CKKIII Help

[andrelim]

I just built a CKKIII headphone amp, however I am experiencing various problems.
1. No sound output on the right channel.
2. Extremely distorted sound on the left channel.

The power part of my circuit seems to be working, the 15V and -15V test points measure 15.1V and -14.9V.

I am unable to get a consistent quiescent voltage on R23 and R47. It will jump from 0mV to 17-130mV.

I have the output transistors and they have heatsinks attached. I got some sound in the left channel after replacing them.

However almost no other voltage measures correctly.

An externally hosted image should be here but it was not working when we last tested it.

Any help is greatly appreciated.

 

[moschfet]

Hi andrelim,

nice circuit 🙂

I estimate, that the hfe of Q9 (BC550C) is to high. Try a BD139, it is not react so sensitive.
And you maybe can increase R23/24 to 1 ohm.

 

[andrelim]

Could it be that I installed the wrong values for R2, R7 and R11?

 

[andrelim]

I have checked R2, R7 and R11 and they are the correct values.

 

[andrelim]

I have gotten both channels to work, but the sound is extremely distorted and intermittent. It cackles, pops and hisses. The severity changes with time, sometimes getting good other times it gets totally unintelligible.

 

[AndrewT]

are the green voltage values actual measurements of your circuit?

A working BJT should have ~600mVbe.
I can see many transistors that are turned off.
Now that you have some operation, can you repost voltage values, particularly Vbe of BJTs.

Inconsistent operation could be a sign of intermittent oscillation.

 

[andrelim]

The green voltages are actual measurements.
I will remeasure them later, but are the transistors supposed to stay cold?