After buying my Son an MP3 player for Christmas I started looking into songs I could down load for him. I really got in the mood to seriuosly listen to music again. I even got the pair of little Bose out of the closet and hooked them up to a small amp and CD player. Knowing that even tho it was enjoyable, the little 5 watter was robing my of the full sound.
So, needing a good amp, I started searching on the net and got into the DIY/Gainclone thing. Since I have a very small budget, I realised that after I got the amp and built it, I would have to save again untill I got the transformer. Then, lo and behold, (this must be a sign
), I had one slapped in my hand from a buddy who had no idea of my new project!
So here is the plan. I am convinced that the best way to go about this is to get the LM3875 kit from Chipamp.com. It's a convient pacage with enough left to do that you still feel like you built yourself. For the supply, I have a 250VA center taped transformer that puts out 36 volts to center tap.
I have a pair of Bose 201 speakers (8 ohm) that I will use as "close feild monitors". No real intensions to fill up a room. In fact IMHO, close feild monitoring is the best way to hear the sound the producer intended, sense room accoustics hardly inter into effect.
Any opinions as to what results I will get, or problems I should anticipate are very much appreciated.
Thanks in advance,
David
Fairmount, GA USA
So, needing a good amp, I started searching on the net and got into the DIY/Gainclone thing. Since I have a very small budget, I realised that after I got the amp and built it, I would have to save again untill I got the transformer. Then, lo and behold, (this must be a sign
), I had one slapped in my hand from a buddy who had no idea of my new project!So here is the plan. I am convinced that the best way to go about this is to get the LM3875 kit from Chipamp.com. It's a convient pacage with enough left to do that you still feel like you built yourself. For the supply, I have a 250VA center taped transformer that puts out 36 volts to center tap.
I have a pair of Bose 201 speakers (8 ohm) that I will use as "close feild monitors". No real intensions to fill up a room. In fact IMHO, close feild monitoring is the best way to hear the sound the producer intended, sense room accoustics hardly inter into effect.
Any opinions as to what results I will get, or problems I should anticipate are very much appreciated.
Thanks in advance,
David
Fairmount, GA USA
Ok, you've convinced me. It's kinda embarassing but, I'm really limited on my budget. I have an ex employer who has a huge surplus of 120/24V single secondary transformers. I'm pretty sure he would let me have a pair. Would that work well? What VA would you recommend for minimum?
Thanks all.
Thanks all.
As a newbie to decent audio (you should have seen the look on my face when I got my 75$ Sherwood amp working!), I was wondering the best way for a newbie to start with Gainclone or chipamps.
I was looking at the 35$ 3875-based stereo kit for use with my current speakers, Advent Baby Legacy's I picked up for next to nothing. They're good speakers, but I think I could make them perform better.
Also, I was wondering if these could be used with, for example, subwoofers. I'd really like a 5.1 surround setup; perhaps with a 3875 stero amp for the main channels, a mono amp for the center and subwoofer channels, and a cheap-O amp for the rear channels.
I've got a little experience with a soldering iron, and would be interested in keeping the price low. I've got access to PCB's and ferric chloride to etch them, so I'm set there; would it be worth my while to just buy a kit? Also, which transformer should I buy?
I was looking at the 35$ 3875-based stereo kit for use with my current speakers, Advent Baby Legacy's I picked up for next to nothing. They're good speakers, but I think I could make them perform better.
Also, I was wondering if these could be used with, for example, subwoofers. I'd really like a 5.1 surround setup; perhaps with a 3875 stero amp for the main channels, a mono amp for the center and subwoofer channels, and a cheap-O amp for the rear channels.
I've got a little experience with a soldering iron, and would be interested in keeping the price low. I've got access to PCB's and ferric chloride to etch them, so I'm set there; would it be worth my while to just buy a kit? Also, which transformer should I buy?
LM3875 is meant only to drive 8 ohms, for max output, (before THD noise levels start to rise) you want to provide 35VDC which will give you about 31W.
With the difficulty in getting a decent multichannel solution, I started on Rod Elliot's Hafler Matrix circuit last night, veroboard as usual !
