Looks like fun. Also would seem to have plenty of power.
post #661 of 1153
1/24/10 at 12:16am
My amp isn't clipping, clipping would be in the dac (I think?). Anyways, when I turn the 9v on with the stock buffers, it works for about 20-30 seconds, then starts going to nothing, then full volume and back about once per second.
Putting in the bypass buffers fixed this, but I like the sound of the buffers better.
I can confirm that clipping is in D4's DAC, not amp. Also, this only happens in some recording. As suggested by previous poster (sorry, I'm too lazy to go back to check who posted it, but, thanks for the solution, albeit, not perfect solution), if I lower the volume in iTune, the clipping goes away, even if I crank up amp to a higher volume.
Initial Solution, quick remedy, (Have not spend much time thinking of the best solution). I decided the quickest solution to the problem is to reduce the gain of the AD8616. It original gain of the AD8616 is 2, by adding a resistor from the output of the 8616 to the negative input we could adjust the gain.
The original resistor across is 2.2K ohm.
The Gain resistors are located on the top side of the board, and to solder on that you need to remove the Big Nichicon HZ cap (On my case it is Rubycon ZL) to troublesome, to fix this way.
So instead of changing the resistor, I found a compensation capacitor beside the AD8616 which is connected in parallel to the feedback resistor. By adding a 2.2K ohm across this I reduce the gain to about 1.5. From the Picture the 2.2K resistor is sitting on top of the capacitor. label C26 and C28.
You could also solder the resistor directly on PIN 6,7 and PIN 1,2 on the AD8616. (If I do that I would be tempted to change the AD8616! )
I so happened to have a 2.2K 1% SMD 0805 resistor at home. How lucky.
So after adding the resistor I test it again and the Clipping would not occur.
Now I could feed signal at 100% resolution to the D4 instead of just 80%
It should be placebo, on initial testing I could hear more details from the DAC now. Sweet. Well in theory it is 100% now instead of 80%, so might not be placebo.
The power is definitely stronger on the dark side.