Need some pointers for my first amp build

[tomb]

 

  Lexan will melt at about 155C so not a great choice likely as it starts to flow a bit below that.

Better than my generic acrylic that melts at 75*c, and the brand name plexiglass that melts at 105*c. Still though I don't think there will be that much of a problem as the temperatures won't be that high. I guess I'll find out when I test it, which I unfortunately didn't get to do today. Oh well, I have some heat resistant cardboard as well but that is 9mm thick... so yeah.

I don't think they're talking about the amp getting hot from running.  It's how the heck are you going to solder parts around a board that melts at 155 deg.C. when the soldering iron will be more that twice that hot (or more)?  The iron doesn't even have to be very close to start things melting.

 

[Rainmaker91]

 
I don't think they're talking about the amp getting hot from running.  It's how the heck are you going to solder parts around a board that melts at 155 deg.C. when the soldering iron will be more that twice that hot (or more)?  The iron doesn't even have to be very close to start things melting.

Yeah that's what I was talking about as well, my point was just not as well articulated as I wanted it to be. When soldering the heat will be concentrated on the pins of the component itself and not directly at the board. While I'm well aware that the board will get some of the heat, my hope is that it will be in such a small area and that the melting will be marginal at best.
 
In a perfect world I would have a protoboard to do all this on, but I don't have that luxury. Until I have tested the lexan and acrylic and know for sure that soldering anything to it won't work, I'm going to keep my hopes up. At any rate I have several other options, but I want to try what I have.
 
Keep in mind that I'm not actually soldering the CMoy on to the board yet. I am simply going to take a spare resistor and LED I have laying around and try out the concept on a small sheet of acrylic. It's simply to have a proof of concept before actually making the CMoy.
 
If all fails I always have the option to source a protoboard locally, it's just that I would rather try out what I have before going to that step.

 

[MisterX]

Anybody have the link for that CMoy amp that was built PTP style on buss bars and cast into a cube?

 

[Rainmaker91]

  Anybody have the link for that CMoy amp that was built PTP style on buss bars and cast into a cube?

The one cast in resin? sure gimme a minute to find it... here you go.

 

[MisterX]

There you go!

 

[tomb]

Yep - that's the way to do it!

 

[Rainmaker91]

  There you go!

Yeah, the last couple of days I have littrally seen dusins upon dusins of CMoy builds to figure out a layout that is easy to follow for a noob like me. Thought about building mine like he did, but that would only be my last resort, as I find a board to be far more easy to handle. 

 

[MisterX]

Do they have the MCM 21-4590 boards at Farnell?
 
http://www.newark.com/mcm/21-4590/small-pc-prototype-board-number/dp/38C9100

 

[Rainmaker91]

screw it... no shipping in the weekends here so I'm just ordering a board from a local site (meaning UPS won't have it here this weekend anyway). Acrylic tests were... not good (but thats why you test stuff before applying it right 

). Anyway, I need some new connectors for some cables I'm doing so I'll have to order some stuff anyway. If anyone can think of anything that would be useful to add or that I somehow missed, feel free to pitch in. I'll be ordering on Sunday as what I order won't be sent before monday anyway.
 
***I'll just keep adding stuff here until someone responds to the thread, I'm not a big fan of double posting when not needed***
 
Some extra stuff I added to make things easier:
4x 3 pin screw terminals (2 for jacks and 2 for pot).
4x 2 pin screw terminals (2 for batteries, 1 for switch and 1 for LED)
Not sure I need any of them but I figured it would make things a lot easier when it comes to mounting it in my final case.
 
Also got resistors @4.7kOhm and @10kOhm, but they only had Vishay MB series. So I chose the ones with the most similar ratings as the RN55 which was the MBA series. No clue whether or not they are worth it though. They have the MBB resistors which is rated at 0.1% tolerances, which at least speaks a bit about the quality.
 
Which reminds me, I'll begin doing the rough work for the case this weekend. Nothing will be finalized until I get it all assembled of-course. I want a solid design and a proper job on the woodwork, so it doesn't hurt to start early.
 
