Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #740 on: December 06, 2017, 10:04:58 PM »
Got the relay bypass boards to work.... I was missing a jumper on the bottom of the board from the coupling cap to a diode leg.

Now to fix the psu filter. Looks like a bad input inductor going to order some.

Otherwise the unit is working perfectly. My portable o scope isn't so accurate so I will have to bring it over to my studio later this week and calibrate using pro tools


pablobolche

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #741 on: March 23, 2018, 11:27:00 AM »
Hello forum...
I am finishing a stereo/midside  492 Eq.. with Harrison Ford filters
I passed some audio yesterday and everything is great..
I did a experiment with a 3 position bypass switch...changing the value of the 330k Resistor of each eq section to 2k5 and got roughly a +-6db operation...is this oka to do or would something go wrong eventually??
I would love for this eq to have selectable +-15db/+-6db operation..
I appreciate all comments


pablobolche

TwentyTrees

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #742 on: March 23, 2018, 11:48:40 AM »
I don’t have an answer to your question, but just wanted to chime in and say I’m currently planning out exactly that - W492 + Harrison filters + mid/side! Great minds.  ;D

Hello forum...
I am finishing a stereo/midside  492 Eq.. with Harrison Ford filters...

sr1200

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #743 on: March 23, 2018, 04:55:54 PM »
where'd ya get the pots pablobolche?
MEI Studio - Long Island, NY: http://www.meirecords.com

pablobolche

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #744 on: March 23, 2018, 05:41:29 PM »
where'd ya get the pots pablobolche?

Gain pots from capi-gear... they have the dual 10K linear with center dent....
capi-gear does have a logarithmic version of the dual 10k but tested them for freq selection and they feel strange (freq...are all together on one end of the pot)  so I have used the center dent ones for everything...as for now atleast..

still looking for a ALPS dual 10k linear conductive plastic...or other options...




pablobolche

sr1200

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #745 on: March 24, 2018, 08:04:30 PM »
That seems to be the biggest problem with this project... wish there were mods that would allow for different pots (other than doing crazy >1% switches.
MEI Studio - Long Island, NY: http://www.meirecords.com



Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #748 on: June 17, 2018, 02:29:16 PM »
Is this project still active? I would really like to build this EQ and wanted to know if there are any boards available or being made for this.

kante1603

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #749 on: June 17, 2018, 02:35:01 PM »
Is this project still active? I would really like to build this EQ and wanted to know if there are any boards available or being made for this.
Yes it is,there are boards available from our friend Gustav:


https://pcbgrinder.com/index.php?route=product/product&path=59_60&product_id=58


Best regards,


Udo.


Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #750 on: June 22, 2018, 12:01:16 PM »
Hello Udo,

Thank you for helping me with locating the boards.
It seems from going through the posts on this W492 EQ is that the hardest parts to find the are the right pots. Can you please help me with where I can get them? and any other parts I may need for this build that are hard to locate. I live in N. America

Thank you,

Michael

kante1603

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #751 on: June 22, 2018, 12:34:04 PM »
Hello Udo,

Thank you for helping me with locating the boards.
It seems from going through the posts on this W492 EQ is that the hardest parts to find the are the right pots. Can you please help me with where I can get them? and any other parts I may need for this build that are hard to locate. I live in N. America

Thank you,

Michael
Hello Michael,
this is an old project,and there were at least two different boards with different footprints for the pots.
Pretty hard to get them,at least the sfernice ones,and they were horribly expensive.
So best is to take others/different brand and wire them to the board.
I used OMEG ECO series at that time and attached them with solid core silver bus wires for my 8-channel build.
There was a friendly  lady called Laura at TAW back then who knew about this project and sold potentiometer  bundles from OMEG to us.I donˋt know if they do that anymore.
You can do whatever you like as long as the values and the tapers are right,but it is imperative to use conductive plastic types.Otherwise they will become scratchy due to the dc in this circuit.
Since you are in North America I would start looking at mouser etc.,maybe Bourns do them.Or look at Jeffs homepage over at CAPI?
For all other parts you can derive them from the components values overlay,I have never seen a BOM for it.
You will find all the info on page one here in this thread,it is well documented,and the links still work.
The parts are all standard,including the ICs.


