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Studio Reference Headphone Amplifier
 Sparrow came from the need for a device, which you can "absolutely" trust. Based on most people's experience, unfortunately there are not too many devices on which you can always rely on. Rely on to operate always, in all conditions, no matter if it's a working day, a holiday, or the room temperature is -20°C... We needed such a device. So we decided to build one.... 
Sparrow just takes line-level signal and amplifies it to headphone. It adds nothing. No character. No color. It just lives on top of your rack, waiting for that moment when you cannot hear something on any other piece of gear. Then you plug it in. Sparrow is your personal debugger for even extremely expensive studio. Used for debugging studio equipment much more expensive than itself. We heard editing glitches on multi-million records. The ones that even the mastering engineers didn't. We also used it when searching for low-level hum and noise in other equipment...
Dejan Vuckovic
Sound Engineer
Studio Barba
Belgrade
Applications Recording Sparrow can be used in situations where the microphone positioning is crucial (binaural, purist recordings), in which the phase-aligment of microphones is essential. Also, in field recording situations, where you feel the need to have highest-possible quality monitoring, but due to other limitations it is impractical to use reference-monitoring speakers.
Editing Due to its technical characteristics and transparency, Sparrow makes it possible to detect editing glitches, hum, and low level noise before you move to the next phase of making a record. Always better than having to go back because somebody heard a glitch, and you're just about to finish your mix.
Mastering When creating the finishing fade ins and outs, it's always important to precisely hear if there are noises left at the end of the song, are there any dither artefacts, or any kind of microscopic details which could easily end up on a thousands of records. Sparrow can help. Specifications
| | Technology
| | | | | | | | Overall | Solid state | | | | | | | | | | | | Impedance | | | | | | | | Unbalanced in. | 50kΩ (unb.) | | | | | | Balanced in. | 2.5kΩ (bal.) | | | | | | Output (default1) | 10Ω | | | | | | | | | | | | Output power
| | | | | | | | Impedance | | | | | | | 32Ω | ~860mW
| | | | | | 150Ω | ~230mW
| | | | | | 600Ω | ~60mW
| | | | | | | | | | | | Output current
| | | | | | | | | 500mA max.
| | | | | | | | | | | | Output voltage
| | | | | | | | 2dB before clip | ~6Vrms
| | | | | | soft clip | ~7Vrms
| | | | | | | | | | | | Connectors
| | | | | | | | Balanced input | XLR
| | | | | | Unbalanced input | RCA
| | | | | | Headphones out | 1/4" standard
| | | | | | | | | | | | Power supply
| | | | | | | | External supply | 15Vac 1A
| | | | | | Consumption | 10Wmax
| | | | | | | | | | | | Dimensions
| | Inch
| mm
| | | | | Width | 5.528 | 140.4 | | | | | Height | 1.520 | 38.60 | | | | | Depth | 8.070 | 205.0 | | | | | | | | | | | Weight
| | lbs
| kg
| | | | | without power supply | 1.9 | 0.85 | | | | | with power supply | 3.2 | 1.40 | | | | | | | | |
1Output protection (10Ω) resistor may be removed, on customer request. Characteristics
Information for single tone test (@1kHz) Single tone,1KHz
| F=1kHz, Att=0dB
| SNR | THD
| | Add. conditions-> | In=+4dBu, Load=102Ω | 110dB | 0.00066% |
| | Freq. response linearity in dB | | Crosstalk vs. frequency in dB | | | |  | | 
| | | | Measuring conditions:
-balanced inputs
-0dB Attenuation
-+4dBu input level
-102Ω load | | Measuring conditions:
-balanced inputs
-0dB Attenuation
-+4dBu input level
-102Ω load | | | | THD, sep. harmonics in dB | | THD vs. frequency in % | | | |  | |  | | | | Measuring conditions:
-balanced inputs
-0dB Attenuation
-+4dBu input level
-102Ω load
-unweighted | | Measuring conditions:
-balanced inputs
-0dB Attenuation
-+4dBu input level
-102Ω load
-unweighted | | Technology
Internal Fully Balanced Design
Sparrow's XLR balanced inputs aren't converted to unbalanced with first amplifier stage (very common praxis in professional audio equipment). All blocks in signal chain are balanced, including the attenuator. This technology needs double component usage, but has the greater EMI/Noise immunity than any other design principle.
Multilayer PCBs
We use standard mixed signal technology for PCBs. Sparrow is fully analog in its working principle. We don't use any clocked digital chip in it. Sparrow actually has six-layer PCB. Balanced design (explained above) and multilayer PCB are two technologies used mostly to suppress noise and EMIs from other devices (Personal Computers, Radio Stations, etc.). Multilayer PCB raises cost of whole device.
Gold Plated PCBs
Because we solder Sparrows by hand; this is the only way to have PCB always ready for work. There is no corrosion that can complicate soldering process. Sparrow's PCBs have all the pads and all the copper regions, unhidden with solder lack, gold plated. Sparrow is soldered with Tin/Silver/Copper alloy, it's Pb-free.
Extremely Precise Resistors
We use 0.1% metal film resistors with temperature coefficient of about 10ppm. This already means that Sparrow sounds always the same in studio,... "-- in the sun, and in the snow -- forever". This also means that gains of your left and right channel are almost identical.
Rotary Switch Based Attenuator
We used small and cute Grayhill's 12 steps, rotary switch. We don't suppress audible "clicks", when you switch from one position to other, because that will degrade high frequency characteristics, and cause phase shift. Sparrow has -3dB frequency response of 4Hz-400kHz and in audible range (20Hz-20kHz) this means almost flat phase response. Gallery Outside view:
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Amplifiers 
