where are the schematics for the lm3886 board? i recieved mine today and built the power supply by looking at the gallery pictures and the posted schematic on www.chipamp.com but i can't seem to find the schematic for the lm3886 board.
i guess i can build it by looking at the pictures brian posted online (but sometimes the resistor values are hard to see because of the onboard flash).
since this is the first DIY kit i am making, i am at lost of what parts to get (like connectors etc.)
it seems like people use an RCA plug for the input; but do i need to be mindful of the ohms of the connectors? (seems like the RCA i was eyeing was 6 ohms)
that route seems not safe since i do not know anything, and adding an input resistance without knowing what i am doing seems like it might affect the performance of the amp, shall i just opt for a simply banana plug connectors for everything?
where can i get a nice stepped anntenuator? (i know there has been many posts about pots etc. but considering so many conflicting opinions it is confusing what to get.)
the only part i know for sure to get is the brian recommended 330va 2x25vac transformer sold by Parts Express.
CLIFF NOTES:
1) just recieved brianGT's lm3886 amp and parts
2) assembled the power supply
3) need to know what other parts to get for a fully working amp
4) i wish someone just listed what i needed (banana plugs, banana jacks, shielded 2 signal wire, cheap stepped attenuator on ebay/digikey/whatnot, the need to make a star ground, etc.)
i mention banana plugs because that is the only connector i know the name of. it seems like allot of people use a screw post type connector to connect their amp to their speakers, but i do not know what that is.
thanks,
i guess i can build it by looking at the pictures brian posted online (but sometimes the resistor values are hard to see because of the onboard flash).
since this is the first DIY kit i am making, i am at lost of what parts to get (like connectors etc.)
it seems like people use an RCA plug for the input; but do i need to be mindful of the ohms of the connectors? (seems like the RCA i was eyeing was 6 ohms)
that route seems not safe since i do not know anything, and adding an input resistance without knowing what i am doing seems like it might affect the performance of the amp, shall i just opt for a simply banana plug connectors for everything?
where can i get a nice stepped anntenuator? (i know there has been many posts about pots etc. but considering so many conflicting opinions it is confusing what to get.)
the only part i know for sure to get is the brian recommended 330va 2x25vac transformer sold by Parts Express.
CLIFF NOTES:
1) just recieved brianGT's lm3886 amp and parts
2) assembled the power supply
3) need to know what other parts to get for a fully working amp
4) i wish someone just listed what i needed (banana plugs, banana jacks, shielded 2 signal wire, cheap stepped attenuator on ebay/digikey/whatnot, the need to make a star ground, etc.)
i mention banana plugs because that is the only connector i know the name of. it seems like allot of people use a screw post type connector to connect their amp to their speakers, but i do not know what that is.
thanks,
1. As far as RCA's are concerned, you're fine with almost any decenct Jack. I like Cardas CTFA but thats just me, the impedance doesn't really matter.
2. As far as the rest of the amp, yes you will have to buy connects, for the power connecter, fuse the primary and secondary power cables. Some just use one fuse others like the security of two fuses.(Primaries and Secondaries).
4. Attuenuator well those are rather expensive, but i'm going to use something like this.
http://www.platenspeler.com/background/attenuator/uk_attenuator_1.html
He has alot of good info. If you want to just use a POT get a Blue Apls "velvet" pot. High quality pot for about $20
5. As far as finishing the circuit, you and I are in the same boat, I have been able to identify some of the resistor values but don't want to leave anything to chance.... so i'm waiting on BrianGT.
hope i helped, i'm building mine too and am stuck where u are.
2. As far as the rest of the amp, yes you will have to buy connects, for the power connecter, fuse the primary and secondary power cables. Some just use one fuse others like the security of two fuses.(Primaries and Secondaries).
4. Attuenuator well those are rather expensive, but i'm going to use something like this.
http://www.platenspeler.com/background/attenuator/uk_attenuator_1.html
He has alot of good info. If you want to just use a POT get a Blue Apls "velvet" pot. High quality pot for about $20
5. As far as finishing the circuit, you and I are in the same boat, I have been able to identify some of the resistor values but don't want to leave anything to chance.... so i'm waiting on BrianGT.
hope i helped, i'm building mine too and am stuck where u are.
Sorry I haven't been to the site in a few days, I have the values that you need.
Resistor Values:
on the board "RF" and "R2" are both 22k (the 4 pack of resistors)
"R3" is a 680ohm, its tape is colored blue
"R1" is a 1k resistor, it has black on the tape.
In the back corner the mute resistor "RM" is a 10k resistor with colored red tape.
The colors I'm talking about are on the tape that holds the resistors together. Brian thought it would be easier to differentiate all the resistor values with colored tape.