Hope to have helped,


best regards,


Udo.


Edit:There is (!) a BOM on page one!Sorry,mea culpa.
Have never seen it,I used the schematics and the overlays.
Also for the front panel pots,you need just two dual pots for the mid bands,the other six can be single/ mono versions.All of them are 10k Ohms linear.
« Last Edit: June 22, 2018, 12:54:36 PM by kante1603 »

mikeyB

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #752 on: August 27, 2018, 09:18:48 PM »
Just looking at various pots for this project.
Some sellers describe their pots as having "synthetic carbon" track - is this indeed conductive plastic or something else??
making better music!

alexc

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #753 on: August 31, 2018, 11:45:38 PM »
I just started using my stereo build of this implementation of the w492 eq  .....  wow!

Where have these been all my life?  I have them on my mix bus feeding some el34 monitoring amps and speakers. The amps have balanced inputs with a Sowter 10K/10K transformer, and these drive it beautifully with super low hum and noise.

The bass boost out of these is very satisfying  and the mid-hi cut sooths the jangles out of my 'toppy' guitars very well.

Very easy to use, with the well spaced control layout on a 2RU racking; the individual band bypass switches are a superb feature.      I added a switchable relay channel-bypass to mine. Pots are those nice conductive plastic, centre detent types for the 'levels' and same sans detent for the 'freq'.

My new fav  eq :)  Takes a couple of seconds to dial in, and done!   Excitement to the max.

Thanks so much  to member 'audiox'  for his efforts.
« Last Edit: October 15, 2018, 12:46:07 AM by alexc »
I ping therefore I am

TwentyTrees

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #754 on: November 05, 2018, 11:58:52 AM »
Hi all,

I recently finished my W492, and wanted to take a few minutes to document the build. I've modified the core EQ pretty heavily with a view to using primarily for 2-bus / mastering work, and also built a number of other functions in, so hopefully this will be useful to some folk down the line. Huge thanks to everyone who's posted on this project across the site, and of course to Audiox - I'm definitely perching on the shoulders of giants here!



Features:
  • Dual mono Audiox W492 4-band EQ with fully parametric mid bands, plus Harrison Ford Filters HPF / LPF
  • Rotary switches for frequency (24 steps/band) & gain (12 steps/band, switchable +/-)
  • Channel components matched to high tolerance (less than 0.1dB difference between channels at all settings - except when boosting or cutting 15dB on the high shelf, when there's 0.2dB difference!)
  • WIMA filter caps for low shelf and low mid bands, Styroflex for high mid and high shelf
  • Switchable mid/side matrix (a la Wayne Kirkwood)
  • Per-channel bypass (inside mid/side matrix) and master bypass
  • Vintage Jensen output transformers (switchable per channel - relaxes the sound very slightly)
  • Switchable gain range per channel (x1 / x0.5)
  • Switchable frequency range for low mid (x1 / x0.5) and high shelf (x1 / x3) bands
  • Variable bandwidth for low mid and high mid bands (Q = 0.45 to 3.6)
  • THAT1246/1646/LT1058 ICs used in HPF/LPF
  • Backlit plexiglass logo badge 8)
  • Panels and NRG case by Frank



It sounds superb - very clean and precise, low distortion, and quieter than I expected given the amount of wiring involved (sub -94dBFS). There are 13 PCBs including filters, M/S matrix, power supplies, relays etc, and all the front panel controls are wired off-board, so hooking everything up took a good few days... The combination of fully parametric mid bands and shelves plus filters makes it really flexible, and I'm very happy with the styroflex caps for the high end in particular.

