Hum Issue with Brand New Optoma NuForce STA220

Adameos · « **on:** 24 Aug 2019, 07:56 am »

Hello to all. New to the Audio Circle community but have looked through the forum many times over the years.

Hoping I can get a little guidance from the folks here..

I received a brand new NuForce STA220 amp yesterday. Got it hooked up today. Thought I would try it with my McCormack Micro Line Drive for preamp, Klipsch RP-600m. I did notice the hum from the start, but it was lower in level and sort of manageable. The sound was staggering. I got moved. The sound was big very dimensional and with really great tempo. That's partly down to the McCormack, which can be used passive or active. As an active linestage it rocks. I went through several CDs, and listened to the whole Kind of Blue album. I had the SPLs pretty high, but the sound was so good. Then i began to notice more and more hum noise, until it became just overbearing. I was worried because I though it could be the McCormack was in need of repair. I bought out the Placette Passive Linestage. Totally different sound, The amazing PRaT was not as strong but transparency was off the charts as usual. Problem was the hum was still there and loud. I think this amp has a problem. Can anyone shed some light? I love this thing and really want it to be good, but could bot live with that hum.
Thanks
Adam

adminRH · « **Reply #1 on:** 24 Aug 2019, 10:53 pm »

Welcome to AudioCircle Adameos!

FullRangeMan · « **Reply #2 on:** 24 Aug 2019, 11:44 pm »

Welcome Adameos

You listen the hum in both channels?

audioengr · « **Reply #3 on:** 24 Aug 2019, 11:52 pm »

If you disconnect the interconnect cables at the amp coming from the preamp and just have the power amp on, does it still hum?

If not, then it is a ground-loop.

Are you using RCA or balanced IC's to the amp?

Some amps rely on the source cables being earth-grounded. This could also be the problem if they are not.

Adameos · « **Reply #4 on:** 25 Aug 2019, 03:02 am »

Thanks much Admin RH

Adameos · « **Reply #5 on:** 25 Aug 2019, 03:04 am »

Thanks FullRangeMan,

Yes I did hear hum in both channels

Adameos · « **Reply #6 on:** 25 Aug 2019, 03:10 am »

Hi Audioengineer,

I did diconnect the ic cables withe just the speakers connected. Dead silent. I think you may be right about a ground loop. I further confimed this by setting up the same system in a different space and hum disappeared. I did install 20 amp socket and may have got the wires messed up when i did so. I will have an electrician out next week to check things over and install a 20amp dedicated circuit.

Thanks guys for your kindness in responding. I will let you know how it goes.

Adam

Posts: 2951
» Gallery
» Systems
http://www.empiricalaudio.com Email

Re: Hum Issue with Brand New Optoma NuForce STA220
« Reply #3 on: Yesterday at 11:52 pm »
Quote
If you disconnect the interconnect cables at the amp coming from the preamp and just have the power amp on, does it still hum?

If not, then it is a ground-loop.

Are you using RCA or balanced IC's to the amp?

Some amps rely on the source cables being earth-grounded. This could also be the problem if they are not.

FullRangeMan · « **Reply #7 on:** 25 Aug 2019, 04:34 pm »

Adam, keep us posted on the issue progress.

Adameos · « **Reply #8 on:** 26 Aug 2019, 02:59 am »

Hi FullRangeMan,

Thanks for your response. I have identified that the amp is not at issue. I brought the system in to another room and the hum disappeared. I think the cause might be a ground loop in the first room. Either that or interference of some sort, but I think its a ground loop issue. This ST200 is a corker, absurdly good value for $499.

charmerci · « **Reply #9 on:** 26 Aug 2019, 04:45 am »

You can try an www.avahifi.com Humdinger which will most likely block the hum. It does have a money-back guarantee. First few times I used mine,it greatly reduced the hum, then eventually completely eliminated it from the transformer in my pre-amp.

avta · « **Reply #10 on:** 26 Aug 2019, 02:02 pm »

If you have not done so already try plugging all your equipment into one power strip. That sometimes helps. Any strip will work for the purpose of clarifying things.

Adameos · « **Reply #11 on:** 27 Aug 2019, 07:15 pm »

Quote from: charmerci on 26 Aug 2019, 04:45 am

You can try an www.avahifi.com Humdinger which will most likely block the hum. It does have a money-back guarantee. First few times I used mine,it greatly reduced the hum, then eventually completely eliminated it from the transformer in my pre-amp.

Charmerci, thanks for the suggestion. The Humdinger seems like really cool device, and Van Alstine is a highly respected brand. As they have a money-back guarantee I think its worth a try.

audioengr · « **Reply #12 on:** 27 Aug 2019, 07:18 pm »

Quote from: Adameos on 25 Aug 2019, 03:10 am

Hi Audioengineer,

I did diconnect the ic cables withe just the speakers connected. Dead silent. I think you may be right about a ground loop. I further confimed this by setting up the same system in a different space and hum disappeared. I did install 20 amp socket and may have got the wires messed up when i did so. I will have an electrician out next week to check things over and install a 20amp dedicated circuit.

Thanks guys for your kindness in responding. I will let you know how it goes.

Adam

Posts: 2951
» Gallery
» Systems
http://www.empiricalaudio.com Email

Re: Hum Issue with Brand New Optoma NuForce STA220
« Reply #3 on: Yesterday at 11:52 pm »
Quote
If you disconnect the interconnect cables at the amp coming from the preamp and just have the power amp on, does it still hum?

If not, then it is a ground-loop.

Are you using RCA or balanced IC's to the amp?

Some amps rely on the source cables being earth-grounded. This could also be the problem if they are not.

If your amps and preamp or DAC are powered from two different phases (there are two in houses), then this will definitely cause hum. Make sure at the panel that all of the outlets your system is using are from the same phase. You can plug everything into one outlet to test this usually, but you have a 20-amp outlet....

Adameos · « **Reply #13 on:** 27 Aug 2019, 07:20 pm »

Quote from: avta on 26 Aug 2019, 02:02 pm

If you have not done so already try plugging all your equipment into one power strip. That sometimes helps. Any strip will work for the purpose of clarifying things.

Hi AVTA, thanks I will try that. I am looking at a power conditioner as a centralized power source to plug my components in to. Still haven’t got the electrician out yet. Just want to give the electrical system a check to make sure there are no wiring problems that could cause excessive noise.

rollo · « **Reply #14 on:** 27 Aug 2019, 07:24 pm »

Quote from: avta on 26 Aug 2019, 02:02 pm

If you have not done so already try plugging all your equipment into one power strip. That sometimes helps. Any strip will work for the purpose of clarifying things.

Correct. Do not put a band aide on it find out what causes hum and eliminate it. Try one outlet with any strip to ascertain the culprit. Then try all digital on one and analog on another outlet. Good luck trying.

charles