Passive Mastering EQ

[ruffrecords]

50£ is for the Elma Switch I suppose

Keep up the great work Ian, can't wait to read more

That is right, it is the switch that is over £50.

Anyone had any experience of using ribbon cable in EQ circuits? I am a bit concerned about the stray capacitance. The advantage of ribbon cable is that DIYers can set the switches at any spacing they like. A PCB will have much lower stray capacitance but fixes the switch spacing. Pros and con s??

Cheers

Ian

 

[salomonander]

personally i try to stay away from any ribbon cable whenever possible. perhaps you could design a bridging pcb between switch and main pcb that has lots of pin holes at different distances and the option to easily saw/break it off where one needs it.

if this does not make sense, i think it would not be to bad if the spacig was given. if one does not like how it is arranged its still  possible to re-arrange with cabling. its what i did on your redd eq and it was no problem. just a bit more work.

 

[ruffrecords]

personally i try to stay away from any ribbon cable whenever possible. perhaps you could design a bridging pcb between switch and main pcb that has lots of pin holes at different distances and the option to easily saw/break it off where one needs it.

if this does not make sense, i think it would not be to bad if the spacig was given. if one does not like how it is arranged its still  possible to re-arrange with cabling. its what i did on your redd eq and it was no problem. just a bit more work.

I imagine the vast majority of EQs built to this design will be housed in 19 inch rack enclosures. Most of these have at least 16 inches of horizontal panel space available. If the EQ has 6 bands spaced 2 inches apart with an inch gap at either end, the total space occupied is 14 inches. This leaves a couple of inches for a mains on/off and or master level control. This is pretty much the spacing between controls of the Pultec MEQ5.

http://lghttp.50970.nexcesscdn.net/8029F77/vk/media/catalog/product/cache/1/small_image/17f82f742ffe127f42dca9de82fb58b1/p/u/pultec_meq_5_front.jpg

Cheers

Ian

 

[warpie]

That is right, it is the switch that is over £50.

Is this the price for the single gang? Stop screw?

 

[malnatim]

I am a bit concerned about the stray capacitance. The advantage of ribbon cable is that DIYers can set the switches at any spacing they like. A PCB will have much lower stray capacitance but fixes the switch spacing. Pros and con s??

imo being able to set the switches at any spacing is appealing, but maybe not worth it if this creates too much stray capacitance.
mike

 

[ruffrecords]

imo being able to set the switches at any spacing is appealing, but maybe not worth it if this creates too much stray capacitance.
mike

The prototype is earmarked for a customer so it will definitely not have ribbon cable in it. Once this one is working I can devise a PCB that allows the bands to be connected by ribbon rather than a PCB. Both choices will then be available.

Cheers

Ian

 

[ruffrecords]

The ELMA switches have arrived at last. Now I can start on the interconnecting PCB.

Cheers

Ian

 

[salomonander]

sounds exciting. let us know how it goes !

 

[frederickalonso]

The ELMA switches have arrived at last. Now I can start on the interconnecting PCB.

Cheers

Ian

Good luck with the design Ian, looking forward for this. Have read all posts here and really like the idea and concept behind it.
Will order one for sure!

I am doing graphic design as freelancer besides making music  : so if you need a nice visual for the case let me know ;-)


Grtz and respect for the input,
Frederick

 

[ruffrecords]

Good luck with the design Ian, looking forward for this. Have read all posts here and really like the idea and concept behind it.
Will order one for sure!

I am doing graphic design as freelancer besides making music  : so if you need a nice visual for the case let me know ;-)


Grtz and respect for the input,
Frederick

Thanks for the offer Frederick. I am planning on a spacing of about 1.6 inched=s between the 5 bands so that  left and right channels should fit aside by side across a 19 inch rack mounting enclosure ;probably 2U or 3U high.

CHeers

Ian

 

[frederickalonso]

Sounds great IAN!  8)

 

[ruffrecords]

here is my first pass at the interconnect board that wires together the level controls of each of the five bands. Turned to be not as bad as I thought it would although there are a lot of vias which seem to be unavoidable.

unfortunately I just checked the orientation of the the header pins and it is not the same as on the switch. For some odd reason the switch has pin 1 on the top RHS not the bottom LHS as is usual which means I need to rotate all five headers through 180 degrees and re-track them. Ho hum.

