Humming from the power transformer JC-1

[Peter Nielsen]

There's no theoretical reason the balanced transformer should be less susceptible to hum than the JC-1's transformer. If this works, the only explanation is that the JC-1's transformer is inferior to Equi-Tech's.

Yes, there is a theoretical reason: The Equi-Tech "Q" transformer is technically different from a regular toroid. (You can easily tell since it is much bigger than a regular toroid with the same rating).

Adding an Equi-Tech transformer also has the great benefit of providing balanced power where the voltage to ground is only 60 Volts instead of 120 Volts.

Personally, I would not ship my JC1s anywhere. The risk of components rattling loose in shipping (most notably the power transistors) is too big. You may end up getting back a JC-1 that hums less, but sounds worse. But if you can drop it off at a service center in person it's another story...

Peter

[Bob Stern]

Personally, I would not ship my JC1s anywhere. ... But if you can drop it off at a service center in person it's another story

Parasound doesn't allow that. You have to drop it off at a customer service center in San Francisco, then Parasound ships it by courier to their repair facility in another part of San Francisco.

[Bob Stern]

I don't see why an ExactPower regulator would help. The schematic in their patent shows an AC-coupled comparator circuit that would not be able to detect or correct DC offset.

I just received an email from Exact Power confirming that their EP15A cannot remove DC offset in the power line.