F6 Amplifier

Official Court Jester
Joined 2003
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first - that hole is not burred good enough for that task (I had few of them in hands)
second - even if that wire is just for e-static shield , never put sole wire through any metal plate hole - always put natural wire pairs (rail and return)

I know nothing will happen in this exact case , but that's just decent engineering praxis

route that wire to the front , then down

https://youtu.be/kFZTko2TXNY

:rofl:
 
That is definitely worth playing with but unlikely to solve your issue completely. It definitely should sound different and maybe more too your liking.

I would be tempted to try adding more feedback, that will increase bandwidth and should brighten up the amp. You could add another 100 Ohm resistor in parallel (for 50 Ohms) just for testing purposes, then start tweaking further after you have performed a listening test.

Would that reduce the gain by a factor of 2? Reason I ask is my F6 is a little dark sounding also, it has IRFP240 and .47 and .57 resistors. This sound is compared to my Aleph J. Although the F6 has deeper and more pronounced bass for sure, the mids and highs don't seem as clear and bright as the Aleph.
 
Would that reduce the gain by a factor of 2? Reason I ask is my F6 is a little dark sounding also, it has IRFP240 and .47 and .57 resistors. This sound is compared to my Aleph J. Although the F6 has deeper and more pronounced bass for sure, the mids and highs don't seem as clear and bright as the Aleph.

Gain goes from about 5V/V (stock) to about 3V/V.

It's definitely worth trying, it's an opportunity to gain some insight in various effects.

Edit: Alternatively you could keep feedback resistor network same and change IRFP240 with Higher Transconductance (maybe 4S) SiC devices
 
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Well, I have read a few reviews of the F6 and there is no mention of dark or dull. I am presuming these are Nelson's production IRFP240 versions. I wonder what Nelson has done differently if anything? One thing with mine I just thought of, I didn't use the Silmic caps I used Nichicon type KA. They are said by them to be high quality "audio" type with prodigious bass capability. I can attest to the bass statement. Could these caps play that much of a role in shaping the F6's sound?
 
hi oreo, don´t know about how the cap is involved soundwise, but my F6 seems to developed to a little more bright/right side for me. Wait at least two days. Maybe it´s my woodoo thinking and because of tweaking the speakers a little i lost reference somehow.
for the resistors, i changed the feedback (a second 100 ohm to make it 50 ohm) what made it a bit more foreward but also a little more tight, less lush. i went back to the original.
For the source R´s, i changed R2 from .56 to .47 and one could say it was clearer, but for me the soundstage, depth, was more flattend. So i went back to original too.

i like it better now :)

st.
 
Biasing up for first time on lab power supply.
Easily achieved less than 1mV dc offset.

Just letting it get up to temperature before making final tweaks to bias.

Used 5.6V Zeners instead of original 5.1V Zener with 7.5k instead of 10k. Works beautifully.

20151113_001056.jpg


(Note to self: counter clockwise to bias up (memory like a sieve)) Hahahaha