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F5 power amplifier
F5 power amplifier
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Old 28th July 2018, 02:26 AM   #15911
ichiban is offline ichiban  United States
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F5 power amplifier
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Currently listening to F4 or F6/w curve matched SemiSouth outputs
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Old 18th October 2018, 03:59 PM   #15912
freyahel is offline freyahel
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Hi everyone
I hope I am not polluting here, I am a huge fan of Don Keele’s CBT 24 and the association with a FW J2 is sublime but the amp is definitely underpowered for these low efficiency arrays.
I have in mind the build a CBT 24 with a re-wiring allowing four F5 modules to power a série of 6 drivers per board.
The 4 modules for each channel should fit in a 5U 500 chassis, maybe biased a little lower than usual, and with a beefy PSU.
Some of you may know already, but in this particular array, the upper drivers have their level lowered gradually by 3 and then 6dB.
I would do this atténuation on the related board instead of using resistances es in the speakers.
Could someone just tell me how to lower the F5 gain by 3 or 6dB ?
Thanks a lot in advance !
Pierre-Antoine
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Old 18th October 2018, 04:07 PM   #15913
rayma is offline rayma  United States
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Originally Posted by freyahel View Post
Could someone just tell me how to lower the F5 gain by 3 or 6dB ?
Use an input attenuator, a series resistor and a shunt resistor.
Changing the values for R9 and R10 would be the simplest way.
You'd need to decide what input impedance you want for the amp first.
For example, if you want an input impedance of 50k,
then R9=R10=25k, for 6 dB less gain.

Please don't alter the feedback network instead.

Last edited by rayma; 18th October 2018 at 04:16 PM.
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Old 18th October 2018, 04:11 PM   #15914
Hikari1 is offline Hikari1  United States
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You can RAISE the gain by changing the feedback resistor values...check the f5 turbo article. That will get get you the gain difference you desire.

You could also lower the gain by playing with the feedback network but it’s likely the amp will become unstable.

Changing the feedback network changes the character of the amp though...they will sound different, it does not just effect gain. I would think some sort of attenuation before the power amp would be a better option for level matching. Even a simple l pad resistor setup (f5 has a high input impedance, easy to do this) would probably a better and more flexible option.
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Old 18th October 2018, 08:01 PM   #15915
gior is offline gior  France
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Wouldn’t a F5 turbo or BA3 better fit the need for more power?
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Old 18th October 2018, 08:40 PM   #15916
freyahel is offline freyahel
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Well...obviously yes, but to me there is something elegant, and unusual, in using multiple small FW amps to power clusters of Fullrange drivers, filterless, instead of using a bigger amp.
But that’s just me😉
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Old 18th October 2018, 09:54 PM   #15917
Hikari1 is offline Hikari1  United States
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I would rather listen to one F5 heavy biased at say 2A than 4 F5 biased at 500ma though.
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Old 19th October 2018, 01:33 PM   #15918
McQuaide is offline McQuaide  United States
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Quote:
Originally Posted by Hikari1 View Post
I would rather listen to one F5 heavy biased at say 2A than 4 F5 biased at 500ma though.

Is anyone running an F5 at 2A? I thought 1.7A was pushing it!
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Old 19th October 2018, 01:56 PM   #15919
AudioSan is offline AudioSan  Norway
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I'm running my F5 at 2.5A bias. But that is a 2 output pair amp.
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Old 19th October 2018, 02:14 PM   #15920
McQuaide is offline McQuaide  United States
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Anyone running a stock 1 output pair F5 well above 1.3A?
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