March 2004
Threshold Audio
S/5000e Stereo Amplifier: Measurements
All amplifier measurements are performed
independently by BHK Labs. Please click to learn
more about how we test amplifiers there. All measurement data and graphical
information displayed below are the property of SoundStage! and Schneider
Publishing Inc. Reproduction in any format is not permitted.
 Measurements were made with 120V AC line voltage.
 Power output and distortion plotted with both channels
driven.
 Gain: 24.8x, 27.9dB.
 Output noise, 8ohm load, unbalanced input, 1kohm input
termination: wideband 0.260mV, 80.7dBW; A weighted 0.129mV, 86.8dBW.
 Output noise, 8ohm load, balanced input, 600ohm input
termination: wideband 0.198mV, 83.1dBW; A weighted 0.100mV, 89.0dBW.
 AC line current draw at idle (warmed up): 1.4A.
 Output impedance at 50Hz: 0.0085 ohms.
 This amplifier does not invert polarity.
Power output with 1kHz test signal
 8ohm load at 1% THD: 300W
 4ohm load at 1% THD: 520W
General
The Threshold S/5000e is a highpower solidstate design
with extremely low output impedance and a relatively high outputstage idling current. The
idling current is quite stable with increasing temperature as the amp warms up.
Furthermore, and most importantly, the idling current stays stable when the amp is heated
up under higherpower conditions.
Chart 1 shows the frequency response of the amp with
varying loads. As can be seen, the output impedance, as judged by the closeness of spacing
between the curves of open circuit, 8ohm and 4ohm loading, is very low. In the case of
the S/5000e, this variation with the NHT dummy load would be about a negligible +/0.01dB.
Chart 2 illustrates how total harmonic distortion plus noise versus power varies for 1kHz
and SMPTE IM test signals and amplifier output load. As can be seen, attainable power is
greater for the 4ohm load, as is usual for most power amplifiers. Total harmonic
distortion plus noise as a function of frequency at several different power levels is
plotted in Chart 3. Amount of rise in distortion at high frequencies is relatively low 
a desirable characteristic. Damping factor versus frequency is shown in Chart 4. This is
one of the lowest output impedance amplifiers tested at BHK labs. A spectrum of the
harmonic distortion and noise residue is plotted in Chart 5. As seems to be the case with
many amplifiers measured, this one has a rich series of AC line hum harmonics with some
sidebands of these harmonics about the nulled fundamental frequency and the signal
harmonics.
Chart 1
 Frequency Response of Output Voltage as a Function of Output Loading 
Magenta line: open circuit
Red line: 8ohm load
Blue line: 4ohm load
Cyan line = NHT dummyspeaker load
Chart 2  Distortion as a Function
of Power Output and Output Loading 
(line up at 100W to determine lines)
Top line: 4ohm SMPTE IM
Second line: 8ohm SMPTE IM
Third line: 4ohm THD+N
Bottom line: 8ohm THD+N
Chart 3  Distortion
as a Function of Power Output and Frequency 
4ohm output loading
Cyan line: 450W
Blue line: 120W
Magenta line: 20W
Red line: 2W
Chart 4  Damping Factor
as a Function of Frequency 
Damping factor = output impedance divided into 8
Chart 5  Distortion and
Noise Spectrum 
1kHz signal at 10W into a 4ohm load
