higher voltage PS

Steven Koay · 9th September 2003, 06:27 AM

I did purchased toroid trans from farnell with 35-0-35 250VA. After passed through bridge rectifer, it access +- 100v which over LM3875 specification. Any one would like to help me on how to modify the PS to reduce the output volatage. Current I managed to reduce it with RC circuit BUT it have distortion when switch on & have some kind like air sound flow from left speaker to right speaker after 10sec switched on the amp.

Hybrid fourdoor · 9th September 2003, 04:36 PM

So you bought a 35V torroid, but it's giving you 100V instead? Could this be a result of internal wiring flaw?

kropf · 9th September 2003, 04:54 PM

Quote:

Originally posted by Steven Koay
I did purchased toroid trans from farnell with 35-0-35 250VA. After passed through bridge rectifer, it access +- 100v which over LM3875 specification.

It's possibly specified for 110VAC primaries. Are your primaries 220 VAC?

Jeremy

moe29 · 9th September 2003, 05:08 PM

sounds like you have the secondaries wired together?

35+35=70, 70*1.414 = 99 (or 100 V)

check your wiring.

as is after rectification your going to get 50V from each secondary.
isn't that a bit much for a GC?

Steven Koay · 10th September 2003, 05:15 AM

Is correct, the calculation from 70*1.414 = 100v, which exceeded LM3875 specification which only allow to have 85v. I did include RC circuit in PS to reduce the voltage to 80v ( put the meter probe to + & - point to get 80v. But the sound have distortion like air sound flow from left speaker to right speaker. But the distortion went away IF the remove the RC circuit.

carlmart · 10th September 2003, 11:29 AM

Quote:

Originally posted by Steven Koay
Is correct, the calculation from 70*1.414 = 100v, which exceeded LM3875 specification which only allow to have 85v. I did include RC circuit in PS to reduce the voltage to 80v ( put the meter probe to + & - point to get 80v. But the sound have distortion like air sound flow from left speaker to right speaker. But the distortion went away IF the remove the RC circuit.

There's an obvious option: you can build a regulator for your GC.

Some have reported good results from regulating, some say the GC sounded worst. Pedja has a nice regulator on his page.

You will have some heat, from the 7.5v x current on each regulator, but it could be worst.

Not everything is lost.

Carlos

9th September 2003, 06:27 AM	#1
Steven Koay diyAudio Member Join Date: Aug 2003 Location: Penang	higher voltage PS I did purchased toroid trans from farnell with 35-0-35 250VA. After passed through bridge rectifer, it access +- 100v which over LM3875 specification. Any one would like to help me on how to modify the PS to reduce the output volatage. Current I managed to reduce it with RC circuit BUT it have distortion when switch on & have some kind like air sound flow from left speaker to right speaker after 10sec switched on the amp.

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
Zen V1 Higher Voltage Rails?	fligti91	Pass Labs	4	13th November 2008 04:00 AM
Cap voltage can I go higher	captaink	Digital Source	3	3rd November 2007 08:56 PM
higher voltage than BC550/560?	kubeek	Parts	10	12th September 2006 04:52 PM
Running BLS on higher voltage	Illusus	Pass Labs	3	12th March 2005 05:21 AM
Super-power amps - higher current better than higher voltage	Circlotron	Solid State	34	28th June 2002 04:01 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

9th September 2003, 04:36 PM	#2
Hybrid fourdoor diyAudio Member Join Date: May 2003 Location: Ft. Worth, TX	So you bought a 35V torroid, but it's giving you 100V instead? Could this be a result of internal wiring flaw?

9th September 2003, 05:08 PM	#4
moe29 diyAudio Member Join Date: Dec 2002 Location: Florida	sounds like you have the secondaries wired together? 35+35=70, 70*1.414 = 99 (or 100 V) check your wiring. as is after rectification your going to get 50V from each secondary. isn't that a bit much for a GC?

10th September 2003, 05:15 AM	#5
Steven Koay diyAudio Member Join Date: Aug 2003 Location: Penang	Is correct, the calculation from 70*1.414 = 100v, which exceeded LM3875 specification which only allow to have 85v. I did include RC circuit in PS to reduce the voltage to 80v ( put the meter probe to + & - point to get 80v. But the sound have distortion like air sound flow from left speaker to right speaker. But the distortion went away IF the remove the RC circuit.