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Old 13th June 2013, 11:17 PM   #1
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Default A little confused

I have been itching to build an active speaker for some time now and I was looking at 2 amp models on ebay.

LME49810 Top Audio Power Amplifier Kit Board Mono 300W | eBay

Stereo HiFi Two Channel Amplifier LME49810 10000uF 63V Power Filtering Protecive | eBay

I can't seem to find a power supply to meet these needs. The first link has a relay attached so the power supply could be build in for all I know. Are the leads going straight to a transformer?
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Old 14th June 2013, 12:47 AM   #2
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I don't know which drivers you are planning to, however, I can say that amount of power is not necessary. It may give plenty of headroom but that sort of power is more suited to passive speakers where there are considerable losses in the crossover.

Because the drivers are being driven directly by an individual amp, far less power is required, even for very high volumes. My active three ways are powered by LM3866TFs and there is not ever any want for more power, and that is driven to about 1/3 of their maximum.

The advantages of lesser powered amps are smaller size, lower power dissipation (not always), and lower cost. Anyway, it is your money and how you spend it is up to you. In this case, overspending won't necessarily confer any, if at all, advantages.
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Old 14th June 2013, 03:32 AM   #3
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I was thinking about an AB amp + D amp (for sub) in an active speaker. You are right about the power but I am still curious about the power supply. In a situation such as yours, how do you implement the potentiometer to control all 3 amps?
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Old 14th June 2013, 05:13 AM   #4
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I should say that I don't want to put you off going active, far from it. I think you will find the benefits immediately obvious and immensely enjoyable.

That said, I believe one of the amp modules requires a split DC supply and the requirements are shown as such, whereas the other needs an AC supply though whether it is centre-tapped isn't clear. You might have to email the vendor. If nothing else, it may also gauge the level of support you may get if you buy.

I control the volume with a pre-amp, using a PGA2310, from which a balanced feed is fed to both speakers. "Smells Like Teen Spirit" can fill the neighbourhood, as can Natalie Merchant.
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Old 14th June 2013, 06:05 AM   #5
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Hmmm, I submitted a post and it vanished.

To control volume, for both speakers where all amps and the crossover are housed, I use a pre-amp with a PGA2310. A balanced feed then goes to the speakers. I'm not familiar with other mechanisms but, nonetheless, I think sticking to a central control is the easiest option. If there rae others, I invite other posters to provide information, for us both.
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Old 14th June 2013, 06:06 AM   #6
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Then it magically appeared!
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Old 14th June 2013, 06:08 AM   #7
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Quote:
Originally Posted by Absconditus View Post
Then it magically appeared!


Because as a new member you are under moderation... be patient
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Old 14th June 2013, 04:50 PM   #8
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@Absconditus

Can you give me a breakdown of your system? It sounds like you have done what I have in mind. I am open to using several lower powered amps for each driver but am inexperienced.
I am not sure if I should utilize multiple power supplies at that point (switching or linear), need a rectifier or attenuator, etc.
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Old 14th June 2013, 04:51 PM   #9
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Also, do you have any recommendations for AB class mono amps between 80 and 100W?
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Old 15th June 2013, 12:53 AM   #10
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I can't give any recommendations for those sort of amps, having not ever used them. There are threads on this forum about such amps, eg the Wire, of which many posters speak highly. There is plenty of information, including building them.

My system is based on advice from a former member of this forum and, for which, I thank him. It uses the chip amp, LM3886TF, for all drivers and in bridge mode for the woofer. I use a 25-0-25 toroidal transformer that gives +-35V and which also allows a +-15V supply for the op-amps in the crossovers and balanced signal driver for the bridged amps.

My system is a three way and I have ever found that volume is lacking. One thing that many don't seem to realise is that an active system can be at ridiculously high levels but does not appear to be that loud because the music is not distorted; it is just louder, as my neighbour in the next street can attest. (Sorry Danny. )

The LM3886 gives about 60W RMS into 8 ohms and bridged gives about 100W RMS. You will NEVER get to use even close to half of that power unless you need to use them for very, very large rooms (or for rave parties where there can be chemically induced deafness). The advantage of them is the small PCB size for the output, particularly when all of the electronics are housed in the speaker cabinet.

I was recommended to use Rod Elliott's PCBs (ESP Sound Products)and I am grateful for that advice. They are the P19 and are small, easy to use and, from my experience, totally reliable. I also use the P05 and P33 boards and have not encoutered any problems at all.

If you need more information, I am happy to give it. Please be specific in what you want though?
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