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Old 10th June 2010, 05:43 PM   #1
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Default F5

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
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Old 10th June 2010, 06:01 PM   #2
Itsmee is offline Itsmee  England
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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.

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Old 10th June 2010, 06:12 PM   #3
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what is the no load and connected in the circuit power supply voltage??

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Old 11th June 2010, 05:18 AM   #4
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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
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Old 11th June 2010, 10:40 AM   #5
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hi all,
well, no one knows the answer to the F5 clipping voltage?
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Old 11th June 2010, 10:57 AM   #6
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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.
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Old 11th June 2010, 02:34 PM   #7
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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?

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Old 11th June 2010, 02:49 PM   #8
AndrewT is offline AndrewT  Scotland
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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.
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Old 11th June 2010, 04:25 PM   #9
DougL is offline DougL  United States
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What load are you using to measure this?

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

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Old 11th June 2010, 09:13 PM   #10
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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
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