Neumann W492 equalizer DIY project (PCB docs added)

[AndersB]

Well i use Conductive plastic pots (Omeg from Rapid)

 

[Moses]

Hey guys..

Just putting together a BOM for myself on this.. Does anyone know if Ptownkid ever did do a kit for this project?

Im *trying* to spec Wima caps, should I be looking which range should I be looking at, there seem to be a few options out there!!

Thanks for your patience guys!!

Mo

 

[stereokillah]

if it's the green pot plastic from omeg try to turn the pin, i had a problem one time and finaly i have turned the pined on the double gang to have a good contact

 

[audiox]

when i turn the P1 clockwise I get some very ugly pops. on the scope it looks like maybe some DC  or some very powerful distortion.
When i back it of a little is disapearing. I useing a tune for testing so its every time the bassdrum get's hit.

Sounds like a faulty potentiometer that is losing wiper contact. The U2B voltage follower gets its bias through the wiper of P1. That is why we use conductive plastic pots.

Try connecting a 100k resistor from P1A pin 2 (the middle pin) to ground. If that solves the problem (or most of it, there can still be rapid level changes during the adjustment), then you most likely have a faulty potentiometer. The resistor affects the gain adjustment scale, so it is only for trouble shooting.

 

[AndersB]

ok thanks I'll try that.

I have  tryed to adjust the other filters. and its working fine. but it's not posible to get  it near the +15 dB. I'm using my scope and it can go from almost infinity to almost 8 v p-p. But when I listen to it it sounds fine, so it's more a queation about proper adjustment.

I've checked resistors and soldering and it looks fine.

Could I change the values of the trimmers to eg. 1K and 50k ?

/Anders

 

[audiox]

but it's not posible to get  it near the +15 dB.

http://audioxxx.googlepages.com/W492_trimmer_adjustment.pdf

If you don't have a level meter, use your oscilloscope:

http://www.sengpielaudio.com/calculator-db-volt.htm

 

[AndersB]

Well I'm using my oscilloscope and i shows aprox. 8 volt p-p but according to www.sengpielaudio.com +15 dB should be aprox 12,3 V p-p. I've read the trimmer_adjustment page 'bout 20 times, and I have done excactly what it says.

Is there something wrong in my dB to voltage calculation? I'm not a pro in diy electronics, so please have a little patience with me

/ Anders

 

[audiox]

Most of the oscilloscopes are not precision instruments, so you can't expect very high accurary. Best alternative is to use your soundcard and some freeware sine generator and level meter software. Since the measuremet is relative you get accurary of something like 0.1dB easily.

If you running the the eq unbalanced the output level is 6 dB lower than in balanced mode. That is probably your source of error. You can find the instructions to compensate that level drop earlier in this thread (in case you are going to use the eq permanently unbalanced).

With unbalanced connection (and without the modification) you should do the adjustment so that the maximum gain is +9dB (not +15dB).

 

[stereokillah]

on my side i've calibrated this Eq with vu inspector on protools ,
i put a signal generator with just the good frenquency ( 15hz for the first shelve for exmple and i turn the trimmer to have +15)
and i have +15 on all bands.

 

[AndersB]

If you running the the eq unbalanced the output level is 6 dB lower than in balanced mode. That is probably your source of error.

Well I think you're absolutly right when the trimmers are adjusted before soldering I'll get somthing like 6 V p-p so that make sense.

I'll try to measure it i unbalanced mode later.

Thanks for your help audiox I'm greatful

/Anders

 

[_casio]

jarlemari -

Thank you! I've been following this thread/slowly putting together this project for months, and just happened to pull open the thread after a rather long hiatus.

An open question to everyone - for those of us who have boards with the original pin layouts and used omeg pots: has anyone put together a front panel layout to accommodate the slightly different spacing as a result of bending the pins? Or does anyone have an idea of the best way to go about creating and/or modifying one for a more accurate fit?

I'm hitting the home stretch on my console build and, having built two 492's and the ssl, I'm just down to panel layouts.



