Threshold

This is the popular power amp by Threshold.

Threshold S/500 Stereo Power Amplifier 

Manufacturer's Specifications: 

Rated Output Power : 250 watts per channel. Both channels driven at no more than 0.1% distortion into 8 Ohms resistive or reactive impedance. 
Bandwidth Response : Halfpower (-3 dB) points at 7 Hz and 100 kHz. 
Slew Rate : 50 volts per microsecond 
Output Transistors : 20 transistors per channel. Transistors are ultra-high speed 200 volt 20 ampere rated power devices. 
Output Current : 12 amperes continuous, 100 peak amperes per channel. All continuous ratings are fuse governed. 
Power Supply : 1,000 watt toroidal transformer, 120,000 microFarads storage capacitance. 
Input Impedance : 75,000 Ohms. 
Output Impedance : Less than 0.1 Ohm 20 Hz through 20 kHz 
Gain Factor : +26.6 dB 
Noise : No greater than -100 Db, unweighted, referenced to 
rated output. 
Permissible Load : Operation is allowed into any load within limits 
imposed by power supply and rail fusing and/or 
thermal protection. 
Dimensions : 17 1/8" deep, 8 3/4" high, 19" wide. 
Weight : 78 1/2 pounds. 

 
The input connectors are gold plated with a multiple contact point inner conductor. This is supported in a machined teflon insulator. The construction quality of the circuit boards is superb! All the circuit boards are military-grade, glass-epoxy with gold over copper over nickel plated traces. This is an amp that you really have to see to believe. The power transformer is huge as are the storage caps. The quality of the wiring and soldering is very impressive. There are a number of high end products that just are not built as well, or sound as good as I found out. 

According to Threshold, all products were given a three day testing period at the factory. This consists of each amplifier being required to pass a dead short power test both before and after the three days of power "burn-in" consisting of self-oscillation into a two Ohm load. That was a SERIOUS burn in. 

Where I was surprised was in the vast difference I heard in comparing the sound of the Threshold to that of my Adcom GFA-555. The VMPS are happiest when there is a lot of power in reserve but it certainly can't be denied that the Adcom, is more that adequate from a pure power standpoint. Up to the point where I had substituted the Threshold into the system I would have considered them difficult to surpass the Adcom. To put it mildly, the Threshold simply blew it away!  

Great condition