Neumann W492 equalizer DIY project (PCB docs added)

[frejo89]

Its been a while since i built mine so i might be wrong but i think maybe you have your pots mounted to the wrong side of the circuit board

Edit - Forget that, i just checked my build and yours look to be oriented correctly.

Yes. Maybe I got the wrong value at the PT2 and PT3. Otherwise I will have to Change the left and Right connections of the pots for the Mix Ranges. But it would be a Strange reason, there must be another one

 

[dario84]

Yes. Maybe I got the wrong value at the PT2 and PT3. Otherwise I will have to Change the left and Right connections of the pots for the Mix Ranges. But it would be a Strange reason, there must be another one

hey all the values are correct just take care of the pot positions on the boards! check here:https://drive.google.com/file/d/1w23IRwzQvTtKFtaYP1vSAV60F0d7T-gD/view?usp=drivesdk

 

[frejo89]

Oh nooooo! Thanks for this hint. Stupid, that I did not recognize, that it is such a simple thing. Thats very clear, ty for that!

 

[emx]

Are the enclosures still available anywhere for this project? I did the pcb and parts years ago, stuck it in storage as I was moving and never completed it. I found one place in Germany but was wondering if there was anything closer or more options in general.

 

[JMan]

I assume the “one place in Germany” you found is Frank at frontpanels.de, who I think is most people’s go-to for this and many other projects. I don’t think there are any other ready-made front panels for this project, but if you want to go with something in the states, you can use the .fpd file in the project docs and get the panel (and if you want, an accompanying enclosure) made by Front Panel Express. If you get a pre-fab enclosure separately from another supplier (like collective cases), just make sure your mounting holes in the front panel files match the enclosure.

 

[zzzzz]

I have a spare one or two pseudo aluminum control "front panels" I made for the Creative Clowns version if that is what you built out. I don't think it is the same as the original.

 

[pstcho]

Anybody try to implement a volume pot on this eq ?

 

[1wildthing]

Hi mates! I‘ve almost finished this build but once at the calibration stage I’ve realized that something is wrong with pot P7. When I turn it fully clockwise a pop/click can be heard on output signal and a huge noise suddenly comes in.
If I turn the pot slightly counter clock wise the noise disappears and the filter section seems to work as expected. I’ve tried to substitute the pot but the problem is still there. I’m building a dual channel and I have this problem only with a single board, the other works well. The 2 boards are identical component wise.
Could you please give me some hints or idea on this troubleshooting?

 

[TwentyTrees]

Hi mates! I‘ve almost finished this build but once at the calibration stage I’ve realized that something is wrong with pot P7. When I turn it fully clockwise a pop/click can be heard on output signal and a huge noise suddenly comes in.
If I turn the pot slightly counter clock wise the noise disappears and the filter section seems to work as expected. I’ve tried to substitute the pot but the problem is still there. I’m building a dual channel and I have this problem only with a single board, the other works well. The 2 boards are identical component wise.
Could you please give me some hints or idea on this troubleshooting?

Assuming you're using conductive plastic pots and not carbon, and that your pots are the right value and taper (and don't have anything weird going on like dead spots at the end of the resistive track), it's interesting that the issue has persisted despite changing the pot. Do both pots you've used test fine over their full rotation, out of circuit? What brand / model are they?

If all is well with the pots themselves, the next thing to look at would be the pot wiring - triple check all is correct at the pot end, and also check the wire-to-board connections too. I'd go so far as to check continuity with your multimeter between the pot terminals and the relevant solder pads of R42, R52 and U8B.

If all that checks out, next thing I'd do would be to test every component in the high shelf filter (page 4 of Audiox's schematic) with your multimeter against those in the working channel. Maybe there's a misplaced or duff component, a short, or a cold solder joint that this may help expose. The fact that you've got one working channel is gold for troubleshooting, as is the fact that this seems confined to a single filter section - check and test that part of the board rigourously and systematically, and you'll no doubt find the culprit. If you upload a couple of decent pics of that area of the misbehaving board (component side, and solder side) we can get some more eyes on the problem as well.

 

[1wildthing]

Assuming you're using conductive plastic pots and not carbon, and that your pots are the right value and taper (and don't have anything weird going on like dead spots at the end of the resistive track), it's interesting that the issue has persisted despite changing the pot. Do both pots you've used test fine over their full rotation, out of circuit? What brand / model are they?

