[chrono]

Ok, I got my parts in the mail today, and I spent 4 hours trying to figure out how to put this thing together.

I'ver got it finished, and I have definate problems, LOL.

When I listen to music through it, I only hear a very static-y right channel (pretty low volume too, I have to turn it up about half way before I can hear it).

There is no left channel.

The op-amp also starts heating up, once it's on for a min or two.

I thought I hooked everything up properly, but appearently not. I didnt test it too effectively when I was making it, either.. heh. I dont think the power segment tested out right.

Are there any things I can check? Or things I can test (please be very specific.. I have a DMM, but I dont really know how to use it effectively).

Thanks for any help!

Oh, Im using a 9V battery.

 

[was ist los?]

sounds like you have shorts. check for solder brigdes. also, for you may look for cold joints, which might be responsible for no left channel.

 

[Dreamslacker]

Check that the Virtual ground from the power side is connected to the ground on the amp side.
Check the connections. Might be the left, right & ground wires connected to the wrong places on the headphone jack.

 

[tangent]

What you're hearing is oscillation, chrono.

First, remove the chip, then power the amp up and measure from one power pin to the other. (1 to 7 for single-channel chips, 1 to 8 for duals.) Do you get the expected voltage? Is it the right polarity?

Then, measure from one of the virtual ground points (e.g. input jack ground) to each power rail. Do you get +/-4.5V or so?

 

[chrono]

When i measured the pins I got a 6.4 voltage (positive).

When I measured each rail to the ground I got a 6.4 on one side and a 0 on the other. How can I fix this?

 

[tangent]

That's not enough information for me to give you a simple fix. But now you know the problem, so look though the amp to find bad connections and such. Evidently something isn't hooked up right.

 

[chrono]

Ok, I figured there were too many things wrong with my cmoy.. I found out that I had completely messed up on the resistors, i had them all in the wrong places, and it was awfull. So, I just plain unsoldered the whole thing, and started fresh on the second piece of pcb.

I completed it properly this time, and it works beautifully!!!!! (to my surprise)

It increases the quality of my AKG-401's by an enormous amount.
I can drive these beasts the way they were supposed to be.
I get atleast 2x more volume (they were really quite before), and the bass with the 470's is hugeeeeeeeeee...

Perfect.

thanks for helping me out everyone (especially tangent for ur tutorial).

But I do have one last question:

How do I hook up the power switch? (sorry Im a diy newb)

 

[andrzejpw]

just putting it between the battery and the place you hook the power to should do the trick!

 

[chrono]

Quote:

Originally posted by andrzejpw just putting it between the battery and the place you hook the power to should do the trick!

lol.. that sounds easy enough!

thanks for the tip, I'll do that part tomorrow.

 

[tigger]

chrono

Congrats on the new homebuilt amp. I have been toying with the idea of a Cmoy for a while. I'm really curious if it will sound better than my Porta Corda. The thing I like about the DIY amps is the tweakability/upgradeability.
What case did you use? I'm thinking Altoids tin to start.
I'll be using AKG K501's and Audio Technica AH500's.

Hope you enjoy the fruits of your labour.

 

[tangent]

A CMoy amp probably won't sound better than a Porta Corda, unless you just don't like the sound of the LM6171 op-amp used in the PC. The PC is a bit more sophisticated than a stock CMoy. You can build a better amp than the PC without too much trouble, but then it isn't a CMoy any more.

 

[chrono]

Ok, I tried installing the power switch and i am having a problem..

it turns on the power fine, but it seems that not enough power is being transfered (the led only lights up about half way, and the volume is drastically lowered.

What i did was take the + wire from the battery, and hooked it up to the power switch. I then took another wire, soldered it to the power switch, and hooked it up to the + battery hole in the board. the - wire I left in place, directly from the battery to the board. I took the 3rd hole on the power switch and grounded it.

What am I doing wrong?

 

[chrono]

And one more thing..

There is a noticable white noise when I use my cmoy.. it's not really noticable when music is playing, but when there's nothing you can hear it quite clearly.

It's strange though..

When I hook it up to my diskman this noise is only present with the XBS on (and doesnt change with volume changes).

When I hook it up to my amplifier I get even more noticeable white noise. when I turn my volume all the way to 0 on the amp, the noise is reduced greately, but as soon as I turn it one notch up, it increases and stays at that level. If I crank the volume, the white noise does increase somewhat. And with every volume change, I can hear a little click sound.

It is only audible when I have an audio signal comming into the amp.

What could be causing this?

I must eliminate it

Edit:
I just hooked my amp up directly to my soundcard via rca and 1/4" adapters. The audio is flawless (but I have to lower my sound card's volume down about 30db for listening levels, which is quite substantial).

Is it possible that my y-cable was causing the white noise? or could it be the output of my amplifier? I never get any white noise from my amp without the CMoy though.

 

[tigger]

tangent

I think I'm going to attempt to build an amp, but as an electronics noob I'm afraid to bite off more than I can chew. So maybe CMoy first to get experience, then a Meta 42.
It's nice to see you cruising the forums and helping to lead the noobs away from disaster and despair!

 

[rm-fr]

I think it is easier to build a meta than a cmoy. The meta board from tangent is sweet, everything just fits in place. It is more cost but well worth it. The cmoy is damn fun though.