change cutoff freq in Equalizer?

[priscilla7391]

I am wondering about changing the cutoff frequency in an audio equalizer. It seems like it shouldn't be too hard; like maybe by changing a capacitor and or inductor or two perhaps?
Anyone here who can tell me about this?

The manual for a Behringer Xenyx 802, which is a 3-band mixer/equalizer says the highest and lowest bands are "shelving filters" which can boost or lower output at all freq above and below 12kHz and 80Hz, respectively. I'm wondering if I might be able to raise that 80Hz cutoff to something more like 300Hz.

Thanks!
Priscilla

 

[ronsimpson]

If you can find the schematic it can be done.

 

[priscilla7391]

If you can find the schematic it can be done.

Well, that sounds promising! I've been looking for that schematic but so far all I've been finding is the user manual.

 

[ronsimpson]

I could not find it!

 

[crutschow]

For proprietary and competitive reasons, the schematic of commercial electronics is often not readily obtained.

 

[priscilla7391]

maybe comparing innards to a basic equalizer circuit

Then maybe comparing the innards of this box to some basic (public domain) equalizer circuit
would allow me to identify the components that are involved in setting that cut-off frequency.

 

[Nigel Goodwin]

For proprietary and competitive reasons, the schematic of commercial electronics is often not readily obtained.

There are a few Behringer circuits 'flying about', but they are very hard to find - I presume authorised service centres have them?, but I think there are hardly any of those around.

Here's a circuit for an MX802, I don't know how it relates to the Xenyx 802 though.

 

[priscilla7391]

For proprietary and competitive reasons, the schematic of commercial electronics is often not readily obtained.

Thank you for trying to find it!

 

[priscilla7391]

Nigel: Hey Excellent!!!! THANKS!!!!!!!
I'll spend some time looking at this.
The MX802A has four input mic channels whereas the xenyx 802 has two.
Xenyx is the name of the type of Pre-Amps used on the mic inputs.
They both have 3-band equalizers
I compared the "Eurorack" MX802 features and block diagram to this Xenyx 802 schematic
and from what I can tell the equalizer section is likely to be the same in these.
They have the same three cut-off frequencies.

 

[ronsimpson]

Nice find Nigel.
The high frequency is set by C132, C136.
The low level is set by C156, C157.
To move the frequency change the caps. 2X the caps moves down by one octive. 1/2 the caps moves up one octive.

 

[priscilla7391]

Thank you!!!!

WHOA! You guys are my heroes!!!!