Nuforce STA200

With my current speakers at 89dB, it rarely ever gets even warm, and I can’t go beyond a quarter turn with my passive pre amp before it gets uncomfortably loud.  Not sure if that translates into having the headroom for a driver that’s 84dB.  I know that every 3dB increase in volume requires twice the power.  So this new driver at 84 dB could require nearly 4 times the power play at the same level.

Yes, one person who has never had a real presence on AG. I'm not saying the person is a troll, however, one must look at what is right in front of them. Even if the amp did "pop" it would not be the first time someone got a defective (assuming the cause was internal to the unit) component. Even the big boys gets returns due to defective units. My STA200 runs quite cool, however my speakers are rated at 101db. In fcat, I have had my amp on for hours upon hours playing at decent levels, no issues. 

You know, one person posted their amp had a problem, and that person never posted again when asked to.  Then an article came out that said the wattage at 8 and 4 ohms was the same and started some worry that this was a problem.  

I ran my amp for about 8 hours straight both days over the weekend.  My speakers are 85 db and nominal 6 ohms and the amp never got warm and has never been warm to the touch. At least with my amp there is no difference in temperature between on and off. 

Had my amp for about a year now, no issues, great sound.  Current speakers (diy) are 89 dB.  Looking at a new design where efficiency would be 84dB.  Be interested in hearing from anyone that’s paired this amp with lower efficiency speakers.

I have my STA200 paired with a Parasound Zpre2 and both have been left on for about a year+ virtually without being switched off, if so, then only briefly turned off then turned straight back on.
Is it scare mongering, or should I be worried about the STA200 going pop? I find the sound quality excellent. I actually bought two, the other is still in its box unopened. For the money $499 they are really nice sounding power amps. Don't know or care about the power rating, they sure do go loud when required. These findings are to my ears. 

The hiss with the Nuforce should be louder than the Sony due to higher than normal gain. Do you have a friend’s house you can take the amp to and try there? Also, light dimmers have caused noises with my systems in other homes. Even if the dimmer is not in same room. 

Hi japol, if I understand your post above you have a hum with both the nuforce and with your sony integrated.  So you are not sure if you have two amps with a problem or the problem lies elsewhere in your system.  You have already determined that your speaker wires are ok. 

I only have a couple of thoughts.  One is are you using shielded interconnects and if shielded you are sure they are functioning properly?  The other is that I have the TV cable box connected to my preamp and this resulted in a hum through my speakers.  I had to purchase a cable tv ground loop isolator which eliminated it. 

Hi Mr. D, jetter, and aberyclark, and everybody on here! So tonight I went ahead and did an experiment. I bought a grounding adapter to isolate (disconnect) the ground from the 3 prong plug from Lowe's. That did not eliminate the problem. I also tried plugging in the amp straight to the wall outlet, but still the same problem. So, I went ahead and used a different speaker wire... problem still there. Then, I tried using my Sony TA-F500es just to see if it produced similar hum/hiss... they're still present but it is more quiet compared to the nuforce. Now, I'm not sure what's wrong with my system. 

I also tried connecting my nuforce to my NHT floorstanders and the noise is present, only louder. 

All these tests were with the sys connected to the nuforce, except the test with the Sony integrated. The hum is isolated to the mid-range driver and the hiss (sounds less of a hiss and sounds more like electricity buzzing) is isolated to the tweeter. I tried recording the noises on my phone but it is difficult to be discerned from ambient noise. 

I feel like I can live with the hum and hiss/buzz, but I also wouldn't want to be keeping a defective amp. Tough call.

Thanks again, guys!

The Nuforce should be dead quiet with Just the sys. When I had my RP-5 in for warranty work, I used my Pro-Ject s2 Pre Dac as a preamp. Dead quiet. I mean dead quiet!!! My Zu's are rated at 101 db. Slight tube hiss is normal (ear against speaker) for the rp-5. The Nuforce has such high gain, along with my efficient speakers, I needed the SYS between the pre and amp to pull things back. 

