yet, for practicing at home get yourself a low output amp, (5W is plenty loud enough) and practice with that!


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buttmonk
post Jun 23 2008, 05:42 PM
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Hi there,

As far as I know there are auto-biasing amps and manual biasing amps, but someone like Andrew probably knows more about this. I have been swapping tubes from different manufacturers in my Tiny Terror and found that at least with pre-amp tubes it can make a surprisingly big difference to the sound. Going from stock tubes to JJ/Tesla tubes added extra gain and freed-up the sound. I would recommend playing around just to see how it changes the tone depending on the biasing issue.

As far as I know u can't change the type of tubes e.g. if you have EL34s then you need to replace them with EL34s, but EL34s from different manufacturers will sound different.


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