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Old 19th June 2012, 12:23 PM   #1
Lumi71 is offline Lumi71  Germany
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Default Help for beginner with L25D amp

hi there,

i am new to this forum.
at the moment i am looking for a four channel or two stereo amp to power my active speakers.



so i came across the L15-L25D boards. Since i am an absolute beginner in this area i asked along (ebay shop) if he could also finish/assemble the whole amp. and he would do.
He made me an offer with following parts:

power supply:

http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MESE:IT

trafo-
http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MESE:IT

boards-

http://www.ebay.com/itm/Assembled-L2...item19ce8749dc



before deciding to buy i just want to make sure if these parts are a good combination.- as i really have no idea...

also important is that the amp should be capable of driving at least 3 ohm (imp. min. of the woofer) .


thanks a lot
stefan

Last edited by Lumi71; 19th June 2012 at 09:47 PM.
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Old 19th June 2012, 10:06 PM   #2
Lumi71 is offline Lumi71  Germany
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no one to help..?
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Old 20th June 2012, 07:59 AM   #3
jogas is offline jogas  Italy
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Location: Milan
Hello
As I understood from the specs on ebay

- the trafo gives 40-0-40 Vac that means 56-0-56 VDC on the caps.
- the caps on the PS board are rated 50VDC (too low)

The L25D needs min 60VDC recommended 70VDC max 80 VDC, therefore you risk to blow up the Caps and even if they survive you have not enough volts to correctly power your L25 amps, moreover, in my opinion a single 300W transfomer is just enough for one amp, (assuming it has the right voltage)

regards
Giuseppe

Last edited by jogas; 20th June 2012 at 08:02 AM.
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Old 20th June 2012, 09:31 PM   #4
exflaco is offline exflaco  Armenia
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Hey Jogas the 50v capacitors are near the l2092 in the zone 5,6v and 12v zeners before the 3k3 resistence 50v are aceptable,sorry my poor english work very well the sound es good as especifications
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Old 20th June 2012, 09:36 PM   #5
exflaco is offline exflaco  Armenia
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Lumi 71 your choice l15d works fine 4ohm ,wats woofer you are? 3 ohm very rare
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Old 20th June 2012, 10:11 PM   #6
Lumi71 is offline Lumi71  Germany
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thanks, so far guys!

the woofer are nominated for 4 ohms, but the impedance minimum is 3 ohm....
the amp boards would be the l25d, not the l15d
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Old 20th June 2012, 11:55 PM   #7
exflaco is offline exflaco  Armenia
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Lumi the l25d Dont work 4ohm i have 6 ld25 and 2 ld15 ,only ld15 work 4ohms l25d cut at 4 the oscilator
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Old 21st June 2012, 12:01 AM   #8
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Hi Lumi,

The 50 Volt Caps on the power supply are too low voltage. The might explode on you.
The 40 Volt transformer will give after rectification 40 X 1.4 = 56 Volts DC which the capacitors have to handle. 56 Volts is a bit too little for the L25D. The designer recommended to me a 45 Volt transformer and a power supply with 80 Volt capacitors. Stick with the L25D, one guy reported some problems with his 2.5 Ohm minimum speakers with the L15D.

Where are you located?
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Old 21st June 2012, 06:22 AM   #9
Lumi71 is offline Lumi71  Germany
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i am in germany
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Old 21st June 2012, 09:59 AM   #10
jogas is offline jogas  Italy
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Join Date: Jun 2004
Location: Milan
@EXFLACO

I was talking about the Power supply board to be ordered by Lumi.
The board is showing 50VDc caps.
If you feed the board with 40Vac -> 56VDC you may blow the caps, therefore that board is not usable with 40Vac tarnsformer and moreover, the recommended values for the L25 are 60-70-80 VDC.
regards
Giuseppe
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