Passive Mastering EQ

[ruffrecords]

Hi Ian,

i was just wondering  , are the inductors  you are going to choose, custom or off the shelf , and will the peaking / shelf  eq  circuit use the same inductor.
cheers

skal1

The inductor for the peaking version of  lowest band is a custom one I had made by Sowter. The results I have posted here for the peaking version and the shelving version both used the same inductor. However, it is clear that the shelving version probably needs a different inductor. I am waiting for guidance on this from my customer.

Cheers

Ian

 

[5v333]

 

[5v333]

Ian, how does it look?

 

[ruffrecords]

L and R look fine to me. How would I mount this on a PCB?

Cheers

Ian

 

[5v333]

the brackets needs a pair of holes to mount with. either on a pcb or to a panel.

the pins are spaced with standard 5.08mm and will even fitt a stripboard. you can solder them to a pcb or if you mount the inductor upside down, you can solder some wires to the pins and a pcb or switch or what ever rocks your ship.

here is the datasheet for all the parts of the inductor. there youll find all measures you want to know.

https://www.mouser.se/datasheet/2/400/pm_50_39-1220248.pdf

 

[5v333]

i have arranged the pins similar to an opamp/ic with pin1 in the upper left corner and last pin in upper right corner.

i thought that by having some windings on both sides it would be easier to fit capacitors around it instead of cramed on one side...

all the windings are not connected in one string but separated for experimentation. for ex you could connect thoose windings not in use to ground to make a shield for the inner windings. or you could make smaller inductors by paralleling.

 

[iampoor1]

There seems to be no accepted definition of the frequency of a shelving EQ so the following plots are listed by inductor value. Draw you own conclusions about how you would define them:

Ian

How do you personally define them?

When designing EQs in LTspice, I always define the "frequency" of a shelving eq at the 3db point at full boost/cut. I dont want to hijack your thread, this may be better suited to its own topic.

 

[ruffrecords]

To be honest I do not have a specific definition. There are really two issues here. The first is the technical definition but the second is how you mark the controls. For the user, when he dials in 6dB boost at 10KHz he expects the boost at 10KHz to be 6dB but it is difficult to know how the user expects the response to alter after that point. We have discussed this here some time ago. It is an interesting and importnt topic so a thread of its own is probably a good idea.

Cheers

Ian

 

[SIXTYNINER]

To be honest I do not have a specific definition. There are really two issues here. The first is the technical definition but the second is how you mark the controls. For the user, when he dials in 6dB boost at 10KHz he expects the boost at 10KHz to be 6dB but it is difficult to know how the user expects the response to alter after that point. We have discussed this here some time ago. It is an interesting and importnt topic so a thread of its own is probably a good idea.

Cheers

Ian

just for say that  it will be great , if "related" with that showed at this link : 
http://mojitomastering.com/gear/
(chandler curve bender)

 

[Mulmany]

How is the progress on this project? Is it in the wild, or still being evaluated?

 

[ruffrecords]

How is the progress on this project? Is it in the wild, or still being evaluated?

It is a work in progress. The basic concept works. At present I am working on specifics for the first customer, Had a problem with inductors recently that looks like it may be solved but it will need a PCB revision to be certain. I will continue to post progress here as it occurs.

I have used the same concept to create an updated low cost version of the three band REDD EQ for the Mark III tube mixer. I have built and tested a prototype of that EQ.

Cheers

Ian

 

[r2d2]

hello Ian
cool project !

any news about ?

 

[ruffrecords]

hello Ian
cool project !

any news about ?

I mentioned the problem with inductors. The new PCBs for the new inductors arrived a couple of days ago and I started populating it. I just ordered the remaining inductors so with luck, by this weekend, the inductor problem will be solved. I know of no further issues with other bands so I should then be able to build a complete five band channel and test it.

Cheers

Ian

 

[MrBlomski]

Nice progress!

 

[ruffrecords]

I have built the new version of PCB which uses shielded inductors. I fitted just the inductors first so I could measure them individually and in total. The total series inductance was 69.46mH. Measuring each individually and adding up the values gave 69.77mH is an error of only 0.44% which is probably similar to the measurement accuracy. I think this  has cured the interaction problem.

Cheers

Ian

 

[JamesW]

Have been following this project from the start to learn about EQ design. Thanks for sharing
I read you have closed the Emporium does this mean boards for this EQ will not be available ?

 

[ruffrecords]

Have been following this project from the start to learn about EQ design. Thanks for sharing
I read you have closed the Emporium does this mean boards for this EQ will not be available ?

I have not decided that yet. Most likely I will make a batch and put them up in the Black Market at cost. All my boards are still available except those that I have made open source which you can make yourself. I closed the Emporium because at the moment I sell so few boards it doesn't cover the cost of being in the White Market.

Cheers

Ian

 

[OTRM]

Well I'm waaay late to this party but following with interest.

Not sure what all has been figured out and written on stone but I'll add a few thoughts:

1- I second (nth?) the motion for 0.5dB steps at least for the first +-3dB
2- I find that I tend to use a bit wider (lower) Q values for higher freqs and narrower (higher) Q values for lower freqs. Anyone else in this camp?
3- I've heard of Shallco switches (not sure which model) being used in mastering applications

I hope this project materializes or at least results in enough info to make it possible to build...
Thnx

 

[echoplex]

about a year later.. any news here?
ian told to have to complete a mixer project. fingers crossed that this is donee by now

 

[MrBlomski]

Curious as (h)well(oween)  ;D