How to reduce voltage from PSU??

oblerum · 8th August 2006, 04:33 AM

Hi!

I am building an Aleph 5 clone, and used PCB-KK pcb's.
Anyone with a god tip how too reduse 42,6V to 33-35V.
(500VA toroids)

I have 6X10000uF (each canal), and I have 42,6V before load is conected. When I connected an 8,4ohm load I mesure 37,1V.
That is a little to high for an Aleph 5 clone.

I planed to 0,235R in series with the + and - just after the bridge, is this a good solution to get the voltage down?
What is the negative with this solution?

O.B Lerum

araven · 8th August 2006, 09:17 AM

Hi,

I'll start this one off, but i'll need alot of correcting as i'm still a bit of a newbie.
Firstly if you put a resistor in series after the bridge and before your filter caps, you have to remember that you are creating an RC filter low pass filter as well. with a 0.235r and a 10000uF filter cap alone you have a low pass filter operating at a frequency of 68hz, this is not good.
Secondly, the power supply should have as close to 0 resistance as possible, to improve the damping characteristics of the PSU, your large array 10000uF in parallel really help to keep overall impedance of the PSU down, it would be a shame to add 0.235ohms there.
You could either change you design to a fully regulated one, or use more wasteful bridges, and/or diodes to reduce the voltage, although this is a wasteful act.

Alex

sreten · 8th August 2006, 10:41 AM

Hi,

Search on CRC filters, common in valve amplifier supplies.

Adding R immediately after the bridge will not work
well as it limits the charging current to the capacitors.

also take a look at this :

http://sound.westhost.com/project15.htm

A Simple Capacitance Multiplier Power Supply For Class-A Amplifiers

/sreten.

Jennice · 8th August 2006, 10:41 AM

I think this issue has already been addressed by others and commented by Mr. Pass. Since it's a class A design, current consumption is fairly stable, which gives alternatives.

Try searching for keywords on this subject, and posts by Nelson Pass.

Jennice

oblerum · 10th August 2006, 07:04 AM

Thanks

I think I'll use an CRC or an CLC.

I got myself the PSU-designer so I'ii take some new calculatins.

8th August 2006, 04:33 AM	#1
oblerum diyAudio Member Join Date: Jan 2005 Location: Raufoss	How to reduse voltage from PSU?? Hi! I am building an Aleph 5 clone, and used PCB-KK pcb's. Anyone with a god tip how too reduse 42,6V to 33-35V. (500VA toroids) I have 6X10000uF (each canal), and I have 42,6V before load is conected. When I connected an 8,4ohm load I mesure 37,1V. That is a little to high for an Aleph 5 clone. I planed to 0,235R in series with the + and - just after the bridge, is this a good solution to get the voltage down? What is the negative with this solution? O.B Lerum __________________ Ole-Bjørn Lerum

8th August 2006, 10:41 AM	#4
Jennice diyAudio Member Join Date: Jun 2003 Location: Planet Earth	I think this issue has already been addressed by others and commented by Mr. Pass. Since it's a class A design, current consumption is fairly stable, which gives alternatives. Try searching for keywords on this subject, and posts by Nelson Pass. Jennice __________________ I get paid to break stuff. My g/f gets paid to play with children. Life is good.

10th August 2006, 07:04 AM	#5
oblerum diyAudio Member Join Date: Jan 2005 Location: Raufoss	Thanks I think I'll use an CRC or an CLC. I got myself the PSU-designer so I'ii take some new calculatins. __________________ Ole-Bjørn Lerum

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
how to reduce PSU DC voltage	space2000	Solid State	11	18th May 2008 10:12 AM
PS Problem: How do I Reduce Voltage?	slor	Tubes / Valves	7	27th April 2008 03:18 PM
Voltage divider to reduce 6v dc to 2vdc	duderduderini	Tubes / Valves	5	26th February 2008 09:28 PM
Reduce wallwart voltage	argonrepublic	Parts	2	19th February 2006 02:51 PM
Help:How To Reduce Transformer Output Voltage?	phill77	Solid State	0	21st April 2003 12:04 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th August 2006, 09:17 AM	#2
araven diyAudio Member Join Date: Aug 2006	Hi, I'll start this one off, but i'll need alot of correcting as i'm still a bit of a newbie. Firstly if you put a resistor in series after the bridge and before your filter caps, you have to remember that you are creating an RC filter low pass filter as well. with a 0.235r and a 10000uF filter cap alone you have a low pass filter operating at a frequency of 68hz, this is not good. Secondly, the power supply should have as close to 0 resistance as possible, to improve the damping characteristics of the PSU, your large array 10000uF in parallel really help to keep overall impedance of the PSU down, it would be a shame to add 0.235ohms there. You could either change you design to a fully regulated one, or use more wasteful bridges, and/or diodes to reduce the voltage, although this is a wasteful act. Alex

8th August 2006, 10:41 AM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Search on CRC filters, common in valve amplifier supplies. Adding R immediately after the bridge will not work well as it limits the charging current to the capacitors. also take a look at this : http://sound.westhost.com/project15.htm A Simple Capacitance Multiplier Power Supply For Class-A Amplifiers /sreten.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read