I bought my second HiFiMan tube USB DAC amp it being the EF2A unit. I sold my first to purchase some headphones I had my eye on. These amps come standard with the Chinese 6J1 tubes. I'm after the best audiophile experience so on the first amp I bought NOS Sylvania compatible tubes. It sounded awesome. For the second EF2A amp I bought some valve electronic CV4010 KQDD/K tubes based on compatibility threads here. At first everthing was cool. I.m plugging the amps USB into my Dell Inspiron with iTunes.
Now I'm getting a strong hiss when the song ends and crackling interference which can and will turn to pure white noise. It's hard on the ears when that happens, I changed back to the 6J1's thinking maybe a bad tube. Music was good then bang it came again. It seems as though when I turn everthing off and then power back up it does ok for a few minutes, but then back to bad.
I called Head Direct for advice. The woman told me the president says not to use any other tubes than what's shipped with it. I can't accept that and told her as such. She still wouldn't help. So is tube rolling a no no wit HiFiMan amps? My successful experience withe first amp tells me no. As of right now I would not buy from Head Direct due to such inadequate customer service. I wasn't being a jerk. I was just trying to get some help.
Any ideas Guys? Thanks.