Hey Jetter, Japol and all you other audio gents. Japol, if your STA is causing a hiss through your speakers, without anything connected to the amp's inputs, I would say this is not normal. Either the amp is defective, and / or, the amp, or the speaker wire, is picking up stray electrical noises from somewhere ( see my earlier post ). If you like the amp, I might suggest you contact the seller and arrange for a replacement. If the replacement does the same as the 1st, I would assume the amp does not work in your environment ( again, the sensitivity and gain situations ). Keep in mind, things such as under cabinet kitchen lights, ceiling fans with remotes, florescent bulbs, and many other things, can be picked up by amplifiers, which could be the situation. Did you try your other set of speakers ? Keep us posted. Always, and Enjoy ! MrD.

Hi Japol, I hope Mr. D posts here quick to help you out as I don’t have enough experience with gain issues, so these are just random thoughts until the voice of experience chimes in. My first thought would be that to determine if you have a gain issue you should just hook up the Sys with the amp, and the amp to your speakers and with no sources connected see if there is a "hiss" caused by too much gain or the if there is still the "high pitched noise". If not, I would think, but may be corrected, that the noise issue is being generated by your sources, wiring or a ground loop.

If you determine that in fact these noises are the result of the amp I would not think twice of exchanging it for another one or if you choose a refund. If it was a noise floor thing I would think the "hiss" would be the same level from both speakers, and no matter what there should be no "high pitched noise". But again, wait for Mr. D.

Hi Mr. D,

I apologize for not getting back to y'all earlier. I got caught up with some other stuff and just decided to order a Schiit SYS to see if that fixed the problem.

I was using a cheap FX Audio Tube pre-amp/buffer with the upgraded GE tubes. The tubes definitely produced a significant amount of noise once the volume knob hits the 9 o'clock mark, and the noise only increases from there on. I received my SYS yesterday and tried it out last night. With my chromecast audio and NEC cd player connected on the SYS, the noise on the speakers was cut down in maybe half. There is still a very faint shhh noise on the left speaker when I put my ear right next to the drivers, while the right speaker has a faint high pitched noise on top of the shhh noise. I'm only a beginner in audio stuff, so I would assume this would be what you call the noise floor of the amp, right? Now with the SYS, music is more detailed and has a very slightly wider soundstage compared to the FX Audio tube preamp. I tried connecting the chromecast audio to the FX Audio then routed the sound to the SYS before going into the amp, and the sound warmed up a tiny bit with a very minimal sacrifice in soundstage. So, based on the different combinations that I've done so far, the noise that I'm hearing is coming from, or caused by, the amp itself.

Last week, before ordering the SYS, I tried the amp plus FX Audio tube preamp on my daily system with NHT speakers. There was still that shhh noise and a slight high pitched noise (I don't exactly know the frequency of the noises). Although the noises that I'm hearing on my NHT's with the amp are similar to the noises that I'm hearing from my Pioneer stereo receivers and vintage integrated amps. I guess the noise floor is normal with such a high gain amp. Kindly correct me if I'm wrong.

Based on last night's listening session, I am happy with the amp. I will give it another go tonight to see if my thoughts change. Before getting this NuForce amp I had a Linn LK140 that I bought used, but decided to return it to seller because one channel was buzzing and when I opened it up there were signs of damage, repair, and a missing capacitor. That amp was quiet though, aside from the buzzing on one channel. My other amp option is to get another used Linn amp and hope I'd get lucky with a good example.

Thanks for your help, Mr. D, and to everyone on this forum! I really appreciate it.

Checking in. Japol, how are things going ? Hello to everyone else. Enjoy  MrD.

