[firefox360]

I just finished up drilling the holes for all the components yesterday, and had the amp working 2 days ago. Ever since I've put the components together on the front panel of the Serpac H-65 case I've been having some issues with the amp. I'm not sure if it's attributed to the interconnect I'm using or not, but here's are the problems:

1. Yesterday I was about to listen to music on my amp after casing it up. I plug in the 3.5mm-3.5mm interconnect going between the CMoy and my computer sound card (a Creative Labs Sound Blaster Live!, with the kX Project drivers). Then I plug in my pair of test headphones (iPod Earbuds) and turn the volume on the pot to the absolute lowest.

I then turn on the power, and pressed "Play" in iTunes (which is the interface for Foobar2k). When I did, all I heard comming out of the headphones were massive distortion comming out of the left earbud. Nothing from the right. It sounded as if the sound was being blasted through those earbuds at full volume from the amp. I recheck my pot, and turned it all the way from left to the right (which resulted in noise from BOTH earbuds), and from right to left (which resulted in noise just from the LEFT earbud).

I don't have a clue as to what the cause of this would be. I checked all the solder joints and everything seems alright. Wiggling my interconnect seems make the sound go back to normal sometimes, but there still something wrong with the sound. I'm not sure if this is due in part to the cheap ass interconnect that I'm using, which has had a past history with bad connections probably stemming from the poor build, or if it's something wrong with my amp.

2. When I first had problem #1, with the loud distortions, I immediately unplugged the interconnect, I then proceeded to wear the headphones to check if there was any background noise which would atleast lead to me to believe that something was wrong with the amp. Rather than noise, I was greeted with the song that my computer was currently playing. So I then pressed "Pause" in iTunes, and the music comming out of the amp stopped. I then pressed "Play" and the music in the amp continued. It was then I realised that I had mini-radio in my hands...

---

So does anyone know what the cause of these problems could be? I've linked some pictures of my amp below which I guess might be helpful. If you need anymore pictures please ask:

56k'ers Beware: Each image above 1MB in size (2560 x 1920 res each)
Top of Amp 1
Top of Amp 2
Top of Amp 3
Top of Amp 4
Wiring of Pot
Wiring of Jack 1
Wiring of Jack 2
Top of Amp 5
Bottom of Amp 1
Bottom of Amp 2
Bottom of Amp 3

 

[firefox360]

*Bump*

Someone's gotta know something about this!!?!

 

[The Monkey]

A few questions:

a) at some point, the amp was working fine, correct?

b) Obvious first step, have you swapped out the mini-to-mini?

c) I'm not sure I understand #2. Do you mean that the tunes were coming through your amp despite the amp not being connected to your sound card?

Also, it's a little hard for me to see, but are your jacks and pot grounded?

 

[firefox360]

Quote:

Originally Posted by The Monkey A few questions: a) at some point, the amp was working fine, correct? b) Obvious first step, have you swapped out the mini-to-mini? c) I'm not sure I understand #2. Do you mean that the tunes were coming through your amp despite the amp not being connected to your sound card? Also, it's a little hard for me to see, but are your jacks and pot grounded?

a) Yes the amp was working before. I was listening to tunes on it through my computer for several hours before.

b) I was thinking about that, but I don't have any other 3.5mm-to-3.5mm interconnect. The other one I have is disassembled because of some problems. I might go out and get another one today.

c) Yep, you are correct. It was like a freaky radio. Although I haven't seen any occurances of that afterwards. But, if it's still there, it's not so much of a problem for me. (I'm ok with being the person to build the first wireless CMoy

)

And yes everything is connected to the ground on the CMoy (which is the 2 center lanes going through the PCB) I've checked the power supply and everything seems ok. Around 4.5VDC going into the op-amps V+, and -4.5VDC going into the V-

Thanks, Alan

 

[The Monkey]

Hmm. It's possible that the wires on your pot could be shorting. I usually put some heatshrink over any bare wire where it is soldered to the lugs because the wires tend to get squished together when I pack it down in a Serpac.

 

[firefox360]

Quote:

Originally Posted by The Monkey Hmm. It's possible that the wires on your pot could be shorting. I usually put some heatshrink over any bare wire where it is soldered to the lugs because the wires tend to get squished together when I pack it down in a Serpac.

Hmm... could be it. I'll try putting tape over each connection tonight. But could there be any other cause?

 

[Gross]

I was having a problem somewhat similar to yours, and it was the input jack. For whatever reason, it didnt quite match up with the plug and I got some strange distortion like that.

 

[Filburt]

When I had a problem like that, I had some short on the ground rail somewhere. I ended up just scrapping the amp and making a new one.

 

[firefox360]

Quote:

Originally Posted by Gross I was having a problem somewhat similar to yours, and it was the input jack. For whatever reason, it didnt quite match up with the plug and I got some strange distortion like that.

I really doubt it's the jacks. They are the expensive Digi-Key ones that Tangent recommend over the regular one.

As Monkey has recommended I've isolated each of the pots connection, and I'm still having the problem... I'm absolutely sure they aren't shorting at the pot, so either I've got a defective pot or something else is admist...

UPDATE: I've measure the output of the amp in VDC mode on my multimeter. It says around -0.005~ VDC on right, and on right it just stays at 0.003 VDC positive. Is that a sign?

 

[firefox360]

OK I've switched out the OP-Amp for another one, and it's still the same problem. So we can officially take the op-amp out of the equation.

UPDATE: Ok somewhere along the line, my right input wire is shorting with my ground. On my multimeter, in resistance mode when I touch the probes on the right input on the board along with the ground I get one little beep and on the screen it shows ".295". But I can't figure out where it's shorting, or if it's even suppose to be shorting....

 

[The Monkey]

Did you switch out or otherwise test the mini-to-mini?

 

[firefox360]

@The Monkey: I've tested the cable and it doesn't seem like the left (tip) is working too well... But other than that everything else in the cable is working well. There aren't any shorts or anything.

 

[firefox360]

OK I've just found out something peculiar. I just decided to plug the amp into my iPod, and guess what? It works flawlessly. Absolutely no problems, besides the left channel not working, which I attribute to the cable. But other than that, the amp works. I used it to drive some old passive (non powered) computer speakers (Creative CS46), and that worked (although there was alot of distortion).

So could it be that something is wrong with my sound card? One thing to note, is that within kX Project, I've switched around the front & rear outputs (since the rear outputs had a Phillips DAC whereas the front used AC97). That might be something of importance. I think I should have just used line-out through the sound card, which never occured to me.

 

[firefox360]

Scratch that, the problem has came back. Although it's not as worse as it was now. Seems like everytime I fix the problem and fit it back into the case, the damn thing acts up again...

 

[firefox360]

*bump* Anyone know whats going on?