I am preparing to build a F5T amp based on the guides in the forum.
See that a stereo F-5T v2 requires a bipolar power supply of (+/- 32V). This will require an 24V+24V (or 48V Center Tapped) transformer from 600-800VA, and PSU capacitance of 80,000uF per rail or more.
Unfortunately the Antek AN-6224 is out of stock at the moment.
What other good options do I have?
See that a stereo F-5T v2 requires a bipolar power supply of (+/- 32V). This will require an 24V+24V (or 48V Center Tapped) transformer from 600-800VA, and PSU capacitance of 80,000uF per rail or more.
Unfortunately the Antek AN-6224 is out of stock at the moment.
What other good options do I have?
AN-8225 - 800VA 25V Transformer - AnTek Products Corp
You probably want 800VA instead of 600VA. 25V vs 24V is trivial. My f5T w/24V transformer ends up with 30.5V rails under load (1.9A bias). Depending on your mains voltage 25V might actually get you closer to 32V rails.
You probably want 800VA instead of 600VA. 25V vs 24V is trivial. My f5T w/24V transformer ends up with 30.5V rails under load (1.9A bias). Depending on your mains voltage 25V might actually get you closer to 32V rails.
If you want to buy American you try Toroid Corporation in Salisbury Md.
Toroid Corporation, US manufacturer of Toroidal Magnetic Components
Part number 782.242 is a 820VA transformer and 798.242 is a 1000VA transformer. Both have 110V primarily and dual 24V secondary windings.
You could also try Hammond or Triad from Mouser or Digi-Key.
Toroid Corporation, US manufacturer of Toroidal Magnetic Components
Part number 782.242 is a 820VA transformer and 798.242 is a 1000VA transformer. Both have 110V primarily and dual 24V secondary windings.
You could also try Hammond or Triad from Mouser or Digi-Key.
You don't need to tune down the extra voltage. The F5T has a cascode circuit for the input jfets so you can actually even go with higher voltage, taking into account the amount of heatsink necessary.
Most power supplies drop about 2-3 volts when you bias the amplifier into class A.
My F4 power supply has 33V rails when unloaded and it drops to about 30.5 when biased (about 2.8 A per channel)
There is cascode in F5T v3. But even for v2, I would not worry about the 1VAC difference.
And if you do find the voltage under load to be higher than you like, you can always
increase the R in the CRC power supply a little to burn some voltage (and lower ripple
at the same time.)
I would pay attention to the Idss of the jfet to make sure their thermal dissipation isn't
too high.
Cheers,
Dennis
And if you do find the voltage under load to be higher than you like, you can always
increase the R in the CRC power supply a little to burn some voltage (and lower ripple
at the same time.)
I would pay attention to the Idss of the jfet to make sure their thermal dissipation isn't
too high.
Cheers,
Dennis
How are you getting 2.8A per channel? monoblocks?
My f5 with 31V rails can only get to about 1.8 or 1.9A bias per channel in the 5U chassis. Heatsink temps are 55C, sometimes more if it's a hot day.
My F5T (no cascode) with 31-ish volt rails and 8ma jfets results in 43C case temps on the jfets. I have little push-on sinks on them. Nothing to worry about I think.
I have about .45-.47 A on each of the 6 output transistors, in a 5U dissipante case. The hottest spot in the sinks on a hot summer day is about 57-59º. My f4 is built without the input jfets as it is driven by a BA3 front end.
.47*30,5V*6= about 86W dissipated in each channel.
My BA3 has 31 volt rails and 1000 VA and has run a long time with no problems.
Russellc
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