[]|[ GorE]

I am so so angry ......been messing around for 6 hours straight on tangents cmoy.
Just yesterday,the voltage divider was working fine with a battery as well as the output of my LM317 (15V) , but today all i am getting is 15V at the V+ and 0V at V-.

Tried replacing the C1 for the negative rail (-7.5V) with another cap.Didnt help.
Removed the lower 4.7K resistor and tested it.its working fine.
Checked all grounds everywhere.Fine.
REMADE the power section once more.Same problem.
Cleaned entire area with isoropyl alcohol.
rewired everything.

Why was it working yesterday ?

 

[]|[ GorE]

Note :

The ground from the Wallwart and the lm317's ground and the virtual ground are all connected together.

 

[grasshpr]

Quote:

Originally Posted by ]|[ GorE Note : The ground from the Wallwart and the lm317's ground and the virtual ground are all connected together.

I don't think your virtual ground should be connected with your wallwart and LM317 ground. The virtual ground is a channel which is split between + and GND in order to provide positive and negative supply, i.e., the positive and virtual ground makes the positive supply and the virtual ground and the wallwart ground makes the negative supply.

 

[Pars]

Quote:

Originally Posted by ]|[ GorE Note : The ground from the Wallwart and the lm317's ground and the virtual ground are all connected together.

That's a major screw-up. The virtual ground is derived from splitting the single input PSU voltage, so in absolute terms, if you are using a 15Vdc PSU to power this, the virtual ground is at +7.5Vdc relative to the PSU ground. When you measure the V+ / V- on the amp board RELATIVE to virtual ground, you will see +7.5Vdc and -7.5Vdc, respectively.

By tieing the virtual ground to the wallwart/LM317 ground, you are forcing it to fight against the wallwart ground. Guess what? It'll lose that fight everytime! Disconnect the virtual ground from the wallwart/LM317 ground. You will also have to ensure that your jack for the PSU is insulated as your input and output jacks will probably be in contact with the whatever case you use for the amp (if its metal). Read some of Tangent's stuff, like the Pimeta instructions, if you need more info. This is an issue in any single supply amp that uses a virtual ground.

 

[]|[ GorE]

if i separate the ground output of the wallwart from the virtual ground,the LED doesnt light up and the dc female jack is insulated as are all the RCA jacks.

 

[grasshpr]

Quote:

Originally Posted by ]|[ GorE if i separate the ground output of the wallwart from the virtual ground,the LED doesnt light up and the dc female jack is insulated as are all the RCA jacks.

At which stage are you using the LED? Between 1) Wallwart and Voltage Regulator, or 2) Voltage regulator and Voltage divider? Having a picture or schematic of your power supply section would really help...

 

[]|[ GorE]

The led is connected as shown in tangents schematic that is before the resistors.
ie led is between output of lm317 and the Voltage divider.

 

[grasshpr]

Quote:

Originally Posted by ]|[ GorE The led is connected as shown in tangents schematic that is before the resistors. ie led is between output of lm317 and the Voltage divider.

Hmmm... LED should turn on irrespective of the voltage divider circuit. Have you checked the voltage output of the LM317?

Also, what does your voltage regulator circuit look like? Does in include filter and transient capacitors? If so, do you have protection diodes included? What happens if you bypass your voltage regulator circuit and directly go from the wallwart to the LED and the voltage divider circuit (given that the wallwart ground is separated from the virtual ground)?

I'm suspecting it has something to do with your voltage regulator circuit...

 

[]|[ GorE]

Hi got the virtual circuit about 5 minutes before,and i am getting audio at the output.BUT,theres a lot of static in the sound.I checked the output for any DC offset but theres none for the left and for the right.
Is the opamp screwed ?

 

[ATAT]

Opamps are pretty durable.. unlikely that it's skrewed..

can you post pictures?

 

[leftshoe]

Firstly, what opamp are you using?

Have you cleaned the flux off of the board?

Are you case components properly grounded?

 

[]|[ GorE]

there is no case !
i get static from both channels and the actual music plays at very low volumes.
And the static persists irrespective of wheter i choose to use the lm317's output or 9v battery.

 

[The Monkey]

Quote:

Originally Posted by ]|[ GorE there is no case ! i get static from both channels and the actual music plays at very low volumes. And the static persists irrespective of wheter i choose to use the lm317's output or 9v battery.

Recheck all your resistor values to make sure you don't have a 10k where you should have a 100k and so on. You'd be suprised how often this happens.

Also, are you using R5?

 

[Ikon]

Note that a CMOY isn't very good at driving low-impledance headphones (like you HP805/UR40). Hiss is a usually a symptom of that sub-optimal situation. Putting in the R5 resistor is supposed to help, but it might not silence the the hiss completely.

Another and better solution would be to either use a high-current op-amp or add a second op-amp (the Apheared-47 modification).

BTW, what op-amp are you using?

 

[MASantos]

If you are getting lots of static and low volume, you might have the outputs connected to ground. this happened in one of my cmoy's! You should check for solder bridges, if all the wiring is done correctly,etc. If you post some pictures, it might help!

Good luck!