Neumann OA10 discrete op-amp (in API 2520 etc. format)

[strangeandbouncy]

Hi Guys,


  many thanks again for your input and help. This story has a happy ending. YAY! I have a working OA10, stuffed it into a mic-pre, and first impressions are very favourable. I can't wait to try it out properly. I am looking forward to trying it in a pultec-type eq for 20dB of gain, and see whether the higher slew-rate/less compensation makes any difference.


    Wonderful!



      ANdyp

 

[strangeandbouncy]

HI,


      Got these in my LA-Z MPA pre. I won't be replacing the Peters DOA's anytime soon, 'cos there is some serious mojo for me in them. This platform does give the the perfect bed to test on, since I am only changing 2 DOA's, everything else the same. These OA10's are the shizzle! I have only DI'd a gtr and done some BV's so far. They are really warm and smooth, and first impression is that they are slightly quieter. Maybe the noise is just shifted to a less audible freq range(?) I will measure later. I am recording a vocal with an artist I know this afternoon, and will be able to tell far more then.

 
      Audiox, you are a marvel! Thank you so much.



    Kindest regards,


      ANdyP

 

[mitsos]

Good news! Was it the output transistors?

 

[strangeandbouncy]

Yessir! Output transistors

 

[geoff004]

does anyone have a source for these transistors in the US?
the dealers I've checked are either not stocked or have them labeled 'obsolete'.

 

[dissonantstring]

geoff004,
seems like digikey has them.  BC327NOS-ND and BC337NOS-ND

 

[strangeandbouncy]

Hi,


  I've been using these all week. I really like them. Very smooth and warm with compensation. I can't wait to try un-compensated.


  I have experienced a strange thing. twice, they went very noisy. I would describe the noise as "windy". This goes away if you turn off and on. ANy suggestions how to cure? More de-coupling of power rails perhaps?


  Kindest regards,


    ANdyP

 

[Tweekhead]

Hello!

I'm trying to source parts for the DOA and learn as much as I can about reading schematics along the way. Anyways, I was wondering, as I can get the BC327-ND, and the BC337-ND from digikey, and  I cannot find the BC212B, could I use one of Mousers substitutions? What would I need to look for? They have options for : Package / Case, DC Current Gain hFE Min, Maximum Operating Frequency, Collector- Emitter Voltage VCEO Max, Emitter- Base Voltage VEBO, Continuous Collector Current, and Power Dissipation! I'm trying to teach myself electronics Kung Fu, so I apologize in advance for any nub questions, but I've learned so much from this forum already I feel like I'm so close to finally understanding!!!! You guys rule and that's not just the liquor talking.)
 
 

 

[Tweekhead]

Hello again,

Could I substitute 2N3906BU for the BC212B?

 

[grantlack]

If you can sit tight for a bit, I'm working on picking up some BC212B's in bulk. Did anyone ever clear up which mill max pins are a proper fit?

 

[RedNoise]

pins holes are too big...Two solutions :
solder a femelle pin (as on the board , same hole diameter) then add a male one between the females.(!)
Or : solder 1N4XXX pins on both main and DOA pcb ...

 

[Tweekhead]

grantlack,

Excellent news! Did you have a time frame of when you might be getting the bulk order?

 

[dmp]

I ordered a bunch of the BC212b transistors from:
http://www.awatronic.co.uk/bc212b/prod_19829.html

 

[Tweekhead]

Thank you!

 

[grantlack]

grantlack,

Excellent news! Did you have a time frame of when you might be getting the bulk order?

Just paid today, they don't have far to travel so if shipping is timely I should be able to send some out early next week. How many do you need?

 

[Tweekhead]

Sorry, I followed dmp's suggestion and ordered them from http://www.awatronic.co.uk/bc212b/prod_19829.html

Thanks anyways.

 

[grantlack]

no worries, they'll go to good use.  come to think of it, i could probably do parts kits if there's interest...  anybody?

 

[maxwall]

When home etching a two layer board like this OA10 API style , what is the best method
for keeping the top and bottom layer aligned ?

 

[geoff004]

no worries, they'll go to good use.  come to think of it, i could probably do parts kits if there's interest...  anybody?

interested
I've got 4 of these PBCs I'd rather see assembled and working.

 

[Moses]

no worries, they'll go to good use.  come to think of it, i could probably do parts kits if there's interest...  anybody?

Are you thinking of doing full kits (ie, PCBs included)? If so I would be interested...

Mo