If all is well with the pots themselves, the next thing to look at would be the pot wiring - triple check all is correct at the pot end, and also check the wire-to-board connections too. I'd go so far as to check continuity with your multimeter between the pot terminals and the relevant solder pads of R42, R52 and U8B.

If all that checks out, next thing I'd do would be to test every component in the high shelf filter (page 4 of Audiox's schematic) with your multimeter against those in the working channel. Maybe there's a misplaced or duff component, a short, or a cold solder joint that this may help expose. The fact that you've got one working channel is gold for troubleshooting, as is the fact that this seems confined to a single filter section - check and test that part of the board rigourously and systematically, and you'll no doubt find the culprit. If you upload a couple of decent pics of that area of the misbehaving board (component side, and solder side) we can get some more eyes on the problem as well.

The potentiometers I used are these: https://www.mouser.it/ProductDetail/858-P092NQC15BR10K
I'll take some photos and I will post them.
Thank you so much. I'll try to follow you hints.

 

[TwentyTrees]

The potentiometers I used are these: https://www.mouser.it/ProductDetail/858-P092NQC15BR10K
I'll take some photos and I will post them.
Thank you so much. I'll try to follow you hints.

Yep, those pots look correct here.

 

[macleod69]

If anyone is interested, there are still W492 pcbs available on ProAudio G.C.

 

[1wildthing]

Thanks a lot to all of you for your help! Simply refluxing some joints in the shelf filter’s components the problem disappeared.
So here is mine eq
Now it’s time to start a new project

 

[TwentyTrees]

Thanks a lot to all of you for your help! Simply refluxing some joints in the shelf filter’s components the problem disappeared.
So here is mine eq
Now it’s time to start a new project

Excellent! I'm glad to hear it's all sorted. Congratulations on your build!

 

[JMan]

Finished up my build a few nights ago, now just need to put some knobs on it. This thing really sounds great, and it was such a pleasure finishing calibration, putting some music through it, and just aimlessly fiddling with the controls for a bit.

 

[bld]

Despite warnings I have decided to publish the PCB manufacturing documents of the W492 equalizer. I hope that it helps those who want to make their own boards. Documents are allowed to use only for DIY purposes.

http://audioxxx.googlepages.com/W492_copper_top_mirror.pdfhttp://audioxxx.googlepages.com/W492_copper_bottom_mirror.pdfhttp://audioxxx.googlepages.com/W492_GERBER.zip

The documentations seems to be invalid, Can someone provide a copy? Thanks a lot

 

[EugeneKei]

A peek inside...

Hello. Could you please share toroid transformer specifications? I mean primary and secondary, as I didn't find such details
Thank you

 

[JMan]

Hi Eugene,

The details of your power transformer depend on your local mains voltage and the PSU you are using. This project did not include a built-in PSU, so you must provide one, but there are many available options — see silent:arts’ White Market thread, for example, or Gustav’s pcbgrinder website for some good, easy choices.

I see that you are in Ukraine. I think that means you have 230V local mains (although you may know something I don’t). So the primary side of your toroid needs to be able to accommodate that — should be very easy to find.

Assuming you are using a common bipolar PSU based around an LM317 & 337 or similar regulator, you will be fine with 2x15 (15-0-15) on the secondary side. You could get away with 2x18 also, but you’d probably want to heatsink your regulators well because they’d be dropping enough voltage to potentially overheat.

Good luck!

 

[Whoops]

Hello. Could you please share toroid transformer specifications? I mean primary and secondary, as I didn't find such details

Just adding to what JMan said,
you can buy any of these options:

https://www.banzaimusic.com/Talema-TRT30215.html
https://www.banzaimusic.com/Talema-TRT30218.html
https://pt.farnell.com/vigortronix/vtx-146-030-215/30va-toroidal-transformer-2x15v/dp/2817645
https://pt.farnell.com/multicomp/mcfe030-15/transformer-30va-2-x-15v/dp/9531726

 

[mariuo]

Hi everyone, I'm interested in building a pair of these for dual mono/stereo tracks and was hoping to add stepped controls for easier matching and recall. May I ask for some info on how to implement this please?