Vintage Tube Amp

Since the late 1950′s, engineers at Audio Research have been aware of these problems. To achieve low distortion under the dynamics of music, Audio Research has investigated many approaches to amplifier design, including the conventional bipolar transistor, FET, V-FET, Class D (switching), tube and various combinations of each.

It is believed to be a TS-24R06U model power supply. UTC has some light corrosion toward the bottom. Unit hasn’t been tested. Cord has been cut. Tubes have not been tested either. Comes with Sprague compactors. Vtg Audio Mono Stereo Tube Amplifier with UTC LS57 Transformer Thordarson Power. Check out our entire store for more great products and deals! We do however make every possible attempt to accurately describe the inventory we sell and stand behind it. Since 2016, 8TEN Industries has been a leading asset recovery provider supporting national retailers, brands, and manufacturers. Our 60,000 square foot processing and distribution facility located in Cass City, Michigan has allowed us to become industry leader in turning difficult problems for manufacturers into great deals for our customers. This item is in the category “Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Parts & Accessories\Vintage Transformers”. The seller is “8ten1944″ and is located in this country: US. This item can be shipped to United States.

• Brand: UTC

This is a MK1 SP8. Contrary to popular belief is better than the MKII. Thoroughly Bench checked works perfect. Best phono section ever. Notice not too many MK1 units for sale. The Mk1 was more expensive to produce. More parts and labor. More power supply storage on the main rectifier.. This item is in the category “Consumer Electronics\TV, Video & Home Audio\Home Audio\Home Audio Components\Other Home Stereo Components”. The seller is “ctech-electronics-store” and is located in this country: US. This item can be shipped to United States, Canada, United Kingdom, Australia, Japan, Korea, South, Indonesia, South Africa, Hong Kong, Bahamas, Israel, New Zealand, Singapore, Switzerland, Norway, Saudi Arabia, United Arab Emirates, Qatar, Bahrain, Malaysia, Barbados, Bangladesh, Bermuda, Brunei Darussalam, Bolivia, Egypt, French Guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Cayman Islands, Liechtenstein, Sri Lanka, Monaco, Macau, Martinique, Maldives, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Uruguay.

• Compatible Brand: Audio Research
• Type: Tube Pre-Amplifier
• Brand: Audio Research

SkyFi Audio – Curators of Vintage Audio Gear. 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. 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. We are big fans of the VT100 variation which we have a hard time keeping in stock. This is its larger brother VT200 MKI at twice the power, but with the same design and build quality. This is a very powerful tube amp capable of driving difficult loads with the same neutral and clear sound that you would expect from Audio Research. It has facilities for balanced and single ended operation and offers speaker connections from 1 ohm to 16 ohms. Serviced in house and working beautifully. Little to no signs of use cosmetically. Includes a custom dust cover (for when the amp is not in use obviously), and the manual. SkyFi Service Notes. All driver tubes replaced. Front end adjustments and bias set to service manual specification. Tube Notes. All driver tubes replaced with matched balanced JJ E88CC. All output tubes are pre-owned matched quads of Svetlana 6550 ribbed plate (Not Winged C). 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 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. More from Audio Research: The VT200 vacuum tube stereo power amplifier is the most powerful of the three VT-series models. Rated at 200 watts per channel into a wide range of speaker loads, the VT200 encompasses a “dual mono” circuit layout reaching back to the massive single power transformer. Eight matched pair of 6650C output tubes and 674 joules of distributed energy storage give the VT200 unwavering control over the most difficult speaker loads, without sacrificing dynamic freedom or musical nuance. Separate left and right input and output circuit boards, with distributed power supplies, keep signal path lengths at a minimum for quicker transient attack and explosive musical dynamics. As with other VT models, constant-current sources in the input stage help maintain stable drive characteristics and differential balance of the output stage under the rapidly changing demands of actual music reproduction. Ultralinear output transformers with partial cathode coupling to the output terminals give the VT200 higher efficiency and lower output impedance than conventional vacuum-tube amplifiers. This results in better control of the loudspeaker throughout its frequency and impedance spectrum. Both single-ended (100K ohms) and balanced (200K ohms) inputs are included to allow use with any high-quality stereo preamplifier. Custom-machined, gold-over-brass five-way output terminals allow a secure, high-contact connection to a variety of speaker impedances: 1, 2, 4, 8 or 16 ohms. Internally, the VT200 presents a very open architecture within a spacious, rugged chassis. A single cooling fan operable at three different speeds provides unobstrusive cooling of interior components, including the vacuum tubes mounted along the chassis sidewalls. Biasing of the output tubes is easily accomplished via two trim pots for each channel, accessible through holes located along each sidewall of the chassis. Complete retubing kits of tested, selected and matched tubes for the VT200 are available through authorized Audio Research dealers, or from the factory. DETAILS and SPECIFICATIONS – MKI Tube stereo amplifier. 200 watts per channel continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 1% at 200 watts, below. 01% at 1 watt. Approximate actual power available at “clipping”:210 watts (1kHz) Note that the actual RMS power output is dependent upon both line voltage and “condition” ie: if power line has high distortion, maximum power will be affected adversely, although from a listening standpoint this is not very critical. (-3dB points) 12Hz to 120kHz. (-3dB points at 1 watt) 0.5Hz to 200 kHz. 2.5V RMS (Bal or SE) for rated output. (27 dB gain into 16 ohms). 200K ohms Balanced, 100K ohms Single-ended. 1, 2, 4, 8, 16 ohms. Approximately 0.8dB 16 ohm load to open circuit. Less than 0.2mV RMS – 109dB below rated output (IHF weighted, input shorted, 16 ohm output). POWER SUPPLY ENERGY STORAGE. 105-125VAC 60Hz (210-250VAC 50Hz) 990 watts at rated output, 1200 watts maximum, 680 watts at “idle”. VT200: (8 matched pairs) 6550C power output, (6) 6922 driver, (4) 6922 input. 19″ (48.3 cm) W x 10½” (26.7 cm) H x 23.6 (60.0 cm) D. Handles extend 1½ (3.8 cm) forward. (46.5 kg) Net; 148 lbs. Yes – Power Only. We have too many items for sale and it is nearly impossible to keep track of offers outside of the official system. 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. 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. This item is in the category “Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Amplifiers & Tube Amps”. The seller is “skyfiaudio” and is located in this country: US. This item can be shipped to United States.

