Building an amp - Page 2

Minion · 4th April 2011, 12:31 AM

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 ....

Cheers

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 ....

AndrewT · 01:01 PM

Quote:

Originally Posted by Minion

.............. 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.

bs1777 · 8th April 2011, 03:45 AM

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.

-Thanks

digits · 8th April 2011, 08:59 PM

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.

bs1777 · 9th April 2011, 02:21 AM

Its class AB. So what will i need now? And there is two amps btw.

digits · 9th April 2011, 06:27 AM

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...

amptech · 30th May 2011, 05:40 PM

Bs1777..have you got a good power supply for your amplifier build?

muddobber · 30th May 2011, 06:24 PM

Read Audio Sector's, Chipamp.com, 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!

Le Pick · 9th July 2012, 02:29 PM

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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4th April 2011, 12:31 AM	#11
Minion diyAudio Member Join Date: May 2006	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 .... Cheers 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 ....

8th April 2011, 03:45 AM	#13
bs1777 diyAudio Member Join Date: Dec 2010 Location: Saskatchewan	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. -Thanks

8th April 2011, 08:59 PM	#14
digits diyAudio Member Join Date: Apr 2011	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.

9th April 2011, 02:21 AM	#15
bs1777 diyAudio Member Join Date: Dec 2010 Location: Saskatchewan	Its class AB. So what will i need now? And there is two amps btw.

9th April 2011, 06:27 AM	#16
digits diyAudio Member Join Date: Apr 2011	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...

30th May 2011, 05:40 PM	#17
amptech diyAudio Member Join Date: Jan 2009 Location: Glasgow	Bs1777..have you got a good power supply for your amplifier build?

30th May 2011, 06:24 PM	#18
muddobber diyAudio Member Join Date: Oct 2010 Location: Houston,TX	Read Audio Sector's, Chipamp.com, 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!

9th July 2012, 02:29 PM	#19
Le Pick diyAudio Member Join Date: Jun 2012 Location: Quebec	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.