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The buffer is a single-channel (mono) buffer, with the following features:
- Differential (balanced, XLR) input, which can easily be configured for single-ended (unbalanced, RCA) operation.
- Fully differential output even when used with a single-ended source.
- Common-mode feedback ensures zero common-mode output voltage to avoid power supply bus pumping.
- Jumper-selectable gain: 11.6 dB, 13.0 dB, and 13.2 dB for a total amplifier gain of 26.0 dB when used with the Purifi Class D modules.
- Gain can be further customized by adding a resistor (1206 size SMD and leaded/PTH supported) or set to unity gain (0 dB).
- Plug-and-play connection with Hypex SMPS1200 power supply.
- Four ultra low-noise voltage regulators power the analog and digital circuits of the Buffer and the amplifier module. Optionally, you can add the Hypex HPR/HNR regulators.
- Speaker output is provided on 6.3 × 0.81 mm quick-connect spades and a terminal block accepting up to AWG 10 (5.2 mm2) in size.
In addition, the following options are provided for advanced users:
- By adding a resistor and a 7-pin connector, the amplifier module can be operated in software mode. See the relevant amplifier module data sheet for details.
- The buffer can be disabled by removing two resistors. A 3-pin connector footprint provides direct access to the input of the amplifier module.
The Universal Purifi Input Buffer circuit board is fully assembled, RoHS compliant, and is designed and manufactured in Canada.
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The full specifications for the Universal Purifi Input Buffer are tabulated below.
| Parameter |
Value |
Notes |
Quiescent Power Supply Current
|
20 mA
27 mA |
Nominal
Maximum |
Maximum Power Supply Current
|
47 mA |
Zload = 1.5 kΩ, +25 dBu |
| THD |
-140 dBc
(0.00001 %) |
1 kHz, Vin = 2.0 V RMS |
| THD |
-130 dBc
(0.00003 %) |
20 kHz, Vin = 2.0 V RMS |
| THD+N |
< -120 dB
(< 0.0001 %) |
1 kHz, Vin = 2.0 V RMS |
| THD+N |
< -120 dB
(< 0.0001 %) |
1 kHz, Vout = 9.6 V RMS |
| IMD: SMPTE 60 Hz + 7 kHz @ 4:1 |
-112 dB
|
Vin = 2.0 V RMS
|
| IMD: DFD 18 kHz + 19 kHz @ 1:1 |
-122 dB
|
Vin = 2.0 V RMS
|
| Multi-Tone IMD Residual |
< -148 dB Ref.: 7.6 V RMS |
AP 32-tone, Vin = 2.0 V RMS
|
| Gain |
0 dB (1.00×)
11.6 dB (3.80×)
13.0 dB (4.47×)
13.2 dB (4.57×) |
Can be further customized by resistor option. |
| Gain Flatness |
±0.007 dB |
20 Hz - 20 kHz |
| Bandwidth |
DC – 900 kHz |
100 mV RMS, -3 dB |
| Slew Rate |
±21 V/µs |
Fully symmetric
|
| Common-Mode Rejection Ratio (CMRR) |
≥ 80 dB
|
20 Hz - 20 kHz, typical
|
| Total Integrated Noise and Residual Mains Hum |
2.5 µV RMS (11.6 dB)
1.5 µV RMS (0 dB)
|
20 Hz - 20 kHz, A-weighted |
| Total Integrated Noise and Residual Mains Hum |
3.1 µV RMS (11.6 dB)
1.9 µV RMS (0 dB)
|
20 Hz - 20 kHz, Unweighted |
| Dynamic Range (AES17) |
132 dB |
Vin = 8 V RMS |
| Input Impedance |
48 kΩ |
|
| Module dimensions and weight |
64 × 84 × 28 mm
45 g
|
(W × D × H)
|
All parameters are measured at an auxiliary power supply voltage of ±20 V, 1.5 kΩ differential load impedance, differential input, and 11.6 dB gain unless otherwise noted.
The specifications were measured on the prototype and should be considered the typical performonce the Universal Purifi Input Buffer. The specifications should not be considered a guarantee and may be changed at any time without notice.
Sound Quality
I designed the Universal Purifi Input Buffer to be sonically transparent and firmly believe I have achieved that goal. I generally prefer precise amplifiers as they render the source material naturally, without any colouration, and offer a spacious and realistic sound stage. This aligns well with the design philosophy of Purifi and Hypex as well.
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A simplified block diagram of the Universal Purifi Input Buffer is shown below.
