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Post subject: a "biased" question,
Posted: Thu Mar 03, 2016 9:45 am
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my question involves amp bias. if there is a thread or source for more info I would appreciate it.

question 1- what happens if you don't re-bias an amp when installing new power tubes? let's say my amp uses 6l6. I'm at a gig and have an issue with the tubes, so I pull out a spare and install it, then play for a few hours. am I risking harm to the amp if the replacement has the same specs?

I want to get a new tube amp, and am still auditioning before making my final decision. I may be making too much out of this, but I would love to be able to take care of this without hurting myself. I don't know if I should look at the different tube amps that don't require biasing, look at one that actually has the ports and adjustment on the back panel, or just bite the bullet and learn how to do it myself from inside the amp.

thanks gang for your help.


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Post subject: Re: a "biased" question,
Posted: Thu Mar 03, 2016 10:38 am
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Go to Eurotubes fr their BIASING videos and watch them.

http://www.eurotubes.com/store/pc/how%2 ... videos.htm

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Post subject: Re: a "biased" question,
Posted: Thu Mar 03, 2016 3:30 pm
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just slap another tube of the same and let it warm up on standby and finish gig

then rebias at home

biasing most of these new amps are so easy you'll wonder why you even Q it....
some amps have the adjustment wheel/screw outside on the back & some you have to loosen chassis mount screws and carefully slide chassis out from cab. IF your speaker/reverb cables/wires are NOT long enough to keep connected, then Disconnect them to slide chassis out. ALWAYS re-connect speaker wire before turning amp back on to bias
use a volt meter to measure current at test points (forums will give you info) and adjust wheel inside of chassis to adjust voltage. My SS22 test points are D35 & D36 on board. My plate voltage test point is D38. When I have tried diff power tubes, I find that they really aren't that far apart. If I didn't care about tube life or tone, you really can just plug and play. But most of us do care, so might as well bias. I listen for the best sound when biasing anyways. Usually works out to be about 80% tube disapation
https://robrobinette.com/Tube_Bias_Calculator.htm


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Post subject: Re: a "biased" question,
Posted: Fri Mar 04, 2016 8:43 am
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If you want to be able to change a power tube on the fly, one consideration for your choice of amp is that many tube amps have internal fuses that also blow when a power tube fails. So a tube swap still has no sound. Some have rear panel access, but most require chassis removal.
Fender amps don't use these fuses.
It improves reliability.
When putting in an unknown tube, generally, the only real risk of damage from mis-bias is to the tube itself


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Post subject: Re: a "biased" question,
Posted: Fri Mar 04, 2016 11:49 am
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twirlyboggs wrote:



IMO this one is easiest ;

http://www.tedweber.com/webervst/tubes1/calcbias.htm


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Post subject: Re: a "biased" question,
Posted: Fri Mar 04, 2016 11:52 am
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With a good bias amp play/ sound better.
With wrong bias and in the worse case , you will burn your tube.


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Post subject: Re: a "biased" question,
Posted: Mon Mar 07, 2016 6:10 pm
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If your in the market for a tube amp and dont want to worry about bias, consider one that is cathode biased. Technically speaking these types of amps shouldnt need to be biased as they are "self biasing". You just swap power tubes and away you go. However, if youre amp is blowing power tubes then there may be other issues that need to be addressed. Hope this helps.

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Post subject: Re: a "biased" question,
Posted: Tue Mar 08, 2016 2:43 am
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socal323 wrote:
If your in the market for a tube amp and dont want to worry about bias, consider one that is cathode biased. Technically speaking these types of amps shouldnt need to be biased as they are "self biasing". You just swap power tubes and away you go.

However, if youre amp is blowing power tubes then there may be other issues that need to be addressed. I will check bias, cathode resistor


Hope this helps.


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Post subject: Re: a "biased" question,
Posted: Wed Mar 09, 2016 3:30 pm
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If you are going to carry one spare power tube to a gig, you might as well carry two matched power tubes.
I'm assuming your amp has two power tubes.
If something blows, replace both power tubes with two matched power tubes of the same general type, or if possible, with the same brand and type.
Continue the gig and check the bias at home later.
You should be fine.


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Post subject: Re: a "biased" question,
Posted: Wed Mar 09, 2016 9:40 pm
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Get a matched quad of output tubes. Install 2 tubes and set bias properly, 2 tubes for back up. If you need to change tubes, use the backup set, the bias on the new tubes will be the same as the ones taken out. :idea:

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