Hey ggetzoff , it was a little warmer these Days and i measured 51,5°C on Heatsink and 78-82C on Fets.Soundwise it got better after changing PSU from CrCCC to CRCRCC and after that i thougt I give it a try and do CRCRCRC (never saw that before) .I really like it a lot now,but I think there is still something to do.Some Things don`t sound right,maybe check out some different Parts.But I think that is just getting the last bit out of the Amp.,which is already way better than F5 was.Wonder what would be the best PSU for it.
Regards DT
Regards DT
The heat transfer between mosfets and heatsinks seems to me to be quite inefficient because I am not sure that 30° difference is acceptable.
People more technical than me can give their point of view but personally I encourage you to review this point.
People more technical than me can give their point of view but personally I encourage you to review this point.
I am still very happy with the USSA5's performance as it still beats all my current amps in terms of clarity. However, I can't say much about soundstage etc because currently I don't have the luxury of space to properly position my speaker system.
It is easy to hear the clarity difference when changing amps for A/B comparison. The USSA5 always reveals much more detail in the music.
I will be tearing apart and rebuilding my USSA5 according to FAB's manual again, to be sure i didn't missed out any steps. Especially the initial P1&P2 adjustments. And started to love those maths on resistors calculations, since i now understand the methods better. I want to make this my "Reference" power amp.
As for the USSPA, i will build it when i have decided which power supply topology to use.
Any recommendation for a low noise superb power supply circuits ?
It is easy to hear the clarity difference when changing amps for A/B comparison. The USSA5 always reveals much more detail in the music.
I will be tearing apart and rebuilding my USSA5 according to FAB's manual again, to be sure i didn't missed out any steps. Especially the initial P1&P2 adjustments. And started to love those maths on resistors calculations, since i now understand the methods better. I want to make this my "Reference" power amp.
As for the USSPA, i will build it when i have decided which power supply topology to use.
Any recommendation for a low noise superb power supply circuits ?
Yes, first you want a dual mono PS. Salas' DCSTB is what i use and it is very good. I think any shunt reg. dual supply will be fine. I think Fab says in the schematic that 15v is the ideal.
Cheers,
Greg
Cheers,
Greg
My USSPA is powered by 12V by the Salas UltraBIB and mono configuration, preceded by an LDR attenuator and the result is quite exceptional on the USSA-5.
Yes 30C difference is a lot and not optimal. With thin mica insulator and thin silicon based thermal paste I can get maybe less than 10C difference between hottest spot on heatsink and Output mosfet body. With normal thermal pad i was able to get about 15C delta T. However, I am not sure how big delta T influences sound but surely temperature compensation bias... the reassuring part is that Lateral mosfet does not suffer from thermal runaway...
Fab
USSPA
For the USSPA +/-12vdc is enough considering a max source voltage of about 4vac and thus allows more bias current for same heatsink temperature. This is assuming that the attenuator is installed before the preamplifier.
Fab
For the USSPA +/-12vdc is enough considering a max source voltage of about 4vac and thus allows more bias current for same heatsink temperature. This is assuming that the attenuator is installed before the preamplifier.
Fab
USSPA
Hi meanie
There is no specific IDSS value requirements for the jfet except BL grade as per the schematics. Higher IDSS will produce more heat to dissipate. With +/- 15vdc you can target IDSS lower than 10ma which in circuit will give a max of about 7ma to produce 100ma which is quite acceptable. Thus any IDSS between 6-10ma will do fine.
Fab
Hi meanie
There is no specific IDSS value requirements for the jfet except BL grade as per the schematics. Higher IDSS will produce more heat to dissipate. With +/- 15vdc you can target IDSS lower than 10ma which in circuit will give a max of about 7ma to produce 100ma which is quite acceptable. Thus any IDSS between 6-10ma will do fine.
Fab
Last edited:
Hi
Fab I did not forget to finish the amp! I do have all the parts for. At the moment I am doing therapy at Toronto, Cham H for PTSD. The Centre for Addiction and Mental Health | CAMH
It will end before the end of summer unless they will send to do some other treatment or therapy. After that I will have more time.
Fab I did not forget to finish the amp! I do have all the parts for. At the moment I am doing therapy at Toronto, Cham H for PTSD. The Centre for Addiction and Mental Health | CAMH
It will end before the end of summer unless they will send to do some other treatment or therapy. After that I will have more time.
First, thanks to Fab for a fab amplifier!! got mine done, and absolutely enjoying it hooked up to my Martin Logan ESLs. dead silent, even with ear on speaker.
This was also a chance to try my hand at a diy chassis, so here are my monoblocks.
This was also a chance to try my hand at a diy chassis, so here are my monoblocks.
Congrats!
Mine also is driving a Martin Logan speaker, the Montis, which is an awesome combination!
Mine also is driving a Martin Logan speaker, the Montis, which is an awesome combination!
Hi surfatwork
Superb realization! You definitely have good skills for Diy chassis. You also seem to have VU meter but the picture is too small to clearly see.
Thanks for reporting your sound appreciation, this justifies my efforts to share this project.🙂
Fab
Superb realization! You definitely have good skills for Diy chassis. You also seem to have VU meter but the picture is too small to clearly see.
Thanks for reporting your sound appreciation, this justifies my efforts to share this project.🙂
Fab
Last edited: