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Old 23rd December 2006, 09:10 PM   #1
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Default Newb amp help

I came here from another site after reading about Gainclone amps.

One thing I cannot find is their wattage output.

How "big" can they go, how big do they need to go?

I drive a set of Deftech 7002's with the 135watt amp built into my Yamaha receiver and wanted to go with a better cleaner sound.

Will these eclipse the internal amp or can it be built to do so?

Has anyone put these together in a group to make a true 5 channel amp?

I've been reading all day and already have 5 new projects

I did do some searching but could not find a concrete answer to what I was looking for.
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Old 23rd December 2006, 09:35 PM   #2
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Hi Eric,

Welcome aboard.

The wattage depends on the chip used and supply voltage. Look at the LM1875, LM3875 etc datasheets for all the information.

http://www.datasheet4u.com/search.php

If you bridge and parallel them you can go up to a couple of hundred watts. Look for BPA-200 on Nationals site. The size you need depends on the efficiency of your speakers and their impedance. I find 30 to 50 watt amps are more than enough.

I have an old '90's Yamaha amp and a simple GC sounds a lot better to me. I guess newer Yamaha's *must* be better than my old thing though.

I remember a few 5 channel threads but they don't interest me so I can't add anything.

I suggest, as these things are so cheap, build a point to point wiring version and see if you like the sound of them. If you are happy with the results, build a bigger more complicated one (if necessary??).

Nuuk's site is a great place to learn all about these things:

http://myweb.tiscali.co.uk/nuukspot/decdun/index.html

regards
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Old 23rd December 2006, 09:50 PM   #3
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Quote:
Originally posted by Greg Erskine
I suggest, as these things are so cheap, build a point to point wiring version and see if you like the sound of them. If you are happy with the results, build a bigger more complicated one (if necessary??).

Nuuk's site is a great place to learn all about these things:

http://myweb.tiscali.co.uk/nuukspot/decdun/index.html

regards [/B]
I think I might have to second this opinion

A basic GC (unregulated supply and the likes) is pretty easy to build (for me, finding, buying and cutting out things in the case was by far the hardest part!).

You might be suprised as to how loud ~30-40W, probably even 10W is (with moderately easy to drive / average sensitive speakers). I was.

Nuuk's site is definately a good place for GC related stuff
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Old 23rd December 2006, 09:51 PM   #4
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I'm just guessing but, according to the description, the internal amp may be the Bash 300s.

I have used the 300 with the LM3886. LM3875, and the LM4780. All with great results. Never a hint of clipping.
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Old 23rd December 2006, 10:06 PM   #5
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Greg,

Thanks for the reply.

I did find a site that I believe was 300 watt.

I've heard very good things about the amp built into the RX-V2600, I believe its a Class D.

Still I like the idea of doing things myself. I have been told by another 2600 owner running a 125 watt external amp that although the internal amp is good, running separate really does help the sound.

I have a set of PE BR-1's upstairs in the wife's workout room. I was planning on building a small unit and just plugging an iPod into it to see how it worked.

The biggest problem that I can see is the overwhelming amount of information. I've seen 15 different approaches to the same thing.

I've read that these amps are the best thing for the money but I guess I'm not sure how much you'd have to spend to get to the same quality.

5 channel would be something I am interested in since I do listen to a lot of surround stuff.

I'll check out the link you sent over.

Thanks
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Old 24th December 2006, 11:30 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
for a first amp project keep it simple.

You can use it for sound reinforcement somewhere. If it turns out to better than the multichannel versions that come later you can always build a second to make a pair of monoblocks.

Build a single channel chipamp and get it working properly. With this experience you can then make informed decisions on what you need for power, channels, etc.

Down load the datasheets (from national.com) for your proposed chips. If you can't understand them, then come back with some/lots of questions.
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Old 24th December 2006, 12:26 PM   #7
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I've spent most of the time since I posted this yesterday and now reading every single page I can find on it.

My biggest problem is a lack of reference in regards to some of the terminology and schematic layout.

I've built a crossover from a schematic, although it did come with a pre-printed PCB.

Most of the designs I've seen do not talk about power output. I guess I should start with the simple stuff.

1. What is speaker efficiency and how does it relate to power output. All the pages I read say build the amp and choose the power supply to relate to the speakers efficiency but I did not find any explanation as to what that means. My current speakers dont' give much info. Just compatible with 8ohms and recommended power rating is 20-400 watts. They are Definitive Technology 7002's and that is the only information I could find on Definitives web page.

2. If I do want 150-200 watts per channel, how many of these things can I bridge together? Do you reach a point of diminishing return or do you start to create problems when you get to a certain number in series?

3. What kits out there relate to what power ratings?

Maybe I'm too stuck on the whole power output thing and if I am I don't understand why I should not be

My goal isn't so much to build one to build one and tinker around. I want to build one if it is going to be superior to what I have now, and or superior to what I could get for 1K USD in a 5.1 200 watt Outlaw amp.

