Dual rail power supply for class A amplifiers

Hi JHUSTON,
I can send you the gerbers. I have redesigned that board using the TO247 Darlington transistor as an alternative to the legendary 2N6284/87.
Please verify which version you need, TO3 or TO247.
Here are the two boards plus CRC.
crc.JPG
TO3.JPG
TO247.JPG


Have a nice day
Spiros
 
I'm in the proces of assembling this P.S. design in order to feed some Class A mosfet amplifiers , operating at 1A per output device.
I'm using Sanken MP1620 / MN2488 darlington transistors simply because i have these in stock.
So far i have tested and adjusted the output voltage without load and works okay so far .
Just wondering about what voltage drop across the darlington will be optimal for proper regulation while keeping the dissipation safely
In relation to the heatsink i'm using right now ... should i measure a certain temperature on the heatsink ?
Thank you in advance
 
First attempt ,
I cannot dial in the 3 Volt drop across the darlington under load .
8 Volt is minimum 🤔
Also , I measure 250mV ripple at both POS. & NEG. rail .
Perhaps the two 7500 uF caps are not sufficient ? Well let me check out tomorrow and grab some higher capacitance value .
Maybe I need CRC as well. It's real nothing more than a bridge and a cap pair right now .
 
I cannot dial in the 3 Volt drop across the darlington under load
How did you try to do that?
Note that the input ripple is high(er) at the input and the 3V needs to be present from the lowest point on the input voltage, the lowest point of the ripple voltage. If the average voltage measured on an average-responding multimeter is 20V, with 4V p-p ripple, your minimum across the darlington should be 5V measured on an averaging-responding multimeter to respect the 3V minimum.
Also, what was the load current for those ripple values?

That heatsink seems adequate for 6W-ish max dissipation.

Jan
 
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This circuit works fine in my 3 class A amps. My heat sinks are a little wider than yours: 48cm X 16cm X 5cm. It gets hot with a 2A QC, but the ripple is just 2 to 6 mV.
The multiturn trimpot adjusts the desired voltage 3 volts below the secondary one. I used 4 X 15000uF smoothing caps before that circuit, just after the rectifying bridge. You can see the circuit board at post #64. Try to lower the 1K5/5W resistor to 1K. What is the output of your trafo secondary, and how many volts do you need for your amp?