DIY equalizer based on Studer 169 (standard and mastering)

[regularjohn]

Does anyone have panel cutout dimensions for these?
How far apart are the rotaries if mounted to the pcb?
And how much room from the outer rotaries to the edge of the pcb?

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

Awesome!  Thanks so much!

 

[audiox]

Why did you use only 5 freq. positions when you have lorlin switches that can have 6 positons/frequencies?

Why there are only seven dwarfs in the Snow White story? There could be eight or even more.

The position six on the switch could also be used as a possible sixth selected frequency, am I assuming right?

You can solder additional capacitors on the bottom side of the board if you need 6 frequencies instead of 5.

 

[Jeremy.Starseed]

Would this fit as is into a Danner A module? the 19 cm by 4 cm seems really familiar...but is it made to fit, I wonder?

Would be all the more tempting...

Does anyone have panel cutout dimensions for these?
How far apart are the rotaries if mounted to the pcb?
And how much room from the outer rotaries to the edge of the pcb?

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

 

[Assistant]

any news on the documents for the mastering version with smaller db steps?
i just ordered the pcbs 

 

[audiox]

any news on the documents for the mastering version with smaller db steps?

Documents published.

 

[spreemusik]

May I ask how you calculate the resistor values for the switches? The original schematic has linear pots, your mastering version has linear steps in the middle (1,2,3 db?), while your "standard" version seems to have log values.
Just wondering, as I'd like to adapt the schematic to more switch positions.

 

[audiox]

The original schematic has linear pots

And that is why the original Studer scale is not logarithmic.

EDIT: But it is not linear either (just to avoid misunderstanding). It is something between log and lin (I know this is not mathematically accurate at all but best describes the situation). Much closer to log than lin anyway.

May I ask how you calculate the resistor values for the switches?

The equations are quite complex. It is much easier to simulate.

 

[spreemusik]

Ah, okay. I wasn't aware of the studer scales. I guess I'll fire up the simulator then. Thanks!

 

[audiox]

I guess I'll fire up the simulator then.

Use a potentiometer in your simulations first and find out the potentiomer wiper positions which match your "steps". Then convert the potentiometer positions "into resistance".

your mastering version has linear steps in the middle (1,2,3 db?), while your "standard" version seems to have log values.

If you take a small part of log curve it is almost a straight line. (In this case the control curve is not log as you might think but the idea is still the same.)

 

[Assistant]

any news on the documents for the mastering version with smaller db steps?

Documents published.

very nice, thank you!

 

[SaMpLeGoD]

Hello! nice project! this one Studer 169 is like the one that is in the Abby Road's studio, isn't it? I think I read something somewhere...
Well, just a question... wich caps are you suggest to do this eq? WIMA? PANASONIC? as long as is plenty of almost sequentialy cap's values... it's nice use them from a unique source... I think.
I just don't want to fall in some "Cap's sound thread", Is there a lot of threads about this... just want some feedback of someone that already did this eq

Cheers,

Eddie

 

[audiox]

wich caps are you suggest to do this eq?

I would be very interested to meet a person who is able to hear any differencies between polyester capacitor brands ("blind method" must be used of course).

How about buying capacitors that are easily available in your location?

 

[SaMpLeGoD]

Here in Portugal? man... just chinese stuff, the worst you can get... well, no prob I'll order some from banzai and that's it
Thanks anyways

Eddie

 

[MikeClev]

I have a suggestion for improving the resolution of the cut/boost rotary switch. Perhaps use an arrangement where you have a 12 lorlin type switch as used already, and a 2 pole 2 way toggle switch to choose between boost and cut. That way you would have 12 steps resolution. You could have for instance: 0dB, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 9, 12, 15dB.

On the High EQ the total of all the resistors on the lorlin rotary switch is about 4.7k, so the total on our new 12 step switch would need to be half that at 2.35k (as we are only using it for half the full cut/boost range at a time) and the 2x2 switch would have to be wired to switch in a resistor of the same value in front or after depending on whether cut or boost is selected.

This probably is a little confusing. Let me draw a crude ASCII diagram of the top of the http://audioxxx.googlepages.com/EQ_169_STD_schematic.pdf diagram, from R23 on the left to R24 on the right:

Original Circuit:

I--*Fully Clockwise end*--0-0-0-0-0-0-0-0-0-0-0--*Fully Counter Clockwise end*--I      With -0- representing each step on the 12 step switch

New circuit, set to Boost:

I--*Fully Clockwise end*--0-0-0-0-0-0-0-0-0-0-0-0-*Fully Counter Clockwise end*---*2.35k Resistor*--I

New circuit, set to Cut:

I----*2.35k Resistor*---*Fully Counter Clockwise end*--0-0-0-0-0-0-0-0-0-0-0-0-*Fully Clockwise end*--I

So the 2x2 switch would have to be wired to flip the whole resistor and lorlin 12x1 arrangement.

I hope this helps somebody. Of course, it doesn't stay true to the original. My only reservation was the 5 step resolution. I think this modification could be made with some creative trace-cutting.

Audiox, sorry for putting the cat amongst the pigeons! I truly appreciate the effort you have put into this EQ, and I love the design and how it all fits onto such a compact PCB. Cheers for your efforts!

-Mike C

 

[audiox]

I think this modification could be made with some creative trace-cutting.

I think you can do it even with not-so-creative trace cutting since the board is very simple. Just keep the switch wiring short and it probably works fine.

If you calculate/simulate new values for the resistor chain, please post them here too. Other info of your experimentation is also welcome.

 

[shot]

@MikeClev - bravo! Please post more details.

I was also thinking of doing two modifications to the original (Audiox's) circuit!
First one is adding more frequency points. High freq. selector could be extended to 6, and low freq. to 9 points (ok, more is even possible on low freq. but it starts to have no sense... 9 is more than enough).
Second mod I find interesting is to add high pass filter to the circuit. It could be very useful to have the ability to shelf low freq but at the same time cut off subs at some point to prevent excessive sub frequencies from overloading the mix. It would be a killer on the bass guitars and kick drums!
Obviously, it wouldn't fit the front plate pcb arrangement any more since it would be fairly bigger size. Switches would have to be wired to the pcb. I'm working on it right now.

 

[Assistant]

i´m finished building and everything is working except the left channel low gain....

when i turn the switch to position 3 it goes to full? boost. the first 2 steps are cutting the lows in the same amount.no difference between position 1 and 2
i tried swapping c16,c18 and r26 around the ne5534 but with no luck. double checked the resistors r1-r10.
somehow i had the +/- 15v connections reversed on first power up. doh!
i guess this caused this error?
strange is that the right channel is working flawless.
i also changed the ne5534
could it be that the lorlin switch is broken?

 

[audiox]

Change the op-amps if you haven't already done that. Dead op-amp is more than likely if you have had reversed power supply voltages. You could also check if R21 or R22 has wrong value. Low value / unsymmetry could cause something like you described.

Generally:
Try to find what is different between the working and nonworking channel. Op-amp voltages first. Then visually compare the units to find e.g. wrong resistor values. If the boards are not electrically tested there can be short circuits between traces. Very unlikely but possible.

Lorlin switches can be ruined with too much heat when soldering but you can easily measure if they are working or not.

 

[Assistant]

i found it! it was a broken trace between r1 and r2.

partytime!  ;D

thanks for this project and all your help audiox!

 

[oragall]

i found it! it was a broken trace between r1 and r2.

partytime!  ;D

thanks for this project and all your help audiox!

you can put photos to view the project... XD