Nuforce STA200

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.

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.

"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.

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.  

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.