{"product_id":"sonic-frontiers-sfs-80-vintage-tube-amplifier-serviced","title":"Sonic Frontiers SFS-80 Vintage Tube Amplifier - Serviced","description":"\u003cp\u003e\u003cb\u003eGeneral:\u003c\/b\u003e\u003cbr\u003eThe SFS-80 is an exceptional tube amplifier in every respect. Not only is it visually stunning, but its sound quality is equally impressive. Delivering 80 watts into 8 ohms, it offers more than enough power for the vast majority of speakers, making it a remarkably powerful all-tube design. The amplifier is fitted with 6550 output tubes and EH 6922 driver tubes.\u003cbr\u003e\u003cbr\u003eThe build quality and overall fit and finish are also standout features. Nearly every surface is finished in beautifully brushed aluminum, giving the amplifier an elegant appearance that catches the light unlike anything else in our shop. If you decide to pair it with the Sonic Frontiers SLF-2 preamp we also just listed, it would make a pretty awesome system.\u003cbr\u003e\u003cbr\u003eDuring testing, we found the SFS-80 to deliver an exceptionally clear, detailed, and engaging sound that made it a genuine pleasure to listen to. \u003cbr\u003eIncluded with the amplifier are its original box for safe transport and a printed copy of the owner’s manual.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eSkyFi Cosmetic Notes:\u003c\/b\u003e\u003cbr\u003eOverall condition is excellent all around with very minor signs of wear on the casing.The included manual is a printed copy.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eSkyFi Technical Notes:\u003c\/b\u003e\u003cbr\u003eThis amplifier came in with some minor issues. We replaced the bias sense resistors, a few other stressed parts, and re-tubed the unit. The output tubes are a strong used set of Svetlana 6550. The driver tubes are new EH 6922. After completing the service, we tested the amplifier and verified proper testing at the bench and in our listening area on long term tests.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eOwnership:\u003c\/b\u003e\u003cbr\u003eSingle Owner\u003cbr\u003e\u003cbr\u003e\u003cb\u003eConnections:\u003c\/b\u003e\u003cbr\u003eRCA inputs, Speaker Binding Posts\u003cbr\u003e\u003cbr\u003e\u003cb\u003eGeneral Sound:\u003c\/b\u003e\u003cbr\u003eSmooth, uncolored, undistorted natural and clean\u003cbr\u003e\u003cbr\u003e\u003cb\u003eCosmetic Condition:\u003c\/b\u003e\u003cbr\u003e7\/10 = Good. One or two minor scratches. Well Maintained. See our detailed rating description \u003ca href=\"https:\/\/skyfiaudio.com\/pages\/our-rating-scale\" target=\"_blank\"\u003ehere\u003c\/a\u003e.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eWorking Condition:\u003c\/b\u003e\u003cbr\u003eWorking perfectly and tested in our lab and listening room.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eIncluded:\u003c\/b\u003e\u003cbr\u003eUnit, Box, Manual\u003cbr\u003e\u003cbr\u003e\u003cb\u003ePacking:\u003c\/b\u003e\u003cbr\u003eOriginal Manufacturers Packing\u003cbr\u003e\u003cbr\u003e\u003cb\u003eOriginal MSRP:\u003c\/b\u003e\u003cbr\u003e$2,750.00\u003cbr\u003e\u003cbr\u003e\u003cb\u003eSpecs:\u003c\/b\u003e\u003cbr\u003ePower output: 80 watts per channel (stereo)\u003cbr\u003eFrequency response: 6Hz to 50kHz\u003cbr\u003eInput sensitivity: 0.95V\u003cbr\u003eValve complement: 4 x KT99, 4 x 6DJ8\u003cbr\u003e\u003cbr\u003e\u003cb\u003eDimensions:\u003c\/b\u003e\u003cbr\u003e18 x 14.5 x 9\u003cbr\u003e\u003cbr\u003e\u003cb\u003eWeight:\u003c\/b\u003e\u003cbr\u003e70 lbs.\u003cbr\u003e\u003cbr\u003e\u003cb\u003eApproximate Age:\u003c\/b\u003e\u003cbr\u003e1992\u003cbr\u003e\u003cbr\u003e\u003cb\u003eLink to Manual:\u003c\/b\u003e\u003cbr\u003e\u003ca href=\"https:\/\/www.hifiengine.com\/manual_library\/sonic-frontiers\/sfs-80.shtml\" target=\"_blank\"\u003eClick Here\u003c\/a\u003e\u003cbr\u003e\u003cbr\u003e\u003cb\u003eRecommended Cables:\u003c\/b\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-hero-interconnects-pair-rca-ultraplate-or-wbt-connectors-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Kable - RCA Interconnects\u003c\/a\u003e - Better\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-silver-streak-interconnects-pair-rca-ultraplate-or-wbt-connectors\" rel=\"noopener\" target=\"_blank\"\u003eKimber Kable - RCA Interconnects\u003c\/a\u003e - Best\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-8tc-8-tc-ascent-speaker-cables-pair-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Kable - Speaker Cables\u003c\/a\u003e - Better\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-summit-series-monocle-xl-speaker-cables-pair-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Summit Series Monocle XL Speaker Cables (PAIR)\u003c\/a\u003e - Best\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-summit-series-bifocal-xl-bi-wire-speaker-cables-pair-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Summit Series BiFocal XL Bi-Wire Speaker Cables (PAIR)\u003c\/a\u003e - Best If Applicable\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-pk14-pk-14-ascent-power-cord-brand-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Kable - Power Cords\u003c\/a\u003e - Better\u003cbr\u003e\u003cbr\u003e\u003ca href=\"https:\/\/skyfiaudio.com\/products\/kimber-kable-ascent-series-pk10-pk-10-power-cord-brand-new\" rel=\"noopener\" target=\"_blank\"\u003eKimber Kable - Power Cords\u003c\/a\u003e - Best\u003cbr\u003e\u003cbr\u003e\u003cb\u003eTesting Process:\u003c\/b\u003e\u003cbr\u003eWe 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 resistors and other passive components for signs of overheating. If tube arcing has occurred in the past we can usually spot discoloration on the output tube sockets. On vintage units we often spot check select capacitors for value and ESR. \u003cbr\u003e\u003cbr\u003eIf the amplifier passes visual inspection, we move on to a full test of all of the tubes. We use a modern Amplitrex AT-1000 Professional Tube Tester which is capable of testing both emission and Gm with a high degree of accuracy. \u003cbr\u003e\u003cbr\u003eWe document the results of each tube and replace any weak or suspect tubes before proceeding. \u003cbr\u003e\u003cbr\u003eWhen we power on tube amplifiers for the first time we usually use a variac and current limited AC supply and slowly raise the voltage up to nominal mains level while monitoring plate, screen, filament, and negative bias supply voltages where applicable.\u003cbr\u003e\u003cbr\u003eIf everything is in order we feed a low level test signal into the amplifier’s input and monitor its output on an oscilloscope across an 8 ohm dummy load. At this point we are just looking to verify basic function and confirm that the output transformers are not damaged.\u003cbr\u003e\u003cbr\u003eOnce we have verified that the amplifier is safe to operate, we connected it to full mains power. For fixed bias amps we set the bias to manufacturer spec. For cathode biased amps we monitor the plate to cathode voltage to determine if the output tubes are operating in a safe range. Once the output section is verified we move onto bench evaluation. \u003cbr\u003e\u003cbr\u003eWe start by feeding the input of the amplifier with a low level 1 KHz test signal, slowly increasing its amplitude while monitoring the amplifier’s 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.\u003cbr\u003e\u003cbr\u003eWe 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. \u003cbr\u003e\u003cbr\u003eBefore 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. \u003cbr\u003e\u003cbr\u003eIf 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. \u003cbr\u003e\u003cbr\u003eFor tube amps we like to run this test at least twice.\u003cbr\u003e\u003cbr\u003eThis allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when it has fully come up to temperature. We find this step to be essential, especially for vintage units.\u003c\/p\u003e","brand":"Sonic Frontiers","offers":[{"title":"Default Title","offer_id":48236463653118,"sku":"107687","price":4490.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0003\/3275\/9084\/files\/sonic-frontiers-sfs-80-vintage-tube-amplifier-serviced-330.jpg?v=1779392594","url":"https:\/\/skyfiaudio.com\/products\/sonic-frontiers-sfs-80-vintage-tube-amplifier-serviced","provider":"SkyFi Audio","version":"1.0","type":"link"}