|
Here are the measured performance specifications
of the prototype "RA-100" Vacuum-tube Reference Amplifier.
Voltages are in RMS unless indicated otherwise.
The output tubes used for the measurements were un-matched,
inexpensive Chinese 6L6GC's, testing done after a burn-in of approx. 100 hours. The THD measurements were repeated October, 2001 using a matched set of premium Tesla 6L6GC's, for comparison. |
| Physical size:
(not including enclosure) |
| Dimensions: | 483 mm (19") W x 178 mm (7") H x 280 mm (11") D |
| Weight: | 16 kg. (35 lb.) |
| Maximum Power Output: |
| Test Conditions:
Input to CD/Aux/Tape inputs, Test Freq. = 1kHz,
Input signal = 1V sine wave, Tone controls = bypassed, Vol. = max., Finals Grid Bias = -72V, "Clean" mode, Supply = 120 VAC. |
| Impedance | Each Channel (singly) | Both Channels (together) |
| 4 ohms | 50 W RMS | 100 W (short-term) 85 W (cont.) |
| 8 ohms (design centre) | 54 W RMS | 108 W (short-term) 90 W (cont.) |
| 16 ohms | 60 W RMS | 120 W (short-term) 100 W (cont.) |
| Frequency Response: |
| Test Conditions:
CD/Aux/Tape inputs, Input = 0.1 V sine wave,
Tone controls = bypassed, Volume = maximum, Mode = "Clean" Finals Grid Bias = -72V, no inline filtering at FX loops. |
| Low 3 dB corner | 7 Hertz |
| Flat +/- 0.5 dB | 12 Hz - 25 kHz |
| High 3 dB corner | 34 kHz |
| Power Consumption: |
| Test Conditions:
Input to CD/Aux/Tape inputs, Test Freq. = 1kHz,
Input = 1V sine wave, Tone controls = bypassed, Volume = max., output load = 8 ohms resistive, Supply Voltage = 120 VAC. Phase factor not considered. |
| Condition: | Bias = -80V | Bias = -72V | Bias = -60V |
| Standby: | - - - - | 138 V-A | - - - - |
| Quiescent: | 245 V-A | 286 V-A | 375 V-A |
| Full Power: | 456 V-A | 480 V-A | 518 V-A |
| Channel Separation: |
| Test Conditions: As above. 54 Watts output from left channel. |
| 37 dB typical |
| Sensitivity: |
|
Definition: Continuous sine-wave signal (volts RMS) required
for full output at maximum volume setting. Test Conditions: As above, test frequency = 1000 Hz. |
| Input: | Volts RMS | Voltage gain | Freq. Response |
| CD/Aux/Tape | 1.00 V | 26 dBv | as above |
| Mag. Phono: (at 1000 Hz.) | 12 mV | 65 dBv | per RIAA |
| Mic/Line, Min. gain | 640 mV | 30 dBv | as above |
| Mic/Line, Max. gain | 4.4 mV | 73 dBv | 3dB down at 16 kHz. |
| Hum and Noise: |
|
Definition: RMS power and "Equivalent Input Voltage"
of total hum and noise (unweighted), average of both channels. dB equivalents relative to full output power (54 Watts) Test Conditions: As above, no shielded enclosure, inputs open. |
| Input: | Volume = min. | Volume = max. | Equiv. Input |
| CD/Aux/Tape Inputs: | 3 µW (-72 dB) |
435 µW (-51 dB) |
2.9 mV |
| Mag. Phono Input: | 3 µW (-72 dB) |
903 µW (-48 dB) |
50 µV |
| Tone Control Range: |
|
Test Conditions:
Volume = 50%, Input = CD, adjusted for 1 W out
with all tone controls centred. Test frequencies = peak response. |
| Control: | Test Freq: | Minimum: | Maximum: |
| Bass | 30 Hz. | -14.6 dB | +15.4 dB |
| Midrange | 600 Hz. | -11.4 dB | +11.5 dB |
| Treble | 4 kHz. | -12.3 dB | +8.25 dB |
| Harmonic Distortion:
Re-done Jan. 2001 to correct errors in methodology |
|
Test Conditions:
Input = Mic/Line @ 50% gain, volume set for 12 W output, tone controls bypassed. Test freq. = 1000 Hz. Output tubes: unbranded Chinese 6L6GC |
|
| Most significant term is 3rd harmonic, at -37 dB ("classic")
THD (by voltage) [classic] = 1.49% [clean] = 0.96% |
|
Test Conditions:
Input = Mic/Line @ 50% gain, volume set for 54 W output, tone controls bypassed. Test freq. = 1000 Hz. Output tubes: unbranded Chinese 6L6GC |
|
| Most significant term is 3rd harmonic, at -26 dB ("classic")
or -32 dB ("clean"). THD (by voltage) [classic] = 4.51% [clean] = 2.88% |
|
Test Conditions:
Input = Mic/Line @ 50% gain, volume set for specified output (54, 12 watts) Tone controls bypassed, "clean" mode. Test freq. = 1000 Hz. Output tubes: new, matched Tesla/JJ 6L6GC |
|
| Most significant term is 3rd harmonic, at -30 dB (full 54 W output)
or -40 dB (at 12 W output). THD (by voltage) [54 Watt] = 2.38% [12 Watt] = 0.76% |
| Intermodulation Distortion:
Re-done Jan. 2001 to correct errors in methodology |
|
Test Conditions:
Input = Mic/Line @ 50% gain, volume set for 54 W output, tone controls bypassed, Clean mode. Test freq. = 100, 3000 Hz. (equal amplitudes) Output tubes: unbranded Chinese 6L6GC |
|
| This measurement is in some ways a superior measurement of amplifier distortion, as it demonstrates the amount of "mixing" that occurs due to non-linearity. This design exhibits very low IMD in both "clean" and "classic" modes, presumbably thanks at least in part to the accurate differential phase inverter. |
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