I’ve built a F6 last year from diyaudio boards, transistors and input transformers. I find the sound warm and topend slightly rolled off. The bias is 520-30mV. I have a Schiit Aegir and this is the observation when I compare both.
my queastion is how can I take the F6 further up a notch? Keeping the same tonal balance in midrange but open up the highs a bit and a slightly tighter bottom end?
Will replacing the 1000uF caps to Mundorfs help? How about building dual mono power supplies feeding dedicated amp channel?
thanks
my queastion is how can I take the F6 further up a notch? Keeping the same tonal balance in midrange but open up the highs a bit and a slightly tighter bottom end?
Will replacing the 1000uF caps to Mundorfs help? How about building dual mono power supplies feeding dedicated amp channel?
thanks
ttl100
I'm on the same path as you on the F6. You are ahead of me with your amp hot. I've gone a little 'extreme' fitting dual mono Bridged all in a single 5U case. A few more parts need to arrive and then we can find out an answer to that question.
Best,
H.
I have the F6 in double mono configuration biased at 611mv. Higher bias makes it sound too clinical in my opinion. I can tune my tweeters (Tannoy's), however don't notice that the highs are rolled off. Find it sometimes a bit bass heavy (but that might be due to the 15 inch woofers positioned in the corners 😉).
I would first try to reposition speakers (e.g. more or less toed in, distance from walls, not too close or far apart from eachother) first.
I would first try to reposition speakers (e.g. more or less toed in, distance from walls, not too close or far apart from eachother) first.
I like you wanted to make the top end a little brighter and so embarked on a crusade so to speak. My first mod was to change out the IRF240's for SiCFet's to achieve both lower input capacitance and increase the amps with lower Rdson resistance. To increase the frequency response I replaced the front end driving the Jenson transformer with a very high speed buffer chip HA5002. To reduce the noise for the biasing then used a good old voltage regulator 7812 with very good filtering. The amp continues to serve me well after all these years. Here is a link to the crusade. https://www.diyaudio.com/community/threads/new-sic-jfets.254622/page-9#post-4437888
As above ;
IMO 🙂 don't believe the F6 is the problem.
Consider better speakers ?? Those are V important . Often more so than the amps.
IMO 🙂 don't believe the F6 is the problem.
Consider better speakers ?? Those are V important . Often more so than the amps.
Had to double check myself ☺️. I did the mod and used irfp150's.
I found that dual power supplies sound better. Mine are dual 400va doughnuts.
Built into a separate case and fed to the amp via a pair of leads.
Raising bias (above 650ma) sounded (to me,) to go bright and harsh.
Built into a separate case and fed to the amp via a pair of leads.
Raising bias (above 650ma) sounded (to me,) to go bright and harsh.
remind me please, which exact Cree type was in question?
I did found few dead links as reference ...
A small touch of positive current feedback can work wonders for the SQ of this amp. It does add some control and definition to the bass. It seems the phase split transformer likes being inside a positive current feeback loop. https://www.lundahltransformers.com/wp-content/uploads/datasheets/feedbck.pdf
https://www.diyaudio.com/community/threads/f6-with-pcf.288725/
Old thread. Lots of ideas and discussion around this topic.
Old thread. Lots of ideas and discussion around this topic.
Regarding sound quality, the biggest improvement may be achieved by using a dual-mono power supply. I would aim for rail voltage of +/– 24V to +/– 26V. If you have a 400mm deep chassis, it is possible to fit. Otherwise separate monoblocks or a separate chassis for the PSU may be the way to go.
Higher bias current is worth trying as well. The green LED bias trick that 2 pico and I arrived at helps higher bias amps reach thermal equilibrium in less time, due to their negative temperature coefficient.
The choice of output devices plays a role as well, especially when working with higher voltage and bias. My preferred devices, the FQH44N10, have been discontinued, though some may stll be found. A good substitute would be the IRFP150.
Higher bias current is worth trying as well. The green LED bias trick that 2 pico and I arrived at helps higher bias amps reach thermal equilibrium in less time, due to their negative temperature coefficient.
The choice of output devices plays a role as well, especially when working with higher voltage and bias. My preferred devices, the FQH44N10, have been discontinued, though some may stll be found. A good substitute would be the IRFP150.