Inside The Filter
This passive filter is a recreation of the Altec 9069 unit connected inside the King Tubby mixer.
We can hear this sound signature in a lot of his mixes back then.
7 years ago I discovered DIY electronics with the help of a new friend discovered by chance at a mutual friend :)
He showed me that it is possible to recreate machines with an equivalent quality, to repair and modify real audio equipment, it is the beginning of my adventure in electronics.
My mixer was our first project. We have customized an old soundcraft 600 series and modified the chassis configuration to put a new auxiliary start and an empty space for the future Hipass of course !!!
As a Musician / Engineer and Reggae Dub Producer, I have always tried to clone this sound ... but never really got there with plugins
So we decide to do some research, prototypes and try to recreate this legendary passive filter.
After 2 years of intense research, we have finally built the first prototype ... the moment I start the routing of the mixer, I start to have a big smile on my lips ... we have succeeded !! ! What a great day ....
After that I put a few videos on the web, started getting a lot of messages from all over the world, people are clearly willing to wait to access these tools with a rare signature. The magic is about the components. Inductors, Film Capacitors and a lot of passion!
- 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 with laser
- 11 positions Hi end Rotary Switch turn at 190°
- Big knob 45mm OT
-Update V2 > new switch to vary the color on the high end registry
- Résonance potentiometer to control the peak cuttoff curve
HPF Wiring, Experiments,tricks & tips
First of all, thanks again for all the Dubbers and friends who have used my filter. I am very proud of what I hear here and there :) I get a lot of cool messages from all over the world.
I really appreciate your support on my products and software!
What a crazy adventure for me! I did not expect that .
I try to explain here what I discover, receive or share for 3 years with this Passive filter
Introduction
The filter is a true passive unit that uses capacitors, inductors and a large notched potentiometer, you don't need a power supply! No insertion loss because it's an HPF so you remove the frequency, not the other way around. The filter is unbalanced and unterminated. This is why it creates a peak on the cutoff frequency selection. If you put a resistor, say 600 ohms at the output of HPF, you will lower the resonance to +/- 3db, we are not looking for that to create a nice filter sweep.
A variable potentiometer can be used at the output to also control this resonance. Your choice:)
The filter is symmetrical on the electronic design, so the input / output is not important. You may have a very slight difference (electronic tolerance) so test what is 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 patched to the INSERT of 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
Thanks & BigUp
At the beginning of commercial project Dr Sean Williams help me a lot to understand the wiring, design and impedance of this particular hipass.I precise that is the only man I know who have authorization to analyse the MCI desk ! He spend a lot of time to research and write a very good book ( I already buy it :)) because of technical knowledge about this sound.
Tubby's dub style: The live art of record production
You can find a link to this book chapter which is freely downloadable HERE
I would also like to thank in my friends Manu Bypass & Jahno for the hours spent talking about our filters tips and tricks !