Cello Performance Amplifier II (Monoblock Pair) Lightly Serviced

General: Very rare and very collectable monoblock amplifiers. "For 15 years Mark Levinson and the engineers at Cello created the world's best high fidelity equipment, and the continued interest in the equipment speaks to the enduring quality and performance of those products. The Cello Ltd. product line consisted of speakers, amplifiers, pre-amplifiers, and peripherals." These are unique Mark Levinson Cello Performance II monoblock amplifiers. They're configured as dual-chassis per channel of amplification, for a total of 4 boxes. These amplifiers are later version Performance II's rated at 200 Watts at 8 ohms, and 400 Watts at 4 Ohms.We performed a light service and a full test in our lab and listing area where they performed admirably at their full rated power.Overall condition is pretty solid with very clean faceplates and all hardware intact. The top covers do have some scratches since they are made of soft aluminum. In my opinion it would be difficult to find a better built and sounding mono amplifier at this price point. These amps use Fischer style input connectors similar to mini-XLR. There are no cables incudes other the umbilicals connecting each chassis and power cables.  Audio cables are available for an additional $900 for 1m or $1200 for a 2m pair utilizing authentic Cello Strings cables.  Custom lengths also available.  More from Cello:The Performance Amplifier is a four chassis set, comprised of two mono power supplies and two mono power amplifiers. The Performance Amplifier includes many engineering features exclusive to Cello, which together provide unparalleled speed, clarity, impact, natural tone quality and reliability. Each amplifier chassis has a balanced audio input, balanced bridging output, and four sets of barrier strip outputs. Three pin Fischer connectors are used to provide balanced line audio connections of the highest quality. The cost of the Performance Amplifier reflects Cello's insistence on the most innovative circuitry and premium parts. The Performance Amplifier offers a combination of sonic purity, power, build quality, freedom from obsolescence, and flexibility that makes a new level of musical integrity and system performance possible.SkyFi Cosmetic Notes:The tops of all chassis show cosmetic wear from stacking including scratches and light depressions near the corners. Some are in better condition than others. The faceplates present very well overall, but one power supply chassis does have a series of scratches near the bottom edge.SkyFi Technical Notes:These amplifiers received a light servicing in house which included the replacement of (2) suspect Sprague capacitors in each amplifier chassis. We also verified the DC offset and bias settings. Both amps tested well past their rated output power.Ownership:Single OwnerConnections:Mini XLR ports, and speaker screw down posts.General Sound:Smooth, uncolored, undistorted natural and cleanCosmetic 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:Exactly as pictured and described above.Packing:Will be packed using our highly developed in-house process and custom packing materials.Specs:Power Output (single amp):@8 OhmsRated: 200 WattsClipping: @1000 Hz >350 Watts@4 OhmsRated: 400 WattsClipping: @1000 Hz >700 Watts@2 OhmsRated: 800 WattsClipping: @1000 Hz >1000 Watts@1 OhmRated: 1000 WattsClipping: @1000 Hz >1300 WattsPower Output (bridged set):@8 OhmsRated: 800 WattsClipping: @1000 Hz >1400 Watts@4 OhmsRated: 1600 WattsClipping: @1000 Hz >2800 Watts@2 OhmsRated: 3200 WattsClipping: @1000 Hz >4000 WattsIMD (SMPTE):0.13% (60 Hz / 40V Output)IMD (CCIF):<0.2%THD (20 - 20000Hz):<0.1% (8 & 4 Ohms / 40 Volt Output)Frequency Response:+0 / -0.8 dB @ 20 - 20000 HzDynamic Headroom:2.7 dBChannel Separation:InfiniteSignal to Noise:< -105 dB (1000 Hz / 40 Volt Output)Input Sensitivity:1.485 V (8 Ohms / 200 Watts / 40 Volt Output)Input Impedance:1 mOhm (Non-Inverting)5000 Ohms (Inverting)Gain:28 dBDimensions:17.5"w / 8.5"h / 18.5"d (each of four chassis)Weight:260 lbs.Approximate Age:1990Link to Manual:Click HereRecommended Cables:Kimber Kable - Speaker Cables - BetterKimber Summit Series Monocle XL Speaker Cables (PAIR) - BestKimber Kable - Power Cords - BetterKimber Kable - Power Cords - BestTesting 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 amplifier passes visual inspection, we move on to a controlled power on sequence using a Sencore safety analyzer to monitor current draw in real time. Once the amplifier is determined to be safe to operate, we connect it to full AC mains for function and power testing. We connect the speaker outputs of the amplifier 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 amplifier's input 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. If the device under test has both balanced and single ended inputs they are both tested at this time.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.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 is moved 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.