Initial setting of F5 bias--help, please! - Page 2 - diyAudio
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Old 16th March 2011, 12:15 AM   #11
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Don't forget to have the input shorted and the output open before starting.
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Old 16th March 2011, 01:57 AM   #12
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Yes, on both counts! Thanks for the reminder.....

Ken
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Old 17th March 2011, 12:12 AM   #13
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howcome does the input need to be shorted to bias it?
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Old 17th March 2011, 12:20 AM   #14
Zen Mod is offline Zen Mod  Serbia
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Don't forget the wife's law, break that and the other two won't matter
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Don't forget to have the input shorted and the output open before starting.
conditio sine qua non for , every amp , biasing procedure




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Originally Posted by crazycody1993 View Post
howcome does the input need to be shorted to bias it?
firmer ground referencing of zero-offset holding mechanism , same as preventing any possibility of polluting input ( in case of F5 very RF suspecting) with unwanted garbage
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Old 17th March 2011, 02:42 PM   #15
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now if you 'un-short' the input, will all of your bias adjustments change? atleast thats what i think your telling me,
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Old 17th March 2011, 05:46 PM   #16
juma is offline juma  Germany
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Originally Posted by crazycody1993 View Post
now if you 'un-short' the input,....,
Depends on what amp's input can pick up from the ambient. Everything present at input will find it its way to output and you don't want that when adjusting the amp. You want it to be steady, undisturbed. That's why you need to short the input - to avoid the ambiental influence.
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Old 17th March 2011, 07:01 PM   #17
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Okay, that makes good sense.
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Old 19th March 2011, 04:42 PM   #18
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Depends on what amp's input can pick up from the ambient. Everything present at input will find it its way to output and you don't want that when adjusting the amp. You want it to be steady, undisturbed. That's why you need to short the input - to avoid the ambiental influence.
I'm fortunate to be in a low RFI and other ambient information level area. I fired it up with no load on the output and inputs not shorted. At the time, I didnt know I should short them, so just got lucky. I've since re set it a time or to in the same manner. guess I better get out the shorting plugs next time, I've been lucky up until now. When I let it cook a while and remeasure bias and output DC, it stays very stable, unless I leave the lid off too long. Then have to shut it back up for a warm up.
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Old 23rd November 2012, 09:48 AM   #19
Nikitas is offline Nikitas  Greece
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Hi all,

I'm about to fire up for the first time my f5!
There's one thing I don't get in the instructions given in the previous page (please excuse my ignorance): what is "Iq"? I checked the FQA datasheet, but couldn't find anything..
Did you mean the current going through the source resistors?
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Old 23rd November 2012, 10:25 AM   #20
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Quiescent current. It is the bias current at which a circuit operates. If you have any questions, feel free to PM/email me. I am more than willing to help.
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