[Ashkii21]

I recently built my first Cmoy amp as my first DIY amp (first time soldering anything significant, I think I destroyed the soldering tip) and I made a mistake when ordering the LED. I ordered my parts from Digikey and I used 160-1780-1 instead of 160-1708 LED, lol. Well everything seems to work fine, the amp works and the LED works also. (lights up and is at just the right brightness for me) I am using a 10 KΩ 1/4 W metal film resistor with the LED (Red 1W, 2.57 V, 350 mA, surface mount, $1.61). I tried figuring out the current with online LED/resistor calculators and I think that the LED is passing 0.643 mA through it. (9 V-2.57 V/10000) I am not sure if I calculated this correctly.

Is it .642 mA or 350 mA?

What are the effects of using this LED instead of the tangent recommended 2.0 V, 20 mA LED besides cost? (battery life?)

Should I run down to Radioshack and buy a 3mm Red LED, 276-026? ($1.49 + tax)

Also for this amp I am using an OPA2227PA, 470 µF 25 V electrolytic caps for C1, .47 µF 63 V metal poly caps for C2, 4.7 KΩ 1/4 W metal film resistors for R3 (gain of 3), no R5 (just a jumper) and using a 9 V battery. I am satisfied with this cmoy although I am using a different LED.

 

[Ashkii21]

Ok I checked my amp. It seems to work fine, sounds good. Except that I noticed that I soldered the right C1 cap in backwards (positive and negative going the same way on both caps, when I completed the power side I tested the voltage and I got a reading of 5.1 v and -4.3 V and was wondering why they were not even 4.5, -4.5). Also I noticed that the top of the right capacitor is popped up. Is this bad? It's not hot or anything, not even warm. Like I said the amp sounds great except that I noticed this mess up. Should I get a new cap and put it in correctly? Also is this why my incorrect LED works with the amp? Should I be worried about touching the metal altoids can when my cmoy amp is on?

 

[MisterX]

Yes, that is bad but it would have been worse if it had blown the top open.
Either way that capacitor needs to be replaced.


The LED functionality has nothing to do with the capacitor, if you are really that concerned about the current consumption I would suggest that you measure it.
(simply measure the current draw of the amp with and without the LED connected to get a rough idea how much the LED will effect the battery life)

 

[vixr]

remember its just a power indicator, not a flashlight. I started out building amps with really bright LEDs and it just runs the batteries down. Set the brightness low to use less battery life. Also search here for tomb's trickle charger circuit, and get some rechargable batteries, you will be glad you did. (look at the CMoy in my sig)

 

[Ashkii21]

Thx for the quick replies, I was just wondering why the amp still works even if one of the capacitors is blown? I bought all of the components from Digikey (except for the protoboard from radioshack), I think I'll go to radioshack to get 2 caps and an LED.

 

[Ashkii21]

Ok I got my 1st DIY cmoy amp working correctly. Wow I can't believe the sound quality that comes out of it when compared to my incorrect configuration. I bought the 2 caps at radioshack, took out the 2 other ones, installed the 2 new ones and everything is working.

Wow I feel like I learned a lot from making this amp. I looked up on youtube to see how to solder correctly. I was wondering what the sponge was used for and I properly tinned a new soldering tip. Thanks for replying, helped me out a lot. If this cmoy amp sounds this good, I wonder how better DIY amps sound. (mini3?)

 

[rembrant]

This
1. Tip Tinner/Cleaner Compound (0.5 Oz.) - RadioShack.com
2. Birdwell Cleaning Copper Scouring Pad 361-36 - Sprayer, Scrub Pad & Sponge - Commercial Cleaning & Safety Supplies
3. Profit

Hands down the best stuff I have ever used. I have no idea whats in that radio shack stuff but Those two items together and you can keep a tip in perfect condition for every joint.

EDIT: Oh yea you can get the scour pads at Walmarx in a 3 pack.