[Co]

Hello JP,

I also have a small problem with EQP501 gain, but decided to open a new thread. If you think, they belong together, feel free to merge them.

I followed your advice from the other thread and did some measurements:

	Unit 1	Unit 2	Reference
Gain	-1,3dB	+0,5dB
TP1	1,95V	1,92V	2V
TP2	1,28V	1,63V	1,7V
TP3	0,09V	0,11V	0,17V
TP1-TP3	11,54kOhm	9,73kOhm	10kOhm
TP1-0V	12,37kOhm	10,68kOhm	11kOhm
TP3-0V	817Ohm	901Ohm	1kOhm

I can live with this problem, but if it is easy to fix, I'd be happy to do so.

all the best
Constantin

[JPK]

Check the potentiometers value. Check R12, R13 & R25 value.
Double check your TP3 voltage values, they do not seem coherent with the TP2 values which should be 10 times more.

If all the potentiometers and resistors are correct then the level difference can be caused by the pots tolerance (+/-20%).
If it is an issue you can match the output level between the units by playing with the values of R12 & R13 which define the gain of the DOA :
g = 1 + R13/R12 = 10.3

[Co]

Thanks for the quick reply.

I measured the voltages again and there only minor deviations.
TP3 gets very close to 0,17V, if I use a square wave as an input signal, but that also changes the other voltages, of course.

The parts have the right values, but there seem to be some tolerances. I measured with all boards attached.
On the quieter unit, I measure P1 11,59kOhm and P4 11,44kOhm.
On the louder unit, I measure P1 9,78kOhm and P4 9,16kOhm.
The other values seem to be pretty accurate.

I'll try to adjust the R12/R13 value.

[Co]

So I replaced R12 (1,62kOhm) with a 1k resistor and a 1k trimmer. Unity gain was very easy to dial in. Doesn't look pretty, but it seems to work.
I might check, how closely the EQ curves are matched mit Room EQ Wizard, only out of interest. Auraly, I have nothing to complain.
Thank you for this great EQ! I really like it.