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

[Matthew Jacobs]

You won't regret building these puppies, I promise. they really sound great.

Well, it is Neumann after all...  ;D

I'm hoping to get some from Gustav and a Studer 169 5K as well.

JD

 

[Ptownkid]

Has anyone come up with a suitable sub for the obsolete bc212B...I know they can be found, but it would be nice to replace it with an available part. I'm not the best with transistor cross referencing, anyone know what the important specs are in this case?

 

[strangeandbouncy]

Hi,


  FWIW, there were loads of BC212 etc on SheBay when I needed some.


  Kindest regards,


      ANdyP

 

[Tweekhead]

Hello everyone! Thanks for all the great info here, as I've learned so much. I built a VP312 yesterday, and a Neumann OA10 with compensation. Everything works great, and sounds great. I'm waiting on 2 germanium DOAs from Pier that I plan on using in the VP312 and I'll put the OA10s in the Studer 169 project.


I used Mouser Part # 575-310320 for the pins. I placed these inside of sockets from classicapi.com and soldered them in.

Thanks again ;D

 

[Tweekhead]

sorry, last pic was huge. I suck at picture editing

 

[pablobolche]

I have finished after some trouble a good working OA10 opamp that I have put in a VP25 Mic pre running at +-16V.. sounds sweet and tighter than the gar1731 I had..
Seems to work ok  but temperature on the transistors seem really high.. over 42 degrees Celsius..my thermometer only goes to 42.... is this normal?
I stuffed this puppy with  1n4148 as i don't have 1n914.. and for R9 I used a 3R9 instead of 3R3 also due to lack of them... might this be the reason of such high temp??
Also can someone comment about the hfe for the 212 transistors? mine are in the range of 330 to 380..
I have 11 OA10 more to go and don't want to mess them up..

Thanks

 

[m.gharibe]

hi there
can resend schematic another place?
im iranian and cant see your schematic

 

[isophase]

hi there
can resend schematic another place?
im iranian and cant see your schematic

search Kubarth site. original schematic should be there somewhere.

 

[irfrench]

Hi all.

I've just put one of these together and am getting R8 burning out  ;D ??? .  Is there anything obvious you can think I should check for before I start debugging?

What wattage are you using for these?


Thanks,
Ian

 

[iprovlek]

I built 5 of this opamp and cant get them works!

I solder every element like in schematics and dont know what i missing......
 

 

[audiox]

I've just put one of these together and am getting R8 burning out  ;D ??? .  Is there anything obvious you can think I should check for before I start debugging What wattage are you using for these?

I built 5 of this opamp and cant get them works! I solder every element like in schematics and dont know what i missing......

perhaps there are different versions of the transistors with different pinouts

Check your 212s... if you didn't use motorolas, flip them around.

 

[irfrench]

audiox,

Thanks for the reply.  I checked all orientation/pinouts before installing using a DMM so am 99.999% sure they are in correct.

I used 0.25w resistors in my build, could this be the issue with R8?  strangeandbouncy confirmed that he'd used 0.4w with success - should 0.25w be OK?

Thanks
Ian

 

[iprovlek]

Finnaly i got two of this Neumann OA10 opamp to work!

It was hard to get measure this outside,cause dont have COM!

But after few fliping i get the work,212 and 182 transitors are the same as schematics,but i must flip 327 and 337 to get it work....

And thanks again Audiox for this great opamp!

I compare it with old Philips 5534 , and OA10 rules all the way....silky an beatifull...

 

[irfrench]

Finnaly i got two of this Neumann OA10 opamp to work!

It was hard to get measure this outside,cause dont have COM!

But after few fliping i get the work,212 and 182 transitors are the same as schematics,but i must flip 327 and 337 to get it work....

And thanks again Audiox for this great opamp!

I compare it with old Philips 5534 , and OA10 rules all the way....silky an beatifull...

THANK YOU!!!

I replaced the burnt R8 and rotated the 327 and 337 180-degrees.  Now I have signal and no fire! Can't wait to do a listening test when the second is built.

Thank you all very much for the help!

Ian

 

[iprovlek]

Im very happy that you get working OA10!

I was totaly crazy and very near to close this project cause gave to make all new gerbers files

and films for this project in PCB manufacter here in my town!

Finaly my stubbornness wins...

And Oa10 sounds wonderfully....

 

[Gustav]

Should be fine replacing the BAV19 with BAV21, right?

http://www.fairchildsemi.com/ds/BA/BAV21.pdf

Gustav

 

[gyraf]

yes, should be the same, just tolerating higher voltage

 

[Gustav]

yes, should be the same, just tolerating higher voltage

Thats what I got out of the data sheet too, just wanted to make sure

Gustav

 

[dmp]

I built 4 of these a few years ago and have tried them in various things off and on.
I put them in a new API pre I just built since I was out of DOAs (vp28)
They were distorting a little bit - I thought there was a problem with the preamp at first. But I swapped out the OA10s and it went away.
Do these crap out in a preamp? They don't seem to have beefy output transistors.
I put them in the Audiox studer 169s that they originally came with and they sounded fine.
I didn't add the external compensation components. But that should only be necessary if they oscillate correct (at unity gain)?

 

[Gustav]

This thread mentions that a few people are rotating the 327 and 337 to make it work, and if I measuring my transistors and reading the schematic correctly, I have the same "problem" (My 327 corresponds to this pinout http://www.ly3kb.eu/gallery/var/albums/Constructions/Schemos/PC-TRX-CW-FSK-PTT-Interface/BC327.jpg?m=1373400671 ) going by the component layout pdf.

So that should be good and fine, but I have to ask - are they depicted correctly in the schematic? It seems to me they are not (An explanation either way would teach me something), and Id like to clear it up before any testing.

Gustav