NTP stero line-amp w/ Beyerdynamic trafos
« on: January 22, 2015, 01:19:36 PM »
Hi everyone!
Some time ago I purchased a NTP stero line-amp (Type 4-30322, Serie A 8 ), it houses two identical pcbs with Beyerdynamic TR/BV 310 003 002 input transformers and RC4558 op-amp. The seller gave me wrong pinout, so I'm hoping to get some help here, to wire it up properly.

This is what I figured out:
+ and - marks on pcb are for power (+/-15V);
main inpuit: one input goes through resistor and capacitor to primary start, other input goes through resistor to TR/BV primary end; from TR/BV secondary end goes to -input of opamp, and secondary start goes to +input of opamp; from opamp output the signal goes to gain trim (marked A on pcb), and comes back (marekd B, C on pcb). And there's a main output next to R10 and R11.
Further on I'm lost. There are two pads on PCB marked D and E, that go to the back (Tuchel) connector - fader or gain/volume pot?
Please correct me if I there's something not right.

Here are the pics:




« Last Edit: January 29, 2015, 10:49:42 AM by Zergonion »


Re: NTP stero line-amp w/ Beyerdynamic trafos
« Reply #1 on: January 29, 2015, 10:50:23 AM »
No ideas???

gyraf

Re: NTP stero line-amp w/ Beyerdynamic trafos
« Reply #2 on: January 30, 2015, 03:07:19 AM »
Try to draw up a schematic?
..note to self: don't let Harman run your company..

Re: NTP stero line-amp w/ Beyerdynamic trafos
« Reply #3 on: January 30, 2015, 02:25:48 PM »
I drawn the parts overlay, hope this helps... I will also try to draw the schemastic.

On the picture green values are resistors, blue are caps - electrolytics are 10uF, with blue dot on the + side; 470pF looks like polystyrene, 0,47uF is film.
On transformer:
1 - primary start
4 - primary end
5 - secondary end
7 - secondary start


Re: NTP stero line-amp w/ Beyerdynamic trafos
« Reply #4 on: January 31, 2015, 03:25:40 PM »
Oh, and I almost forgot - there's an unsoldered lug on the PCB, next to op-amp; looks like it's ground...