Krell FPB300 - mechanical transformer noise.


I have an FPB300 that does not have the pinging issue discussed on another thread - my problem is a noisy transformer. I have measured approximately .75 volts of DC on my incoming line (dedicated 30A) and plan to try a DC trap such as PS Audio's UPC200HB.
The unit makes the most noise and is most noticable when the music stops or when the music transitions from loud to very soft - unit almost growls for several seconds and then fades away. I am assuming that this is related to the class A biasing scheme. Krell had no suggestions even after I asked if DC could be saturating the transformer - they acted like they never heard of toroids and DC issues. I am feeding the amp directly with a Wadia 850 (balanced) and it is driving Apogee Duetta Signatures (Audioquest Midnight Cables) Anyone experience this or have ideas? I am very happy with the combo except for the noise. Thanks in advance for any help.
landshark75
Did you e-mail Jim Ludoviconi he is the Assistant Vice President of Sales and Marketing & Director of Technical Support. He seemed to answer all my Krell questions very knowledgably.
Joeyboynj,

Thanks - I will do that. Jim is not the person I spoke with. Instead of using "they" to refer to Krell, I should have referred the person in technical support. Hopefully Jim can shed some light on the cause.
You may want to open it up and tighten the transformer. Don't overtighten but with it heating up and cooling off it may need to be cinched down again.
I don't think tightening will help the transformer. It is probably a bad transformer or a bad filter capacitor. It would be best to send it to Krell for evaluation. You can check for DC leakage from the Wadia. Krell does have a setting for tube preamps that may help in this case.