Hi again all. Japol, if this shhhh sound is audible from your listening chair, again without anything connected to the amp’s input, through your speakers, I would not worry about it, although I understand the concern. Some of my other amps, specifically high wattage amps ( 200 + wpc ), do have a hiss, but not audible from my listening seat, under the same conditions. My experience with, not only high gain audio equipment, but " wide bandwidth " equipment ( Spectral as a good example ) might be prone to spurious noises from things such as digital gear, certain lights / switches, some kitchen appliances ( refrigerators and microwaves ) and even dirty electrical and nearby wires, might create this shhhh you are hearing. Do you have another amp you can try this with ( other than the STA200 ) ? Are you using the supplied power cord with the STA ? Try plugging the amp into another outlet, even if it means using a power strip, or extension cord, and see ( hear, lol ) if the Shhhh gets lower. Your speaker cable can also be acting as an antenna. Keep the speaker cables away from any electrical cables, and if you cannot, do not run them parallel with one another, if possible. Don’t give up, we are all here to help. Enjoy ! MrD.

Japol316

What Pre amp are you using? You could always hook up a DVD or CD payer directly (do not play anything...it could damage speakers) and see if the hiss is there. I had a hiss issue but it was due to my RP-5 tube pre output. I solved with a Schitt pasive pre between the rp-5 and my STA200. The amp was dead quiet with 2 different solid state preamps

Hi japol, waiting for Mr. D to chime in.  

But when you mention having a noise without any input connected.  Do you mean the noise is coming from the amp when there is no preamp or speakers connected?  If that is the case I would think it is defective and send it back and ask for a replacement.  But again, definitely wait for Mr. D.

Hi Mr. D,

My amp, without any input connected, produces somewhat of a white noise (shhh sound). Is this normal or do I have a defective amp? I will try connecting my amp to a set of floorstander NHT’s at 8 ohm tonight.

Thanks!

With either of my STA 200s connected to my Lascalas, at 104 db efficiency ( no input connected to amps ), they are dead quiet, as I hear no hiss or hum ( of course, the amps are on ). I did have issues with hum through a few preamps I owned ( own ), and now own a top model Luminous Axiom Walker unit, without problems. Unless the amp is defective in some way, I believe it is simply amplifying any  noise preceding it. Enjoy ! MrD. At this time I am using the amp pair to vertically biamp ( passively ) Signet SL 280ex speakers I have set up in another room, and the system is excellent, without any hiss or hum, using a DoukAudio passive preamp, hifi version, which I have found to be cleaner than the Schiit sys ( $40. or so from the Bay ). Currently rotating amps for the purpose of selling many of them. Enjoy ! MrD.

Hi mesch, not to worry, you don’t come off as faulting the amp at all. The way I look at it, whatever faults it has, it doesn't owe me anything. 

Again, I want to make it clear that I am not faulting this amp for it's quality. I like this amp!  

Jl35, yes I agree with both your points, re power output and preamp use. My thing is that I buy an amp for the long haul, and using one in a way that it is not designed for (underpowered for the load presented) is not conducive toward that end.

Jetter, I have not yet used the STA200 with my all tube Jolida preamp, as that was not the intent when I bought it. The Jolida has a gain of 20dB. I expect that I would find that I am using it's volume control at very low settings with this amp. Not sure about the hiss issue. I will give this a try and get back on that.

I did not have the too high a gain preamp/amp mismatch with my tube preamp.  While we have certainly discussed this problem here and read about it, I am curious if anyone has actually experienced the gain issue and if so:

1. Did the problem create an auditory hiss? or if no hiss,
2.  Was the problem not being able to turn the volume control up high enough to adequately use the preamp's sweet spot?

Thanks in advance

Luminous Audio Axiom ii passive preamp works great with this amp.  I use one, and I think another poster here does as well.  Dead quiet even with the STA-200’s high gain.

I think it's the preamp match which is difficult...

smallish room, about 12x14...I think the amp is fine into 4 or 8 ohms, as long as it is looked at as a fairly low power amp, which is what it was designed as...many amps put out same or similar power into 4 or 8 ohms, such as McIntosh...

Jl35, that is good to know. The speakers I own are rated higher than that, however do drop below 4ohms in the bass region. Phase angle at these frequencies is benign however. In what size room is your system?

I've had no trouble with 4 ohm speakers...currently Dynaudio Focus 220 mkll...

