Nelson,
I have just had an inquiry about resistor selection for an F5. Looking at the THD plot (Figure 9 http://www.firstwatt.com/pdf/prod_f5_man.pdf) I was wondering if you also ran these curves at a lower frequency to see if the third harmonic distortion was a thermal artifact indicating a resistor type source?
ES
(Yes I am too lazy too look at all of your .25 zillion posts to see if this has been addressed. )
I have just had an inquiry about resistor selection for an F5. Looking at the THD plot (Figure 9 http://www.firstwatt.com/pdf/prod_f5_man.pdf) I was wondering if you also ran these curves at a lower frequency to see if the third harmonic distortion was a thermal artifact indicating a resistor type source?
ES
(Yes I am too lazy too look at all of your .25 zillion posts to see if this has been addressed. )
I did not, but the answer is that the 3rd harmonic is primarily a function
of the transistor characteristic.
Thanks for the prompt reply.
Based on my resistor measurements I would suspect that at around 10 volts the distortion from the Panasonic resistors of the types I measured would begin to be dominant as shown used in this applications feedback loop. Not sure of your exact choice other than you mention Panasonic.
Just curious, as I suspect modern designs are getting good enough that such issues are emerging.
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F5 hum, only one channel.
My F5 is now at service for 2 months. At the beginning I noticed a hum, only at the left channel and only audible when I put my ear close to the speaker. So no problem I thought. Sound is fantastic.
Now I planned a bias Vdc check last week and after this the hum changed. Adjustment were small, Vdc around +/- 10 mV and measured V sourceresistor is 0.6V, but the character change of the hum was big. After switching on the "cold" amp there is silence at first from the left channel, that's new. Seems good but after a few minutes suddenly it starts humming, first like a engine sputtering but then constantly and only the left channel. Not loud but audible. Tried to measure it: left 9 mV AC, right 0.5 mV AC. Sometimes after a while when the amp is more hotter it stops. This is suddenly worse than before. Guess it's not a grounding issue, right? Anyone an idea where to start? TIA
Regards,
Joffrey
My F5 is now at service for 2 months. At the beginning I noticed a hum, only at the left channel and only audible when I put my ear close to the speaker. So no problem I thought. Sound is fantastic.
Now I planned a bias Vdc check last week and after this the hum changed
. Adjustment were small, Vdc around +/- 10 mV and measured V sourceresistor is 0.6V, but the character change of the hum was big. After switching on the "cold" amp there is silence at first from the left channel, that's new. Seems good but after a few minutes suddenly it starts humming, first like a engine sputtering but then constantly and only the left channel. Not loud but audible. Tried to measure it: left 9 mV AC, right 0.5 mV AC. Sometimes after a while when the amp is more hotter it stops. This is suddenly worse than before. Guess it's not a grounding issue, right? Anyone an idea where to start? TIARegards,
Joffrey
Thanks Juma, for your quick respons. After a short phase of denial (me, make a cold solder point
) it makes sense. So ... I have to resolder all connections left channel, I guess. Nice weekend job.
Normal CD has 2V rms output (single ended), so +/- 2.8V pk-pk.
Say you need some sort of volume control (I certainly do), minimum 6 db, pure passive.
That reduces the input to the F5 to +/- 1.4V.
The F5 has a gain of 6, which means 8.4V.
The standard F5 should has maximum output at around 20V, a balanced F5 with 4 FETs at around 12V per side.
Still quite some room from 8.4V, don't you think ?
Patrick
Say you need some sort of volume control (I certainly do), minimum 6 db, pure passive.
That reduces the input to the F5 to +/- 1.4V.
The F5 has a gain of 6, which means 8.4V.
The standard F5 should has maximum output at around 20V, a balanced F5 with 4 FETs at around 12V per side.
Still quite some room from 8.4V, don't you think ?
Patrick
A CDP is generally 2Vac to 2.2Vac, near enough 3Vpk or 6Vpp.
An F5 gain of 6 times gives speaker voltage of 18Vpk, or 36Vpp. That is very close to maximum power.
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need help
Hi,
I replaced my mosfet Q4, R14, r16, & 18 ( &R11 + R12) because my amp blew r14, and blackened R11 & R12.
I've hooked it up again, but I'm getting no voltage (.000v) across R12 when I attempted to check the bias.
So I'm guessing one of the transistors isn't functioning? Would it be Q2 or Q6 that powers that mosfet?
Hi,
I replaced my mosfet Q4, R14, r16, & 18 ( &R11 + R12) because my amp blew r14, and blackened R11 & R12.
I've hooked it up again, but I'm getting no voltage (.000v) across R12 when I attempted to check the bias.
So I'm guessing one of the transistors isn't functioning? Would it be Q2 or Q6 that powers that mosfet?
PM Me, I can send you some.
In the interim, you can disable the protection circuit and still run the amp if you set up the bias carefully.
f5 cviller 1.0
Hi,
I really missed the boat on Q5 & Q6. I've got the right transistors in place but I've got them backwards I believe.
The bubble on the circuit board aren't correct right? I've orientated my transistor towards the bubbles.
I'll have to clip them out and pop in some fresh ones and make sure they're in correct before if blows up on me again.
Hi,
I really missed the boat on Q5 & Q6. I've got the right transistors in place but I've got them backwards I believe.
The bubble on the circuit board aren't correct right? I've orientated my transistor towards the bubbles.
I'll have to clip them out and pop in some fresh ones and make sure they're in correct before if blows up on me again.