PM6004 phono hum

[admin_exported]

I've just noticed that my new PM6004 has a hum on the phono input. The amp is just over a week old and is connected to an RP1. It is quite noticeable at any volume above '9-o'clock', even when the RP1 is off. When I unplug the inputs from the back completely, it is slightly better with just the left and much worse with just the right. With normal music it's not noticeable however on soft music of in between tracks at normal listening levels it's quite noticeable. Has anyone experienced this before, and is it likely to be the Marantz or the RP1?

 

[Anonymous]

Sorry, I meant to say when the inputs are both removed there is no noise, is slightly better with just the left and much worse with just the right.

Update: I attached another RP1 to the amp and have the same noise. What I did notice though was that the noise greatly depended on the position or movement of the RCA plugs into the amp. Moving them made the noise much worse and a few times caused enough of a spike to trip the amps circuit when the volume was above 9 o'clock. Could it be a bad internal phono RCA plug on the amp?

 

[shooter]

Hard to know exactly but it sounds like grounding issue. The RP1 has the ground built in to the cable, is the cable okay and did the RP1 work fine with the last amp you had? Or it could be the amp.

If its the amp i would send it back and get a replacement.

 

[Anonymous]

I pursued the grounding issues and started to isolate the power cables, turns out the Fiio D3 DAC is the cause. Switching it off stops 75% of the hum when on phono. Even when I move the Fiio to another wall plug the noise comes back. The only way to stop it is to turn it off while on the phono input. Perhaps I need to look for a better Micro USB power source for it.

 

[shafesk]

Sounds to me like the ground cable on the rp1 hasn't been attached properly to the ground input on the amp. Give it another go.

 

[shooter]

I pursued the grounding issues and started to isolate the power cables, turns out the Fiio D3 DAC is the cause. Switching it off stops 75% of the hum when on phono. Even when I move the Fiio to another wall plug the noise comes back. The only way to stop it is to turn it off while on the phono input. Perhaps I need to look for a better Micro USB power source for it.

I have had the same experiance with a Fiio, they obviously have a major issue with these units.

This was my find, post 13 onwards:

http://www.whathifi.com/forum/dacs/£30-ish-dacs-on-amazon-anyone-tried-these

Can you report this kind of thing, trading standard or the like?

 

[Anonymous]

I've got another mini USB charger that Im going to try with the Fiio tonight. At the moment the only sollution is to turn the DAC off at the wall when using the Phono input, hardly a long term solution.

 

[Anonymous]

I replaced the mini USB power supply and the noise went away. It's crazy that they use such a 'irrelevant' inferior part which can make such a difference to the overall system.