Neumann W492 equalizer DIY project (PCB docs added)

[kante1603]

I have build 3 W492 units, with SSL9k PSU.
When the machines are cold and i turn on i have no signal out(audio), the +15V is missing (on the PSU). I have to  turn off and on, and the +15V come and everything work ok.

I tried to deconnect the W492 PCB, and the +15V on the PSU board is ok, no need to turn off and on. It same on 3 unit.

Hi Marc,

I had some issues with LM78xx and LM79xx regs a while ago.Have you tried to exchange it to a new one?
Mine tended to do the same as yours,and after  I used better regs (just a little more expensive-no no-names!) the issues were gone.
Personally I do not use those regs when ever possible and go the LM317 and 337 route.....just a thought.

[/quote]My transformer is 25VA, my EQ with true bypass consume less than 200mA, so it's more than enough

Does anyone had the same problems?  :-[
[/quote]

Current consuption of about 200mas seems a bit high to me,as far as I can remember there are 8 pieces of NE5532 on the board,right?
If so then look at the data:8 x 6mAs (typical current)=48mAs,max. is 8 x 16mAs(max.supply current)=128 mAs.
I am not sure if there are other active/current-eating parts on board...... ???
Maybe I am wrong with this but it seems pretty high for this circuit (did you mean a single board?).....


Anyway-try to swap the 7815 to a well-known brand because it is just some cents of your money.

Best,

Udo.

 

[marcfrom]

My units have two channel+ 4 relais for true bypass over a second PSU.

I already test to deconnect second PSU with true bypass and one channel, but it's the same

I seen Jarlehal in this thread had same problem, actualy +0.8V out on the 7815.

When i changed the 9K PSU insted a Mnats PSU, the problem was gone.

Does he use a better quality Regulators??  : I don't know.

But i will try it.

Thanks

 

[diezel_addict]

Hi All

Has anyone got any comments with regards to sound of these EQ's?  Anyone used them on a project yet?

 

[Kevin]

i'm thinking about this pots
http://www.musikding.de/product_info.php/info/p2299_CTR-Poti-16mm-Stereo-10k-lin.html
they fitting perfect on the board... having two laying around but not sure about sound quality
is it real that many pots scratching after a while

and other question is there any difference between the green omegs and just normal omegs?

 

[kante1603]

i'm thinking about this pots
http://www.musikding.de/product_info.php/info/p2299_CTR-Poti-16mm-Stereo-10k-lin.html
they fitting perfect on the board... having two laying around but not sure about sound quality
is it real that many pots scratching after a while

and other question is there any difference between the green omegs and just normal omegs?

Hi Kevin,

here´s the quote of audiox (reply#40 in this thread):
Conductive plastic pots must be used because the circuit is DC coupled. Normal pots start to scratch quite soon.

Best,

Udo.

 

[marcfrom]

I want to build a Stereo W492.
Does anyone know where i can find a Quad 10K lin pots with 6mm shaft?

 

[Danny1107]

Hi,

are the PCB's from Gustav for the Sfernice potentiometers or the Omeg potentiometers?
I need the 7,5mm Spaces for the dual pots...

Cheers Danny

 

[audiox]

are the PCB's from Gustav for the Sfernice potentiometers or the Omeg potentiometers?

As far as I know the boards manufactured by Gustav are for Sfernice.

 

[3nity]

Hi guys.
Can any of you comment on the calibration??

i cant i have an ossciloscope but not a real meter...

i tried using PT 9.7 meters to read the dbs but i cant get the right values.

Please give me some advice.

 

[kante1603]

Hi guys.
Can any of you comment on the calibration??

i cant i have an ossciloscope but not a real meter...

i tried using PT 9.7 meters to read the dbs but i cant get the right values.

Please give me some advice.

Hello 3nity,

in case of doubt you can simply do it like specified following the link of the 1st page here:

NO TEST EQUIPMENT ?

If you don't have generator & level meter, adjust PT1 & PT4 to 100 ohms and
PT2 & PT3 to 5 kohms before soldering.

I didn´t get if you have a scope or not (i cant i have an ossciloscope but not a real meter...).

If yes then you can do it as follows:

Generate the specified sine waves with your ProTools (internal sig.-generator).
With all switches at the w492 set to off hook up the scope to the eq output and trim the generator level until you read 0 dBu on the scope.
This should be 0,775 volts eff. or 2,19 volts peak to peak.
Proceed as in the "Pot-Trimming-Guide",the +15 dBu must read 4.36 volts eff. or arround 12 volts peak to peak on the scope.
That´s it.

If you´re unsure about how to read it or want to calculate dB things then I recommend this very useful site (originally in german but has an english version too):
http://www.sengpielaudio.com/calculator-db-volt.htm

Best regards,

Udo.

 

[3nity]

oops sorry i have a scope and a signal generator but i need a vu meter or something to read dbs??
unfortunately i solder everything before reading the calibration stuff!

 

[Neily]

oops sorry i have a scope and a signal generator but i need a vu meter or something to read dbs??
unfortunately i solder everything before reading the calibration stuff!

Hey dude...Just curious... What did you end up using for pots? The expensive pots are the only thing keeping me from doing this project...

 

[3nity]

i used omegs from TAW electronics.

 

[kante1603]

oops sorry i have a scope and a signal generator but i need a vu meter or something to read dbs??
unfortunately i solder everything before reading the calibration stuff!

Hi, well-you can´t make the measuring stuff when the pcb isn´t stuffed ;D
So-no,you don´t need something other to read the dBs-you can read levels in volts (e.g. peak to peak for sine waves) on the scope.
Just take 0 dBU for reference which is 2,19 volts peak to peak on the scope (equals 0,775 v eff.).

Best,

Udo.

 

[3nity]

I have another problem or its maybe the cables that are not properly wired.
it doesnt sound good unless i run it unbalanced...balanced it sounds like some bad low resolution audio.
Any hint please?

 

[kante1603]

I have another problem or its maybe the cables that are not properly wired.
it doesnt sound good unless i run it unbalanced...balanced it sounds like some bad low resolution audio.
Any hint please?

On a first sight at the schematics it looks like an issue on wether the input de-balancing amp (U1) or the output balancing (U7).
If you have another board or even some NE5532 left you can simply drop new ones in,one after the other and see if it disappears.These are just parts for arround 30 cents (here) so no biggie.

Anyway I would check the cabling first,then swapping op-amps.If this all fails the signal must be traced trough the circuit,and the surrounding parts at U1&U7 should be checked.

hope to have helped,

good luck,

Udo.

 

[AUDIO-ON]

Hi there,
After more than one year with two pcb's for this project in my room I finally ordered pots, resistors and caps for this cool project from TAW.
I'm very newbie in this so I have a stupid question: how can I implement input and output gain for the EQ's? Shall I only add dual gang pots at the balanced input and output?

Thanks

 

[AUDIO-ON]

Any ideas about input and output gain for this project?

 

[craigmorris74]

I'm interested in adding transformer inputs to my channels, similar to the originals.  What would be the best way to accomplish this?

Thanks,
Craig

 

[benlindell]

I don't have a front panel in fpd but I do in Adobe Illustrator, http://benlindell.com/diy/W492%20to%20Laser2.ai if that's any help