Advice wanted - regulated PSU for Vin 42 V / Vout 25-40 V

Groundloops · 15th February 2007, 02:16 PM

I want to build kinda "universal amplifier PSU", adjustable from 25 to 40 volts and giving enough current to drive GC, MyRev, Symasym and others. I got a pair of 30 V / 240 VA dual secondary transformers and no clue. What regulator is recommended? All I found is the LM317HV, but it doesn´t give enough current ...

Don´t want to spend so much for transformers anymore.

Thanks.

richie00boy · 15th February 2007, 02:21 PM

Look on the LM317 datasheet for how to add pass transistors to boost current.

Given the cost and heatsinking required for this project, I would just build a simple fixed unregulated PSU from a 100VA 2x25V transformer. There's rarely any need to have any more voltage than this just for testing.

Groundloops · 15th February 2007, 02:36 PM

Thank you, richie00boy. But it´s not meant for testing only.

richie00boy · 15th February 2007, 02:40 PM

Well even more reason to build a simple fixed unregulated supply then. Just build it with the most voltage whatever circuit you anticipate to use in the future will take.

blmn · 15th February 2007, 02:59 PM

Try LM338 (5A regulator). It must be enough.

[url]http://www.datasheet4u.com/html/L/M/3/LM338_STMicroelectronics.pdf.html

Best regards,

AndrewT · 15th February 2007, 03:13 PM

Hi,
an advantage of a regulated supply is flexibility for testing prototype circuits.

I see the main advantage as adjustable current limit.

For power amp duty, stay with unregulated.

Groundloops · 15th February 2007, 03:17 PM

@ blmn: Vout of LM338 is 32 V max. ...

@ richie00boy: And what¢¥s about lower voltages then? For example a LM3875 with 4 §Ù load is ~25 V. A MyRev takes ~34 V. A Sysmasym ~36 V. And so on ...

In the future I don¢¥t want to burn money for all the transformers, that¢¥s in the back of my mind.

richie00boy · 15th February 2007, 03:20 PM

Just build a 25V supply then. The other amps will still work perfectly fine with this voltage.

The heatsinking cost, size and messing about building a powerful enough regulated supply might as well be spent on a new unregulated PSU for each amp as you need it.

valveitude · 15th February 2007, 03:31 PM

Quote:

@ blmn: Vout of LM338 is 32 V max. ...

Put a 10V zener from the "Adjust" pin to ground. This will float the reg., making it 11.2-42V instead of 1.2-32V.

-Casey

blmn · 15th February 2007, 03:32 PM

No,

VDiff for LM338 is 35V, If properly designed, fits OK for your needs.

It must be a problem in case of short-circuits, but, since you don´t need less than 25V, you can pre-regulate or drop the voltage to achieve what you want.

But, for linear power supplies, is not a easy task achieve well regulated 40V from more or less 43 volts. The transformer must be very good. For this level of voltage I sugest you work in non regulated mode. A switch to bypass the regulator could work.

Best regards,

15th February 2007, 02:16 PM	#1
Groundloops diyAudio Member Join Date: May 2004 Location: Hamburg / Northern Germany	Advice wanted - regulated PSU for Vin 42 V / Vout 25-40 V I want to build kinda "universal amplifier PSU", adjustable from 25 to 40 volts and giving enough current to drive GC, MyRev, Symasym and others. I got a pair of 30 V / 240 VA dual secondary transformers and no clue. What regulator is recommended? All I found is the LM317HV, but it doesn´t give enough current ... Don´t want to spend so much for transformers anymore. Thanks.

15th February 2007, 02:21 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Look on the LM317 datasheet for how to add pass transistors to boost current. Given the cost and heatsinking required for this project, I would just build a simple fixed unregulated PSU from a 100VA 2x25V transformer. There's rarely any need to have any more voltage than this just for testing. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

15th February 2007, 02:40 PM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Well even more reason to build a simple fixed unregulated supply then. Just build it with the most voltage whatever circuit you anticipate to use in the future will take. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

15th February 2007, 03:20 PM	#8
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Just build a 25V supply then. The other amps will still work perfectly fine with this voltage. The heatsinking cost, size and messing about building a powerful enough regulated supply might as well be spent on a new unregulated PSU for each amp as you need it. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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15th February 2007, 02:36 PM	#3
Groundloops diyAudio Member Join Date: May 2004 Location: Hamburg / Northern Germany	Thank you, richie00boy. But it´s not meant for testing only.

15th February 2007, 02:59 PM	#5
blmn diyAudio Member Join Date: Feb 2001 Location: .	Try LM338 (5A regulator). It must be enough. [url]http://www.datasheet4u.com/html/L/M/3/LM338_STMicroelectronics.pdf.html Best regards,

15th February 2007, 03:13 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, an advantage of a regulated supply is flexibility for testing prototype circuits. I see the main advantage as adjustable current limit. For power amp duty, stay with unregulated.

15th February 2007, 03:17 PM	#7
Groundloops diyAudio Member Join Date: May 2004 Location: Hamburg / Northern Germany	@ blmn: Vout of LM338 is 32 V max. ... @ richie00boy: And what¢¥s about lower voltages then? For example a LM3875 with 4 §Ù load is ~25 V. A MyRev takes ~34 V. A Sysmasym ~36 V. And so on ... In the future I don¢¥t want to burn money for all the transformers, that¢¥s in the back of my mind.

15th February 2007, 03:32 PM	#10
blmn diyAudio Member Join Date: Feb 2001 Location: .	No, VDiff for LM338 is 35V, If properly designed, fits OK for your needs. It must be a problem in case of short-circuits, but, since you don´t need less than 25V, you can pre-regulate or drop the voltage to achieve what you want. But, for linear power supplies, is not a easy task achieve well regulated 40V from more or less 43 volts. The transformer must be very good. For this level of voltage I sugest you work in non regulated mode. A switch to bypass the regulator could work. Best regards,

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