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Modding EQ Freq points on 70´s Raindirk Mixer
Old 4 days ago
  #1
Modding EQ Freq points on 70´s Raindirk Mixer

Hi friends.
I have a beautiful Raindirk Mini Mixer from 1973.
This is a smaller broadcast version of the more famous "Series 3" console.

Since this specific mini mixer was designed for broadcast, they limited the frequency choices on the EQ compared to the Series 3 that has the same eq but with selectable freq´s in the Top shelf and Bass shelf.
The Mid and Bass bands are inductor based.

I was wondering, without even looking at the schematics (Wich I could provide) is there a "general" easy way to mod it to have at least one more freq choice on Bass & Treble?
I´m hoping that it would just be a matter of adding a different resistor value, but I´m guessing it is waay more complicated than that?

Even though I solder DIY kits from time to time, I am total noob of electronics, so I am basically asking if this is an easy thing for a tech to do, or likely something more of a scientific labour to make it right?

Thank you for your time!
//Ted Krotkiewski

Last edited by Ted Krotkiewski; 3 days ago at 09:56 AM..
Old 4 days ago
  #2
Lives for gear
It’s probably as easy as drilling a hole in the metal, adding a mini toggle switch (2 or even 3 positions) and then removing the “send” leg of the eq cap and adding a wire to the “ins” of the switch. Then connect the open leg of the original cap to one position on the switch. Now add the second (and third if you go that route) to the other “out” position on the switch and tie them back into the pcb at the same place the original cap joins it.

Really it’s easier if you remove the original cap and connect it along with the new cap (or two) right to am the switch, but size can play a factor too. This bit is my personal opinion and there might not be 100% correct.

The schematic should tell you which cap and where to lift it then you can calculate which cap values you would need to get the frequencies you want.

I can draw it out for you if you want!

This also is depended on the way they did their eq
Like if it is inductor it’s a lot trickier I think because it’s harder to find good inductors than it is caps. Caps are easy.
Old 3 days ago
  #3
Lives for gear
 
ruffrecords's Avatar
Bass and treble controls very often use some version of the Baxandall schematic. This means there are two capacitors for each frequency - effectively one for boost and one for cut. SO to change frequency you would need to switch both.

Cheers

Ian
Old 3 days ago
  #4
Quote:
Originally Posted by enginefire View Post
It’s probably as easy as drilling a hole in the metal, adding a mini toggle switch (2 or even 3 positions) and then removing the “send” leg of the eq cap and adding a wire to the “ins” of the switch. Then connect the open leg of the original cap to one position on the switch. Now add the second (and third if you go that route) to the other “out” position on the switch and tie them back into the pcb at the same place the original cap joins it.

Really it’s easier if you remove the original cap and connect it along with the new cap (or two) right to am the switch, but size can play a factor too. This bit is my personal opinion and there might not be 100% correct.

The schematic should tell you which cap and where to lift it then you can calculate which cap values you would need to get the frequencies you want.

I can draw it out for you if you want!

This also is depended on the way they did their eq
Like if it is inductor it’s a lot trickier I think because it’s harder to find good inductors than it is caps. Caps are easy.
Wow, How very nice of you to offer your help!
Very valuable info here, So it is capacitors, and not resistors. heh .. Cool!

The Mid and Bass band are Inductor based.
I´m uploading a pic of the inside of a channelstrip, maybe it can add to the picture of what we are dealing with here?

I will also take a pic of the schematics, however I do not have the "Exact" schematic of this very console, they were boutique made so, it might not be 100% But I´m guessing the Eq section should remain the same between models though.

Thanks again!
Attached Thumbnails
Modding EQ Freq points on 70´s Raindirk Mixer-raindirk-mini-mixer-1973-ch_strip.jpg   Modding EQ Freq points on 70´s Raindirk Mixer-raindirk-mini-mixer-pic-1.jpg  
Old 3 days ago
  #5
Lives for gear
Nice little mixer
You are right you definitely have inductor based eq.
All my above suggestions were for RC type eq, yours doesn’t have the capacitor.
I think I wrote above you don’t hmwant to change out the inductors. That would be a very bad idea

Changing the resistor should work, same method with the switch as the caps above. However, def get a second opinion re which resistor to change and to what value.

Why not start with checking the schematic you have and seeing if it actually matches up? If you don’t have a matching schematic you will have to figure it out (trace and draw) so that you know what you are doing, and for anyone else to help you in any meaningful way.
Old 3 days ago
  #6
Cyril at Raindirk is very helpful..

Last edited by Gem69; 3 days ago at 01:55 PM.. Reason: Remembered name.
Old 2 days ago
  #7
Lives for gear
 
ruffrecords's Avatar
If you can upload the schematics that would help us help you.

Cheers


Ian
Old 2 days ago
  #8
Here´s the schematics for the EQ´s.
Once again. We are not 100% sure it is the exact same schematic for my mixer, but, regarding the EQ section, I doubt it would be different from mine.

I am truly thankful for all your help so far!
This reminds me of how an amazing place Gearslutz is.


//Ted
Attached Files
File Type: pdf rai-EQmodsV2aFlat.pdf (104.5 KB, 9 views) File Type: pdf raindirk_31raw.pdf (541.8 KB, 6 views)
Old 2 days ago
  #9
Lives for gear
 
gyraf's Avatar
 

If that schematic holds, then try experimenting with the capacitors in series with the wiper of high/low pots. Looks like highs will be an octave up/down per doubling or halving of capacitor - the lows being less than an octave variation with doubling because of the inductor in series.. Should be easy to try out...

Jakob E.
Old 1 day ago
  #10
Lives for gear
The caps are probably the two yellow cylinders that are mounted on their sides in the middle area of the pic you posted. Check and trace to be use.
Those are where you can add the switches.
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