Loud hum on single ended inputs to CT-2300
 

Folks

I'm getting a VERY loud hum when trying to connect to the RCA single ended inputs on my Classe CT-2300

I'm switching out my setup from and XLR DAC (Oppo HA-1) to a single ended one (eventually a Chord Hugo 2). In prep, I've been trying to get the setup working with my Chord Mojo (single ended output)

I have shorting pins installed between pins 1 and 3 on the balanced inputs to the 2300.

Even with the Mojo disconnected from everything and powered off, I have a very loud hum when I connect to the headphone out on the Mojo. Same thing happens when connecting to headphone out on a powered off Pono and a powered off iPhone.

I have swapped cables and changed electrical outlets for the Classe, and have the same behavior.

Any thoughts/suggestions for how to diagnose and fix what is going on?

Thanks in advance

Ray

Ray,

1. try to take the shorting away from XLR-input.
2. Can you try the single end input with another unit than you your Mojo?

Best regards
Lasse

Thank you for the reply.

I did try with shorting pins removed, and the hum was even louder.

I get the same hum (with shorting pins) from Mojo, iPhone, and Pono

Even with no device connected, simply moving around the disconnected RCA cable creates very audible noise (confirmed with multiple cables).

I should say that when connecting the Classe via single ended RCA to a preamp, I get no noise (clean as expected). I'm wondering if the amp may require a proper preamp (loading?)

I think that if everything works well with a regular preamp then you have your answer.
In any case connecting something like an iPhone directly to a Classé power amp is a bit blasé. Not really what the power amp, iPhone or Mojo is designed to do.