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QSXM2 questions.

Started by zz1969, March 07, 2013, 05:48:59 AM

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Hi P-A!
I need your advice on my final checking of my QSXM2.
The system is the following:
I 'm using  15v supply with 2 x JSSR04; BC850/860C; LEDs (forward voltage 2.1v, current 20 mA) – 1863179 – Farnell code
1.   MM cartridge (Ortofon 2M Blue):  47K, 150-300 pF – Should I change C1 to 300 pF?
2.   IC5, IC6 - TEXAS INSTRUMENTS - OP07CP - IC, OP AMP, LOW OFFSET, DIP8 – It takes up to 18v so I removed dz9/10 and C61/62. Is that right?
3.   Do I understand right that R2 should be 0 ohm if there's no RF interference?
4.   I could't find the correct LED so I used the LED above. There's  1.85 v across the LEDs – do I need to change R42...47?
5.   Also I have some unbalance between Left and Right PreAmps: voltage across R33 – 1.35v E33 – 1.88v, R35 – 0.7v, E35 – 1.22v. I guess I heated too much some of the transistors. Where do you recommend to look?



  • Deside yourself.
  • Yes
  • Yes
  • No, unless it gets too hot but you got almost the same as I!
  • This will be take care with the feedback. NPN and PNP devices aren't 100% the same.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


I would also recommend to go to 150pF. I did with my Ortofone MM and it gave the best result.