A brief 24-hour update after our announcement regarding the hissing issue of N30LE.
We have continued our study on the hissing problem. According to our working theory by the end of day 1, the problem is related to specific capacitive loading characteristics that show up in unit variance occasionally. It only exhibits in Class A and Hyper mode, so we focused on the working current of the discrete headphone amplification circuit.
After numerous tests and auditions, we managed to eliminate the hissing problem on the returned N30LE by adjusting the bias setting of the discrete headphone amplifier circuit. For those who are unfamiliar with the discrete circuit of N30LE, please refer to our explanation in Post #195, in which I quote the most relevant paragraph below for your reference:
We have noticed that by re-biasing the circuit to a new parameter, the hissing problem is eliminated completely, and if we adjust the bias setting back to previous parameters, the hissing problem will reoccur, so we are pretty sure that this will solve the problem from our Engineering point of view. The bias setting will affect both Class A and Class AB playback, the change to audio performance is minimal and inaudible.
However, we need some time to verify our solution. As of today, we have received 3 hissing complaints from China (including Hong Kong) out of the 120+ units we delivered. We have only received one returned unit and that’s the base of our problem-solving exercises. We’ll pick three N30LE from our inventory, adjust the operation bias to our new reference parameters, go through the QA process again, and send out these DAPs to the dealers of the three users who reported the hissing problem. Assuming the new batch of DAP can pass the hissing test with the IEM/headphone/cable that they had trouble with previously, we’ll send out another batch of N30LE to our overseas dealers immediately, and they can replace the hissing N30LE of their client. We believe this arrangement will minimize the delay of our users from sending out their N30LE DAP to receiving an N30LE replacement.
@Andykong
This is great progress and news!
Thank you for everything you do with transparent updates to coordinating with dealers and assisting affected owners.
Also big shout out and sincerest thanks to Andrew and his team at @MusicTeck for their always amazing support.