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Post subject: How not to bias an amp
Posted: Sat Feb 01, 2014 6:44 pm
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Amazing what you find on YT. Never measure bias of any particular amp/tube setup by simply reading the negative voltage of the bias supply. This reading DOES NOT take into account the current being passed by the specific tubes tested.

In fact, you will get a reading at this point on the board when there are NO tubes inserted. A reading that will vary when you twist the bias pot. You need a bias tester adapter or some such device that goes between the output tube and its socket to read the actual voltage drop (and thus mA drawn) across your specific tubes. There are other methods to measure current draw of the tubes, at idle. Tester is the easiest, IMHO.

Adjust the bias to a ballpark range using a bias tester adapter (in terms of idle wattage of dissipation desired). Then, you can SLIGHTLY tweak the bias pot to tone.

PS: when the Tech can't even get the model amp correct, it makes you wonder... :lol:

http://www.youtube.com/watch?v=p3dEY9FcSuo


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Post subject: Re: How not to bias an amp
Posted: Sat Feb 01, 2014 8:18 pm
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Location: Harvard IL
Yeah I hear ya', Beemer!! But like the guy says, he didn't check the current draw. For a novice to make a very gross adjustment to check the bias, that's OK. And is fairly safe. Totally agree about the bias probe!!! Art

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Post subject: Re: How not to bias an amp
Posted: Sun Feb 02, 2014 2:28 am
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Joined: Sun Apr 14, 2013 4:41 pm
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Thank you BMW2002Ti,

Another useful info from you. :D


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Post subject: Re: How not to bias an amp
Posted: Sun Feb 02, 2014 2:39 am
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BMW2002Ti wrote:
Amazing what you find on YT. :lol:




I must amazing how many false informations we read on the web :lol:


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