Bias adjustment Toshiba 1943/5200

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
In schematic for my Nad C272 it says adjust bias to 6-7.5mv.

but cooling fins basically never get any hot. It sounds good but after about 2h playing music it starts to sound much better i think.
My old 216, 214, 218 in the past and other amps i've owned before getting quite hot right away..

Only thing that gets really hot are the 68v regulator and all parts in pre and gainstage (suppose to run i class A so..) but the 4 pairs of Toshiba 1943/ 5200 doesn't really. after many hours of playing music putting the hand om the lid it barely is fingerwarm.

IS it any real danger of adjust higher like say 10 or even 15mv on bias? (my old 216 was biased at 18 i think but other trannies from Sanken)

Anyone experinced from this amp or another with this output trannies? Is the regulator or other parts take a beating if i adjust the bias upwards. Think really there is nothing wrong with the amp. Recapped and done. It was the same before this too.


  • Nad_c272_service.pdf
    1.1 MB · Views: 165
Last edited:
I can only say that in general I have not seen any negative effect on distortion when increasing current. In theory there is usually a optimal Iq, but from what I have seen in practice, distortion usually decreases with Iq higher than the theoretical set point.
Try it, but watch the temperature so it does not run too hot. With good airflow to the amp, you might be able to increase it quite a lot.

EDIT: you should be aware that the higher currents and temperatures will age the components faster.
Last edited:
Do you mean that those 5w resistors would go too hot or what parts would suffer? They are stonecold btw.

On each channel there is (R444, R434, R344,334) 2.2k 3w replaced with 5w is running very very hot now. I’m not sure how they would react to adjusting bias higher.
Am i right this parts will suffer from higher current draw? These i need to check carefully? These all are mounted on a pretty heft heatsink (and they get hot, 50-60 celcius degress atleast. See pic with red X on my amp


  • D20DF8B0-7536-48D9-8059-A4E25DC5FF3B.jpeg
    628.7 KB · Views: 115
  • 6EE859FF-BD23-4727-9FFF-BD97DA04707C.jpg
    219.1 KB · Views: 117
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.