DIY equalizer based on Studer 169 (standard and mastering)

Standard version (+/- 3,6,9,12,15 dB)

http://audioxxx.googlepages.com/EQ_169_STD_schematic.pdf


Mastering version (+/- 1,2,3,6,15 dB)

http://audioxxx.googlepages.com/EQ_169_MAS_schematic.pdf


Shared documents (for both standard & mastering version)

http://audioxxx.googlepages.com/EQ_169_STD_layout_designations.pdf
http://audioxxx.googlepages.com/EQ_169_STD_copper_mirror.pdf

http://audioxxx.googlepages.com/EQ_169_STD_frq_selection_lo_filter.pdf
http://audioxxx.googlepages.com/EQ_169_STD_frq_selection_hi_filter.pdf
http://audioxxx.googlepages.com/EQ_169_STD_frq_selection_table.pdf

http://audioxxx.googlepages.com/EQ_169_dimensions.pdf


Earlier this year I built a mastering eq for a friend of mine. It is based on Studer 169 mixer channel which has an equalizer that I like a lot (and there are many others sharing my opinion). The feedback that I got was very very positive. So I decided to draw a PCB for it to make it available to all of you (the prototype was a ratnest/veroboard version).

Several changes has been made to the original circuit. Potentiometers are replaced with rotary switches (for accurary). Original fixed frequency is replaced with 5 selectable frequencies.

The eq section contains only one op-amp. It can be used in unbalanced mode (input and output section not assembled) if extremely pure signal path is required. Debalancing and balancing amplifiers are however included in the pcb. If all components are assembled, it provides balanced input and output.

The eq op-amp is classic NE5534 but there are huge amount of pin compatible alternatives available. So you can replace it with better (or at least more expensive) if you want.

The PCB is single sided and suitable for home etching (large pads and thick traces). The board size is 194x38mm. So it fits easily in 1U rack case as well as in standard 40mm mixing console channel module.

Switches are Lorlin series CK. They are available everywhere and there are number of equivalent types from other manufacturers too. Types used are 1x12 shorting and 2x6 shorting. Non-shorting switches can be used but some additional switching noise is likely.
http://www.lorlinelectronics.com/pdf/CK.pdf
I have made a lot of work to make this unit tidy looking and easy to assemble (all switches are on PCB). Please don't wire the switches. First, it looks horrible. Second, it increases noise pickup and long wires can cause oscillation (it is unlikely but possible).

As usual, I don't sell boards, components or anything related to this project.

Boards are available from Gustav:
http://www.groupdiy.com/index.php?topic=10776.0

**********

My other projects:

Neumann W492 EQ
http://www.groupdiy.com/index.php?topic=28332.0

Neumann OA10 discrete op-amp
http://www.groupdiy.com/index.php?topic=34105.0

Balanced 12 input summing amplifier
http://www.groupdiy.com/index.php?topic=29082.0

Balancing/unbalancing amplifier
http://www.groupdiy.com/index.php?topic=29333.0

Hi!
That looks great, really looking forward to it!
Is it hard calculating these frequencies? Maybe we can come up with a table so people can choose them to their liking...
If not, I'm thinking of frequencies like:
-80Hz or 90Hz depending on the steepness of the curve (meaning close to 100 but not too much)
-110Hz or 120Hz though I would rarely use it, or completely up to 250Hz to use as an effect of some sort.
-5KHz
-Move the 10K in the 8K area (again depending on the curve)
-Move 16K in the 12K area
-Move the 20K in the 18K, or maybe not...
I'm interested in people's opinions on this choice!

awesome!!! i was wanting as filter circuit on this forum!!

for me (depending on the slope) i would say 20hz 30hz and 40hz on the low and 20khz 18khz and 16khz on the highs (again dependent on slope)

thanks for this project, very cool

nice project! the EQ on the later 970 is very similar, I really enjoy it for tracking. The "presence" filter is nice too but needs a double 100k neg log potentiometer.

j.frad said:

Maybe we can come up with a table so people can choose them to their liking...

Click to expand...

That was my original idea too. See the first post of this thread for the frequency selection table table and two graphs. Schematic also added. More documents in a few days...

I decided to publish the general purpose version first (+/-15dB gain range in 3dB steps). The mastering version (+/-5dB in 1dB steps) will follow if there is enough intrest.

E: I still encourage all of you to give your suggestions for those 5+5 preset frequencies. I believe it lowers the threshold for building this project for those not so experienced with equalizers. 

martthie_08 said:

the EQ on the later 970 is very similar, I really enjoy it for tracking.

Click to expand...

Variations of this circuit are used in many Studer consoles. The circuit is technically very clever and also sounds good. So it is not a surprise that it is recycled...

