Mesa Boogie Graphic Eq REAL FREQUENCIES!!

[gugabrandao]

Hi, fellows... The values I've found with a RLC Calculator tells the 'label' frequencies are so different from the real ones:

80Hz -> R=470 / L=1H / C=3.3uF ---> Real F=87.61Hz / Q=1.171
240Hz -> R=470 / L=0.39H / C=0.47uF ---> Real F=371.7Hz / Q=1.938
750Hz -> R=470 / L=0.22H / C=0.22uF ---> Real F=723.4Hz / Q=2.128
2200Hz -> R=1K / L=0.068H / C=0.15uF ---> Real F=1576Hz / Q=0.6733
6600Hz -> R=1K / L=0.033H / C=0.033uF ---> Real F=4823Hz / Q=1.000

The resistors, inductors and capacitor values are from the Mesa Boogie Mark IV/V specs...

I'd like to discuss about it... The real frequencies are too far to ignorate...

Please, anyone can help??? IS THIS RIGHT???

This is the RLC Calculator link: http://www.cvel.clemson.edu/emc/calculators/RLC_Calculator/index.html

 

[elvis]

These values are consistent with my Studio Pre schematic.

1. The circuit also reacts with the source and load impedances, which you don't account for here (like the 50k potentiometers). This will likely give changing frequency and Q depending on settings.

2. Does it really matter? The EQ does what it does. Are you trying to model it or something?

 

[gugabrandao]

@elvis, need to adapt to this synthetic inductor circuit... I'm gonna build a micro pedal with the MB Mark V f-bands.

http://www.muzique.com/lab/gyrator.htm

So, I wanna achieve the right band and the right Q. Didn't know the pot would affect at all... Assuming it is only the gain control. But its impedance can adjust the difference..

Still need to be sure about it...

Thank you for the reply, buddy! Appreciate that. :wink:

 

[elvis]

Interesting.

The gyrator will behave differently, which is likely why Mesa still uses the LRC circuit.

Are you trying to put together a 5-band EQ just to save the $250 Mesa will charge, or are you building one as a fun project?

 

[gugabrandao]

I'm trying to build a micro eq, inside the hammond 1590A Box... Kinda fun, but actually because of pedalboard size! =D Take a look! I really need this to be smaaall... Veeery small.