-drew 

 

[Ptownkid]

Hey guys..

Just putting together a BOM for myself on this.. Does anyone know if Ptownkid ever did do a kit for this project?

Im *trying* to spec Wima caps, should I be looking which range should I be looking at, there seem to be a few options out there!!

Thanks for your patience guys!!

Mo

 

[Ptownkid]

Hey guys..

Just putting together a BOM for myself on this.. Does anyone know if Ptownkid ever did do a kit for this project?

Im *trying* to spec Wima caps, should I be looking which range should I be looking at, there seem to be a few options out there!!

Thanks for your patience guys!!

Mo

No i didn't get around to it. Money got a little tight around here for a while. It is in the works still. As for your cap question, don't get too bent out of shape about getting the most amazing (or expensive) caps out there. It's been shown time and time again that it makes very little difference.

 

[kazper]

jarlemari -

Thank you! I've been following this thread/slowly putting together this project for months, and just happened to pull open the thread after a rather long hiatus.

An open question to everyone - for those of us who have boards with the original pin layouts and used omeg pots: has anyone put together a front panel layout to accommodate the slightly different spacing as a result of bending the pins? Or does anyone have an idea of the best way to go about creating and/or modifying one for a more accurate fit?

I'm hitting the home stretch on my console build and, having built two 492's and the ssl, I'm just down to panel layouts.



-drew  

One issue is that they are not going to fit in a 1 U space in a par metal case... but I'm right there with you, home stretch with the Omeg's

I would think it would be as simple as moving the Hole's and legends slightly more out (what ever the difference of the pots is)

 

[kazper]

The omegs measure about 45mm (1.74") from top to bottom. I measured about 25.5mm from center to center, but we should verify that value to the data sheet. Bad part is I have the knobs for the stock pots, which may not look right with the extra cm between the pots.

 

[AndersB]

Well I made a frontpanel just by measureing, a it came out ok. But for the next W492 (the right side) I'll place the pots first and the solder them. It was a little tight, but it works. so my advice is mount in frontplate first and then solder.

/Anders

 

[a2d]

I think Ptownkid should hurry up and get that done,,, lol right after the 1176's and the La2s 

Hey guys..

Just putting together a BOM for myself on this.. Does anyone know if Ptownkid ever did do a kit for this project?

Im *trying* to spec Wima caps, should I be looking which range should I be looking at, there seem to be a few options out there!!

Thanks for your patience guys!!

Mo

No i didn't get around to it. Money got a little tight around here for a while. It is in the works still. As for your cap question, don't get too bent out of shape about getting the most amazing (or expensive) caps out there. It's been shown time and time again that it makes very little difference.

 

[Moses]

Hey a2d thanks for the dig, I consider myself slapped down!! I was asking purely because there had been talk of it!!

@Ptownkid, I guess everybodys got it a bit rough just now, eh? Sorry to hear you are suffering though. Thanks for the advice on the capacitor front! I was looking at the boards and it looks like (from the layout, to a noob like myself!!) the caps have to be axial, and  'boxes' rather than 'tubular' in order to fit the allocated real estate?!? Further to this, (assuming for now that Im 'stuck' with Wimas..) which range of Wimas should I be looking at, and what is the difference between, say MKS4 and FKP2 of the same value?

Thanks for your help so far!!

Mo

 

[outoftune]

if you are looking for parts for this, check with laura at taw electronics. i ordered all my parts from her, including the pots. only thing she didn't have was trim pots and 5532's!

does anyone have a 2 in a 1U front panel for this that fits the green omeg pots? seems like a few people would be interested in this if there is one.

 

[kazper]

The omegs I believe will not fit inside a standard 1U case.... with out some strange modifications. You can get about 4 in a 3U..... or 2 in a 2U and I know that is something you may not want to hear...

I've thought about ordering another 4 PCB's and buying the correct type of pot so I can do them in a 1U.... maybe next Gman order...


I said the omegs would work for the application but the size is off from the beginning.