[tangent]

Quote:

I'm still not getting any sound.

Did you build using my guide, and if so, did you test at all the points I recommended? What happened with each test?

Now that you've got the board populated, try tracing a signal through the amp. If you have a test CD with a 1 kHz test tone, play that with a CD player; if you don't, make one with Cool Edit and a CD-R.

Anyway, use an AC voltmeter to check:

1. What the voltage is directly out of the CD player, between ground and one of the channels.

2. What the voltage is on the other side of the input cap (C1).

3. What voltage you get on the op-amp's output and inverting inputs.

Quote:

is there any way I can use a larger board?

Yes, but it won't make the holes any bigger. Have you considered using a magnifier?

Quote:

You should stop when you start to enjoy the smell of solder

You should stop when you fire up the soldering iron just to burn some rosin to inhale.

 

[fyleow]

Hey Tangent I have a problem with my CMOY. I followed your guide and the sound is only one channel. Just wondering could this be due to a damaged Opamp? I'm going to resolder everything again tomorrow but just wanted to check if that could be a problem....

 

[tangent]

I would suggest the same thing to you, fyelow: follow a signal through the amp until you can pinpoint the fault.

If it gets to the op-amp's input and doesn't come out the output, swap the op-amp out, if you can. Even if you have to go find a crummy TL0[78][12] class chip just for testing, it will tell you whether sound _can_ get through the op-amp, or if there's something else wrong.

 

[m3guy87]

Wow, thanks tanget. I was a little taken aback that you actually post here. Haha, you're a minor celebrity in terms of headphone amplifiers. I have a voltmeter, however this being my first project I'm still learning how to use it. Right now I've been testing from the batter to the ground and I've been getting approximately 6v on one side and about 2 on the other. I'll try to figure out your technique though. Can you explain how to solder a jack to the wiring? Which pins do I use. I'm using the digikey 3.5mm jack from digikey 274-0246. Any help that you can provide would be greatly appreciated.

 

[tangent]

Quote:

you're a minor celebrity in terms of headphone amplifiers.

Thhhhbbbbtt. I'm just zis guy, you know?

I've been doing DIY now for less than a year; the oldest of the articles was started only about half a year ago. As far as I'm concerned, I'm just barely getting some clues about this stuff...

Quote:

I've been getting approximately 6v on one side and about 2 on the other.

You probably have low-impedance headphones, too. What you're seeing has complex causes, but the point is that it's probably the source of your problem -- the OPA132 family requires about 3 volts from the rail to the "top" of the output signal. So, if your signal is 1V, you need at least 3.5V from ground to each rail -- 3V for the headroom the op-amp requires, plus 0.5V for half of the audio waveform. You don't have that, so the op-amp is sitting there in massive clipping. It probably isn't even trying to function under those circumstances -- it may shut down completely to avoid damaging itself.

The cheap and sleazy fix is to add more voltage. The right fix is to balance the power supply, which either requires more components, or knowlegeable resistor tweaking. The first option is covered in the Tweaks section of the tutorial -- the "buffering the virtual ground" section. The latter you only want to get into if you're thinking of becoming an amateur electrical engineer...lots of theory involved. Personally, I do know what's going on here, and I _still_ don't bother to balance impedances to fix this. Improving the power supply is a better option.

 

[Clay]

Radrd, I have been thinking about building a amp also.

These look really cool.

Mapletree
Nick Dangerous tube rolling page
Tangentsoft instruction page

I also have buit PCs and I think we can do it.

 

[fyleow]

I'm at a real lost here.

Nomad 2 MG jack 0.011
After Caps, measure point is on Pin 5 0.011
After Caps, measure point is on Pin 3 0.011
Opamp Out, measure point is on Pin 7 0.081
Opamp Out, measure point is on Pin 1 0.079

Everything looks ok to me and yet it still doesn't sound right...

The voices are echoy and the sound is really messed up, osccilation?

 

[tangent]

Quote:

Nomad 2 MG jack 0.011

Thats an _AC_ voltage? If so, that's pathetic. You should be getting a significant fraction of 1 VAC out of a portable with a full-scale signal; a few hundred millivolts at least. Or, did you test with music? That doesn't work very well, because it's constantly varying in amplitude.

The rest of the numbers look reasonable, if the first numbers are reasonable.

Quote:

The voices are echoy and the sound is really messed up

Okay, I know what you're hearing. You're hearing everything _besides_ the parts that are mixed front-and-center. The vocals are usually centered in the sound field, so if you remove them, what you're left with is the instruments and the echoes of the voices bouncing around the room and into the mics. The parts that are mixed to the center of the sound field are present in equal amounts in both channels, so you can remove them by tying the two channels together out of phase. The phase reversal could be happening in the op-amp chip, so don't look too hard for this aspect of the problem. Concentrate on the channel-mixing part.

Try disconnecting one channel and see if that helps. (Use an RCA connection and connect only one of the lines at a time.) If you can listen to one channel at a time without a problem, you're probably crossing the channels at some point within the amp circuit.

 

[fyleow]

Looks like that is exactly my problem Tangent. If I only have one of the channels connected and the other one grounded I don't hear the echoes anymore. The vocals become clearer.

As to the strange voltages, I don't know. I didn't have my Nomad turned all the way up and I used a test tone for that. I did swap my Opamp to an OPA2132P and I still have the same problem so it's crossing in the circuit somewhere.

That gives me some hope and explains some of the strange things that has been happening, thanks. Now I'm debating whether to just start from scratch or try to diagnose the problem.

I suppose that if solder connects some of the pins it isn't supposed to it will cause the cross, but I don't see any of that happening.

 

[fyleow]

Ok Tangent here is an update

So I decide to resolder everything, guess what? The SAME problem again! So I start to trace it back using my headphones and a jack. Before it enters the amp it's already echoy. So I put the thing jack to jack and it's still echoy. I think my jacks are defective or something. The amp is working fine I think, since it's being fed an echo it will amplify an echoy sound. I think I will go grab some jacks from Radioshack or something.

I have the CP-3535 you recommended from Digikey right now. According to this chart http://www.cui.com/connectors/connec...jk_SJ3535N.pdf
I connect them to 2 and 5 and it is still messed up.

Hmm...

 

[tangent]

The jacks probably aren't defective, you probably melted them when soldering. With 1/8" jacks, the components are all so close together inside that even a little bit of melting will cause problems.

You need to replace them, for sure, but I wouldn't go do a mail order for them unless you had something else to get. Get some new jacks locally, even if they're not as good as the ones you're currently using. That will get you by until the next time you need to place a big mail order.

Pins 1, 2 and 5 are right, by the way. 1 is ground, 2 is right channel, and 5 is left channel.

 

[fyleow]

I solved the problem. I grounded the jacks....

 

[kelly]

I am a Journalism major and fellow electronics idiot who also wants to jump into doing some DIY stuff and trying to understand the guts of the amps more. I hope I've made enemies of few enough of you to still get assistance when I get started.

I feel that I'm kinda coming in through the back door. It seems like a lot of people start out DIY because of budget and then move into buying a commercial amp when they can afford it. I'm a bit older and dumber both so I started out with commercial but haven't yet been fully satisified with any commercial amps (even the ones far more expensive than what I own). Maybe beating these amps is a lofty ambition, I dunno--but it seems worth persuing given that I'll likely learn something either way.