That should sound good.
But also a genuine 'underuse' of the F6's capabilities.
Those cannot reproduce the frequency range the amp outputs.
True, Bare, but my ears cannot perceive the full audio spectrum produced by the FW amps any longer either....sigh....
Matt
Easy. Connect audio generator to input, measure output voltage without load and under the standard load (8 or 4 Ohm resistor). The damping factor is: Df = output voltage under load / ( output voltage without load - output voltage under load)
Thank you for the formula .
I did some test with some non inductive resistors i have :
load : 4.7 ohms
in voltage : 2.56 v / out voltage under load : 8.16 v / out voltage without load : 11.24 v
DF : 2.65
load : 9.5 ohms
in voltage : 2.56 v / out voltage under load : 9.46 v / out voltage without load : 11.24 v
DF : 5.31
I also did some test with 1.00 v in voltage and the DF was 4.07 for load : 4.7 ohms / DF : 8.35 for load : 9.5 ohms
these are the numbers i got , damping factor of 16 is far from my numbers ?
and the gain is not 5 , specially at 1.00 v in , and the gain is lower under load ?
it may be normal
.
I did some test with some non inductive resistors i have :
load : 4.7 ohms
in voltage : 2.56 v / out voltage under load : 8.16 v / out voltage without load : 11.24 v
DF : 2.65
load : 9.5 ohms
in voltage : 2.56 v / out voltage under load : 9.46 v / out voltage without load : 11.24 v
DF : 5.31
I also did some test with 1.00 v in voltage and the DF was 4.07 for load : 4.7 ohms / DF : 8.35 for load : 9.5 ohms
these are the numbers i got , damping factor of 16 is far from my numbers ?
and the gain is not 5 , specially at 1.00 v in , and the gain is lower under load ?
it may be normal
.
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Thank you for the formula .
I did some test with some non inductive resistors i have :
load : 4.7 ohms
in voltage : 2.56 v / out voltage under load : 8.16 v / out voltage without load : 11.24 v
DF : 2.65
load : 9.5 ohms
in voltage : 2.56 v / out voltage under load : 9.46 v / out voltage without load : 11.24 v
DF : 5.31
I also did some test with 1.00 v in voltage and the DF was 4.07 for load : 4.7 ohms / DF : 8.35 for load : 9.5 ohms
these are the numbers i got , damping factor of 16 is far from my numbers ?
and the gain is not 5 , specially at 1.00 v in , and the gain is lower under load ?
it may be normal
.
Do not measure input voltage.
You measure only the output.
With or without the load.
not really
.
From http://www.firstwatt.com/pdf/prod_f7_man.pdf
Most of your “better” amplifiers have higher damping factors like 20 or 100, and this amplifier
[F7 before the positive feedback was added] was only about 5 or so........
Modest amounts of negative feedback are balanced in counterpoint to small amount of positive
current feedback, creating an equilibrium where the output impedance approaches zero,
improving transient and frequency response.....
[F7 after the positive feedback was added] Damping Factor >100
I sent an sine 1 khz signal .
my number are from real world measurement and i am not able to explains them , what i know for sure is that the amp sound great this way
may be some people who know's can give some nice explanations
.
What is the value of Rsense? I suspect you positive current feedback did not work properly and Rsese in series with load gives you results with low (and dependable of load) Df.
So, stock F6 has Df=16 @ 8 Ohm. Rsource=0.5 Ohm (8Ohm/16). You Rsource = 1.5Ohm (Rsens + 0.5 Ohm). At 4.7 Ohm load Df = 3.1 (4.7Ohm/1.5Ohm) .You got 2.65. Close value (especially if we add resistance of wires). At 9.5 Ohm calculated Df=6.3, also close to you results. Maybe you positive current feedback don't work, because in case of F7 it significantly increases Df (from 5 to >100) as mentioned above.
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