My STA200 is also dead quiet. Have used it with two speakers of 6-8ohms, 87dB for limited hours as it is new  Might be a compatibility problem with your preamp. Does hiss get louder as you turn up volume? Usually a gain driven hiss problem becomes more a concern with highly sensitive speakers. That said, I would not choose this amp for use with a speaker having an average load of 4ohms (see discussion above). 

My STA200 was/is dead quiet.  I am told some systems could have a gain issue which from what I understand means that if you pair the STA200 which has a high gain with a preamp having high gain you can end up with the hiss you mention.  One fix for this is a Schitt Sys passive for $49 between the amp and preamp.  Its set once and forgotten.  Unfortunately it does not sound like you have time to work through all of this, and really may just have a "bad" amp and not an gain issue.  If I have this wrong someone please jump in and correct me.

Hey guys! I'm new on here and signed up just for the STA200. I've been lurking for a few months now and decided to get the STA200 based on everyone's amazing feedback on the amp. My amp is paired to Linn Kaber's (4 ohms, 87dB), and there is an audible hiss (without signal) when I bring my ears about a foot from the speakers. Is this normal for the amp? I'm still within the return/replace period of Amazon. Thanks!

Mike, your making me laugh.  In the late 70's I answered a classified ad and purchased a used Sansui receiver and Cerwin Vega speakers, just for a back patio room. I just came to expect compliments on the sound of that low $ stereo, and never again on any other set-up, including some plus $20K systems.  I eventually gave it to a friend.

George, Yes in the old days (1970) I had a Sansui AU 555 integrated at the heart of my system. 30wpc. Currently I use a BEL 1001MK5. 50wpc. Course the BEL is in a different league entirely in its ability to drive speakers. Mike

Holding over a hundred amplifiers qualifies you as a collector (of decibels) lol. Would you kindly rank the STA 200 (or range, say within +-5)? Thanks!

Glad you happened by mrd, best to you and yours.  George

The poster of the blown amp might be a competitor ( or owns a competitors amp ) at or near the $499 price. You never know. I do know a few individuals who returned the STA 200 because it did not work in their system, but the majority of people who private message me are very happy, as some others here. BTW, it is a great little amp when used properly. However, I am currently rotating amps ( again ), as I will be cleaning out another closet full of amplifiers. When this started a few years ago, I had over 100 amplifiers in my collection. Just saying. Happy New Year to all. Enjoy ! MrD.

I have been on A'gon for a whole lot of years.  You will note that the poster with the blown amp has exactly one post on A'gon.  I have found throughout the years that people who post once or twice with something negative often have some beef somewhere down the line.  Not saying this is the case here about the poster, but I now think the risk of blowing an amp is pretty much the same as the risk of blowing any other amp lower powered amp.  By the way, in the old days SS amps often had much lower watts at all ohms than this unit.

Jetter, Thanks. I was not familiar with the Copland pre. Looks to be a fine unit.  

Aberyclark, Yes we need more info re the blown amp. So far no response to your previous post asking for clarification.

My speakers are so easy to drive (101db efficiency), a clock radio hooked to them will fill the room. As far as the amp blowing, there are so many variables it would be hard to figure out what happened with so little info. This is the first time of hearing of such happening with the STA200. Hopefully, the person purchased new with a reputable dealer

Thanks mesch for your clarification, truly appreciated.  From your earlier post I got the mistaken impression that you were saying that you knew of an identified amplifier design weakness that could result in possible serious amp failure.  I don't think this any longer.  These things do happen though, for example, I have a pair of Goertz alpha core speaker cables that without the use of zobel networks have resulted in some amps going into oscillation with not pretty results.

So blue skies on this end.

Well, I might just be overly cautious. I need to spend more time with my STA200. I certainly am happy with it's sonics and it seems compatible with my PS Audio Digital Link III via the SYS. In addition to the speakers I mentioned earlier, I also have a pair of Dali Zensor 1s which don't drop lower that 5ohms and are 88dB sensitive. I will try the amp with these as well. 

