Nuforce STA200 issue. Rumble every couple minutes

Does it exhibit the problem with no input connected? Have you tried it with another source? Could be an issue with your preamp.

@dspringham i might have found the issue. 
 

it either doesn’t like my preamp or my subs connected to speaker terminals. 

I went straight from DAC to amp, controlling volume with my Innuos. And turned my REL subs off (they are connected directly to my speakers post along with speaker cables). I never had issues like this with my tube preamp and tube amps. 

gonna test with subs turned on next. Then test back to preamp with no subs. That should test all possibilities and tell me what the Nuforce likes/doesn’t like

In my opinion the STA200  is aa perfect match for a passive preamp. It is highly sensitive (350mV), very high gain unit. I own one. 

It did not work with a Joilda tube preamp I once used. A low gain  active SS pre may work.

I’ve had 3 over the years, though match could be difficult, never any problems...always worked well with passive pre, and for me a great match with Schiit Freya S preamp...and low efficiency speakers

Thanks @mesch 

I was just using it as a 3rd amp for when I don't want to burn my tubes 8hrs a day... so I don't really want to build another system around just this amp... it's very good. but with my current configuration is not a very good fit for it, 96db speakers... there's more hiss than I get from my tubes amps.... 

Great amp sound, but not a particular good fit for more all around setup. 

it can be a difficult amp...but great sound and incredible value in right system...

Yes, I agree it has a great sound. It is that the sensitivity and gain make it not a universal pairing. Likely why it became so highly discounted. Maybe a good fit for a vinyl system with lower output cartridge and phonostage.

I am using mine with a 

’volume control on a box’ preamp driven by a 2V output DAC. 

The STA200 is an incredible amp, given the " proper system " it is paired with, and of course, the $499 selling price. People are giving them away it seems. 

Yes, people are giving them away because the amp doesn't serve their system. I have been thinking of selling mine. 

Another possibility would be to pair it with a DAC with an analog volume control. 

Another issue is that it isn't meant for speakers that represent a difficult load to a speaker, providing the same power at 8ohms or 4 ohms( 80wpc). 

do you guys know of a amp with similar sound characteristics to the STA200 with much lower gain?

@kray, it was designed to work with a passive preamp. @Mesch, it is not the perfect amplifier ( point me in the direction of " the one ", please ). Knowing it’s limitations, I bought my 1st one, and based on how much I enjoyed it, I quickly sold off locally, several other amplifiers I had in my large amp collection ( Mc 2105, Son of Ampzilla, Bedini 150, Hafler 200, B&K ST202, and a few others that I enjoyed,  and had good reputations. These were all up to spec, and they all had upgraded, heavier gauge power cables hotwired into them ( not a joke, when I tell you they improved greatly from this tweak alone ). I bought 2 more, to vertically biamp a pair of Signet SL280ex....an awesome system. I still have the speakers, but sold the two of the STA200’s, because I was down to one system ( with my Lascalas ), and felt someone else should enjoy them. I will keep my original STA200, as it takes up no room, and for what it does, it is a keeper. My best, Always, MrD. Enjoy !

Thanks @mrdecibel appreciate the response. I totally get that :)

But for me it's 3rd in line amp, and I'm not going to build a whole system around it, so my tube preamp/amps are first and are staying. My tube pre is only 6db gain, but with that and my high efficiency speakers I can't live with this loud hiss coming from my speakers (which is silent with my tube gear)

It sounds wonderful, so I will move it along to someone that can enjoy it in the right setup, and find a SS amp I can use as a third option that integrates better into my system. 

I’ve found my STA200 works best with a Schiit Sys., a combination MrDecibel mentioned in a thread a while back.  I don’t think I’ll ever sell this amp.  It just sounds too good when paired appropriately.