I also took a look at the TLE2426, but the only ones available is the TLE2426ID and the 3-pin TLE2426CLP. Then there is the fact that I'm not entirely sure I want to make the power supply even more complicated than it already is. What do you guys think? could I be facing a problem using the resistor based virtual ground instead of the rail splitter? The power supply will be based on a pair of new 170mha 8.4v GP batteries.
 
Also, considering I haven't soldered components directly to a board before (mostly deal with wires and simply fixing connectors on a board) I'm looking at wire for use on the board but I'm torn between silver plated copper and tinned copper? isolated or bare wire? or should I simply dissect the tons discarded cat5 cable that I have?

 

[Rainmaker91]

Just put the order in with the terminals, the protoboard, the MBA resistors (for fine tuning gain), LED reflector (makes mounting the LED easier), some contact pins and some isolated single strand .50mm wire.
 
didn't want to bother with the TLE2426 at this point since I already have a design with a virtual ground.
 
If I'm lucky (which I'm usually not), I will have both the new one and the Mouser package in the mail tomorrow.

 

[Rainmaker91]

got all the parts today, the new "laboratory" board seems to be to spec. Now all I need to do is actually solder the thing...
 

 

[Rainmaker91]

It works! well kind of anyway... The LED still doesn't shine, but other than that it's working flawlessly.
 
The soldering is shoddy as hell and the layout is less than optimal, but it works fine.
 
Now I jsut need to make the case for it as well as cut down the board. Also fix the LED I guess
 

 

 

[tomb]

I can't tell from the pics where the LED is located.  However, a typical mistake (we've all done it) is soldering the LED in backwards.  You might try reversing it, first, and see if that makes it light up.

 

[Rainmaker91]

  I can't tell from the pics where the LED is located.  However, a typical mistake (we've all done it) is soldering the LED in backwards.  You might try reversing it, first, and see if that makes it light up.

I utilized screw terminals for all components that would not be specifically soldered to the board, so reversing the LED sould be quite easy. That said, I think it's the resistor that is the issue here (I checked before doing the LED wires and they are colour coded for positive and negative). I tried the LED with it before soldering and all that and it didn't work properly then either. It could be that mouser sent me the wrong LED, or simply that the resisor in use is to strong for the LED.
 
This is what I have atm: This LED, and this resistor running from aproximatly 19.2v (the batteries say 8.4v each but the multimeter shows differently).
 
I have some more resistors laying around and some different 3mm leds that I can try, but it would be good to know wheter or not my math was wrong on this one.
 
I'll also take some better shots tomorow so that the layout is shown more clearly.

 

[tomb]

 

  I can't tell from the pics where the LED is located.  However, a typical mistake (we've all done it) is soldering the LED in backwards.  You might try reversing it, first, and see if that makes it light up.

I utilized screw terminals for all components that would not be specifically soldered to the board, so reversing the LED sould be quite easy. That said, I think it's the resistor that is the issue here (I checked before doing the LED wires and they are colour coded for positive and negative). I tried the LED with it before soldering and all that and it didn't work properly then either. It could be that mouser sent me the wrong LED, or simply that the resisor in use is to strong for the LED.
 
This is what I have atm: This LED, and this resistor running from aproximatly 19.2v (the batteries say 8.4v each but the multimeter shows differently).
 
I have some more resistors laying around and some different 3mm leds that I can try, but it would be good to know wheter or not my math was wrong on this one.
 
I'll also take some better shots tomorow so that the layout is shown more clearly.

 
My math says 11.2 ma at the 8.4V rating of the batteries (16.8V).  I still say you have it backwards.  LEDs are not "ON-OFF."  You will get a gradual, dimming glow all the way down to 0ma, almost.  The brightness is not proportional, either, which is why many of us select something in the range of 1/2 current rating to make them last forever. One-half current is still 75% brightness, or something like that.
 
If it's connected correctly, it's going to glow at some brightness level if it's getting the voltage you say.  Regardless of the voltage of the LED you selected, it's still rated for 20ma max - that's similar to every other LED made.