Hi all, I'm venturing into separates for the first time after building a discrete RIAA stage. I recently picked up an SGA Unity line stage which appears to have been built by Steve Giunta from Corey Greenberg's design in Stereophile, and a Hafler 9180 to drive a pair of Hansen-Zylberberg speakers I rrefurbished the insides of. Right now the Hafler is having an issue with DC on the right channel during startup that caused oscillation I'm working through.
Hello, be sure to only use a dummy load on the Hafler until it is working properly.
Is it high DC offset, or low DC?
Is it high DC offset, or low DC?
Definitely high DC, charges up to the HV rail before being brought back down once the soft start comparator turns on the input stage. The same is appearing in the cascode stage, shown by the blue trace. The bases of the cascode current source seem to indicate something is turning on too early with the first dip in the yellow trace. What is a little more confusing to me is the drain of the PMOS in the middle of the input drifts toward the negative rail when turned off, and once it is closer to 0 V is when the DC comes back down, so I'm thinking it may be an issue with the input stage.
I can totally start a dedicated thread with some more info, I'm hoping to get a better idea of what's going on before throwing new components at it.
I can totally start a dedicated thread with some more info, I'm hoping to get a better idea of what's going on before throwing new components at it.
