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Old 22nd August 2005, 08:30 PM   #1
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Default Some Guidance

I would like to get some advice on a good first amp project. I currently am running two Infinity SM115's and a couple JL audio 10w3 's in an enclosure as a subwoofer. The sub is powered by an Apex Jr subwoofer amp. Prob a little low on the power side for the 300w rating on the 10w3's but it seems to drive them quite well.
Anyway I have this old sony STRDE505 reciver that I'm running the front speakers with.
I guess what I need is someone to just give me a little rundown about what exactly I need to go to some gainclones. Do I need to buy a preamp to use them?

I want to have a really good sounding home system for listening for music but I also plan to use it for home theatre surround as well. So what's the skinny?
I have a PC with an D-Audio 10 channel soundcard that I use for a home recording studio, I thought I could use it to do the surround processing when necessary.

Any guidance would be appriciated.

My Skills:
I have some basic electronics understanding and have done quite a few small electronics projects throughout my life. Soldiering would not be a problem. I guess what I would be looking for is a good quality kit that I could assemble myself that is going to give me the best sound quality for the money. I have a woodworking shop so I could make my own enclosure for the amp.

Thanks in advance for any help
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Old 22nd August 2005, 10:36 PM   #2
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How many watts do you think you will need?

How many channel you plan on using?
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Old 23rd August 2005, 02:26 AM   #3
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Location: Texas
if you live in the US check out BrainGT's kits
www.chipamp.com

if your outside the US use Peter's site. (he doesn't have any of the lm3886kits)
http://www.specializedkits.com/

They are both the same kits just that one guys handles the US and the other is International orders. You might be able to use your soundcard as a preamp, not to sure. Many use passive pre's from what i have read and there are some with active preamp's.
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Old 23rd August 2005, 01:42 PM   #4
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Default watts

Watts... Well from my studies on this site I have gotten the impression that wattage is not as important as I once thought. I assume that 50-100 watts would be adaquate. But I read about guys running tube amps that are 4 watts and are extremly loud.

On the kits. . I have looked at the chipamps site and am a little confused. The kits are two channel? Or one? Also they don't come with a power supply so I assume I have to get a transformer to run them. Does the Transformer size end up dictating how much wattage the amplifier makes? Does the way you make the amp decide which type of preamp you need to use?
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Old 23rd August 2005, 02:14 PM   #5
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Default Re: watts

Quote:
Originally posted by thermonuclear
Watts... Well from my studies on this site I have gotten the impression that wattage is not as important as I once thought. I assume that 50-100 watts would be adaquate. But I read about guys running tube amps that are 4 watts and are extremly loud.
It depends db per watt of your speakers. For tube amps it is around 94 to 100db per watt. For typical speakers (especially home theatre) 4 watt will not cut it. You are right to stick with 50-100watts


Quote:
Originally posted by thermonuclear

On the kits. . I have looked at the chipamps site and am a little confused. The kits are two channel? Or one? Also they don't come with a power supply so I assume I have to get a transformer to run them. Does the Transformer size end up dictating how much wattage the amplifier makes? Does the way you make the amp decide which type of preamp you need to use?
Most of the kit have everything but transformers. The kits are two channels. For a multi-channel amp a large transformer will be required. 25-0-25volt 250 to 300va per two channel is near normal
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Old 24th August 2005, 06:58 AM   #6
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does the size of the transformer dictate the wattage of the amplifier?
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Old 24th August 2005, 08:44 AM   #7
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The voltage does if you check data sheets for 4ohm speakers recommed voltage is 28volts and 8ohms is 35volts. If you read Brian's guide for building his amps he talks about the transformers. Generaly 160va is min. for a single channle, your amp will run out of gas when bass is going at high(er) volumes.
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Old 27th August 2005, 02:58 PM   #8
sr2002 is offline sr2002  India
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i would suggest making a pin 2 pin board instead of buying the kits.

kits cost more. and other thing is that the gainclones are so simple to build that u dont even need a pcb. Incase if ur building an amp with descrete components then maybe u need a pcb, but not here

that is if u have the patience to do proper p2p.

and be sure that u use good wires otherwise they'll smoke if ur tranny is big.

i have recently made a stereo lm3886 gainclone with p2p it sounds amazing.


if u want surround sound just make 5 lm3886 amps and add a common psu. ur trafo. should be more than 500va 20-0-20v.

remeber that after rectification the voltage increases by -- square root of 2 times.

that is if u use 25-0-25v trafo output is 35-0-35 approx.

so be sure to check the peak voltage of the chip ur going to use.

i am personnal thinking of building a surround amp. by useing lm4731. which a 25watt stereo. and they also operate at lower voltages. and if u want more power u can simply bridge the amp and get 50w.

u can even think of this chip. it will be easier. and sice ur just using the pc as the preamp, i would not suggest higher end chips like the lm38xx which operate at high voltages and will really need a pricy trafo.

another option is the lm4780 which is a bit complex for p2p.

ofcourse u can consult others on this forum, after all , those guys are more genius than me.
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Old 27th August 2005, 05:05 PM   #9
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I bought two 3886 monoblocks and a 3875 stereo kit. We will see how it all comes together.
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