cs4398 blown gigaworks big dac

[overdrive69]

Hi all

recently fitted monacor lt110's to my dac, since doing this it hasn't been right. initially it worked fine and sounded stunning then it started breaking up on one channel once the dac warmed up. I have now disconnected the transformers and gone back to op amps and still have the same problem but its got worse. One channel works fine for say 4-5 minutes the other channel is lower in volume and lacks bottom end. once the dac warms up it starts to distort and break down on both channels eventually it stops working. I feel it could be the cs4398 that is blown as the signal getting to the chip is fine. ohm readings off the outputs on the chip are different, one is 180ish and the other is 250 ish, to me this explains the lack of volume on one channel and indicates a short in the chip. It also explains why there is earth hum on the channel that is faulty..

Anyone got any idea's or answers ?

[Bill Fuss]

I don't have direct answers but I'll try to help. I'm assuming you have a scope if you verified the I2S signal is getting to the chip. If you are using upsampling you can try removing it and jumpering the header.

I'm not familiar with the Monacors but if they have a primary center tap and you connected it to the board ground that would most likely be the kiss of death for the 4398 dac chip. A trafo across the output pins should not hurt it.

The boards are so damned fragile it's very easy to damage them when modding. Definately look for board damage.

I successfully replaced a damaged 4398 so it's possible to do. It was not mine so I don't know how it was damaged in the first place. I also assume that you checked the voltage at the supply pins.