I spent a long time planning, listening and testing with this one - a good couple of years of reading and planning, and dozens(!) of iterations of front panel design. With all the potential for issues with such a complex build I was more than usually nervous when firing it up for the first time, but debugging was mercifully straightforward this time - the biggest issues were a bad solder joint in a SMT frequency switch, and popping on some switches (see below). In terms of mods to the W492, here's what I did following a ton of research, breadboarding and measuring (all component references are to the Audiox schematic, and I used REW for measurements):

Variable bandwidth
10K pot (RP) with 3k3 series on CCW (RB2) across U3A (low mid) and U5A (high mid), wiper to ground via 330R series (RB3). This involved running wires to one side of each of R16, R17, R26 (low mid) and R31, R32 and R41 (high mid) - I left little loops in the resistor leads to allow this when populating the boards. One caveat - the centre frequency wanders a little as the bandwidth is changed from wide to narrow (e.g. a few Hz at +15dB at 1k), so there may be a better way to implement variable bandwidth on this circuit, but after using it extensively on a variety of material it doesn't feel like a major issue. And ideally I would have preferred rotary switches to pots for stereo matching, but front panel space didn't permit that so I matched the pots instead as best I could.



Gain switches
5k resistor ladder with 5k resistor from CCW switch position. The +/- (boost/cut) switch swaps the CW and CCW poles going back to the EQ board, so the CCW position on the switch is always flat. Note that the shelves popped loudly at first when switching between boost and cut - putting a 1M resistor from each end of the switch to the wiper reduced this to manageable levels.

Gain range
For low & high shelves:
R8, R45 = 620R = +/-18dB gain range
R8, R45 = 1k2 = +/-8.5dB

For the low and high mid bands:
R15, R30 = 220R= +/-15dB
R15, R30 = 4k7 = +/-7.5dB

Frequency range
High shelf x3: swap C16 & C17 28.8nF for 10nF (lovely air boost)
Low mid x0.5: use empty C8 and C10 pads to switch in an extra 100nF at each point

Here's some photos from the build:

Testing bandwidth mod (lots of wires coming off the PCB!):
http://ringlefinch.co.uk/wp-content/uploads/2018/11/4-W492-bw-testing.jpg

Populating the internal control panel:
http://ringlefinch.co.uk/wp-content/uploads/2018/11/5-W492-control-panel.jpg

Control panel done:
http://ringlefinch.co.uk/wp-content/uploads/2018/11/6-W492-control-panel.jpg

Assembling and wiring it all up:
http://ringlefinch.co.uk/wp-content/uploads/2018/11/7-W492-populating.jpg

And all racked up!
http://ringlefinch.co.uk/wp-content/uploads/2018/11/8-W492-racked.jpg

I'm really pleased with how my W492 has turned out - it's been a major labour of love, and a great exercise in learning about state variable filters (and pushing the bounds of established designs...). Hope some of this helps someone further down the road!

Andy

kante1603

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #755 on: November 05, 2018, 12:15:02 PM »
A serious amount of clean work you‘ve done here,congrats Andy!


Best regards,


Udo.

[silent:arts]

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #756 on: November 06, 2018, 03:06:22 AM »
Wow. The spirit of DIY is finally coming back!
An understatement calling it W492.
Congratulations

TwentyTrees

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #757 on: November 06, 2018, 04:59:25 AM »
Thanks Udo & Volker!  ;D

rob_gould

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #758 on: November 07, 2018, 02:32:05 AM »
This is the most exciting and best looking build I've seen on here for quite some time. All your efforts have paid off Andy - congratulations!

TwentyTrees

Re: Neumann W492 equalizer DIY project (PCB docs added)
« Reply #759 on: November 08, 2018, 05:08:19 AM »
Thanks for the kind words Rob!

This is the most exciting and best looking build I've seen on here for quite some time. All your efforts have paid off Andy - congratulations!


 

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