[Bert Hornikx]

Hi there,

Sending the mixbus through MP573s lately, I noticed the output volume of my two units is different.
Using a mono signal, ProTools meters and Waves PAZ analyzer, I have to set the trim knobs in a different position to get a centered image.
Not a big issue, but it would be nice to match the preamps.
Is there a way to do this?

Thanks,
Bert 

[JPK]

This is surely due to the gain potentiometer tolerance which is 20%.
How many dB's of level difference do you get for the same position of the pots?
Is there still a difference for the extreme positions?
You could try to play on the value of R22 on one of the units to reduce the gain difference.

[Bert Hornikx]

Thanks!
At +10 the output is nearly identical.
At -10 there is about 1db of difference.
What values should I try? Is there a way to measure/calculate this?

[JPK]

You can temporarily wire a 2k or 5k linear potentiometer in place of R21 (not R22 in this case) and adjust the value to get the same gain at minimum rotation. Then replace the measured value of the pot by a resistor of the closest value.

[Bert Hornikx]

Thanks, JPK!
That's a doable fix.
Will try it as soon as I can and post the results..

[Bert Hornikx]

So .. I finally managed to try this fix and it works perfectly.
Very happy my trim knobs on the stereo bus are matched!

One more question: can I do the same with my 5.99 and 5.12?
What resistor do I look for.

Thanks!

[JPK]

For the maximum gain you can play with R15.
For the minimum gain you can play with R12 for LOW and MID gain.
For the minimum gain you can play with R11 for HIGH gain.
But there will be some interactions.

[sdiazmun]

So .. I finally managed to try this fix and it works perfectly.
Very happy my trim knobs on the stereo bus are matched!

One more question: can I do the same with my 5.99 and 5.12?
What resistor do I look for.

Thanks!

Hi Bert! What value do you use finally? I understand you changed the resistor in one preamp only, did you?
Thanks!!!