[nitsujH]

I've been working on my very first DIY project, a CMoy amp off an on for a week or so now. I started to install all the input jacks, and they worked before I grounded both of them, after grounding them, there was no noise except for a humming/hissing noise and some static burps every once in a while. I connected the input jacks like this
__1___2___3__
____4___5___

With the plug to the left. 1 was ground, 4 right, and 5 left channel. Any ideas as to why it's reacting like this?


I tested the V- and V+ after the In/Out jacks were installed and V- was at 0.00 and V+ was at 8.16. I removed a jack, tested, same results, removed other, tested, same results. There were no obvious solder bridges, so I scraped all the gaps between patchs of solder with a knife, and tightened up some of the more sloppy solder joints, then retested it again and got V- at 3.36 and V+ at 4.80 does anyone have any ideas what I should do to fix this?

 

[Pars]

What kind of jacks? Have you ohmed the jack connections out to a plug to determine tip, ring and sleeve (L, R and gnd) respectively? Normally a stereo jack with 5 connections has 1 gnd, 1 each L and R normal, and a pair of switched connections for L and R, which switch out when a plug is inserted. Examples of this type of jack would be the Switchcraft (Mouser), some of the CUIs from Digikey, etc.

Is the amp cased? In metal? The 0V V- 8.16 V+ sounds like what would occur if you were powering the amp with a wall supply with the power jack grounded to the case along with the input output jacks. Since the CMoy is a virtual ground amplifier, this won't work as the PSU gnd and the virtual gnd will fight it out, and guess who wins?

If none of these guesses are helpful, pics would be.

 

[nitsujH]

Quote:

Originally Posted by Pars What kind of jacks? Have you ohmed the jack connections out to a plug to determine tip, ring and sleeve (L, R and gnd) respectively? Normally a stereo jack with 5 connections has 1 gnd, 1 each L and R normal, and a pair of switched connections for L and R, which switch out when a plug is inserted. Examples of this type of jack would be the Switchcraft (Mouser), some of the CUIs from Digikey, etc.

They are just the suggested ones on Tangent's page. I probably should have mentioned that earlier, sorry. I did test them with the Ohm meter, I wasn't compleatly sure of what I was doing, but I tested the bare mini jack connected to a cd player, and tested all the different points on the mini cable, then I connected it to the jack and compaired the numbers. I took both off and rearranged the wires on the pins and then I got a clipping noise that repeated over and over.

Quote:

Originally Posted by Pars Is the amp cased? In metal? The 0V V- 8.16 V+ sounds like what would occur if you were powering the amp with a wall supply with the power jack grounded to the case along with the input output jacks. Since the CMoy is a virtual ground amplifier, this won't work as the PSU gnd and the virtual gnd will fight it out, and guess who wins? If none of these guesses are helpful, pics would be.

The amp is currently not cased, it's still flailing about on my work table. I figgured out the problem, it was just a lead clipping that was stuck to the top of the amp, basicly acting as a soldering bridge, but I hadn't been paying attention to the top of the amp, so I never caught it.


Thank you Pars for your help so far.

 

[skyskraper]

ok if you have a bare mini plug (one not attached to the cable) or a mini to mini cable, plug it in to the jack, then put one multimeter probe onto one of the conductors on the mini plug then poke the other probe around the mini jack (whilst the initial one is still on the plug) until you find whichever connection on the jack that shows no resistance, that connection on the jack coincides with the conductor on the plug that you have the probe on.

 

[nitsujH]

Thanks for the help guys, I have no idea what I did, but some how I managed to make it work, I got it into the mint tin no problem, and now it's working great.
Thanks to everyone who helped me in the 343423 threds I've created so far.