Midrange passive eq

[wizard60]

Hi all!
I'm just registered and I make my compliment for this community  8). My question is about a simple passive Mid Eq with some switchable peak freq. Someone is experienced in this ?

Thank you all!

Marco

 

[warpie]

Welcome..

"Passive" and "peak" don't go together.

Maybe you mean "passive and dip" or passive filter with make up gain stage?

 

[Sleeper]

I recently researched this, because the pultec's in my mastering chain do not have a mid...
I suspect you have similar problems.
Check out Ian's EQ system - ruffrecords–
I like the helios which has a switched mid section_lot's of frequencies_ +-12db
He also has done the MEQ

But the system is cool, it's just the EQ, makeup gain is on a separate board, or you could go totally passive and just use one of your mic pre's for makeup.

 

[ruffrecords]

Many of the passive EQs I have designed have a mid boost/cut section and it would not be too hard to build one with only this section if you wanted. All passive EQs with boost do require a gain make up amplifier of some sort.

Cheers

Ian

 

[wizard60]

Many thanks guys!

... I know the passive and peak doesn't go together, I forgot to specifie one tubed make-up added. I'm thinking to a filter LC switchable from 0.3 to 3/4 KHz...

Many of the passive EQs I have designed have a mid boost/cut section and it would not be too hard to build one with only this section if you wanted. All passive EQs with boost do require a gain make up amplifier of some sort.

Cheers

Ian

Thank Ian, did you design this?

https://www.dropbox.com/s/1g8rt01aavot861/unipassiveEq.jpeg



@Sleeper, yes you're right....!



Thanks! 

Marco

 

[ruffrecords]

Yes, that's one of mine. You can make just about any EQ using that PCB. Just add the gain make up of your choice.

Cheers

Ian

 

[wizard60]

Thanks again Ian!

... just to start to experiment... do you have a simple LC calculator to suggest to me? I need to check differents impedance scenario

Cheers 
Marco

 

[ruffrecords]

Thanks again Ian!

... just to start to experiment... do you have a simple LC calculator to suggest to me? I need to check differents impedance scenario

Cheers 
Marco

This should give you a basic starting point:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/UniversalEQ/PCB/InductorCalcs.pdf

Cheers

Ian

 

[wizard60]

Thank you again Ian !!

I'll let you informed


Marco

 

[wizard60]

Hi again Ian,
hope to not bother you... something is missing in my brain... Rcut and Rfix, how I must consider them?

Thank!

Marco

 

[ruffrecords]

Hi again Ian,
hope to not bother you... something is missing in my brain... Rcut and Rfix, how I must consider them?

Thank!

Marco

This document gives a broader overview of the Universal EQ:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/UniversalEQ/PCB/UNIEQConfiguration.pdf


Cheers

Ian

 

[wizard60]

Thank you again Ian... now all it's more clear to me. One more question please:

When the RCL mids are setted in boost, the variable partition is made by the pot and by VR2 (Hi-cut shelf). When we're in cut position, supposed that we dial the mids for max attenuation, the partion is made by Rfix and Rcut, but is VR2 in parallel to Rcut?

Sorry for may bad English...

Cheers
Marco

 

[ruffrecords]

Thank you again Ian... now all it's more clear to me. One more question please:

When the RCL mids are setted in boost, the variable partition is made by the pot and by VR2 (Hi-cut shelf). When we're in cut position, supposed that we dial the mids for max attenuation, the partion is made by Rfix and Rcut, but is VR2 in parallel to Rcut?

Sorry for may bad English...

Cheers
Marco

In the cut position the basic potential divider is Rfix and VR2. However, VR6 and Rcut are connected across VR2. As VR6 is rotated clockwise, more and more of VR2 is shorted out by the RLC so we get cut. When VR6 is fully clockwise we could in theory get infinite cut. The purpose of Rcut is to limit the maximum cut to the desired value.

Cheers

Ian

 

[wizard60]

Thank you!... very kind 

marco