Thats for our main setup. Now for my office, the wife's office, etc I would be interested in building a smaller model.

I guess my best place to start is I have a set of Parts Express BR-1's that I built to test out my soldering skills. They current are in my wife's workout room and what I would like to do is build a amp to drive them and use something simple like an iPod for music.

The speaker I built has the following specs from their site:


System Specification: Frequency response: 43-18,000 Hz, SPL: 85 dB 2.83V/1m
Power handling: 100 watts max.

What can I go do this week to build something for that? We have a large electronics store which carries pretty much everything you can imagine so I should be able to get the parts. I don't care if its in a box I can rough wire it together, try it out, then worry about doing it ina box or something similar.

I tend to understand more when I see cause and effect. I have some more reading to do on electronic theory from some of those pages. I'm sure once I have more of an understanding of why it works it will help out quite a bit.

Yesterday this started out trying to find out where to install some accoustic panels and EQ'ing my room, I read one thread and now here I am

Thanks for everyones help
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Old 24th December 2006, 01:08 PM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Eric_B_C
1. What is speaker efficiency and how does it relate to power output. All the pages I read say build the amp and choose the power supply to relate to the speakers efficiency but I did not find any explanation as to what that means. My current speakers dont' give much info. Just compatible with 8ohms and recommended power rating is 20-400 watts. They are Definitive Technology 7002's and that is the only information I could find on Definitives web page.

2. If I do want 150-200 watts per channel, how many of these things can I bridge together? Do you reach a point of diminishing return or do you start to create problems when you get to a certain number in series?

3. What kits out there relate to what power ratings?

Maybe I'm too stuck on the whole power output thing and if I am I don't understand why I should not be

My goal isn't so much to build one to build one and tinker around. I want to build one if it is going to be superior to what I have now, and or superior to what I could get for 1K USD in a 5.1 200 watt Outlaw amp.

Thats for our main setup. Now for my office, the wife's office, etc I would be interested in building a smaller model.

I guess my best place to start is I have a set of Parts Express BR-1's that I built to test out my soldering skills. They current are in my wife's workout room and what I would like to do is build a amp to drive them and use something simple like an iPod for music.

The speaker I built has the following specs from their site:


System Specification: Frequency response: 43-18,000 Hz, SPL: 85 dB 2.83V/1m
Power handling: 100 watts max.

I said keep the first one simple. I really mean that. Get more ambitious later.

Sensitivity is measured in 85db/2.83V.
This means that an amplifier that can push 100W into 8r and 200W into 4r and 400W into 2r will try to maintain 2.83V into the speaker at any frequency. The 100W will produce an output +20dbW above the 85db reference equating to a maximum output of 105db. This is loud, loud enough to damage your ears in the short term and deafening , in the literal sense, in the long term.
But, average music levels are 10db to 20db below maximum, so the 100W amp & 85db speakers when the volume control is set to loud BUT WITHOUT CLIPPING will produce between 85db and 95db. This range is still quite loud but not deafening. Turn the volume down another 10 to 20db and that is a loud conversation.

So, using power and sensitivty you can predict the range of SPL the system will produce and decide if this is suitable to your needs/wants.
Build your first amp and try it out, remember I said "informed decision" making.


The attraction of chipamps is simplicity. Start bridging and that advantage disappears. I believe that higher powers are better achieved with discrete. However there is a chipamp that I only recently became aware of, it is the whole chipamp but without an output stage and with care can be scaled from 20W to 200W into any conventional load impedance. It will not drive 2ohm speakers to high power. It is the next level of complexity above the true chipamp and fills the gap between simple discrete and chipamp, but includes a number of nice add-ons that would normally make discrete quite complex.

Don't get bogged down in the power game like the car audio folk have.
BTW 90db speakers and 50W (achievable with a chipamp) will give about 107db maximum, just a little bit louder than that previous example.
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Old 24th December 2006, 03:22 PM   #9
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Thanks, that makes more sense, I'll have to do some more diggiing around about my speakers efficiency.

I assume this is at a A weighting?

I do listen around 85 a A weighting, disregarding the readings I get when bass is playing. I'll see 105db out of my sub but have been lead to believe that is not dangerous, its the midrange stuff at those levels.

One of the things I thought having more wattage did was drive up the low end. Its tough to explain. At low volumes my system is, well low Some of the smaller details are lost at those volume levels. I thought with an amp where you had a higher wattage starting point at the low end you would get more definition and clarity even at the low volume levels.

There are so many designs out there. Can you point me in the direction of a simple small 2 channel unit. I want to build a 2 channel because it will give me a direct reference to other 2 channel stuff I have in the house. I don't care if it fits in a box, I just want to solder something together and try it out.

Thanks
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Old 24th December 2006, 03:22 PM   #10
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One more question since I can't edit my posts yet.

On the wattage, isn't that split between the drivers?

In one tower I have 6 drivers. 4 mid ranges and 2 tweeters. So if your 50watt example was applied to my speaker would I not need 300 watts? 6x50 so that each speaker was given 50 watt?
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