My thoughts on the LF shelf (based from your documents): 20, 40, 60, 85, & 120

I think that'd cover all shelving needs.

Hi,


  I am really interested in this eq. It looks so simple. it MUST sound good! Just one thing, might I suggest a cut/boost switch, so that you could have 0 to +/-15dB in 1.5dB steps instead of either 3dB steps(+/-15dB) or 1dB steps(+/-5dB)? Jakko did this with his Sontec eq build. This would give more range at small increments.


    see Fabio Bauman's page here for details


    http://www.thediypill.phx.com.br/diy_sontec.htm


    Kindest regards,


      ANdyP

Would it be stretching the capabilities of the EQ to have a high shelf at 1k and a low shelf around 600-800? I find "tilt" type EQ's very useful.

Gold said:

I find "tilt" type EQ's very useful.

Click to expand...

My thought excatly, ive been looking for something like this.


Maybe 200nf something in the Hf shelf?

I've been vaguely drawing up plans to build myself a ~16-20 channel line level mixer with simple but nice sounding eq (enough to tweak highs and lows, or add a bit of a smile curve, but nothing too drastic) and a simple tube output stage to bring the level back up.

I'd have gain, pan and perhaps four aux sends per channel, plus direct outs for multitracking everything, and a master eq. Eq's would be switchable in and out of circuit.

Anyway I thought your eq might fit the bill really nicely for the channel eqs and wondered what you think?

It is based on channel eq, so it probably works fine as a channel eq...

I have also designed a super simple version of the 169 eq with just lo and hi cut/boost switches (no selectable frequencies). It has unbalanced input and output. Since it is very compact, it could be optimal for your mixer application. It is however not very well documented, so it takes some time to get it published.

audiox thanks for sharing this great project. i've been looking for an EQ to build. is there a PCB for the simple version of this project or only the multiple band mastering version? i'll keep watching the tHreAD to find out.

audiox said:

It is based on channel eq, so it probably works fine as a channel eq...

I have also designed a super simple version of the 169 eq with just lo and hi cut/boost switches (no selectable frequencies). It has unbalanced input and output. Since it is very compact, it could be optimal for your mixer application. It is however not very well documented, so it takes some time to get it published.

Click to expand...

Actually I really like the idea of being able to vary the shelves' cutoff so I'd definitely go for that version!

Is there much to be gained from having an internally balanced line level mixer? I'm sure there must be a discussion on this somewhere...

Presumably it would cost me a fortune in transformers if I wanted the internals to all be balanced?

Eje2005 said:

Gold said:

I find "tilt" type EQ's very useful.

Click to expand...

My thought excatly, ive been looking for something like this.

Click to expand...

Do most tilt-circuits simply join bass & treble controls in a CW & CCW fashion ?

Apart from having seen a tilt circuit in an old EW+WW magazine that did it otherwise as I seem to recall,
I can't recall any others.

Bye,

  Peter

clintrubber said:

Do most tilt-circuits simply join bass & treble controls in a CW & CCW fashion ?

Apart from having seen a tilt circuit in an old EW+WW magazine that did it otherwise as I seem to recall,
I can't recall any others.

Click to expand...

This was the first EQ I built as a kid in the early 80s.

The TILT tone control was developed in the 70s by Quad and it is implemented in the old Quad 34 preamp.
The whole thing can be done with only one linear pot that will tilt the freq response in the favour of lows or highs.
Here is the schematic of this preamp (look only at the upper pot in the tone control how is wired):
http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Schematics/QUAD-34-Schematic-Circuit.pdf

The same circuit presented in a simper manner at Headwize (TILT EQUALIZER):
http://www.headwize.com/projects/equal_prj.htm

If my memory serves not so long ago someone was offering a TILT eq in 500 format.

chrissugar

chrissugar said:

If my memory serves not so long ago someone was offering a TILT eq in 500 format.

Click to expand...

I was wrong, not 500 format EQ, it is the Tonelux MP1A preamp with TILT eq tone control:
http://www.tonelux.com/mp1info.html

Thanks Chris for the Quad-info, nice. Simple circuit to put on vero, added to the list 

The asym supply (+8.6V & -9.4V) they use is interesting too (not in jest).


Cheers,

  Peter

seavote said:

is there a PCB for the simple version of this project or only the multiple band mastering version?

Click to expand...

Yes there is. But some of the documentation needs to be redrawn before I can publish it.

clintrubber said:

Do most tilt-circuits simply join bass & treble controls in a CW & CCW fashion ?

Click to expand...

Yes, I was referring to the end result more than the controls. I'd prefer separate controls for low and high anyway.