December 2005
Raysonic SP100
Integrated 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, including graphical
information displayed below, is the property of SoundStage! and Schneider
Publishing Inc. Reproduction in any format is not permitted.
 Measurements were made at 120V AC line voltage with both
channels driven and with volume control fully up unless otherwise noted.
 Input sensitivity for 1W output into 8 ohms: 177mV.
 Gain, output voltage divided by input voltage, volume at
maximum: 16.0X, 24.1dB.
 Output noise, 8ohm load, unbalanced input, 1kohm input
termination, volume control fully up (clockwise position, worst case): wideband 0.37mV,
77.7dBW; A weighted 0.15mV, 85.5dBW.
 Output noise, 8ohm load, unbalanced input, 1kohm input
termination, volume control fully down (counterclockwise position): wideband 0.23mV,
81.8dBW; A weighted 0.08mV, 91.0dBW.
 AC line current draw at idle: 1.77A.
 Output impedance at 50Hz: 0.77 ohms.
 This integrated amplifier does not invert polarity.
Power output with 1kHz test signal
 8ohm load at 1% THD: 40W
 8ohm load at 10% THD: 60W
 4ohm load at 1% THD: 28W
 4ohm load at 10% THD: 44W
General
The Raysonic SP100 is a mediumpower stereo pushpull tube
integrated amplifier utilizing one pair of EL34 output tubes in each channel. This
integrated amp has a digitally controlled volume control and selector switch ahead of the
power amplifier.
Chart 1 shows the frequency response of the amp with
varying loads. This amp has a nicely controlled highfrequency response with some
wayoutofband outputtransformer aberrations above 100kHz. The output impedance, as
judged by the closeness of spacing between the curves of open circuit, 8ohm, and 4ohm
loading over most of the audio range is somewhat lower than typical for tube power
amplifiers. The variation with the NHT dummy load in the audio range is about +/0.7dB. Of
academic interest with this design, the output impedance actually becomes 0 at 80kHz and
becomes negative between 80kHz to about 160kHz where it becomes positive again.
Chart 2 illustrates how total harmonic distortion plus
noise versus power varies for 1kHz and SMPTE IM test signals and amplifier output load. As
is usual for most tube power amplifiers, the power at the onset of clipping is greatest
for tap "matched" impedance, in this case, 8ohm loading on the 8ohm output.
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 low and high frequencies is admirably low in this design.
Damping factor versus frequency is shown in Chart 4 and is
amazingly constant over the whole audio range.
A spectrum of the harmonic distortion and noise residue of
a 10W 1kHz test signal is plotted in Chart 5. ACline harmonics are numerous but decrease
in magnitude as the harmonic number goes up. The 120Hz line harmonic does intermodulate
quite noticeably with the nulledout 1kHz signal fundamental frequency. Some further
intermodulation can be seen on the skirts of the second and thirdsignal harmonic also.
The decay of the amplitude of the signal harmonics is quite uniform and is judged to be
desirable in some quarters.
Chart 1
 Frequency Response of Output Voltage as a Function of Output Loading 
Red line: open circuit
Magenta 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 10W 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 
8ohm output loading
Cyan line: 30W
Blue line: 20W
Magenta line: 10W
Red line: 1W
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 8ohm load
