F4 parts, basic beginner's questions


Paid Member
2017-09-10 6:33 pm
Good evening!

Short story long: I try to get into the beginning of the build: Basic understanding. I'm far from there... So I'm reading through and take every detour there is.

Along that route, in the f4-thread, was a builder who had troubles, and great ZM found out that the store's BOM didn't follow Nelson Pass's specs. Correcting it solved the problem.
Plus, about PSU: Nelson's schematic says 15'000 uF 35 V. Many builders use higher Capacities and Voltages. I read about the advantages of bigger caps.
But Papa says 15'000.

Long story short: Should I follow the BOM, or rather FW's schematic? What's the trade-off of either way?

What should I do now?

(I can almost see that red optical interface popping in: "Just what do you think you're doing, Dave?" but that's presumptuous)


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living an country with that flag , you know what's Law and Order :)

so , please post here both schematic and BOM , write your dilemmas and we ( at least Mighty We) will reply ....... something :rofl:

15mF is for Sissies , but it's good enough ..... if you have plenty of them

if you want blind fate approach - just look at my builds - Modushop 4U/400 ,one IEC , one mains switch, two fuses , two mains NTCs, two 250VA Donuts , 4 Graetz bridges , 2 Cap Banks

Recipe for Disaster ..... when you try it , you'll never try simpler :devilr:


Paid Member
2017-09-10 6:33 pm


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OK, next step :

print schematic; print PSU schematic, print BOM

compare , write down questions , write them here

first tip: all resistors are plain vanilla 0207 size MF , except those 0R47 , and they're either MOX or MF, 3W

second tip : Papa is Cheapskate - his caps are 15mF/25V , 8pcs in shared PSU for both channels; I'm Leacher , so I can use 33mF/25V , 4 per channel , 2 per rail , CRC where R is 0R1/5W/WW



Paid Member
2017-09-10 6:33 pm

Thanks, picoDumbs!
I realize there is this tendency to BIG capacitance, which I am encouraged to follow...
I don't doubt the advantages, but I'm still tempted to try to keep it on reasonable grounds. I mean, the original schematic said 4*15mf, and Papa Nelson is known to not be miserly, isn't he?
I know I can, I know I'm allowed to, but—should I? <- This is more a question of aesthetics and, uhm, "authenticity" than anything else.

Set aside my lust to build a killerbeastthing/beastkillerthing of an amplifier, my real need is more something like a sissy :) micro-amp of something between 2-5 good watts...

2 picoDumbs

2013-09-06 9:35 am
My left ear

Consider a few things.
1) Benefits of more capacitance is going to be lower noise, not just a beastly psu.
2) Pass Labs XA25 uses more capacitance than F4. Pretty sure F7 also has more capacitance than F4. So going with more is not doing anything that Papa wouldn't do himself.
3) If you are going to build another amp after F4 (this hobby is addictive), then you are probably going to appreciate you went with more on your first build. Cause later I guarantee you will want to do more than stock specs, probably even go dual mono.


Paid Member
2017-09-10 6:33 pm

If I get it right (forgive incorrect terms), everything above the required voltage principally works.

If I stay below the minimal capacitance requirement, it won't sound good cause it discharges on heavy loads.
The more capacitance, the longer can it deliver (doesn't discharge).

The higher the rated ripple, the better the cans can sustain (not offenbach :)) the voltage's ripple etc.

The lower the ESR, the better some anyhow (haven't got that yet... :eek:)

I searched a bit at Mouser and from those I found, I'd rather choose the

380LX473M035A082 | 35V | 47mF | 9.5A | 0.015Ohm
Correct voltage, highest capacitance, highest ripple rate, lowest ESR.

Am I right insofar? Do I really only win from bigger cans? there isn't a drawback?

Thanks for comments, corrections, complements everyone!