Neumann W492 equalizer DIY project (PCB docs added)

[p0ulp]

thanks a lot for the fast answer.

ed

 

[Greg S.]

hi,
Got one of those EQ's ready to work and I measured a bit around there

PSU - Unfiltered Voltage by using a Traco TMP10215 SMPS(Switch Freq. 100kHz, Max Cap Load 1000uF each Rail)
      V              Noise-RMS(<22kHz)
+15V                        -62dBV
-15V                          -62dBV
not bad for a SMPS

I filtered the Supply Voltage from the SPMS delivering +-15DC via an two stage RC-Ladder Filter: each 10R and 470uF/V Rad FR Low Noise Cap.

Fg is 33,86Hz at -3dB,  for both Stages in common -6dB at 33,86Hz
Voltage Drop 1Vdc over each 10R
So I got +-13VDC.
measured the Voltage Noise after the Filter
here what I got:
      V                  Noise-RMS(<22kHz)              Noise-RMS(<100kHz)
+13,07V                      -104dBV                                            -83dBV
-13.03V                      -105dBV                                            -88dBV

Thats ok

Measure across +-filtered Voltage
V                          Noise-RMS(<22kHz)              Noise-RMS(<100kHz)
26Vdc                              -86dBV                                                -64dBV


After that I checked the Symmetric Out
It was that  horrible,

Out                  Noise-RMS(<22kHz)              Noise-RMS(<100kHz)
pos                                -72,5dBV                                              -50,5dBV
neg                                -73.3dBV                                              -53,2dBV

It is that bad!!!!!

Made a look over the Schematic, there are just 100nF across Pos and Neg Supply.
I will take 'em out and add some 100nF/MKS2 against ground, but I believe it won't change anything!
Will also try some Boucherots at 10kHz or so..

I used LME49720 OP-Amp's

My Question:
Did anyone here made a similar measurement at the Symmetric Out by using highly smoothed Voltage and a Torroid?
Perhaps i got some Common-Mode Problem or the Layout isn't that good!

Cheers

 

[p0ulp]

Ok this is a great simple and cheap build, the only thing is concerning those pot which are excessivly expensive, I did go for the OEP from buerklin and that was a mistake ( not the green one) , those OEP fits on the board after a little bend work ,  but the 4mm shaft is a pain if you are looking for usual knob ( don't want skinny knob on a 2U rack don't you ?), that's ok for a custom format console were you can fit the EQ pretty easily in compact enclosure and I think they ll go this way in my studio.

Also if anyone know replacement pots please let the next builder know with manufacturer reference or mouser n°, while sourcing the part I did contact many supplier for conductive plastique PCB mount stereo 10kA and wasn't able to find source for them that could be in my budget range . I see on gustav's website there are other one but didn't dig info at the time I was building.

I think I will definitly rebuild them with stepped switches for mastering purpose, got to work on an extra pcb though, I don't want to solder resitor lugs for hours and not be able to replace them easily. in few years.

 

[Greg S.]

Alpha 10k are the standard Pots
But if you use 'em, the 492 won't fit into a 1HE 19" Rack,
You ma use other Pots as Alps RK09, mit the Footprint differs so you have to wire the Pins
And, you'll have to fix the PCB!

Cheers

 

[kante1603]

Alpha 10k are the standard Pots
But if you use 'em, the 492 won't fit into a 1HE 19" Rack,
You ma use other Pots as Alps RK09, mit the Footprint differs so you have to wire the Pins
And, you'll have to fix the PCB!

Cheers

d
Hello Greg S.,


the board was designed for sfernice pots,hard to source and expensive.
So Alpha pots aren't the standard types for this build.
A lot of people including me used the green Omeg,I think it was the "Eco"- series.
Plastic conductive is imperative,so the Alps rk09 might be the wrong choice.
And why shouldn't other types fit in 1ru?I made 8 channels fit in 4ru easily.I even did not need to fix the pcbs to the frontpanel,they're happily held by the pots connected with solid wires.See my post #487.


@pOulp:


You can easily widen up 4mm shafts to 6mm,adaptors are available for this.Same as going from 1/8" to 1/4".
And you only need two stereo pots,not eight.The rest is single pots.See schematics.
For pot choices,just search for plastic conductive types,I think there are Bourns types available as well as others.
I sourced my green ones from TAW,a lady named Laura helped me and others here,she's very friendly and they even had a full set (6 mono and 2 stereo) for this project.I bought 8 sets for my 8-channel build,none of them failed so far.

Best,


Udo.


Edited typo.

 

[p0ulp]

Thanks udo for this answer, I know about the only 2 stereo, but mono were almost same price so .. blind lug are just here to maintain the pot on the board

I have to admit that I didn't go through the whole pot question on this topic, my bad, would have been happy to meet Laura for sure :/

Anyway thank you for the shaft adapter tips, I didn't know those

 

[iprovlek]

Is this Eq can be built with stepped switch(Lorlin) instead potentiometers!?

 

[miszt]

If I were to use 12 position switches instead of 10K pots, would I use 910ohm resistors to make up the full 10K linear? or is there more to it than that?

(910 X 11 positions = 10.01K, plus 1 with no resistor?)


also wondering why the pots used have 6 pins, the only ones I can find with 6 pins are dual-lin/log and dual gang with 2 rails - but looking at the schematic, it seems to just be standard single rail pots?