Cheers

Ian

 

[ruffrecords]

After a fairly marathon session I rotated all five connectors through 180 degrees and re-connected them Sent Gerbers of to have some prototypes made.

Cheers

Ian

 

[sr1200]

Please let me know if these become publicly available!

 

[ruffrecords]

Please let me know if these become publicly available!

The plan is for them ultimately to be available via the Emporium. I ordered five prototypes because that is the minimum order. I only need two for the first customer so, assuming they work as designed, the other three will then become available.

Cheers

Ian

 

[petermontg]

Cool work Ian.


I have a spare pair of  Gyraf SRPP I have been wondering what to do with 8)

Keep up the great work.

 

[Jonte Knif]

Are you still thinking to build at 600 ohms impedance and RM8 coils? That sounds like the way to gross saturation.  In my Soma mastering EQ I use bigger coils, 4:1 input trannie and much higher impedance level to keep distortion low enough for mastering.

Another question: How do the bands interact when they share the same resistor ladder? Of course passive parallel EQs will always have weird interactions with closely spaced frequencies but sharing the resistor ladder sounds like a way to some *very* weird situations. Have you simulated and compared to separate ladders?

 

[ruffrecords]

Are you still thinking to build at 600 ohms impedance and RM8 coils? That sounds like the way to gross saturation.  In my Soma mastering EQ I use bigger coils, 4:1 input trannie and much higher impedance level to keep distortion low enough for mastering.

Yes and no. It will be 600 ohms. Core sizes will depend on inductor value. what makes you think saturation will be an issue?

Another question: How do the bands interact when they share the same resistor ladder? Of course passive parallel EQs will always have weird interactions with closely spaced frequencies but sharing the resistor ladder sounds like a way to some *very* weird situations. Have you simulated and compared to separate ladders?

I have simulated interactions and if anything, they are less weird than with separate ladders.

Cheers

Ian

 

[Jonte Knif]

Yes and no. It will be 600 ohms. Core sizes will depend on inductor value. what makes you think saturation will be an issue?I have simulated interactions and if anything, they are less weird than with separate ladders.

Ian

Well, I know the saturation levels of my own design, and compared to it ferrite RM8 or even RM14 @ 600 Ohms and low frequencies is going to have a lot of  distortion. Also the inductance modulation will be one issue. So, I just recommend that you measure the distortion levels and the frequency shift according to level before you decide the core sizes and impedance and signal levels.

If you want to work with low impedance consider iron or mu cores for bass.

Shielding is mandatory for critical use. Mu metal shields are luckily fairly easy to make. 0,2mm thick annealed sheet can be cut with scissors  and soldered with normal electronic solder and will easily provide 10-15dB attenuation.

Best,
Jonte

 

[ruffrecords]

Well, I know the saturation levels of my own design, and compared to it ferrite RM8 or even RM14 @ 600 Ohms and low frequencies is going to have a lot of  distortion. Also the inductance modulation will be one issue. So, I just recommend that you measure the distortion levels and the frequency shift according to level before you decide the core sizes and impedance and signal levels.

If you want to work with low impedance consider iron or mu cores for bass.

Shielding is mandatory for critical use. Mu metal shields are luckily fairly easy to make. 0,2mm thick annealed sheet can be cut with scissors  and soldered with normal electronic solder and will easily provide 10-15dB attenuation.

Best,
Jonte

Thank you for your comments. Could you post a copy of the schematic of your EQ so I can make a comparison?

I agree that the area of concern is bass frequencies. Saturation is proportional to amp turns. Bass frequencies need more turns and low impedance means higher currents both of which can lead to saturation. Fortunately low impedance requires lower inductance so fewer turns so the situation is not as bad as it might seem a first sight. But inductance is proportional to turns squared so higher impedance fare better. Unfortunately, higher impedances can lead to in band parasitic resonances in inductors which is why I favour lower impedance. However, you are right, the bass end needs careful design(core selection)  and measurement.

Cheers

Ian