Neumann W492 equalizer DIY project (PCB docs added)

[tommypiper]

Seems wire pots should work, even since there is coupled DC...

Where's Audiox on the subject?

Do you have a part number?

Which pots need to be double, and which are single?

 

[mitsos]

If Omegs work maybe we can convince audiomaintenance to stock them? Colin is going to do kits for the S800 eq... maybe he'd do this one too?

TommyP, IIRC, only two pots need to be doubles... looks like P4 and P6. Audiox said he made them all doubles for mechanical stability.

 

[audiox]

Did some internet searching and found this:

http://www.audiomaintenance.com/acatalog/potentiometers_conductive_plastic.html
SF-01-009 - 11mm - 2 gang 10k linear

Looks the same type that I used in my design.

 

[mitsos]

Audiox, I did see those. With all the options with SF I wasn't sure.

Can you or anyone else confirm, if you think the Omegs would work? They are much cheaper (I just got a quote from Omeg... only 0.71 GBP each if you buy 100!) , so I can't imagine they'd be of the same quality, but if they would work, it would make this project much more affordable.

here is the data on it:
http://www.omeg.co.uk/e16data1.htm

thanks!

 

[audiox]

Is it conductive plastic (or just a potentiometer with plastic enclosure)? I didn't find any info about the resistance track material.

You should use conductive plastic potentiometers because of the dc coupling. Potentiometers with carbon track start to scratch quite soon.

 

[mitsos]

I wasn't sure either... I assumed Kazper had checked...

Anyway, from Omeg's home page: (Third line of opening paragraph)

"We use conductive plastic elements in our potentiometer range to give over twice the life of carbon."

http://www.omeg.co.uk/index.htm

Does this mean it's ok then?

 

[audiox]

Send them e-mail and ask if they use conductive plastic element in that specific model.

 

[tommypiper]

[quote author="Rossi"]Would wire wound pots do? Reichelt has 10k 4W wire pots @ € 2.50 apiece. [/quote]

Rossi, what's the part number, please?

 

[Rossi]

The Reichelt number is P4W-LIN 10K.

There is a link to the datasheet on the product page; according to that it is manufactured by AB ELECTRONIC SACHSEN

http://www.reichelt.de/?;ACTION=3;LA=4;GROUP=B26;GROUPID=3138;ARTICLE=54296

Andybody know if wire pots are okay with DC? I have no experience with wire pots so far.

 

[wolfgang]

@MartyMart:

Do have any news from nobeleelctronics?

In the meanwhile i am also contacting an Czech Electronics Supplier, maybe they want to sell something!

Is that Code you postet for the pots correct?

Regards,
Wolfgang

 

[MartyMart]

Wolfgang, I have news but it was not great.

there's 20 weeks lead time for an order !!
Plus they have three weeks in August off for holiday.

200 + pieces are £6.51 each, may be slightly better for 500 pieces.

My work schedule means that the group buy/ organization could be a problem and I would need all orders paid up-front.

I'm seeking an alternative for the dual pots and have all the single 10k's I
need for 2 complete stereo boards.
You only need 2 duals per project and not 8.

Marty.

 

[audiox]

Marty check this:

http://www.audiomaintenance.com/acatalog/potentiometers_conductive_plastic.html
SF-01-009 - 11mm - 2 gang 10k linear

 

[MartyMart]

Audiox, thanks for the link, hey could you tell me the specific pots that have to be a
dual on the layout and it it the front or back pin connection that does the job
on the single 10k's ? ( one row of pins against two )

I have Bourns conductive plastic for those .... pin spacing needs some bending though
as it's 2.54mm !

Marty.

 

[audiox]

P4 and P6 are duals. Front connections are used on singles.

 

[mitsos]

I just got an email from Omeg about their pots. They are conductive polymer.
If you order 100, the dual gang cost 1.11 GBP each + shipping. 4 weeks lead time, but they don't have 4mm shafts in stock. She didn't say if/when they would get more, but they have 6mm and 6.35(1/4"?)... round. Colin said they won't be stocking pots for this EQ. Is there a reason to choose the PA11 over these? I`d be willing to try it with these, if it doesn't work properly, we're out 10 GBP per channel.

I can't organize a GB because of where I live... anyone else (prob best in UK)?

 

[Fredrik]

Rapid online stock omeg pots for around 1 euro a pop. The duals are about twice that price, not bad.

 

[mitsos]

That's cool, so we can buy smaller quantities. I just checked shipping with 2 channels' worth of pots and it came to 40 Pounds! :shock: :shock:

wow. I sent an email to the US rep to see if there's any there..

 

[mitsos]

That's cool, so we can buy smaller quantities. I just checked shipping with 2 channels' worth of pots and it came to 40 Pounds! :shock: :shock:

wow. I sent an email to the US rep to see if there's any there..

 

[shabtek]

started getting this together and noticed there is no value given for c8, c10.

anybody know why?-- is this part of a symmetric layout style or only to facilitate tweakery? according to the schemo, these are parallel to other caps so it will work without them, but will the corner frequency be as it should?

 

[audiox]

C8 and C10 are not installed. They are included in the layout because it makes it easier to change the frequency range (if you need a cap value that is not standard).