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
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
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.
😎
but the F5 had plenty of feedback already, so no big loss.
It may easily be that you will prefer this after a while.
😎
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)
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)
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
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
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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
Yes, same resistor type!
Actually the original 2 parallel resistors of 100ohm each are oversized to 5W. So I could easily desolder one of them.
Actually the original 2 parallel resistors of 100ohm each are oversized to 5W. So I could easily desolder one of them.
the feedback resistors see the full output voltage.
20Vpk through the 100||100 + 10r gives a current of 333mApk
the 10r dissipates an instantaneous peak of 1.1Wpk
the 100r dissipates an instantaneous peak of 2.8Wpk
Fortunately the average power dissipations are only 1/2 of these peak instantaneous values.
20Vpk through the 100||100 + 10r gives a current of 333mApk
the 10r dissipates an instantaneous peak of 1.1Wpk
the 100r dissipates an instantaneous peak of 2.8Wpk
Fortunately the average power dissipations are only 1/2 of these peak instantaneous values.
I went back to the original feedback values (and lower gain).
In my system (and to my ears) the open sound and high resolution came back. So be careful then changing gain!
It might also be an impedance issue, trying to feed the F5 directly from a BIIISE and Legato 3.1😕
I'm using the bufferad SE output on Legato.
In my system (and to my ears) the open sound and high resolution came back. So be careful then changing gain!
It might also be an impedance issue, trying to feed the F5 directly from a BIIISE and Legato 3.1😕
I'm using the bufferad SE output on Legato.
Probably just a simple slew rate factor. Increase the gain and the amplifier has to move faster to produce the voltage and that will affect the HF response and stability.
Usually increasing feedback can lead to instability/oscillation, it doesn't usually occur when reducing feedback.
Changing the gain doesn't affect the input impedance of the F5 it only changes the output impedance
Changing the feedback will change the stability margins.
A change in the stability changes the relative multiplication factors for different speed signals. This change, particularly the way the amp amplifies the HF part of the signal, can produce an output that is different from the input, that is audible.
This is why we try to avoid excessive rounding of test squares and excessive overshoot (and worse ringing) of test squares waves that are in the passband of the amplifier.
If Pass ended up with that 5:1 ratio of feedback by accident, I would be very surprised. I suspect Pass designed the amp to perform well with the 5:1 ratio.
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