HPF PASSIVE FILTER 

WF Filter 222A Module

This passive filter is a recreation of the Altec 9069 unit found inside King Tubby mixing desk

We can hear the signature sound in a lot of his mixs back in the day.

7 years ago  I discover the DIY electronics with a big help of one of my best friends.

He show me that is possible to recreate gears , repair and mod actual audio gears , that the point I begin to learn and try .

My mixing desk was our first project. We convert an old soundcraft in hi end spec and change the chassis configuration to put new aux send and an empty space for the futur Hipass !!!

As a reggae Dub beat maker and Dub producer , i always try to clone this sound ..but never archieve it correctly with plugin or active filters.

So we decide to make reasearch , prototype and try to make this filter ALIVE

After 2 years of intense research , we finally built the first prototype ...at the instant  I engage the routing of the mixing desk , i start to have a big big smile in my face ...we have succeeded !!! What a big day ....

After that  I put some videos on the Web , i start to receive a lot of messages arround the world, people will clearly wait to access of this rare "signature " tools.

Inside The Filter

- WIMA hi quality spec capacitors

- Custom Multitaps Inductors from Cinemag

- 2 X Jacks TRS

- 50 wires !

- Main PCB 

- Metal case from hammond case

- NEW ! Professional Metal Face plate with Values engrave

- 11 positions Hi end Rotary Switch turn at 190°

- Big knob 45mm OT

Price = 350 euros include Tax / exclude Shipping cost 
- UK = 18 euros ( 2 days ) FedEx
- FR = 10 euros ( 2 days )  Colissimo
- US = 30 euros ( 7-10 days ) My Delivengo
- JA =  30 euros ( 10 -15 days ) My Delinvengo
- EU = 15 > 20 euros  ( 3 days ) FedEx / DHL

HPF Wiring, Experiments,tricks & tips

First, Thanks again for all Dubbers & friends who used my filter . I m very proud of what I hear here and there :) I receive a lot of nice messages from the world.

I really appreciate your support on my products and software !

What a crazy adventure for me.

I try to explain here i what I discover , receive or share from last 3 years with this HPF

Intro

Second :) the filter is a real passive unit witch use capacitors, inductors and big knob, you don't need PSU ! No insertion loss because it's an HPF so you remove frequency , not the contrary .Filter is unbalanced and unterminated . That why it create a peak over the cutoff frequency selection.If you put a resistance, say 600ohms at output of HPF, you will lower the resonnance to +/- 3db, we don't research that to create a nice sweep of filtering.

A variable potentiometer can be used at output to control this resonnance too . Your choice:)

Filter is symetrical on design so Input / output aren't important .You can have a very slight difference ( electronic tolerance ) so test what is the best for your ear .

Impedance

The Input / Output circuit / respective impedance and headroom are IMPORTANT .The filter will sound different if you use a mixing desk with discrete opamp, transformers, Chips etc …So you need to experiment . If your desk is really cheap , maybe it s better to put a good circuit around the filter . It change the signature sound and raise the resonnance up to 15db on certain configuration. 8 to 15db to be exact. If your hear a very ringy sound, it inform that your circuit use the maximum headroom avalaible. So lower the input or wire it on another point in mixing desk

Some desk include like old Tascam use another level reference -10dbv =0VU

Soundcraft, Trident, Allen etc use +4dbu=0VU for reference

So the filter will sound different because of the signal it receive or transmit.

Wiring

Aux, Insert point , direct out or Subgroup ( insert and output ) ….both can work ! Personaly I use ONLY the send of my subgroup insert with a Y cable ( unbalanced ) to the input of HPF and filter output connect to a empty channel . Sometime I put a compressor + pre EQ before the HPF , it will control the first transient of the source and create a good sweep , less agressive.

Some people who don’t have insert point on subgroup can cheat . Use your aux send and wire  to an empty channel , then patch the filter with an Y cable to the insert point . Open the aux send at 3/4 to give good signal on the filter input ( you can’t burn it :) ) and play with it to find the sound.

Exemple of Y cable I use

https://www.thomann.de/fr/cordial_cfy_15_vpp.htm

Exemple of Insert ( INS ) on mixing desk ( Allen , Soundcraft , Trident etc ....) 

https://homestudiodoctor.co.uk/wp-content/uploads/2016/01/Inserts-2-tagz.002.png

So for filter , use the mono jack of the Y cable 

Use the stereo jack > INS of the mixing desk 

Pop & Click & Noise

Yes the filter can create this things

There are several reasons.

First i STRONGLY advice to take a look on your ground sheme in studio

On a professional studio , all ground are separated and return to a central point to remove all ground loop and give an « equipotential to all ground and chassis .That important for your recording quality and mix too !

If you setup all the things , turn the volume up on master and hear a lot of strange things , that indicate that you have a « problem » . Normally you should hear only a clean hiss, no buzz, no hum . That way, you sure that all your gears share the same potential

When you turn the filter , the capacitors discharge energy so if all ground and potential are the same , you will minimize this « problem ».

Ground is one of the number one rules on audio and often the most complicated to explain or apply .

In my studio i use the old technique whow in my manual Soundcraft 600, i also see it on Trident 65, MCI JH400 too . So ALL the shields are wired only at ONE end on TRS or XLR cable

All safety ground ALWAYS connected too .Use a circuit breaker for all your audio system and another for light, dimmers etc etc

 

Smoke & Dust

When I built filter and send it to the world I take attention to clean all contacts of each switch stages with Deoxit product ( D5 ) so the NOS ( new old stock ) rotary switch is almost new:) and free of dust or old grease.

If you smoke on studio or never get time to remove dust , yes you can have problem in futur.

If ground sheme is OK , the only pop/click you will hear are often create with a square wave sound ( bass frequency ) so one trick is to send a clean signal with no sub on it . Exept if you use it on recording ( no sweep turn )

Before get bored with this, use other cable , clean your jack contact, use a good one too ...not the cheap cable see on some hifi stuff.

For info Cordial make a good Y cable for a good price or use a good shieldeded cable too .

 

Tubby or not Tubby, that is the question ?

For Tubby trick, I really don't know the « secret » . His MCI used a real 600ohms IN/OUT, a patchbay too and a lot of creativity too ...so the most important = be creative and make a lot of test ...maybe one day we sucess to reach this sound . The filter isn't magic, the magic is arround it

Some people include me maybe overlook for this trick , but i m almost sure it's really a clever trick...maybe phase cancellation, reverse polarity, Mid Side FX ...don't know but maybe one day, a person will share what it find ...ahahah maybe if we are lucky , a weel know Jamaican engineer will show it, but i have doubt.

Enjoy !!!

Best

Seb Westfinga Bzy

 

PS :I would also like to thank in particulary to my friends Manu Bypass, Jahno and Jideh High for the hours spent talking about this filter !