70mV on both channels is absolutely in the high end.
The datasheet does not show or mention anything about offset adjustment. From your photo I cannot see any potentiometer(s) likely to be for such adjustment. So, the official reply is it is not foreseen.
First, are the 70mV measured with dummy loads or speakers at the outputs? Without loading of the outputs you cannot rely on the measurements. It is not like class AB.
Next, we DYIs always look for a way around the standard use:
It requires you are familiar with delicate soldering work!
Pin 14 is the input reference pin. The datasheet says this pin should be decoupled with 100nF and nothing else. 100nF is little decoupling and I will suggest to put 10uF-47uF across the small 100nF for better decoupling. That in itself may change the offset if the offset is caused by noise at the input.
If that is not enough, you may try to "pull" a little with a high impedance resistor (1MOhm or more) to ground. Thus, connect such a high impedance resistor between pin 14 and ground. We do not know if it should be pulled towards ground or the supply voltage for less offset and how much the reaction will be, so use dummy loads or old speakers (test speakers) when carrying out this experiment.
The datasheet does not show or mention anything about offset adjustment. From your photo I cannot see any potentiometer(s) likely to be for such adjustment. So, the official reply is it is not foreseen.
First, are the 70mV measured with dummy loads or speakers at the outputs? Without loading of the outputs you cannot rely on the measurements. It is not like class AB.
Next, we DYIs always look for a way around the standard use:
It requires you are familiar with delicate soldering work!
Pin 14 is the input reference pin. The datasheet says this pin should be decoupled with 100nF and nothing else. 100nF is little decoupling and I will suggest to put 10uF-47uF across the small 100nF for better decoupling. That in itself may change the offset if the offset is caused by noise at the input.
If that is not enough, you may try to "pull" a little with a high impedance resistor (1MOhm or more) to ground. Thus, connect such a high impedance resistor between pin 14 and ground. We do not know if it should be pulled towards ground or the supply voltage for less offset and how much the reaction will be, so use dummy loads or old speakers (test speakers) when carrying out this experiment.
See post #465
http://www.diyaudio.com/forums/1888645-post465.html
As stated in the post, circuit is for one channel.
Last edited:
Just plugged my Fluke straight to the speaker outputs like in the class AB
I'll get another measurement with the speakers connected as i don't have any 8 Ohm dummy resistors
I'll get another measurement with the speakers connected as i don't have any 8 Ohm dummy resistors
No difference, still 70mV with and without the tone control engaged.
Don't have the skills to do the trim pot modification
Sad because it sounds great
Don't have the skills to do the trim pot modification
Sad because it sounds great
The trim pot addition is easy to do if you can solder. If you can't, you should learn to, it's a basic DIY skill.
Admitted, working on a rather compact SMD-layout board can take basic DIY skills to the limit. This was why I proposed to work on the common pin 14 instead. As both outputs are around 70mV offset, a common (both outputs together) compensation should work. If you had +70mV on one output and -15mV on the other, you would need individual compensation. Working on pin 14, a single resistor may do the job.
Don't you have a friend who can help?
Don't you have a friend who can help?
- Status
- Not open for further replies.