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Old 21st June 2012, 10:12 PM   #1
sam18 is offline sam18  United Kingdom
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Default help with power supply, really stressed

hey guys been pulling my hair out trying to find a power supply schematics for a +45v and -45v power supply. its the only thing holding me up in my build and im not going to lie i need help as everything i try just doesn't seem to give me the negative voltage i need.
any help with be much appreciated.
thanks sam

this is the amp im building if its any help.
300 Watt MOSFET Real HI-FI Power Amplifier | EEWeb
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Old 21st June 2012, 10:19 PM   #2
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Hi Sam I've moved your thread to the powersupplies forum. You might want to have a read through this Elliott Sound Products - Linear Power Supply Design It's pretty long but should give you a good grounding in powersupply design

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Old 21st June 2012, 10:25 PM   #3
sam18 is offline sam18  United Kingdom
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hello thanks, sorry still learning where things go on a seccondry note, how do i workout what the primary and seccondry inductance will be on a 300va 45-45v transformer?
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Old 21st June 2012, 11:42 PM   #4
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by sam18 View Post
how do i workout what the primary and seccondry
inductance will be on a 300va 45-45v transformer?
Hi, Why would you want / need to know that ?, rgds, sreten.

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Old 21st June 2012, 11:45 PM   #5
sam18 is offline sam18  United Kingdom
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because im using a software called proteus (what i was trained on) and need to know how to set up a transformer
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Old 22nd June 2012, 12:25 AM   #6
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Default What do you have so far for your power supply?

Quote:
Originally Posted by sam18 View Post
hey guys been pulling my hair out trying to find a power supply schematics for a +45v and -45v power supply. its the only thing holding me up in my build and im not going to lie i need help as everything i try just doesn't seem to give me the negative voltage i need.
any help with be much appreciated.
thanks sam

this is the amp im building if its any help.
300 Watt MOSFET Real HI-FI Power Amplifier | EEWeb
Do you have a picture, schematic, or a basic list of parts for your power supply? If you're only getting the positive rail and not the negative, it could be something as simple as a measuring problem, all the way to something possibly lethal. If we have something to start with, we can give you some much better advice where to proceed.

In the mean time, utilize extreme care with the supply, and I'd definitely do some reading on the suggested Elliot Sound site. That site is a wealth of audio and power information that seems to be very accurate and science/measurement-based.

On a side note, you may want to search this site for information on the amp you built/are building. A cursory look shows an issue with the bias circuit and a couple other potential problems. With the vast history of amp reviews done on this forum, your amp is bound to have been looked into, so you shouldn't need to start a new thread.
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Old 22nd June 2012, 12:41 AM   #7
Minion is offline Minion  Canada
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A simple Dual rail linear PSU for a power amp isn"t really that tough ......

A 2 x 35v AC transformer or a 70v CT transformer with a 25A bridge rectifier , 4 x 10,000uF 50V+ caps , a couple 1w resistors and a couple small film caps for the snubber will get you a quiet reliable PSU for a power amp ......

I have never had to simulate this type of PSU as most are very simular , some with more capacitance and some with less ......

the designer of this amp says he prefers to use a lower capacitance PSU which i don"t agree with at all but to each his own .....

Cheers
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Old 22nd June 2012, 08:45 PM   #8
sam18 is offline sam18  United Kingdom
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here is my current design, it uses a 300va 45-0-45 transformer (currently being substituted with two alternators running at 45v each) bridge 1 is a 200v/35a and the +/- 45v is working perfectly. its the +25v im having trouble getting to work, its very unstable, anyone got any ideas? thanks sam
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Old 22nd June 2012, 11:32 PM   #9
sam18 is offline sam18  United Kingdom
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Bump
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Old 22nd June 2012, 11:54 PM   #10
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Your schematic is very small and hard to read. What voltage is coming across C6? It looks like you are missing a voltage-dropping resistor on your 25v+.
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