volume drop with 6 band EQ of GGG

[bent]

Hi,
i build the 6 band EQ from GGG, and it's working fine, but it'S the first time i have a EQ so i was wandering if it's normal that the volume is a little bit lower when i engage the pedal.....

exemple:
imagine on a scale of 10....
- pedal off (true by-pass): volume at 10
- pedal engage: volume at 8.5

what do you think?

thank's

bent

[Dean Hazelwanter]

Hi Bent...

There is a 250k trim pot on the pcb that controls gain - have you tried adjusting it? With all the frequency band pots set to the center of rotation, the gain pot should give plenty of gain.

[bal704]

I'm getting ready to build this one, and just noticed the 250k pot is a trim pot.  The stock list doesn't indicate that.  What do you set the gain to?  Just turn it until your amp starts distorting and back it off, or something else?  Could I use a regular pot for that?

[bent]

quote author=Dean Hazelwanter link=topic=50654.msg378605#msg378605 date=1161265946]
There is a 250k trim pot on the pcb that controls gain - have you tried adjusting it? With all the frequency band pots set to the center of rotation, the gain pot should give plenty of gain.
[/quote]
yes it was adjusting, but i use a pot instead of a trimmer,  do you think it can be the problem?

thank's

bent

[Mark Hammer]

When the MXR 6-band equalizer first came out, it HAD no bypass switch so nobody knew about any possible volume drop.  Heck, I used mine for a booster.

[bent]

When the MXR 6-band equalizer first came out, it HAD no bypass switch so nobody knew about any possible volume drop.  Heck, I used mine for a booster.

interesting to see that you boost, and mine is dropping 
Mark, do you have any clue, what can be doing this...?

thank'S

bent

[Dean Hazelwanter]

yes it was adjusting, but i use a pot instead of a trimmer,  do you think it can be the problem?

Using a pot is fine, as long as it's hooked up right. Make sure the wiper of the pot is connected to one of the 3 pads that are connected together and then run up to the opamp, and one (and only one) of the outer pot terminals is connected to the pad that goes to the 10uF cap. Check the value of resistor after opamp stage 2c. It should be 100 ohms (100R), not 100K. Also check the value of the 10K resistor in the feedback loop of that stage, as well as the 100K at the input of that stage.

When you adjust the band pots, do you hear the frequency in question boost and cut?

What do you set the gain to?  Just turn it until your amp starts distorting and back it off, or something else?

As Mark said, you can use it to boost if you want. You can also set all the band pots to center (for unity gain for each band) and then set the volume pot for unity gain (level out = level in). Then you are boosting or cutting each band. But certainly, feel free to play with the gain pot to give it overall boost. Do whatever sounds good.

Could I use a regular pot for that?

Sure. You can even mount it on the panel with the band pots, for a gain control.

[bent]

DOH  DOH  DOH  DOH  DOH  DOH     

DEAN YOU ARE MY SAVER..... 
I'M REALLY REALLY REALLY.....DISTRACT, I PUT A 100K INSTEAD OF 100ohm AFTER OPAMP STAGE 2C.........

I READ TOO FAST THE SCHEMATIC....

THANK'S TO ALL YOU, AND A SPECIAL THANK'S TO DEAN.....

BENT

[Dean Hazelwanter]

Glad to help!

[Unclerny]

Hi Forum, I have a question about this subject.

In the build from GGG it says it can be powered with a bi-polar 9V supply.  What exactly is that?  I'm used to 9Vac and 9Vdc wall-warts.

Thanks UE