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Chip Amps Amplifiers based on integrated circuits

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Old 4th April 2011, 12:31 AM   #11
Minion is offline Minion  Canada
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Yes that will work well , it also has a dual primary so you will have to wire the primaries in Paralell and because it has a dual secondary and wire it in series and use the connecting point between the secondaries as your ground ....

hopefully your transformer will have instructions on how to do this , if not post back and someone will help you ....


PS: you also going to need a 6v-0v-6v transformer for your preamp , maybe you can find a transformer that is 6v-0v-6v and 35v-0v-35v so you don"t have to buy 2 seperate ones ....
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Old 6th April 2011, 12:52 PM   #12
AndrewT is offline AndrewT  Scotland
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Originally Posted by Minion View Post
.............. And because each channel of the amp is 125w or 250w total you need about double that amount of power in the power transformer as most amps of this type are at best 50% effecient .....
where did this come from?

It seems like you have drawn a conclusion on transformer power based on a completely erroneous efficiency statement that is simply untrue.

A 125W amplifier will run well from a 125VA to 250VA transformer.
Two channels will run well from a 250VA to 500VA transformer.

These 125W amplifiers will also work with transformer ratings outside that restricted range, only less well. Above the 500VA the transformer provides less performance value for the monetary value expended.
Below 125VA the performance deteriorates much more than what could be saved in transformer cost.
One has to apply a cost benefit analysis. How much performance do I need? How much can I afford to spend?
Do not believe a fixed figure of 250VA for a 125W amplifier.
regards Andrew T.
Sent from my desktop computer using a keyboard

Last edited by AndrewT; 6th April 2011 at 01:01 PM.
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Old 8th April 2011, 03:45 AM   #13
bs1777 is offline bs1777  Canada
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So if i have a 240 watt RMS amp. What will power it to its full potential?

And i also need help with a case, cause right now, im am not sure that with all the things i have, it will meet my budget. So anything cheap for a case, or a used or burned out amp case will work.

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Old 8th April 2011, 08:59 PM   #14
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That depends, is it class A, then a small nuclear substation is in order, class B 500VA is more than enough, and less is fine depending on the load and volume at which it is driven to. Class D, takes what it puts out and sips a little bit extra.

A 250VA transformer is more than enough for a stereo pair of LM3875 driven into 8R at 35VDC supply, and will only get mildly hot when driven hard.
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Old 9th April 2011, 02:21 AM   #15
bs1777 is offline bs1777  Canada
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Its class AB. So what will i need now? And there is two amps btw.
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Old 9th April 2011, 06:27 AM   #16
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I had a look at your amp, it says 2 x 120W at + and -50V. So I would at a minimum use a 500VA 2x35VAC transformer.... I'd certainly also use bigger heatsinks than the ones in the product shots...
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Old 30th May 2011, 05:40 PM   #17
amptech is offline amptech  Scotland
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Bs1777..have you got a good power supply for your amplifier build?
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Old 30th May 2011, 06:24 PM   #18
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Read Audio Sector's,, and Decibel Dungeon's sites for tons of basic info on building amps and power supplies. Lots of ideas and common practices as well as safety issues addressed. These sites were invalueble to me when I first got started in DIY Audio. Good luck!
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Old 9th July 2012, 02:29 PM   #19
Le Pick is offline Le Pick  Canada
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How did you hook up your wires for the power to VEE, VCC and GND? From what I've saw, I think that you need -50V / GND / +50V.
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