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Old 2nd May 2012, 11:37 AM   #421
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by ZachAttack420 View Post
When putting on the heat sink compound which side of the silicone pad does it go or does it go on both sides?

Silver compound okay?
Heatsink compound used to ensure that any gaps between the two surfaces you are mating (ie the component and the heatsink itself) are filled with something that will transfer heat, so that the heat is consistently(and efficiently) transferred from the component to the heatsink.

If there is already a non-electrically conductive pad like a silicon pad being used, it will do that job by itself (fill any gaps that is) without additional heatsink compound.
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Old 2nd May 2012, 03:34 PM   #422
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I have read that you must install heat sinking grease with the l 25 d in addition to the silicone pads. I have read that on this forum as well as from zoe........as I understand these get very hot when operating at higher levels. The listing I bought these from says you need both....confirmation from LJM, please?

The silver compound may be electrically conductive.....any concerns?

Last edited by ZachAttack420; 2nd May 2012 at 03:42 PM.
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Old 3rd May 2012, 02:34 PM   #423
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What kind of power can I expect @ 8Ohms with 110VCT / 2.5A transformer (Per L25D board)... Will they be starving for current?

Last edited by DarpMalone; 3rd May 2012 at 02:54 PM.
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Old 3rd May 2012, 06:18 PM   #424
MrSlim is offline MrSlim  Canada
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Originally Posted by DarpMalone View Post
What kind of power can I expect @ 8Ohms with 110VCT / 2.5A transformer (Per L25D board)... Will they be starving for current?
Well if we use P = V*I, then you'll be able to supply just over 250 watts with that with no wiggle room. The L25D's are supposed to be 97% efficient at 100% load, so you should get pretty close to that out..

That's not accounting for losses in the rest of the power supply though..
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Old 3rd May 2012, 06:39 PM   #425
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Originally Posted by MrSlim View Post
Well if we use P = V*I, then you'll be able to supply just over 250 watts with that with no wiggle room. The L25D's are supposed to be 97% efficient at 100% load, so you should get pretty close to that out..

That's not accounting for losses in the rest of the power supply though..
Thanks MrSlim... Should I not base this formula on the voltage after rectification (+-78v x 2.5A) or am I dreaming?

Last edited by DarpMalone; 3rd May 2012 at 06:49 PM.
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Old 3rd May 2012, 07:54 PM   #426
alkasar is offline alkasar  France
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Yes, you dream
Your transformer can deliver 2.5amp ac max.
Considering the amp efficiency close to 100%, the max rms power you can get in 8ohms is P=R*IČ=50Wrms

Your amp will not be able to use the full 78V, because the available current from power supply will be limited first.
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Old 3rd May 2012, 08:02 PM   #427
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Quote:
Originally Posted by ZachAttack420 View Post
I have read that you must install heat sinking grease with the l 25 d in addition to the silicone pads. I have read that on this forum as well as from zoe........as I understand these get very hot when operating at higher levels. The listing I bought these from says you need both....confirmation from LJM, please?

The silver compound may be electrically conductive.....any concerns?
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Old 3rd May 2012, 08:16 PM   #428
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Quote:
Originally Posted by alkasar View Post
Yes, you dream
Your transformer can deliver 2.5amp ac max.
Considering the amp efficiency close to 100%, the max rms power you can get in 8ohms is P=R*IČ=50Wrms

Your amp will not be able to use the full 78V, because the available current from power supply will be limited first.
So you 're saying I'd need 5.6A (give or take) to get 250 watts RMS? (more or less, a 600VA transformer)
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Old 3rd May 2012, 10:17 PM   #429
alkasar is offline alkasar  France
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Originally Posted by DarpMalone View Post
So you 're saying I'd need 5.6A (give or take) to get 250 watts RMS? (more or less, a 600VA transformer)
not really that much for one amp
To get 250Wrms in 8ohm you need 44.6Vrms and 5.6Arms.
To get 44.6Vrms music, the amp must be powered at about 68-70Vdc or above (to take into account voltage drop of power transistors).
+-70Vdc translates back into about 2x50Vac transformer. It should be rated 50*5.6=280VA or more.
For a stereo amp, 2x250Wrms, you indeed need a 2x50V 600VA transformer.
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Old 4th May 2012, 01:13 AM   #430
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Quote:
Originally Posted by alkasar View Post
not really that much for one amp
To get 250Wrms in 8ohm you need 44.6Vrms and 5.6Arms.
To get 44.6Vrms music, the amp must be powered at about 68-70Vdc or above (to take into account voltage drop of power transistors).
+-70Vdc translates back into about 2x50Vac transformer. It should be rated 50*5.6=280VA or more.
For a stereo amp, 2x250Wrms, you indeed need a 2x50V 600VA transformer.
Wouldn't the VA rating on a 100Vct / 5.6A be 560? Pardon my ignorance
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