Hi KBK,
The input coupling cap on an NAD is critical, although I'd include it on any amp. There is a 0.5~0.6V DC offset between the base and emitter of a bipolar transistor that is temperature sensitive. This is cancelled in a differential pair, but not with the classic NAD input. They achieve DC offset control by injecting a current that hopefully tracks temperature. The result is that the DC offset "wants" to drift with temperature. If you replace the input transistor, it may or may not be outside the gain range to be compensated. Same for other transistors in this circuit.
It's an iffy circuit that relies on component tolerance to a "bogey" value to work. I can't tell you how many techs get hopelessly stuck on these. Even when using real exact replacements.
-Chris
The input coupling cap on an NAD is critical, although I'd include it on any amp. There is a 0.5~0.6V DC offset between the base and emitter of a bipolar transistor that is temperature sensitive. This is cancelled in a differential pair, but not with the classic NAD input. They achieve DC offset control by injecting a current that hopefully tracks temperature. The result is that the DC offset "wants" to drift with temperature. If you replace the input transistor, it may or may not be outside the gain range to be compensated. Same for other transistors in this circuit.
It's an iffy circuit that relies on component tolerance to a "bogey" value to work. I can't tell you how many techs get hopelessly stuck on these. Even when using real exact replacements.
-Chris
Hi hash_dac,
Sorry this thread is quite old now, and you may have moved to other horizons away from this amp...
I recently got a nad 3130, for a very low price too.
And face quite the same distorsion problem as you on the left channel; it ihappens not all the time,
It is lasting only a few minutes then disappears. Seems occur when the amp is cold but not always.
It goes away if i disconnect-reconnect the left input ...
Did you finally find out the cause and get it resolved on your amp?
Thanks for your rep.
Sorry this thread is quite old now, and you may have moved to other horizons away from this amp...
I recently got a nad 3130, for a very low price too.
And face quite the same distorsion problem as you on the left channel; it ihappens not all the time,
It is lasting only a few minutes then disappears. Seems occur when the amp is cold but not always.
It goes away if i disconnect-reconnect the left input ...
Did you finally find out the cause and get it resolved on your amp?
Thanks for your rep.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.