My Carvin Legacy needs a tune-up!

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Posts: 286
Joined: Tue Sep 20, 2005 12:18 am

Well, It's been a while since I've been on the forums, however I figured i would be able to get a good response from all of you. I've had my Carvin Legacy head for about 3-4 years now. I've never changed the tubes, even when I bought it used at Guitar Center! Yet it still gallops like the stallion it is. However It's really beginning urking me how dull it sounds. I FINALLY am financially able to replace the tubes now so I was wondering how I should go about this? Purchase the tubes online and replace only the EL34's? Should I get it checked out by a technician as well due to lack of regular maintenance?

Also I have questions about this "bias" thing. I wouldn't have to adjust that if I get the exact same tubes? or would I still need to?

Thanks! :D
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Joined: Fri Jun 22, 2007 2:18 am

Eutow wrote: Also I have questions about this "bias" thing. I wouldn't have to adjust that if I get the exact same tubes? or would I still need to?
Thanks! :D
If you had a Mesa Boogie amp then yes just put the same tubes and its fine but not with a legacy it would likely need to be rebaised

i'd suggest finding an amp repair man to do the job, esp since it was purchased used and you've had it quite long

get it tuned up/retubed and biased shouldnt be too much but it will be worth it and probably last you another 3-5 yrs.
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Joined: Fri Sep 30, 2005 4:54 am

Jeries wrote: If you had a Mesa Boogie amp then yes just put the same tubes and its fine but not with a legacy it would likely need to be rebaised

Tubes get measured. If they have the same code, you don´t need the amp to be rebiased. Also the fixed BIAS of a Boogie is a myth.
I actually don´t know why the hell they muck people like that. It´s obvious.

If you wanna change the sound of your Legacy, I suggest to get different pre-amp tubes before changing the power tubes. They don´t need to be biased. But change the power tubes as well. The power tubes and the pre amp tubes will change your sound. Depends on what you get.
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Posts: 89
Joined: Tue Aug 05, 2008 3:54 am

If you've had the amp for 4 years & used it a fair amount but not changed the tubes it's probably not a bad idea to change them all.
I would strongly recommend that you re-bias the amp after changing the power tubes if you want to get the best out of the amp, even if they are still EL34's and even if they are of the same type.
Tubes can vary considerably even if they are supposdly "matched" & also other factors can effect the bias over time such as the age of resistors capacitors & other parts of the circuit. I know this from experience! It's true that if you buy a matched quad of power tubes they should in theory be the same within a certain percentage....however they may be damaged in shipping and also the amps circuitry itself can alter the bias of each individual tube once it is fitted into the tube socket, particularly as the amp gets older.
If you don't check the bias you will not know this.

Here are some links to some instructions on how to Bias the Legacy using either the standby switch method or using a bias probe.
It's really not that difficult, but you need to be careful as you are dealing with lethal voltages in excess of 400V!

I would recommend the bias probe method as this allows you to measure the bias of each tube individually which will highlight any mismatch between the tubes such as one that is maybe a dud.
Using the standby switch method you may not notice this & if you have one tube which is out this may result in you setting the bias for some of the tubes too hot.
Carvins factory recommended Bias setting using the standy switch method is 100ma, this is across all 4 tubes and is very cold.
The reason it is set so low is to allow you to swap & change tube types with a reasonable margin for safety.
So if you opt to just fit new tubes and not change the bias there is every chance that you may not damage your amp, particularly if the bias was previously set around this level but as I said if you want to be sure & also get the best tone from the amp it's always best to re-bias.

One important point to remember if you decide to have a go is make sure the power switch is set to the 100W setting or you will not be setting the bias correctly.

A bias probe & a decent meter will not cost you much & once bought you have it forever.

Also last of the links below is a sheet I made up for recording the bias readings on my amps if it's any use to you.
If you want it in MS Word format so you can edit it PM or e mail me.
Good Luck!" onclick=";return false; ... _vl100.pdf" onclick=";return false;" onclick=";return false; ... 4&hl=en_GB" onclick=";return false;

If you look at this last link you will see it has the results of the most recent set of bias readings from my 3 Carvin amps.
If you look at the bias readings for each tube (particularly the X100B which is as it came from the factory!) it illustrates my point quite well!
Notice the X100B tubes are not very well matched at all, wheras the Legacy 1 & II tubes are all pretty close.

The idea is to calculate what your ideal bias setting should be then after measuring the bias of each tube to find out which one is running the hottest (highest bias current) set that hottest tube bias to your calculated reading and your tone should be good & also ensure none of your tubes are running too hot, as the other 3 tubes should be running at a bias current which is less than that figure.

It's obvious that if I had used the Standby switch method to set the bias on my X100B to around 140ma which is a reasonable level for that plate voltage tube V4 would have been running pretty hot because of the mismatch.
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Joined: Tue Oct 01, 2013 2:41 am

I don't want to hurt anyone's feelings about the Legacy but it is a fixed bias amp make sure the tubes are the right ones ,make sure they are matched but you DO NOT fuck with the bias, we lets say it is not a need like if you owned a Soldano or Mesa or Marshall .. Steve did this with simplicity in mind. Everyone believes Steve has the best of the best and he has to learn everything about it and he says it multiple times I enjoy simplicity and the Legacy is just that SIMPLE. Buy Matched tubes select the type with the switch , put 12AX7 x 5 back in and you have a hard working machine with very little work .. :guitar
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