Any update on more F5 boards being available please? I've finished my first pair and it was so much fun I want to build another set (so I can go fully active) 😀
cheers
Nick
<Homer_Simpson>
DOH!!
</Homer_Simpson>
Just fell over the PCB Bank after I posted
(F5 PCBs - PCB Bank)
apols for the noise
Nick
Yes, my speakers are ~84.5dB Mark Audio CHR70 drivers in a fonken cabinet. The F5 biased up that high kicks pretty good.
My heatsinks are reasonably large - 4U chassis sinks rated at .31C / W so they get pretty warm but not too hot.
My heatsinks are reasonably large - 4U chassis sinks rated at .31C / W so they get pretty warm but not too hot.
I bought a pair of these suckers. Hard to drive to to high levels with this amp. Maybe a series of 3 of them would do.
My newbishness is going to be exposed in asking this, so please forgive me... but what the heck is all the fuss over this "F5" thing?
What is an F5? I see a lot of talk about it, but I can't gather what it is besides an amp. Is it special?
What is an F5? I see a lot of talk about it, but I can't gather what it is besides an amp. Is it special?
It is simply one of the best amp, diyselfer can build.
But I recommend to use speakers with 90dB/W or higher.
I think for myself: if N- and P-tubes would exist, this circuit could be the amp valve lovers would build. But they cant, he he.
Just read FIRST WATT F5 and download the manual.
Franz
But I recommend to use speakers with 90dB/W or higher.
I think for myself: if N- and P-tubes would exist, this circuit could be the amp valve lovers would build. But they cant, he he.
Just read FIRST WATT F5 and download the manual.
Franz
naah ...... not really ;
catch 22 is in few other things :
- weed is better when dried on high temp heatsink
- it's more pleasant to spend time making amp and later listening da muzak , then fooling around at night
Just to make the information complete, all those FETs have less transconductance than IRFPs, so they won't deliver equal performance as cap-multipliers.
> Just to make the information complete, all those FETs have less transconductance than IRFPs
According to my own measurements and not datasheet numbers, the transconductance of the mentioned MOSFETs at 1.3A are :
IRFP250 2.35S
FQA19N20C 2.34S
2SK1530Y 2.14S
And if I am not wrong, IRFP250 has quite a bit higher transconductance than IRFP240.
I vaguely remember Nelson saying that one could replace 2x 240 with one 250.
Unfortunately I no longer use IR FETs, so I cannot verify by actual measurements.
But I am sure Nelson could confirm these numbers.
Most of the measurements have already been published here in this thread, rather at the beginning a few years back.
Best regards,
Patrick
.
According to my own measurements and not datasheet numbers, the transconductance of the mentioned MOSFETs at 1.3A are :
IRFP250 2.35S
FQA19N20C 2.34S
2SK1530Y 2.14S
And if I am not wrong, IRFP250 has quite a bit higher transconductance than IRFP240.
I vaguely remember Nelson saying that one could replace 2x 240 with one 250.
Unfortunately I no longer use IR FETs, so I cannot verify by actual measurements.
But I am sure Nelson could confirm these numbers.
Most of the measurements have already been published here in this thread, rather at the beginning a few years back.
Best regards,
Patrick
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A slight correction to the above (and my apologies). The values quoted included a 0R22 source resistor as the measurements were done for the F5X.
With 0R source resistor, again at 1.3A :
IRFP250 4.78S
FQA19N20C 4.77S
2SK1530Y 3.11S
The only old (2003) record I can find for IRFP240 is 3.2S at 1.3A.
But the data is probably not very accurate with only 6 measurement points, where as the rest has 1000.
Note that these were all measured with Vds = 24V, and a constant case temperature (steady state on heatsink) at 55°C.
Patrick
With 0R source resistor, again at 1.3A :
IRFP250 4.78S
FQA19N20C 4.77S
2SK1530Y 3.11S
The only old (2003) record I can find for IRFP240 is 3.2S at 1.3A.
But the data is probably not very accurate with only 6 measurement points, where as the rest has 1000.
Note that these were all measured with Vds = 24V, and a constant case temperature (steady state on heatsink) at 55°C.
Patrick
Euvl,
Thanks!
It is nice to see spurious "facts" demolished by carefully obtained measurement and real data.
Thanks!
It is nice to see spurious "facts" demolished by carefully obtained measurement and real data.
To be fair to Juma he did say nothing wrong.
4.78S is larger than 4.77S, and 3.2S is larger than 3.11S.
Also the performance would never be equal, if only for the simple fact that the dropout voltage is lower.
People who tried both also knows that Toshiba's has a "faster" sound, and you can look at the follower pass device almost as a cascode.
But I agree it is better to put facts on the table than to make simple rhetorical statements.
Patrick
4.78S is larger than 4.77S, and 3.2S is larger than 3.11S.
Also the performance would never be equal, if only for the simple fact that the dropout voltage is lower.
People who tried both also knows that Toshiba's has a "faster" sound, and you can look at the follower pass device almost as a cascode.
But I agree it is better to put facts on the table than to make simple rhetorical statements.
Patrick
Which resistors should I spend more money on, and what should I set the pots to before soldering them in? Thanks 🙂
I believe that NP uses Vishay RN55 or CMF55 for the 1/4 watters, and Panasonic for the 100R, 10R and 0.47R.