F5

[Williams Audio]

built a kit F5
is written that will not clip until 20 v peak, mine is clipping at 15-16 v peak
what can be the cause for it
williams

 

[Itsmee]

Have just checked the F5 thread, with a 20V supply, 15V peak (11V rms) output is correct, there is approx 4.6V across the output FET.

 

[bear]

what is the no load and connected in the circuit power supply voltage??

_-_-bear

 

[Williams Audio]

my pwr suplly is +/-23.7vdc under load, it is filtered by 0.2 Farad for each rail.
the voltage across the vcc and fet source resistor is 0.6v quite stable=1.3A
over 15v peak i get the start of clipping signal
i think that the current protection circuit may be cause
best regards
williams

 

[Williams Audio]

hi all,
well, no one knows the answer to the F5 clipping voltage?
williams

 

[bobodioulasso]

Normally it should be around 20v, in order to deliver the rated power.

I remember there had been a change concerning limiter resistor values.

Why not just disconnect those limiters and see.

 

[bear]

Indeed, many have reported it "sounds better" when the limiters are not present... are you sure the output is clipping and not ur input signal??

Got 'scope?

_-_-bear

 

[AndrewT]

Nelson has not sent me to jail, yet.
But I am going to repeat what I posted earlier.
I believe the current limiter is set too low.
It should allow all valid audio signals to pass to all valid speaker loads.
I think the transient currents into reactive loads are clipped with the existing resistor values.

But that should not show up when testing into resistive loads.

 

[DougL]

What load are you using to measure this?

I assumed an 8 ohm resistor until I realised no one had specified.

Doug

 

[Williams Audio]

hi all,
i use a 7 ohms load at the channel tested
i don't know what are the quality of the active components I received with the kit, if this could be the cause of the problems, i don't know
in the real world my speakers are ACOUSTAT 3, and this small pwr amp is driving not so bad at all, but with small dynamic range
1- i will increase the vcc to +/- 30 vdc
2- readjust the bias to 1.5amps
3- this will result in a 45watts dissipation for each fet
4- my heat sinks can dissipate about 60 watts for each fet
will see how is running this way
hi dougl, where did you got the Latin
best regards
Williams