hybrid stereo Pro-Ject Stereo Box RS Stereo Integrated Amplifier

hybrid stereo Pro-Ject Stereo Box RS Stereo Integrated AmplifierGeneral: The Pro Ject Stereo Box RS is a small dual mono integrated amplifier that is built to the high standards you've come to expect from Pro Ject Box systems. It's perfect for a desk setup, or even a larger system thanks to its formidable 2 x 80w of power in such a small package. Five unbalanced RCA inputs and 1 balanced XLR input provide versatile connectivity options for connecting to just about anything. Despite it looking like a solid state

General:
The Pro-Ject Stereo Box RS is a small dual mono integrated amplifier that is built to the high-standards you've come to expect from Pro-Ject Box systems. 

It's  perfect for a desk setup, or even a larger system thanks to its formidable 2 x 80w of power in such a small package.

Five unbalanced RCA inputs and 1 balanced XLR input provide versatile connectivity options for connecting to just about anything.

Despite it looking like a solid state amplifier, It actually utilizes tube buffers. Two E88CC (6922) tubes located inside add warmth and richness to anything it plays. We loved the sound quality of this amplifier during testing.

Below the Stereo Box RS in our photos is the matching Pro-Jectlinear power supply "Power Box RS". This power supply is also finished equally in brushed aluminum, and can supply steady power for two separate RS components (extra cable included).

Included with both units are their original boxes, power cords, and reprinted manual copies.

SkyFi Cosmetic Notes:
Almost no signs of wear only a few light scratches.

Ownership:
Single Owner

Connections:
RCA, XLR, IEC power, 5 way binding post.

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
8/10 = Very Good. Excellent front faceplate, one minor flaw on chassis side or top. See our detailed rating description here.

Working Condition:
Working perfectly and tested in our lab and listening room.

Included:
Unit, remote, and power cord.

Packing:
Original Manufacturers Packing

Specs:
Stereo-Box:
- Tubes: 2 x ECC88 (6922)
- Power output: 2 x 80W/120W at 8 ohms/4 ohms (both channels driven)
- Frequency response: 20Hz – 50kHz (-1,5dB/-3dB)
- Noise floor: 90dB (A weighted)
- THD: 0,1% (100W)
- Gain: 31dB
- Pre out (variable): RCA/phono sockets, gain 12db
- Subwoofer out: RCA/phono socket, gain 18dB
- Record out (fixed): RCA/phono sockets, gain 0dB (fixed output signal)
- Line-level inputs: 4 pair RCA/phono sockets and 1 pair XLR sockets
- Input impedance: 50kohms for RCA inputs 1-5, 20kohms XLR input 6
- Wiring XLR sockets: 1 ground, 2 “hot” and 3 “cold”
- Speaker connectors: 4mm banana plugs, spades connectors or naked wire
- Outboard power supply: ±48V/2,5A DC, suitable for your country’s mains supply
- Power consumption: 2,5A DC, <1W in standby
- Replacement battery remote control: 1 x CR2032 / 3V or 1 x CR2025 / 3V

Power Box: 
- Input voltage: AC 230V/50Hz IEC C15 connector (120V/60Hz US version)
- Output voltage: two outputs by 2 x 48V / 2.5A DC each
- Filtration capacity: 40.000 μF
- Output voltage ripple: 7mV peak to peak

Dimensions:
Stereo Box: 21 × 20.6 × 7.2 cm / Power Box: 19.5 × 20.1 × 7.2 cm /

Weight:
Stereo Box: 5.84 lbs / Power Box: 10.58 lbs.

Link to Stereo Box RS Manual:
Click Here

Link to Power Box RS Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Kimber Kable - Speaker Cables - Better

Kimber Kable - Power Cords - Better

Kimber Kable - Coaxial Digital Interconnect

Kimber Kable - Optical Digital Interconnect

Kimber Kable - Select Series Reference USB Cable

Testing Process:
We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

If the device has the ability to decouple the preamplifier from the power amplifier, we remove the jumpers and independently test each section. If the device cannot be decoupled, we assess the electronic condition of the piece by analyzing the speaker level output only.

We start by connecting the "Pre-Out" jacks of the integrated to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1 KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope.

We then switch to a 1 KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment.

Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources.

If the preamp section is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve.

Next we test the power amplifier section by connecting the integrated amplifier speaker outputs to a Sencore PA81 Power Analyzer which acts as a dummy load, DC offset monitor, and oscilloscope interface. We start with a low level 1 KHz test signal at the "Main In” jacks and slowly increase its amplitude while monitoring the output on an oscilloscope for signs of noise, clipping, distortion, or improper channel balance. We continue increasing the signal level until the amplifier reaches clipping.

At this point we take an output power measurement and compare it to the spec sheet of the amplifier to verify proper performance. We finish off the bench evaluation with a 1 KHz square wave check and a 20 Hz to 20 KHz sine sweep to assess the amplifier’s frequency response characteristics.

This battery of tests will usually reveal if the amplifier has any issues that need further attention.

If the preamp and power amp both pass these tests, we reconnect the sections and verify that the preamp section can drive the power amp to rated power with a 1KHz tone on one of the line level inputs.

Before the device leaves the bench, we perform a listening test with actual music using a variety of preferred test tracks. Our benches are outfitted with familiar monitor speakers which help us identify inconsistencies that will not always show up on our test gear. The main things that we are listening for are hum or noise with no signal present, proper center image, clicks, pops, or any other obvious undesirable audio characteristics.

If the unit passes all of these tests it moves to our long term testing rig where we simulate real word operating conditions for 6-8 hours minimum. This allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when the unit has fully come up to temperature.