[drutland]

Hi
I have trouble with my first cmoy. I am useing tangents website for guidance useing the opa2132pa. I have the protoabaord all soldered up. The power supply checked out fine with 4 volts to each side (My meter is a cheapie). I rigged up a cd player as recommended in the article. I got sound out of both channells but there was a loud buzzing going on as well. I removed the cable that was running from ground of the headphone plug to the vg on the board and the sound cleaned up real nice. When I replaced the line the buzzing came right back. I have checked my soldering for bridges and found none. I have used the meter to confirm all the joints are solid and that the pins have the proper amount of resistence between them and the vg. Would it be ok to leave it as is and just not hook a connection from the virtual ground to the ground of the output jack? If you have any ideas that I could try next I would appreciate the help.

 

[diredesire]

Hello there! Is this amp cased up? Is it powered by 9v battery?

 

[drutland]

Sorry, I forgot to post the pics. Here they are front and back. It is not cased up yet. I have it running on a 9v battery.

 

[diredesire]

any chance of those in a higher res?

 

[drutland]

head-fi rejected any image greater than 25k that I tried to upload

 

[tangent]

Quote:

Originally Posted by drutland Would it be ok to leave it as is and just not hook a connection from the virtual ground to the ground of the output jack?

No. Something's wrong, and you need to fix it. Any chance you melted something in your headphone jack? That's easy to do before you get some good solering skills. Desolder the jack, and test for resistance between all the solder lug combinations. It should be inifinte between all of them.

Quote:

head-fi rejected any image greater than 25k that I tried to upload

Yes. You'll have to find a separate server to host those pics on, and then use the IMG tag to link to them. Do a search. Options for image hosting have been posted many times before. The best option is to use some space on a web server somewhere, if you have some available to you.

 

[drutland]

No, I couldnt have melted anythning on the headphone jack yet as I haven't soldered it in yet. I have the headphones connected with alligator clips as the tutorial recommends. I will work on the picture thing, try and get some larger shots up. Thanks for all the help

 

[drutland]

Ok larger picks, I hope.

[/IMG]

 

[Teerawit]

Your two cables on the underside of the board....(that power the opamps) why is one soldered to ground at the other end? the one on the right in that pic.

In the same pic, the cable on the left -- shouldn't the bottom end of the cable be soldered two pads to the left?

 

[Rix2357]

I believe Teerawit is right about the the first picture right cable. It looks like the "virtual" ground and the circuit's actual ground got mixed together. Use your multimeter and probe to see if there is zero resistance from the black negative wire that goes to the battery and the middle 2 lines on the PCB. If there is, that is your problem right there.

If not, is there any way to adjust the exposure for the first picture a little? It is a little dark to see all the details. I threw it into photoshop to see if it could get any better, but that's a negatory.

 

[drutland]

The cable on the right appears to be going to ground due to the way I bent it around but it actually is in the pad to the right of ground in the picture, 3 holes below where you hook in the diode. I Ohmed it out just to make sure it wasnt touching but it wasn't. The one on the left runs from 3 holes below where you solder in the diode to the same pad as pin 4 of the opamp. If it was moved two pads to the left it would be all by its lonesome over there.

 

[drutland]

Rix,
I got 2.5 kohm from the middle lines (vg) to the black cable of the battery.
I got 3.5 kohm from the vg to the red cable of the battery

I will try and work on a better photo in a couple of days. I have to go out of town for a couple of days and I have run out of time to play around with it for tonight. thanks for everybody's help.

 

[Win0ver]

Is it me or the 2 wires are not soldered on the right spots on the power supply?

From Tangent's website (keep in mind your pic is reversed) :

 

[diredesire]

Quote:

Originally Posted by Win0ver Is it me or the 2 wires are not soldered on the right spots on the power supply? From Tangent's website (keep in mind your pic is reversed) :

As long as it's on that pad it shouldn't matter, that whole thing should be considered one big pad.

I recommend checking the jacks either way, and there SHOULD actually be some continuity, as many jacks have two prongs shorted when nothing is plugged into them.

I can't really tell what's going on because those pictures are pretty grainy, but the solder joints look OK, i can't really see what's going on with the wiring though.

 

[tangent]

Quote:

Originally Posted by Win0ver Is it me or the 2 wires are not soldered on the right spots on the power supply?

It has to be at least somewhat correct, as the op-amp is powering up. The most likely symptom if V+ and V- weren't hooked up is no sound at all.