Redesign of NAD receiver PS

tvrgeek · 19th January 2010, 08:58 PM

As mine failed, I was thinking of a re-design. Kind of clever, NAD. They have two taps on the transformer. The main one at about 30V, and a second at about 40. This is a "40W" receiver, so full rated power is withthe supply collapsed to 24V or so. They have a regulator between the tow. What seems to happen is that under very small load, the ps floats up to the lower full voltage. Low current, low ripple. The regulator does nothing. But when average current pulls the main supply down, the regulator uses the higher voltage to smooth the ripple. Slick. This provides a huge dynamic capability with a power supply suitable for a MP-3 player.

OK, plus side blown, trans obsolete, thermistor unknown.

Would it work to use a pair of 3-terminal regulators to try and regulate to "a ripple's worth" over whatever the main rail is floating to? Same idea, just 20 years newer parts.

tvrgeek · 24th January 2010, 02:35 AM

No suggestions, so I just ordered some new caps and some thermistors. Just going to double the bank and add an inrush limiter. Looks like a box of nails, so a hammer should do fine. I have too many projects to worry about it.

wwenze · 24th January 2010, 04:04 AM

They call it "Power Envelope" or something.

But I wonder if they could've just used a bigger PSU.

tvrgeek · 24th January 2010, 12:34 PM

Yup, I remember they called it that now. Slick actually.
Why not a bigger PS? Iron and caps cost money. Big iron, big money. That is why "real" power amps are bigger and heavier than an equivalence receiver.

Just found this
Quasi-Parallel Voltage Regulator - Patent application - Improved regulation and transient response are provided by a power supply architecture providing both unregulated and

Seems to be a "new" patent application for a 20 year old idea.

I think I understand it well enough I am going to try and pull it off with a 317 type setup. As long as the output does not collapse to the lower voltage, there would be almost no current in the regulator. I still need a pass transistor as peaks could be over an amp. My worry is if for some strange reason, it got turned up way louder than I need and the average power was over the 6 or 7 Watt threshold that causes the main supply to droop and it asks for more than an amp out of the regulator. I wish I understood the NAD circuit better, like why they have a bypass thermistor. My guess is it takes the current if the regulator drops out. I think a warning LED would be a good idea too.
Sorry, rambling while I try to visualize what is going on.

tvrgeek · 3rd February 2010, 04:51 PM

Got a nice thank you from NAD on bringing this to light. Yes, exactly as they did years ago. Note they have progressed from their original design to holding at the higher voltage unless the heat goes up.

My Mouser order should get here today so I can start playing.

19th January 2010, 08:58 PM	#1
tvrgeek diyAudio Member Join Date: Dec 2009 Location: Md	Redesign of NAD receiver PS As mine failed, I was thinking of a re-design. Kind of clever, NAD. They have two taps on the transformer. The main one at about 30V, and a second at about 40. This is a "40W" receiver, so full rated power is withthe supply collapsed to 24V or so. They have a regulator between the tow. What seems to happen is that under very small load, the ps floats up to the lower full voltage. Low current, low ripple. The regulator does nothing. But when average current pulls the main supply down, the regulator uses the higher voltage to smooth the ripple. Slick. This provides a huge dynamic capability with a power supply suitable for a MP-3 player. OK, plus side blown, trans obsolete, thermistor unknown. Would it work to use a pair of 3-terminal regulators to try and regulate to "a ripple's worth" over whatever the main rail is floating to? Same idea, just 20 years newer parts.

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
NAD 7250PE receiver	jazzy nate	Solid State	7	23rd April 2010 09:10 PM
NAD 7020 receiver	chemicall	Solid State	0	13th December 2008 04:42 PM
Looking for manual for NAD 7020e receiver	MatthewK	Solid State	0	24th October 2007 03:10 AM
Backlights for NAD Receiver, CD Player	tchp	Parts	4	8th March 2007 07:48 AM
FS: NAD T753 6.1 receiver	tunemanjjw	Swap Meet	1	17th October 2004 08:04 AM

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


	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

24th January 2010, 02:35 AM	#2
tvrgeek diyAudio Member Join Date: Dec 2009 Location: Md	No suggestions, so I just ordered some new caps and some thermistors. Just going to double the bank and add an inrush limiter. Looks like a box of nails, so a hammer should do fine. I have too many projects to worry about it.

24th January 2010, 04:04 AM	#3
wwenze diyAudio Member Join Date: Mar 2008	They call it "Power Envelope" or something. But I wonder if they could've just used a bigger PSU.

24th January 2010, 12:34 PM	#4
tvrgeek diyAudio Member Join Date: Dec 2009 Location: Md	Yup, I remember they called it that now. Slick actually. Why not a bigger PS? Iron and caps cost money. Big iron, big money. That is why "real" power amps are bigger and heavier than an equivalence receiver. Just found this Quasi-Parallel Voltage Regulator - Patent application - Improved regulation and transient response are provided by a power supply architecture providing both unregulated and Seems to be a "new" patent application for a 20 year old idea. I think I understand it well enough I am going to try and pull it off with a 317 type setup. As long as the output does not collapse to the lower voltage, there would be almost no current in the regulator. I still need a pass transistor as peaks could be over an amp. My worry is if for some strange reason, it got turned up way louder than I need and the average power was over the 6 or 7 Watt threshold that causes the main supply to droop and it asks for more than an amp out of the regulator. I wish I understood the NAD circuit better, like why they have a bypass thermistor. My guess is it takes the current if the regulator drops out. I think a warning LED would be a good idea too. Sorry, rambling while I try to visualize what is going on.

3rd February 2010, 04:51 PM	#5
tvrgeek diyAudio Member Join Date: Dec 2009 Location: Md	Got a nice thank you from NAD on bringing this to light. Yes, exactly as they did years ago. Note they have progressed from their original design to holding at the higher voltage unless the heat goes up. My Mouser order should get here today so I can start playing.

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