48 VDC from 60 V unregulated

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Why not pre-regulate the LM317T. Use a simple Zener + Transistor regulator before the LM317T to reduce the voltage to just above the minimum input voltage for the IC.


Indeed, a transistor bypass design is wise in some cases, and insures things are well within the safety area.
I've implimented countless designs like that with excellent reliability and results.
 
You don't seem to get it do you?

One last attempt:

During startup conditions, the load and its bypassing will keep the output node at ~GND.
The additional 317 bypass cap will ensure the startup OP voltage is ~0 (1.25V in fact).
But, at that time, the input voltage is already ~60V, thus the differential seen by the 317 is ~60V.

Now, you can argue about the rate of rise of input supply, try to reduce the bypass cap to just pass, etc, but that's like rearranging the deck-chairs on the Titanic: weak attempts to manage a certain disaster.

Now, I give up: I you cannot comprehend the above, there is nothing more I can do
 
I found this online. I breaded boarded it to see if it works and it did.
It worked up to over 300 vac on the input and regulated down from
that. I also used a 50 vac transformer and it worked down from that.
I did not use it in a circuit so I don't know how it sounds.
 

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Another solution would be to use a TL783 - see chapter 9 of the PDF file below, there are some useful examples:
http://www.ti.com/lit/ds/symlink/tl783.pdf
Yes, that is one of the option I recommended

I found this online. I breaded boarded it to see if it works and it did.
It worked up to over 300 vac on the input and regulated down from
that. I also used a 50 vac transformer and it worked down from that.
I did not use it in a circuit so I don't know how it sounds.
It is not a regulator: it is a crude voltage reducer + protection.
In addition, it will require a much higher dropout voltage than what is available here
 
I found this online. I breaded boarded it to see if it works and it did.
It worked up to over 300 vac on the input and regulated down from
that. I also used a 50 vac transformer and it worked down from that.
I did not use it in a circuit so I don't know how it sounds.

If I can say, I know and tested this circuit and it is not much fine. It's useful for higher voltages and an output within 100 mA max.
 
Thanks, I will simulate it and see. The circuit seems to be good, I've just left a TIP122 left.

Why would you need to simulate anything? LV’s circuit is simple, almost foolproof, and easy to analyze by hand with a pencil, paper and a calculator.

And you don’t need to be limited to a TIP122. Any darlington or darlington connected pair with sufficient ratings (calculated with pencil and paper) will work.

I like this circuit a lot - I prefer something like this as opposed to using 3 terminal regulators in most applications. Especially ones where capacitive loads can risk the regulator misbehaving and blowing out a board full of IC’s that have to be replaced....
 

PRR

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A transitorized zener regulator, simple, good...but doesn't the zd add some "noise" for the amp circuit?

So? There's always some noise. Low noise was not in the requirements. IMHO a 48V 500mA load is likely to be a High Level stage and not noise-critical. If this is really a Phantom Power supply for 48 microphones, a little filtering might be wanted, but Phantom is fairly uncritical of supply noise, and it is customary to put say 220r+220uFd on each output.

The OP requires only a 12 volt drop from 60V to a regulated 48V, so there's no problem. The LM317T would only be absorbing 12 volts, so where is the problem?

At start up. The input power goes to 60V with full force of the power company through the transformer. Any capacitor on the regulator output will start from ZERO and lag significantly behind the rise of input of raw DC. This does not always pop a '317; to puzzle the builder, sometimes it works a dozen start-ups before failing.

Also, for self-protected regulators, in overload. Load rises over 1 Amp. Regulator turns-off. Now it feels the full 60V input voltage. The cut-off breakdown may be a little higher than the 35-40V operating breakdown, but maybe 20% and not always 50% over.
 
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