[infinitesymphony]

I promised pictures, so here they are.

3 CMoys

In a row

"Custom" bypassing

 

[Joshatdot]

nice work, I like how you did the bypassing. I need to fiddle with EAGLE and my board to make that EZ'er.

How do they all sound?

 

[infinitesymphony]

I haven't done a direct comparison, but my initial impression is that they all sound the same--very good!

It didn't seem to make a difference whether or not there were resistors in the C2_L and C2_R positions in place of the input capacitors. The first amplifier I built (bottom of the first picture) has them while the others are jumpered. I plan to remove the resistors from these positions on the first amp just because the other amps work very well without them.

As has been discussed by a lot of people by now, bypassing is absolutely essential for high-bandwidth ("fast") op-amps like the LM4562 and OPA2228, otherwise the chips oscillate and cause an unlistenable amount of distortion. I have a feeling you'll sell even more boards once they're guaranteed stable with those op-amps, just because they sound so good.

 

[Max Power]

Hi, n00b here putting together my first electronics project. Seems to be going pretty well so far but I have a question. I am using a 1.03 joshatdot board.

Do I put a R5 on each side of the board in the "OPT R" and "OPT L" spots? The picture I am going by is an older 1.01 board and I only see the R5 on one side.

ImageShack® - joshatdotheadfi's images

Also, what do I put in the RLED spot?


Thanks!

 

[infinitesymphony]

Welcome to the world of DIY, Max Power.

You should consider starting your own thread about your build if you anticipate having as many questions as I had.

Quote:

Originally Posted by Max Power /img/forum/go_quote.gif Do I put a R5 on each side of the board in the "OPT R" and "OPT L" spots? The picture I am going by is an older 1.01 board and I only see the R5 on one side.

What kind of headphones are you using? For most types, resistors in R5 aren't necessary, and the pads can be connected ("jumpered") using resistor legs.

Quote:

Originally Posted by Max Power Also, what do I put in the RLED spot?

RLED = resistor for LED. The value of the resistor you use will determine the LED's brightness, which will diminish as the batteries drain. I used a value of 10Kohm, which makes cheap LEDs very dim. The blue LED Joshatdot specifies in his guide is reasonably bright with that value, though. Keep in mind that the LED uses battery power, so the more resistance you use (i.e. the dimmer you're willing to make the light), the longer your batteries will last.

 

[Max Power]

Thanks for the reply infinitesymphony.

Right now the only headphones I have are Denon AH-D1000. What would be the difference in the sound using the optional R5 as opposed to jumpers?

 

[Joshatdot]

Quote:

Originally Posted by Max Power /img/forum/go_quote.gif Thanks for the reply infinitesymphony. Right now the only headphones I have are Denon AH-D1000. What would be the difference in the sound using the optional R5 as opposed to jumpers?

To quote Tangent:
Quote:

Originally Posted by Tangent Quieting Noises (R5) Normally the R5 position in the CMoy amplifier is shorted. (0 Ω) This gives the amplifier the best control over the headphone drivers, and results in the best sound in most circumstances. Sometimes, however, putting some resistance in the R5 position is necessary to quiet some sort of noise you hear in the headphones. Before I go into more details, please read all the information on noise in the companion article Basic Troubleshooting for Headphone Amplifiers. The solutions in that article, if they work, are superior. Adding R5 should only be done as a last resort. Having tried everything else to get rid of noise, try putting 10 Ω to 100 Ω in the R5 position. Higher values will be more effective, but because lower values have fewer bad side effects, your incentive is to use the lowest value you can get away with.

I would add R5 resistors for your Dennons, as they are 25ohm, they might need the R5's.

 

[Max Power]

Thanks josh. I had already finished the amplifier with the jumpers in the R5 position before I read your response. Is the only purpose of the R5 resistors to quiet noises? I have not noticed any noise with the jumpers.

This was my first real electronics project and it was much easier than I was expecting it to be. The soldering was really easy even with my cheap radio shack iron. The pcb seems to be laid out well and is very easy to assemble... getting it in the altoids tin was definitely the toughest part. Thanks for the pcb josh!

 

[Joshatdot]

Awesome Max Power! (hehe your name from The Simpsons I assume?). The optional R5's are for low ohm IEM types. Yeah it should be EZ to assemble, I designed it that way. After making afew Tangent proto CMoy's..I just didn't like the wires everywhere & difficult assembly.

Yep, the Mini Tin is abit of a tuffy, a Single paper hole punch really helps. But a real sheet metal punch would be best, for the different hole sizes, and I think it could punch thru the lip of the top lid.

 

[infinitesymphony]

Detailed parts list added to the first post. All of the parts have been carefully chosen, and should work well for almost any CMoy configuration.