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Old 18th March 2012, 08:11 AM   #371
clm811 is offline clm811  United States
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Hi.

Similarly, I've purchased two L25D from ebay and want to use an existing power supply (very "stiff" +/-75vdc dual channel) from an old 200wpc (high-end) stereo power amp.

My woofers are 4ohms, and am hoping to get good results here, replacing a pair of 10 year old 250W plate amps...

Any experience or advice here?

-Chas

Last edited by clm811; 18th March 2012 at 08:22 AM. Reason: Typo
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Old 18th March 2012, 11:28 AM   #372
norazmi is offline norazmi  Malaysia
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how about u tell us after power it up clm811 ?
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Old 18th March 2012, 09:51 PM   #373
clm811 is offline clm811  United States
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I only ordered yesterday.
May take a few weeks to receive from Hong Kong.

Just wondering if anyone here used such high voltage rails, as
the ad said 70v gives 350W into 2 ohms...

-Chas
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Old 18th March 2012, 11:31 PM   #374
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So from what i read there are lots of people building these amps! But no one has posted anything about how they sound, and how they compare in sound quality to other Diy amps. ?? Can anyone please share their opinion?
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Old 19th March 2012, 12:33 AM   #375
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Quote:
Originally Posted by solviken View Post
So from what i read there are lots of people building these amps! But no one has posted anything about how they sound, and how they compare in sound quality to other Diy amps. ?? Can anyone please share their opinion?
I have built a 2092 with 2 off IRFB4227 and it sounds very good.

I have also built a 750 watt with 4 off IRFB4227 into 2 ohms and that sounds great too.

To drive the 4227's I used TC4420 driver chips.
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Old 19th March 2012, 12:59 AM   #376
cwier60 is offline cwier60  United States
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Quote:
Originally Posted by clm811 View Post
Similarly, I've purchased two L25D from ebay and want to use an existing power supply (very "stiff" +/-75vdc dual channel) from an old 200wpc (high-end) stereo power amp.

My woofers are 4ohms, and am hoping to get good results here
Quote:
Originally Posted by clm811 View Post
Just wondering if anyone here used such high voltage rails, as the ad said 70v gives 350W into 2 ohms...
I'm assuming that your very "stiff" +/-75vdc dual channel supply is a linear unregulated transformer/bridge. The key is how high the idle voltage will be, since the idle dissipation of the 2 channels will be only ~15W. 70v gives 350W into 2 ohms must be a typo, as I think it's more like 350W into 4 ohms.

You really need to figure out a few things, though. I'm not sure from your posts whether you have 2 or 4 channels, but your L25Ds driving 4 Ohms per channel could deliver up to 1.4KW if your very "stiff" supply really were. Regardless how high-end your 200W amp was, I doubt the supply has that much margin. If it does, then that explains why many audiophile equipment companies don't stay in business.

If you know you'll be driving 4 Ohm loads only, then you'd be much better off with a lower voltage supply, such as +/- 50V unless you're really looking for 350W/ch. If you're going to stick with your "stiff" +/-75vdc dual channel supply, then you need to figure out the supply's load regulation over the load range you expect in your application to make sure it's acceptable for your L25Ds.
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Old 19th March 2012, 01:40 AM   #377
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Default TC4420

Hi Nigelwright7557
greetings

Quote:
Originally Posted by solviken View Post
So from what i read there are lots of people building these amps! But no one has posted anything about how they sound, and how they compare in sound quality to other Diy amps. ?? Can anyone please share their opinion?
I have built a 2092 with 2 off IRFB4227 and it sounds very good.

I have also built a 750 watt with 4 off IRFB4227 into 2 ohms and that sounds great too.

To drive the 4227's I used TC4420 driver chips
TC4420EPA or TC4420MJA which one do you use to drive IRFB4227
warm regards
andrew lebon
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Old 19th March 2012, 06:21 AM   #378
clm811 is offline clm811  United States
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Quote:
"...L25Ds driving 4 Ohms per channel could deliver up to 1.4KW if your very "stiff" supply really were. Regardless how high-end your 200W amp was, I doubt the supply has that much margin...
This was a PS Audio 200C, a 70lb monster with a huge transformer and 20,000ufd of computer-grade cans each channel. It was rated (and reviewed by Stereophile) for 200wpc/8ohms, 400wpc/4ohms and 1,000wpc into 1.5 ohms! I'd say the supply has the margin for this application; The question is: is the amp capable of handling the supply and the load (nominal 6ohms, 4ohms min).

-Chas
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Old 19th March 2012, 10:41 AM   #379
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Default Tiny phase inverter for L15 , 20 and 25 D

I build this tiny phase inverter to drive 2 of the 5 amps in my HT amp with 5 L15Dís with opposite phase to avoid bus pumping .
The schematic is from the reference design IRAUDAMP7D REV 2.8 page 32
The PCB measures 16 x 16 mm and fits well under the amp with double sided tape . Youíll need some higher stand offs .


Works great
The scope pic is driving my front channels in a 4 ohm dummyload .
The decoupling caps are mounted in the IC socket
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Old 19th March 2012, 01:42 PM   #380
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With reference to power supplies:

LJM recommends a psu board earlier in this thread with many capacitors. Can these run a stereo pair of boards or do I need to buy one for each amplifier board? They seem to have 25A rectifiers. Is this the limiting factor, and will 25A be enough to power two boards with +/-70V (2 x 50Vac transformer)?

I am trying to decide whether to go for a linear PSU with the above PSU board (more expensive) or SMPS from connexelectronics for my 8 channel power amp (8 x L25D boards).

Kind regards,

Jai
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