frankwas

Ok. Because I forgot to put that in but it still sounds ok. But I'lll have to put it in. Do you think it's wise to buy a active car audio amp, since all my speakers are car speakers anyway?

Yeah. I am actually disappointed in velleman for that. I have another question: What is the purpose of the 2R7 resistor and the 100nF cap on the output? Also, what would you recommend I use for a low-pass crossover for a sub? An inductor or a electronic crossover. If an inductor, how do I make one? Thanks in advance!

I got a pcb from a site and had it made for very cheap. I actually had two made for R180, which is about $25. You would believe it, I finished the velleman kit, and it sounds pathetic in comparison and it is twice as expensive!!!

I would just like to say thanks guys for all your input!! I have built one of the amps so far and it sounds great!!!! I will post some pics when I have completed the whole project, and ahen I get my bro's cam :) Thanks once again!

How do I seperate my input ground from my speaker ground? Where do I get ground for my speaker and/or signal? TA.

Oh ok. I think that it's my layout that is giving the problems. Do you perhaps know of a pcb layout for this circuit? I really appreciate your input!!!

I built the first prototype today and it worked really well! Except, I have a lot of noise as soon as signal is fed into the amp. Can the be because the gain is too high? Or what can I do to remoce the noise? Thanks!

Ok. Will this transformer do the trick? 230V to 18-0-18V 2x4.44A 160VA Or must I get another one? Can I still use Rod's design for the LM3886 just as it is with the PSU I mentioned earlier with two 4700uF's and a 400V 35A bridge rectifier? I also have another question about pots. What is the difference between a linear and log pot and which one will work best for this project? Thanks.

Oh ok. The closest that i can get to that is a 18-0-18. Will that be ok?

Ok. I have another quesiton. You said earlier that I can use a 21-0-21 transformer. This will work perfectly for a 4 ohm load then? How many VA's must the transformer be? I apologise if we are going in circles. :P

Oh ok. I understand. But let me ask this, it might sound very strange: I'm only going to power, or need, 40W rms out of each amp and probably not constantly. Won't that give the transformer a little room to breathe? Or would you recommend that I get another transformer?

Ok. But in the LM3886's datasheet it says it puts out 68W on 4 ohms at 28V. Will my IC be damaged if I use the 25-0-25 160VA transformer with two 4700uF caps and a 400V bridge rectifier as in the diagram? I am really confused right now. ???

Thanks once again for all your replies guys!!! I think I have finally decided what I'm gonna do. I am going to build the two velleman kits, and then two LM3886 amps. I am going to go with Rod Elliots design and his power supply. But in his notes he says that his power supply is only good enough for one dual opamp. Does he mean that it will only be string enough for a single LM3886? Another question I have is heatsink ratings. Is lower oC/W better or how does it work? I am going to use fans on my heatsinks anyway, so will these values be that significant? If Rod's psu design can pull two 3886's then I can really save a lot of money cause I can get a 160VA, 25-0-25 toroidal transformer for really cheap. TA!!!

Ok. Thanks for clearing that up for me. Ok then. I will just biuld a amp with a single LM3886 ocnfig and the two velleman kits. I really appreciate all your input Audioguru! You have really helped me a lot! Do you perhaps know of a site where I can get amp schemes that might have 100W amps that are not too difficult to build?

Ok. But I am going to use 4 ohm speakers. I am busy reading through the datasheet. It's very complicated. I don't understand. Do I do this modification after the two amps are built as in the shematic I posted? I was looking at figure 3 on page 8 of the application note. They say at +-35V the amp at bridged mode puts out 100w. Will the quality still be good?

Sorry, I forgot to mention that in ESP's desing notes, he says you can use a LM3886 IC that willl give 68W power.

Ok. Then I am going to go for that one. But is there a possibility to bridge these IC's or AMPS to give me a 100W amp? Or do you perhaps know of an amp design that is not too difficult to build that has about 100RMS? TA.

I also want to add, I found the datasheets for the transformers if you would like to see them?

Ok. Thank you for the clarity. The guy (like any normal salesman) tried to sell me a transformer for each amp! Where I live that is R400 x 4 = R 1600 which is about $200! Then I don't even have one amp!!! So, I have changed my mind again, please tell me what you think of ESP's amp. I am still gonna build two of the velleman amps, but for my other speakers, I wana build the ESP amp with his recommened PSU. Please let me know what you think and if you have any recommendations.

Hi GURU! I just numbered it to show that i am connecting 1 with 1 in my diagram. The colourcoding is correct. I went to the shop and checked on the transformer. I need to make sure of something. If I connect two of these amps on one 300VA transformer 30-0-30 2x5A, will the transformer be string enough to pull both amps without being pulled dead? TA.

Thanks for the reply! I made a very crude sketch of how i am going to connect the two amps at a time. Could you please have a look and tell me if it looks ok? Thanks. P.S. I know the sketch is not up to standard! ;D

This is why you guys are called "Electronic Gods"!!!! Thank you for your replies! I'm starting to see a clearer picture. Let me be more specific. I am going to use 2 amplifiers per channel in my system, so that is why I need to know the rating for 4 amps. Sorry about that. I think that I am going to go with the Velleman because it looks like it puts more power out. I will be using 4 ohm speakers throughout the system. Let me just make sure I understand. If I build four of those velleman amps, and I buy two 200VA, 2x30V transformers, like this one: Transformer, toroidal, 225VA, 0-230V pri, 50/60Hz, 2x0-30, (they don't have 200VA) or i buy one of these ones: Transformer, toroidal, 500VA, 0-230V pri, 50/60Hz, 2x0-30V sec, i can power all four amps (two each on the first transformer, or all four on the second one?). The thing is the power supplies for these amps are built onto the kit. If I run all the amps in parallel, (i mean as in from one or two transformers), will it work? Thanks in advance!

Hi Everyone! This is my first time posting in this forum! I would like to know if anyone can please help me determine a few things about two power supplies that I want to build for two amplifiers. The first amplifier is this one: http://www.kemo-electronic.de/en/bausaetze/b086/index.htm I was thinking of using a toroidal transformer, a bridge rectifier and two electrolytic caps. But I have no idea what the specs must be. On the site it sats this amp needs 24 to 40V. But what must the VA rating of the transformer be and is it possible to power two of these amps from one psu? Lastly, for this amp, how many RMS watts does it put out? Cause I need to power a 40W rms speaker off one of them. The second amp: http://www.vellemanusa.com/us/enu/product/view/?id=522104 They recommend a 2 x 25VAC output toroidal transformer. But they say this reduces power by 15% (15W rms)! I want to know which transformer would you guys recommend I use to get the full 100wrms? I would also, like the first amp, power two amps from one psu. If anyone can point me in the right direction, or even give me a design or anything I would really appreciate it, cause I don't want to build an amp that is underpowered, and I'm on a really tight budget, but am willing to buy the right components for the jobs, just not unneccasary ones :D . Thanks all! Francois.