Description

Music Reference RM-9 Tube Amplifier With EL34's SkyFi Audio - Curators of Vintage Audio Gear SkyFi Audio is a small startup business specializing in the purchase, reconditioning, and reselling of high end audio equipment. We only buy equipment that we admire and are passionate about. No mid-fi, no gimmicks, no junk. Each piece of equipment is cosmetically restored and fully tested in our well-equipped lab by an engineer with 30+ years of experience in the HiFi world. If it does not meet or exceed the original manufactures specifications, it will not be sold. We are very selective about the equipment we purchase, focusing on mostly analog, high-build quality, American, and European built units. Through our sister company, which is an authorized dealer for McIntosh, Audio Research, Sonus Faber, ClearAudio, Project, and Sony ES, we have access to OEM parts, service, and support. ---------- Great review from Stereophile can be found via the link below where it received a class B rating. Manufactured in the early 1990's and is now quickly becoming a collectible piece. This arrived to us in working condition and only needed a bit of attention, including replacement of the power switch and moving some 6DJ8s for better balance. Tested nicely to about 90W on the bench. As of this writing we also have the matching Music Reference RM-5 MK II Tube Preamplifier with Phono listed on eBay. Cosmetic Notes: • Paint chip on back of power transformer touched up • Blemishes to wood sides The SkyFi Testing Process for Tube Amplifiers: 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 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. If the amplifier passes visual inspection, we move on to a full test of all of the tubes. We use an Amplitrex AT-1000 Tube Tester which is capable of testing both emission and Gm with a high degree of accuracy. We document the results of each tube and replace any weak or suspect tubes before proceeding. When 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. If 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. Once 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. We start by feeding the input of the amplifier with a low level 1KHz test signal, slowly increase 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. We finish off the bench evaluation with a 1KHz square wave check and a 20Hz to 20KHz 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. For tube amps we like to run this test at least twice. This 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. Item Included Original Box Not Included Manual Not Included Remote Not Applicable Cables Yes - Power Only Physical Condition 7 / 10 Working Condition 10 / 10 ---------- PURCHASING GUIDELINES: 1) We do not review or accept any offers that do not go through the official eBay system. We have too many items for sale and it is nearly impossible to keep track of offers outside of the official system. Please do not message, email, or text any offers. 2) All listings are eligible for the eBay Global Shipping Program unless the item exceeds the maximum weight/price requirements to your country. If this is the case simply message us via eBay as we accept bank wire transfers for international payments and frequently ship worldwide via UPS. 3) Please ensure your shipping address is correct within eBay as we will ONLY ship to the eBay/PayPal Confirmed Shipping Address. No exceptions. 4) eBay may charge and collect sales tax to your state/jurisdiction which we have no control over. SCHEDULING AN APPOINTMENT: We are currently operating from our shop inside our dedicated building in Glen Rock, NJ. We’re not a store, so please don’t make an appointment if you’re just curious as to how a speaker or piece of equipment sounds. In essence - no tire kickers please. You can message us here on eBay with any questions or to schedule an appointment. We can also arrange to install, calibrate, and tune your newly purchased gear in your listening room if you’re local to our area. This is super useful when purchasing large speakers or heavy amplifiers. It’s also great for ensuring your new turntable is setup correctly in its final resting place. eBay v1.4 eBay integration by