• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

How to test pre-amp

qguy2000

Member
2018-09-24 2:50 pm
I built an Aikido pre-amp, I am not sure If the left and right channels are balance, sometimes I sense that the left channel is louder, having a room where the left and right sides are not symmetrical makes it even harder. Is there a way to test using a multi-meter if the outputs of my pre-amp are balance?
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
If all you have is a multi meter then things get a little difficult.

You could apply test tone sweep (mono signal) to both channels and have the DVM connected between L and R outputs. Any difference in AC voltage between the two channels would show as a variation away from zero volts. You need a meter that can respond across the audio bandwidth and that is also reasonably sensitive to do this.

You can also apply spot frequencies (100Hz, 1kHz, 10kHz and 20kHz) and check and compare the actual output voltage from each channel. Accuracy isn't important as you are really looking for differences.
 

OlegSh

Member
2010-12-01 11:00 am
Germany
You can use one of the online sine wave generators or an mp3 sine wave sample of 400Hz. Just play it through your pre-amp and measure the output level with the multimeter set to measure AC voltage. This should give you an accurate measure of the output levels of both channels.
 
You can use one of the online sine wave generators or an mp3 sine wave sample of 400Hz. Just play it through your pre-amp and measure the output level with the multimeter set to measure AC voltage. This should give you an accurate measure of the output levels of both channels.
^^^^^^^^^^ this.

https://www.mediacollege.com/audio/tone/files/440Hz_44100Hz_16bit_30sec.mp3

Set player to Loop or Repeat one so it automatically restarts and you have a continuous tone.