KVR Audio

seamoss · Post by **seamoss** » Fri Jan 13, 2006 1:51 pm

I need to replace the tubes in my fender twin and I was curious if this was something that's easy to do or should I only use a qualified professional?

bias...etc...

egbert · Post by **egbert** » Fri Jan 13, 2006 2:01 pm

I would humbly suggest - save yourself the grief and get someone who has the tools and knows what they are doing to do it. A tube amp wiz with a lot of experience and a selection of tubes might even be able to voice it to suit your preferences.

G&L_player · Post by **G&L_player** » Fri Jan 13, 2006 2:13 pm

seamoss wrote:I need to replace the tubes in my fender twin and I was curious if this was something that's easy to do or should I only use a qualified professional?

bias...etc...

No biggie!

The KEY, is knowing/buying the correct replacement tubes. Once you have them, they're a cinch to swap. If you put the wrong tubes in, you might be disappointed. What kind of amp?

zeoy · Post by **zeoy** » Fri Jan 13, 2006 2:14 pm

I 've changed mine a few times. Not hard at all. BUT my amp is fixed bias so there's no need to tweak anything. Don't know about the Twin...

seamoss · Post by **seamoss** » Fri Jan 13, 2006 2:19 pm

G&L_player wrote:What kind of amp?

It's a Fender "The Twin" produced in the late 80's early 90's

http://www.ampwares.com/ffg/twin_redknob.html

Jafo · Post by **Jafo** » Fri Jan 13, 2006 2:36 pm

You can do it yourself, but setting the bias is another matter.

One good way -- but not the only! -- is to go with Groove Tubes, and have somebody bias it for you. The advantage here is that as long as you use the same tubes and the same hardness, you won't have to re-bias. Just swap out and in, and you're done. Well, modulo perhaps a few screw turnings.

Another good way is to bite the bullet: buy a biasing kit and learn to use it. If you change tubes a lot, this will be cheaper than paying somebody else.

Not biasing, is another strategy. But your tubes will probably suffer.

fabio_gonazales · Post by **fabio_gonazales** » Fri Jan 13, 2006 2:37 pm

There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.

Jafo · Post by **Jafo** » Fri Jan 13, 2006 2:43 pm

fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.

Good advice indeed! 'Nuff said.

G&L_player · Post by **G&L_player** » Fri Jan 13, 2006 2:51 pm

fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.

I'd go along with that, if the strategy is to just get it done, as opposed to learning how, for future changeups. If you go this route, you'll surely pay more for tubes. Replacing all of the tubes in a Twin (I had one ver similar; "The Twin"; no red knobs) is going to cost some bucks, particularly for Grooves. I'd call around and get some pricers, firstly, else you may be surprised when you get the amp back.

seamoss · Post by **seamoss** » Fri Jan 13, 2006 2:53 pm

G&L_player wrote:
fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.
I'd go along with that, if the strategy is to just get it done, as opposed to learning how, for future changeups. If you go this route, you'll surely pay more for tubes. Replacing all of the tubes in a Twin (I had one ver similar; "The Twin"; no red knobs) is going to cost some bucks, particularly for Grooves. I'd call around and get some pricers, firstly, else you may be surprised when you get the amp back.

like what type of price are you talking about?

egbert · Post by **egbert** » Fri Jan 13, 2006 2:55 pm

fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.

High Voltage DC is a good way to kill yourself

In tube amps, the high voltage output from the power transformer is rectified but then the AC frequency ripple needs to be smoothed out by some big high voltage caps which store a fair whack of charge. Even after you turn it off these take a while to discharge - depends what sort of arrangement is in place to discharge them - if any. So even some time after you turn if off there can be high voltage DC in there and it can still be lethal - if you get in there and touch the wrong things you can give it a convenient route to ground ...

Hink · Post by **Hink** » Fri Jan 13, 2006 2:58 pm

fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.

the only pent-up eletrcity would be in the the caps...I have changed tubes on many amps with no problem, if you're concerned leave the amp unplugged for 24 hours...but no one has asked the obvious...is this a full scale change ot just power tubes, or jut pre-amp tubes?

I did not like my Plexi after I put in Groove Tubes, just to let you know. That' when I bought a Boogie...if you're not using boogie tubes make sure the lot numbers are the same...as long as your tubes are matched you should be all set...boogie has all the tubes matched so matching isn't a concern...

Hink · Post by **Hink** » Fri Jan 13, 2006 3:01 pm

btw boogie makes tubes for all amps...all totalled you're likely looking at between 125-150 bux depending on what tubes you use...the power tubes cost yah the most...

seamoss · Post by **seamoss** » Fri Jan 13, 2006 3:04 pm

Hink wrote:...but no one has asked the obvious...is this a full scale change ot just power tubes, or jut pre-amp tubes?

well....not sure. None of the tubes have ever been replaced and this amp is about 13 years old.

the lows are pretty muddy.

guitar, organ, synths.....are some of the things I run through it and I usually run it pretty clean.

G&L_player · Post by **G&L_player** » Fri Jan 13, 2006 3:04 pm

seamoss wrote:
G&L_player wrote:
fabio_gonazales wrote:There is a lot of pent-up electricity in a tube amp. A professional can change your tubes and bias everything correctly in minutes. You could fry yourself. I'd let someone else do it.
I'd go along with that, if the strategy is to just get it done, as opposed to learning how, for future changeups. If you go this route, you'll surely pay more for tubes. Replacing all of the tubes in a Twin (I had one ver similar; "The Twin"; no red knobs) is going to cost some bucks, particularly for Grooves. I'd call around and get some pricers, firstly, else you may be surprised when you get the amp back.

like what type of price are you talking about?

Let's see...the 6L6's are about $35-$40 a pair. I believe that there are four of them in a Twin. The 12AX's are about $15-$20 each. I believe there are 6 of these guys in the Twin. A service shop is most likely not going to discount the tubes at these prices. So you have about $160 or so...just in tubes, and this is working off discounted prices that you prolly won't get. Go figure...

re-tubing a guitar amp