[damitamit]

Hi, i've built 2 MINT amps before and both have worked fine first go.

but this third one. im having problems.

First broke one channel of the ad8620 somehow, so ive replaced that with a ad823. But now when i play the amp with my HD600s the bass is distorted.

anyone know any likely causes for this kinda problem?

 

[tangent]

Is the bass still distorted at low volume?

What supply voltage are you feeding it?

Does it happen in both channels?

 

[damitamit]

the bass is not distorted at very low volumes.

It is using 9V, but ive tried with 18V as well and still the same.

Im pretty sure its in both channels.

btw, im using 1000uF caps for C2 if that makes any difference.

 

[damitamit]

looked at the pcb some more.

cant seem to find anything wrong?

I can see quite a bit of flux residue (if thats wat u call it) on the board. Would this affect it?

Amit

 

[tangent]

Quote:

the bass is not distorted at very low volumes. It is using 9V, but ive tried with 18V as well and still the same.

The one suggests clipping, while the other refutes it.... Hmmm...have you measured virtual ground relative to V-? Is it roughly 1/2 the V+ to V- value?

Quote:

im using 1000uF caps for C2 if that makes any difference.

It shouldn't.

Quote:

I can see quite a bit of flux residue (if thats wat u call it) on the board. Would this affect it?

Yes. Sometimes flux is conductive, or it can trap conductive material.

 

[damitamit]

checked the voltage from the center pin of the rail splitter to each of the side pins.

one is ~5V and one is ~2V. Replaced the rail splitter and still the same.

any ideas why?

 

[tangent]

That explains the distortion, then; the amp's clipping.

The likely cause is that the rail splitter is overloaded. This can be caused by improper resistor values (too low), shorted rail caps, etc.

 

[damitamit]

hmmm.

ive tried nearly everything i think. Checked all the connections. Increased the LED resistor. used a yellow instead of blue led. Checked all the resistor values. Resoldered rail caps. Changed coupling caps.

And still one rail is higher than the other.

How do I clean flux off? Might as well do that too..

 

[tangent]

Quote:

How do I clean flux off?

Alcohol and a stiff-bristled toothbrush. Get the purest stuff you can find; you can find 99% in some drug stores. Failing that, Radio Shack's tape head cleaner is a blend of alcohols totalling 99.x%. If you settle for common 70% stuff, use a compressed "air" duster to blow as much of the residual water off the board as you can before powering it up.