OA10 for 2520 socket modified for 312 style preamps

since the Neumann OA10 is not mached for the high ratio input trasformers I have thought to change some components on it, just to have an OA10 clone usable for the 312 clone preamps.
Moreover, I have changed the old and discontinued BC212B, BC182B and all original diodes with modern  BC560C, BC546B, BC556B and 1n4148.
I have made a protoype just electrically tested and measured.     

attached the schematics, one is the opamp modified with modern components but similar to the original and the other one is for the 312.

8) 8) 8)

so the unchanged version could be used with the OV560?

[silent:arts] said:

8) 8) 8)

so the unchanged version could be used with the OV560?

Click to expand...

yes, I have derived the 312 version from the unchanged version I have developed to be used with the OV560. 

HI Pier Paulo,

  hope you are very well.

  the second diagram still has bc212b and bc182b marked on it, not the newer transistors. Is this a mistake? Do the new transistors improve the performance? If so, what difference? Less noise, distortion, higher slew rate?

  I have a few OA10 I have built using the pcb's that gustav has, and i think they sound wonderful! I think they are my favourite of the "vintage" designs. Are these going to be for sale?


    KIndest regards,


      ANdyP

strangeandbouncy said:

HI Pier Paulo,

  hope you are very well.

  the second diagram still has bc212b and bc182b marked on it, not the newer transistors. Is this a mistake? Do the new transistors improve the performance? If so, what difference? Less noise, distortion, higher slew rate?

  I have a few OA10 I have built using the pcb's that gustav has, and i think they sound wonderful! I think they are my favourite of the "vintage" designs. Are these going to be for sale?


    KIndest regards,


      ANdyP

Click to expand...

yes, with the BC550C's and BC560C's the slew rate is higher (40% more), the THD at the mediums and at the highs is lower (40% less), noise is lower. I have could to modify two components' values for these performaces.

yes, this project is going for sale.
I am going to offer these 3 versions, since the PCB is the same for both.
The PCB + MILLMAX PINS for who wants the original version.
The full kit for the original version improved with modern BC's
The full kit for the version for 312


kind regards
Pier Paolo

    Wonderful!

Hi Pier Paulo,


    does it still need the same compensation cap(s) for lower gains?


 
      ANdyP

strangeandbouncy said:

Hi Pier Paulo,


    does it still need the same compensation cap(s) for lower gains?


 
      ANdyP

Click to expand...

the cap is onboard so there are no required the outboard net. Moreover I have designed a new one for better performances .

kind regards
Pier Paolo

So can you still get the 50V/us that you can with the un-compensated original OA10( at gain of more than 20)? Mine sound great at unity gain(5V/us slewrate), but are truly stellar at the higher gain in a mic pre.

strangeandbouncy said:

So can you still get the 50V/us that you can with the un-compensated original OA10( at gain of more than 20)? Mine sound great at unity gain(5V/us slewrate), but are truly stellar at the higher gain in a mic pre.

Click to expand...

I have 15V/uS of slew rate that's near to that of the JE-990 in the OA original version with new BC's.

kind regards
Pier Paolo