Question about BA3812 EQ IC !!

[Minion]

Hey Folks , I have a couple BA3812 EQ IC"s and wanted to try them out to make a simple 5 Band EQ... in the Datasheet Circuit it has 100k pots to controll the Boost/Cut ..
My question is what effect does the Value of these Pots have on the curcuit ??

I know that they don"t effect the frequency as when doing the Calculations for the Filter Frequencies the 100k pot is not taken into account ....

is it like a Gain pot ?? or like a Volume pot ?? what effect would a different Pot Value have on the circuit ??

Sorry for the stupid question .....




thanx

[MetalGuy]

I have some experience with those chips and I can tell you that regular /linear/ 100k slide/pots don't work well in this circuit although they are suggested in the datasheet.
100k pots will give you some "action" only close to the "up" or "down" positions of the slide pot. My advice is to try 50k or 20k and listen to the result.

[Minion]

Ok , so the pot is more like a Volume controll for the specific frequency band and not a Gain pot for the frequency band ?? so the Value of the pot has no effect on the amount of cut and boost but has an effect on the sencitivity of the Boost
/cut ??

Thanx

[jacobyjd]

oooOOooo...this looks interesting. Dangit--I'm already working on two other major projects...

[mth5044]

I know, I really hope something comes out of this chip. I don't have the time to buy and and play around, but I wouldn't mind putting a 20ish part EQ pedal on the list 

[Minion]

well I do have a PCB design for this, the problem is I don"t have a ba3812 Footprint in my PCB program so I had to create a custum component useing the Datasheet measurments of the chip as a guide ,and my Ba3812 are in the mail so I can"t check to see if the pins match up , I"m sure it will work it is just scaleing the PCB to the correct size.....

The PCB is rather Big cuz I tried to do it so i can mount the Pots on the PCB , no I"m not useing slide pots , Im useing regular pots with a center detent......





Cheers

[mth5044]

Forget what this post used to say.

That pin out is MESS UP

[mth5044]

According to the datasheet, it looks like the pins of the chip are 0.1" apart from the front of the chip, but the distance from the side is only 0.05". This chip is freaking me out 

[mth5044]

Here is mine, a bit smaller but doesn't have the option of mounting the pots right the pcb. I have them all lined up next to each other though, making it easier to use some ribbon cable. Abot 1.2" L x 1.7" W


Also note a jumper is needed between 7 and ten, the reason for 6 pads off of pin 7. The Rl on the schematic is assumed to be wired across the jack to save some space on the pcb.

Can't wait to here how it sounds when you get it done. Don't forget to check back in 

[mth5044]

Sorry for another bump, but just found that the BYOC 10 band eq is two of these chips in series if you want to check it out.

[Minion]

Hi Guys , Ive got another question about these chips .... it seems from the datasheet that these chips might have a low threshold for clipping , it has a 200mv input sencitivity and and 2.1v output voltage with a 8v supply , I am afraid because my input voltage might be in the 2v-4v Range , if I use a 16v DC supply it should give me added headroom but will it be enough to avoid clipping ?? Should I use a Voltage divider on the input signal to attenuate the signal before it goes into the EQ Chip ??

Thanx guys !!!

[MetalGuy]

I see 2.1 Vrms at 8V in datasheet /page 1, top/.

[Minion]

I see 2.1 Vrms at 8V in datasheet /page 1, top/.

Um .... Yea , I know , I posted that info in my in my question , That is the output voltage with an 8v supply ..... But that doesn"t answer my question , Does the output voltage before clipping increase with a 16v supply ?? Will 2v input cause it to clip at 16v ?? should a put a Voltage divider on my source signal to attenuate the input voltage ?? Wait , I think I hear an echo ..... LOL


Thanx