Sorry for the delay, If you have any more questions I'll be back on later.
edit: I'm not sure but I think most of the values are like the 3875 boards
Be sure to post reviews when your done, Gook luck
Thanks,
Josh
Resistor Values:
on the board "RF" and "R2" are both 22k (the 4 pack of resistors)
"R3" is a 680ohm, its tape is colored blue
"R1" is a 1k resistor, it has black on the tape.
In the back corner the mute resistor "RM" is a 10k resistor with colored red tape.
The colors I'm talking about are on the tape that holds the resistors together. Brian thought it would be easier to differentiate all the resistor values with colored tape.
Sorry for the delay, If you have any more questions I'll be back on later.
edit: I'm not sure but I think most of the values are like the 3875 boards
Be sure to post reviews when your done, Gook luck
Thanks,
Josh
Yes i actually do have one LAST question...
Whats the deal with the three holes for R3? Something about legacy support?
On Brians site he has a picture of using both, from the layout it looks as if one bypasses a cap, while the other uses it?? I don't know what I should do?
Edit: here is the pic:
http://www.briangt.com/gallery/lm3886amp/3886_037
Whats the deal with the three holes for R3? Something about legacy support?
On Brians site he has a picture of using both, from the layout it looks as if one bypasses a cap, while the other uses it?? I don't know what I should do?
Edit: here is the pic:
http://www.briangt.com/gallery/lm3886amp/3886_037
llmobll,
Sorry I don't know what the extra hole is for. I can't tell really what it does, (I actually didn't really think about going into the extra hole). I went into the closer hole, on the picture, the way Brian did it on the right board. I'm sure Brian can answer it when he gets back.
How much more do you have left?
Has anyone else finished?
Good Luck,
Josh
Sorry I don't know what the extra hole is for. I can't tell really what it does, (I actually didn't really think about going into the extra hole). I went into the closer hole, on the picture, the way Brian did it on the right board. I'm sure Brian can answer it when he gets back.
How much more do you have left?
Has anyone else finished?
Good Luck,
Josh
llmobll said:
I think you answered your own question, one hole choice uses the cap while the other one (closer one to top hole) bypasses the cap. This is what Brian is illustrating in the picture you linked, (one pic has no cap, the other does).
so what to do? decide if you want a cap in your input path or not. the role of the cap is to block DC from your source and control impedance. But this brings along sideffects, caps are never good for sonics in a filter function. I would use the lower hole first, as it is the safest bet, then experiment with no cap.
After Brian and I had a listening test, I went home to build the amp, I heat up the soldering iron, and then ask myself what goes where. I went online and couldn't find a schematic except for the snubber, so I had to call Brian. Its not fun.
Homer09 did you get a kit?
llmobll, hurry up
, I want to hear your review.
I've been listening to the amp quite often on my wr125s, the amp sounds very good on some songs, and not so good on others (I think it also has to do with my speakers). I'm going to hook the amp up to my B&Ws in a minute. It would be a better comparison if I could get one of P.D.'s DACs
Josh
Homer09 did you get a kit?
llmobll, hurry up
, I want to hear your review.I've been listening to the amp quite often on my wr125s, the amp sounds very good on some songs, and not so good on others (I think it also has to do with my speakers). I'm going to hook the amp up to my B&Ws in a minute. It would be a better comparison if I could get one of P.D.'s DACs
Josh
I am about to decide which kit to buy: LM3886 or LM3875. All I know, is that later model is better in driving low impedance loads due to higher current handling.
Any suggestions?
Also, does PCB make a big difference in comarison to prototyping board?
And final question is about transformer. The recommended one is about $50US, so the final price will be around 80CAD with shipping to Toronto. That alone is well above kit's price. Are there any other cheaper versions and how bad are they compared to recommended model?
If that helps, A-1 Electronic Parts (http://a1parts.com/) and Active Surplus are the stores that are close to my home and work, so it would be best to pick up from there.
Thank you
Any suggestions?
Also, does PCB make a big difference in comarison to prototyping board?
And final question is about transformer. The recommended one is about $50US, so the final price will be around 80CAD with shipping to Toronto. That alone is well above kit's price. Are there any other cheaper versions and how bad are they compared to recommended model?
If that helps, A-1 Electronic Parts (http://a1parts.com/) and Active Surplus are the stores that are close to my home and work, so it would be best to pick up from there.
Thank you
lomtik said:
I think the difference between the LM3886 or LM3875 is minimal. If i learnt anything reading the countless threads comparing them, the real difference lies in their implimentation. A well implemented LM3875/LM3886 will sound great. If you want the low end bass, or if your driving 4 ohm speakers, get the LM3886, or else, i wouldnt worry too much.
If you really want to be sure, build both
lomtik said:
A difference between PCB and what?
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