I purchased this amp for use with a passive pre in an attempt to build a low cost high quality system.  Though I don't believe specs tell the whole story, I do believe there are some that certainly help to insure electronic compatibility between components when putting together a system. I have learned much from this forum toward that end. I remain with much more to learn.

Happy New Year to all!

Mesch, I have two pairs of nominal 6 ohm speakers, both probably in the 85db range.  One is a 2&1/2 way with two 7 1/2" or so scanspeak mid/woofers.  I can run the unit all day, with the STA200, being fed by this tube preamp, http://www.divertech.com/coplandcta305.html and the amp never is even warm to the touch.  I have a Schitt sys, but honestly it is set to not reduce the output to the amp at all as it is not needed.  In other words, the volume control can be turned up far enough (high enough) from the zero position with the sys in or out of the system to not worry about the preamp volume control not being high enough to function fully.  I don't understand the impedance matching thing to know if I happen to have a more compatible preamp than normal or what.

Kalali, if my understanding is correct, because the voltage required to reach max output is low, sensitivity is high.  Given the output voltage of most sources today, the sensitivity and gain of this amp would call for judicious use of the volume control of any preamp. I have not yet approached 11 o-clock with my SYS passive.

Jetter, not knowing any more about the specifics of aysancorluham's situation it is hard to guess at why his amp 'blew up'. I would be cautious about using this amp with any speaker not known to be easily driven by an amplifier. To me that mean a speaker that doesn't dip below 6 ohms across the frequency range, and having a sensitivity of 87dB or higher depending on the size of the room in which the system is to be used.  

Finding such a speaker, one I feel fits into a budget commensurate to a $500 amplifier and $50 passive, is the difficult part. I am still looking.  

"At 51K ohms input impedance and the high input sensitivity a good candidate for a passive..."

The 0.45V input sensitivity is not much of an issue, its actually relatively low, but the 35dB gain is more of a concern. A passive with a low output impedance may work depending on the output voltage of the source.

Here's a bump to mesch, or anyone else.  We have a first time poster declaring his amp blew up, and mesch stating he will use his amp with caution.  I am not savvy enough to understand or otherwise translate from above what "the degree of attenuation becomes too low overdriving the input stage" means or how it creates a situation that can be hazardous to the amplifier.  Since it has been brought up as a potential danger, lets hear what the danger is?  There are not that many posts on A'gon where using an amplifier for its stated purpose can create a potentially dangerous situation, that perhaps an amplifier has been built without normal protections built in, since this has now been brought up, lets hear the background behind it and potential danger.  Thanks in advance.

mesch, in layman’s terms, please explain exactly what are you being cautious about? Are you worried about the amp being driven into oscillation?  How does the fact that the amp produces the same power at 8 and 4 amps create a potential problem? If neither of these are the concern, what is the worry? Thanks in advance.

This amp produces no more power into 4 ohms than into 8 ohms.
Sensitivity is 0.45V for full output.
Gain is 35dB.

Very sensitive to source voltage and speaker load. At 51K ohms input impedance and the high input sensitivity a good candidate for a passive. Maybe try to set a stop on the passive pre so that volume can't be turned such that the degree of attenuation becomes too low overdriving the input stage. 

I will be using my STA200 with caution!

aysancorluhan,, I already have the STA200, and the truth is worrying about it blowing up is the last thing I am doing.  I have not popped the hood to look myself, but it sounds like you are saying it is not fuse protected, which seems unusual.
 
While I am not currently thinking about new hard to drive speakers, I was really wanting someone to provide their input (thank you jl35) regarding the sound quality differences between the STA200 and a Parasound A21.  For example, does one image better than the other, better separation of instruments, anything else at all you can relate.

Out of warranty?

My STA200 blew up and cannot be repaired. Stay away at any price.

I'm so sorry to hear this. I have one and asking for my personal info:

1.Just blew with normal use I assume?

2. Did it just not turn on? Or did it actually pop and go dead?

3. was it after the amp was on a while or when you first turned it on?

4. Where did you purchase?