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Old 24th August 2015, 08:00 PM   #1
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Default F5 - higher gain changing sonic signature

Hi

I wanted some extra gain in my F5. Doubling feedback resistors for another 6dB.
So far so good, everything works fine.

However, now I'm getting my doubts if some life and upper details disappeared.

Will the sonic signature change with higher gain?
Other distortion pattern perhaps?

Any experience or theory is welcome!
Thanks
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Old 24th August 2015, 08:48 PM   #2
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off course that different feedback amount will change THD spectra
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Old 24th August 2015, 09:13 PM   #3
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As you raise the gain, there is less feedback, so things will change a bit,
but the F5 had plenty of feedback already, so no big loss.

It may easily be that you will prefer this after a while.

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Old 25th August 2015, 02:00 AM   #4
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MOSFET models from Bob Cordell.


Patrick

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Attached Files
File Type: txt F5 Effect of Gain.txt (1.5 KB, 30 views)
File Type: asc F5 Gain_6.asc (4.4 KB, 10 views)
File Type: asc F5 Gain_11.asc (4.4 KB, 9 views)
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Old 25th August 2015, 02:20 AM   #5
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Spectrum plots.
Left is G =6, right G=11.

Patrick

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Attached Images
File Type: jpg F5 FFT G6.jpg (123.0 KB, 139 views)
File Type: jpg F5 FFT G11.jpg (125.7 KB, 140 views)
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Old 25th August 2015, 03:15 AM   #6
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I have a question.
A quiet room measures about 40dB.
If I listen to music with peaks never exceeding 100dB would it be fair to say that harmonics that sit below 60dB down on the FFT are completely inaudible (100-60 = 40dB Silence)
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Old 25th August 2015, 03:48 AM   #7
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Quote:
Originally Posted by deerhunt View Post
Hi

I wanted some extra gain in my F5. Doubling feedback resistors for another 6dB.
So far so good, everything works fine.

However, now I'm getting my doubts if some life and upper details disappeared.

Will the sonic signature change with higher gain?
Other distortion pattern perhaps?

Any experience or theory is welcome!
Thanks
Could be simply due to change in output impedance (damping factor).
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Old 25th August 2015, 04:03 AM   #8
jcx is online now jcx  United States
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and you can't really believe your ears unless you've amplitude matched the listening comparison to ~ 1% V, 0.1 dB SPL

Loudness Curves, articles from mixing engineers say small, too small to be clearly labeled by ear alone as loudness differences still give differing perceptual frequency balance

blinding protocol, ability to switch quickly and you can be more confident of such subjective statements before theorizing over the circuit causes


soundcards ( even motherboard chipsets), dividers, free sw can easily let you see clearly audible frequency response changes by measuring the loaded amp output V

Last edited by jcx; 25th August 2015 at 04:15 AM.
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Old 25th August 2015, 05:07 AM   #9
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Originally Posted by jcx View Post
soundcards ( even motherboard chipsets), dividers, free sw can easily let you see clearly audible frequency response changes by measuring the loaded amp output V
From memory the F5 amp has a frequency bandwith of around 1MHz. I doubt any subtle differences in frequency response around 1MHz will be audible.
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Old 25th August 2015, 05:50 AM   #10
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if output Z interacts with load Z, especially multiway loudspeaker, XO peaks and dips then you can have frequency response variation at audio regardless of amplifier bandwidth
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