(noobie at this, sorry if the answers should be obvious lol)

 

[miszt]

so I've read nearly the whole thread, and it seems i need dual linear pots - so that would mean i want to either have dual gang switches with resistors adding to 10K, or single gang with the resistors adding upto 5K rather than 10K? ...or?

or are they dual pots simply for physical stability? the schematic doesn't show the signal being split between 2 rails on the pots?

 

[skeeler87]

Hey Guys!

New to the forum here! I'm thinking of building some of these. Would these pots work?

http://ca.mouser.com/ProductDetail/Bourns/PTD902-2015K-B103/?qs=sGAEpiMZZMtC25l1F4XBU1xwXnrUt%2fuovO4kg%2fgeLiI%3d

Thanks!

 

[Greg S.]

I guess not!
Check the Footprint!

 

[kante1603]

Hey Guys!

New to the forum here! I'm thinking of building some of these. Would these pots work?

http://ca.mouser.com/ProductDetail/Bourns/PTD902-2015K-B103/?qs=sGAEpiMZZMtC25l1F4XBU1xwXnrUt%2fuovO4kg%2fgeLiI%3d

Thanks!

Hello,


element type is carbon so it will get scratchy soon.Use conductive plastic instead.


Best regards,


Udo.

 

[skeeler87]

Hey Guys!

New to the forum here! I'm thinking of building some of these. Would these pots work?

http://ca.mouser.com/ProductDetail/Bourns/PTD902-2015K-B103/?qs=sGAEpiMZZMtC25l1F4XBU1xwXnrUt%2fuovO4kg%2fgeLiI%3d

Thanks!

Hello,


element type is carbon so it will get scratchy soon.Use conductive plastic instead.


Best regards,


Udo.

Thanks very much, Udo! Will definitely stick to conductive plastic.

 

[maniman]

Hi guys , how goes ,  I'm very happy to can say , PROJECT ACHIEVED

https://youtu.be/zgp1fZA3ZVM

The power transformers are momentary solution until find the right toroid for 1 u. rack.

next thing , I gonna calibrate the detents at real 0 and test L and R frequency similarity moving knobs from pots if necessary , all  checkin with SMAART ... and this goes directly to my disc cutting system chain , yes , the place where this piece go.

The POTS : The B.I. pots from capi-gear.com.....I only can say the same than mr. Steiger , "don't let the price fools you !" , because is totally true ,  THE FEELING OF THE POTS ARE ABSOLUTELY AWESOME , even better than tens I touched in glorious well made equipment , really sure an hard over the entire path , the find of the year for me (and .... ejem... have center detent version.... where people get the center detent version of the OMEGs ? I can't believe people have this project without center detent.)

The ICs = NOS Philips NE5532AN (That is where my powers problem start over the encapsulated transformers , reach 50º C easy!! hahah , but I'm very happy with the character , can be very very subtile , this is a thing I don't expect from a 553X based filters , and the sound are less metallic than I expected too , I'm very happy. )

- The boards from the man Gustav of pcbgrinder.com (Ough! how can I forget the foundations , noboody begins the house through the roof. )
- All resistor Metal Film 1% , checked In pairs at soldering time.
- All capacitors 2,5 % , 5% , and 10% on 2 or 3 values ( one can go until 1% in capacitors but become a not so cheap project as all people suggest , REALLY I don't think is a so so cheap project.)
- The case is a recycled adam hall housing case I never used at all , a crossover project in the past.
- The frontpanel is mechanized by frontpanel.de
- The relay bypass boards and the knobs are from diy-tubes.com
- The power supplies are classic Velleman regulable kits (LM317 /337)

*I do a little thing for the bypass , with a 2 color led (the 3 pins one) , playing a bit with the switching can go for :

-Geen light when both L and R are running
-Orange Light (both green and red poles) when 1 of the channels is bypassed
-Red Light when 2 channels are bypassed.


The B.I pots are soldered using a holes proto board I cutted in very little squares of 3 x 3 holes.

wire , thermo retractile and think is all friends!

Best Regards
Mani.

 

[dribro]

hi guys

will these do the job?

http://pt.mouser.com/ProductDetail/BI-Technologies-TT-Electronics/P0925N-FC15AR10K/?qs=sGAEpiMZZMtC25l1F4XBU7XpbFdDDzhrX9wNBWhNwoQ%3d

 

[noviygera]

Can each W492 board be used for stereo (in unbalanced mode)? Basically, I want to have a mixer with a W492 on each stereo channel. Doable?

 

[Gustav]

Can each W492 board be used for stereo (in unbalanced mode)? Basically, I want to have a mixer with a W492 on each stereo channel. Doable?

I am not sure I understand the question, so just to make sure its clear.

Are you asking if a single board in the current layout can be used for unbalanced stereo instead of balanced  mono?

If thats the question, the answer is no.


Gustav

 

[Greg S.]

Can each W492 board be used for stereo (in unbalanced mode)? Basically, I want to have a mixer with a W492 on each stereo channel. Doable?

One Board --> One Channel,
Two Boards -->Two Channels e.g. Stereo

If you want to use one Borad in Unbalanced Mode, connect the Neg-In to GND

 

[pvision]

Hi guys , how goes ,  I'm very happy to can say , PROJECT ACHIEVED

What knobs are those?

I appreciate you putting details of the parts you used, just want to know about the knobs!

Thanks

Nick Froome

 

[rmaier]

I finally got around to finishing my build after being diverted by a bunch if different diy projects. Everything seems to be working as hoped. Very nice sounding eq  - thanks to everyone who helped me on this!

A few pictures: