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Old 14th September 2011, 10:46 PM   #111
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Quote:
Originally Posted by petegt View Post
Isnt the output device irf4020 a major factor in the output??
I use a tc4420 buffer to drive 4 irfb4227.
With a single pair it will drive 500 watts.
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Old 14th September 2011, 10:51 PM   #112
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Originally Posted by petegt View Post
Nice What rail voltage are you running?
+/-70V.
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Old 14th September 2011, 10:51 PM   #113
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Is that something you have designed yourself? Im in need of something suitable to run on 86V rails (54 0 54 V transformer 2x 15000uf caps ). Id did have one of these boards which the ebay seller assured me would run fine on my power supply and that it would not put out 86v dc even after I measured it.
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Old 15th September 2011, 12:15 AM   #114
Bernie7 is offline Bernie7  Singapore
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Originally Posted by rickedd46 View Post
I got these boards yesterday and have been listening to them every time I get a break. My fear of them not handling 4 ohms is gone after playing them fairly loud for about 1 hour. They only get warm to the touch but I'm not using all the power these can produce. With a small fan they're cold like a corpse.
Good to hear that! Anything to say about the sound compared to your other gear?

Got my modules some time ago, but still waiting for my smps
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Old 15th September 2011, 04:04 PM   #115
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by petegt View Post
Is that something you have designed yourself? Im in need of something suitable to run on 86V rails (54 0 54 V transformer 2x 15000uf caps ). Id did have one of these boards which the ebay seller assured me would run fine on my power supply and that it would not put out 86v dc even after I measured it.
DC + -86V,about 500W 8OHM。1000W 4ohm.

The voltage is a little on the high side.
L20D is the default recommend DC 65 V + 200 W 8 OHM.

If you must use this voltage L20 D. Need to change some resistance.

Let L20D work in this voltage and also need to change the higher compression capacitance.

And the output power can't more than 300 W8R
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Old 15th September 2011, 04:14 PM   #116
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by nigelwright7557 View Post
I use a tc4420 buffer to drive 4 irfb4227.
With a single pair it will drive 500 watts.


This is a good plan.
I also have a lot of IRFB4227. But more than 500 W power inductor is very expensive.
Digital special inductor need to use SAGAMI 7G31A. (In IRAUDAMP9 )

For most of the people may be wasted money.
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Old 15th September 2011, 04:16 PM   #117
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Originally Posted by Bernie7 View Post
Good to hear that! Anything to say about the sound compared to your other gear?

Got my modules some time ago, but still waiting for my smps
Hello,

I will do some serious listening and do comparisons several times this week then I will give some feedback.

Last edited by rickedd46; 15th September 2011 at 04:20 PM.
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Old 16th September 2011, 01:36 AM   #118
Bernie7 is offline Bernie7  Singapore
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Originally Posted by ljm_ljm View Post
Hello, you can't change this only resistance.

Because he will affect the switch frequency.
So is there any other way to increase the 3.3k input impedance to 20k or 50k without affecting switching frequency?
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Old 16th September 2011, 02:33 AM   #119
ljm_ljm is offline ljm_ljm  China
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Originally Posted by Bernie7 View Post
So is there any other way to increase the 3.3k input impedance to 20k or 50k without affecting switching frequency?

Why did you do this?
Are you going to put input capacitance into small capacity of the MKP?

Suggest parallel is more than 10 UF
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Old 16th September 2011, 12:53 PM   #120
Bernie7 is offline Bernie7  Singapore
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Originally Posted by ljm_ljm View Post
Why did you do this?
Are you going to put input capacitance into small capacity of the MKP?

Suggest parallel is more than 10 UF
We were earlier discussing the possibility of increasing the 3.3k input impedance by increasing Rin and Rfb. You said this would change the switching frequency. So I'm now asking if there is any other way to increase input impedance perhaps by changing other resistors too. This is nothing to do with input blocking cap.

3.3k is very low for a power amp and may deter many from using L20D if they're using passive preamps.
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