Please note it has no delay circuitry (so it can be improved on), nor does it have a lowpass filter on the subwoofer channel, so don't run this on a passive woofer without makeing the neccesary crossover adjustments... most commercial units can be plugged in without a problem.
I have not tested it yet, but this is what I got so far... (r and L are both input and output, ground connections can be made to the ground rail... still have to spend time on it.)
Will need a day or 3 to get some NE5532 chips to test with... oh and I need to pick up a tranny too for it.
http://sound.westhost.com/project18.htm
With the difficulty in getting a decent multichannel solution, I started on Rod Elliot's Hafler Matrix circuit last night, veroboard as usual
!Please note it has no delay circuitry (so it can be improved on), nor does it have a lowpass filter on the subwoofer channel, so don't run this on a passive woofer without makeing the neccesary crossover adjustments... most commercial units can be plugged in without a problem.
I have not tested it yet, but this is what I got so far... (r and L are both input and output, ground connections can be made to the ground rail... still have to spend time on it.)
Will need a day or 3 to get some NE5532 chips to test with... oh and I need to pick up a tranny too for it.
http://sound.westhost.com/project18.htm
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I would suggest to any of you that might be new to Chip Amps (as am I) vist Karma's Web Site or any of the websites of members of this forum.
Karma,
I just visited your site and WOW! Great links. I also liked your LM3875 project! The one I invision making will be very simular. Using 2 tranformers, EI type, I think it will be critical that I put the power supply in a separate unit. I plan to temporally put the amp on a board to experiment with placement before I build an enclosure.
I have a few questions if you don't mind. Assuming I go overboard with the heatsink, how critical is ventilation? I'm thinking of a wooden box with vents on bottom and back end only. On your project, what is the twisted yellow pair to the volume control? Ground? And are those bare copper wires going to the outputs?
Thanks again,
David
P.S. Incase you don't see this post, I may email you after a while.
Karma,
I just visited your site and WOW! Great links. I also liked your LM3875 project! The one I invision making will be very simular. Using 2 tranformers, EI type, I think it will be critical that I put the power supply in a separate unit. I plan to temporally put the amp on a board to experiment with placement before I build an enclosure.
I have a few questions if you don't mind. Assuming I go overboard with the heatsink, how critical is ventilation? I'm thinking of a wooden box with vents on bottom and back end only. On your project, what is the twisted yellow pair to the volume control? Ground? And are those bare copper wires going to the outputs?
Thanks again,
David
P.S. Incase you don't see this post, I may email you after a while.
assuming you go overboard on the heatsink, you should be plenty fine. i know a lot of people just use a little half inch thick slab of copper bolted to the chip with some thermal grease between them.
If you are using EI type trafos, I would reccomend a second enclosure, or a single one with a decent amount of space beetween the power supply and amps, and a metal wall between them as well if you can swing it. If you make the boxes out of wood, I hear that using spray adhesive to line the insides of your power supply box with aluminum foil does nicely to keep your amp box clean of noise.
If you are using EI type trafos, I would reccomend a second enclosure, or a single one with a decent amount of space beetween the power supply and amps, and a metal wall between them as well if you can swing it. If you make the boxes out of wood, I hear that using spray adhesive to line the insides of your power supply box with aluminum foil does nicely to keep your amp box clean of noise.
what is the twisted yellow pair to the volume control? input rcas.
i was lazzy and its what i had at the time the case was grounded so the rcas where allready grounded to the case.
are those bare copper wires going to the outputs?
there is a Clear coating on the copper that keeps it from shorting out thay need to be sanded off so the solder will stick
you will find after you build a few you can start playing around
with wire and caps to see if you can improve the sound.that gainclone only ran on 12v but it sounded so good
cheers
i was lazzy and its what i had at the time the case was grounded so the rcas where allready grounded to the case.
are those bare copper wires going to the outputs?
there is a Clear coating on the copper that keeps it from shorting out thay need to be sanded off so the solder will stick
you will find after you build a few you can start playing around
with wire and caps to see if you can improve the sound.that gainclone only ran on 12v but it sounded so good
cheers
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