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Old 7th July 2005, 10:55 PM   #1
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Join Date: May 2005
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Default before I order my gainclone LM4780's....

Couple of questions...

I'm going to build 2 gainclones... one will be a 4 channel LM4780 which I simply want to use to around 70 WPC (whatever the max is)... for midranges

the other gainclone amp will be a parallel amplifier with 2 4780's per channel at around 100+ wpc paralleled for tweeters... for 4 ohm driving

1. Should I buy 8 4780 kits then? I'm assuming so...
2. Should I purchase the 3 snubberized PSU boards for this also?
3. What transformers with dual secondaries (this means I can run 2 channels of one transformer right?) should I purchase... I'm assuming the ones for the smaller non-parallel will be smaller than for the parallel amplifier

Help please?? purchasing these before the end of the night hopefully
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Old 8th July 2005, 01:10 AM   #2
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Old 8th July 2005, 02:14 AM   #3
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Can I ask why you only need 70 watts for your midranges, and 100(!) watts for your tweeters. Surely you don't need that much?

In answer to your questions,

1) Yes, if you want one amp with 4 channels and another amp with 2 paralleled channels, then you will need 8 LM4780 boards.
2) Not sure how you'd wire up three PSU boards to 8 boards symmetrically though. I would have gone with 4 PSU's personally.
3) a 500-700VA toroidal should be enough for each amplifier.
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Old 8th July 2005, 03:39 AM   #4
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I need more power like that simply because there is an ambience tweeter and they're far more inefficent than the midranges (PHL 1120's)

I need those PSU boards correct? the rectifier boards is somethign different right?

also that 500-700VA split to 2 channels right? and how many volts and amps should that be on the secondaries?
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Old 8th July 2005, 04:08 AM   #5
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Ah ok, I didn't know what type of speakers you were trying to drive.

The PSU boards are the rectifier boards. There is no difference between the two. The PSU board contains the Diodes, and capacitors.

For your 4 ohm loads, you'll want a lower voltage (for more current). I'm not entirely sure what the maximum would be (considering the chips are in parallel) but a safe voltage would be 18v secondaries (which will give roughly 25v after rectification).
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Old 8th July 2005, 04:10 AM   #6
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Forgot to answer your other question. Yes the single toroidal should be able to handle both channels. If you want, you could get two smaller toroidals (say two 300VA) for a dual mono type supply which has its own benefits too.
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Old 8th July 2005, 04:45 AM   #7
sachi is offline sachi  United States
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Hello ther..
sorry to butt in..i just received my PCBs for the 3886 and the 4780 from Peter..

Now i am building a 3 way active monitor and am planning to use these two amps along with a Nad 320BEE..

I would want to know ur suggestions regarding the transformers VA and secondary rating ...how many trannies will i need for the 3886 and the 4780..

also which amp should power which driver..considering the load and power handling of the drivers ?

The tweeter is
http://www.partsexpress.com/pe/showd...number=264-526
midrange
http://www.partsexpress.com/pe/showd...number=299-492
woofer
http://www.partsexpress.com/pe/showd...number=295-315

please advise...
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Old 8th July 2005, 05:54 AM   #8
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Quote:
Originally posted by mangrovejack
Ah ok, I didn't know what type of speakers you were trying to drive.

The PSU boards are the rectifier boards. There is no difference between the two. The PSU board contains the Diodes, and capacitors.

For your 4 ohm loads, you'll want a lower voltage (for more current). I'm not entirely sure what the maximum would be (considering the chips are in parallel) but a safe voltage would be 18v secondaries (which will give roughly 25v after rectification).
alright that's what I thought about the rectifier boards... the kits come with those and parts to populate the boards
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