• Brand: Audio Research
• Type: Tube Amplifier
• MPN: VT200 MKI
• Model: VT200 MKI
• Country/Region of Manufacture: United States

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. 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. The ARC 76A is a favorite among vintage audio collectors and tube rollers. This one is in what we call “survivor” condition, original and unmolested. We fitted a new set of tubes and did a light service to get it working nicely. Cosmetic condition is good with only a few visible signs of use, please look over our photos for more info. SkyFi Service Notes: This unit appeared to be all original on initial inspection. After testing all of the tubes it became clear that the output tubes needed replacement. We swapped out all of the 6550′s and biased them up to service manual spec. The input attenuators and jacks were also cleaned. After service, this amplifier tested clean above up to its rated 75W with ease. SkyFi Cosmetic Notes. The terminal strips exhibit the typical cracked barrier guards that we normally see on units of this age. Using period correct small spade connectors or spade to banana adapters is encouraged. Light marking under left handle of face plate. Light black paint marks on face plate. All 6CG7s are vintage GE, all testing well on our Modern and Professional Amplitrex AT1000 Tube Tester. 12AX7′s are a mix of GE and RCA, also tested well on our Amplitrex. The original GE 6550′s were at the end of their lifespan and were replaced with two matched sets of known good Svetlana Gold Label 6550 from our stock. All tubes biased to service manual spec. The 6550 in the power supply section was also replaced with a Svetlana tube. More from Audio Research. POWER OUTPUT 75 Watts per channel minimum RMS (both channels operating) into a 4, 8 or 16 ohm load from 20 Hz to 15 kHz with less than 1% total harmonic distortion. 1.5 volts for rated output. 80K ohms at 20 Hz; 30K ohms at 15 kHz. 4, 8, 16 ohms. 14 at 8 ohms (1 kHz). Intermodulation distortion: less than. 5% at rated power. More than 80 dB below rated output. 100, 120, 200, 220, 240 VAC; 50-60 Hz, 550 watts at rated power output. (4)12AX7, (8) 6FQ7, (2 matched pairs) 6550, (1) 6550. 19″ W x 7″ H x 12-1/4 D. The SkyFi Testing Process for Tube Amplifiers: We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking. We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to “burn in” on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested. We also test all tubes for output gain and leakage on our calibrated B&K 747 tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory. Final testing involves pushing actual music thorough the amplifier. We’ve learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage KEF speakers that we’re very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice. We have too many items for sale and it’s nearly impossible to keep track of offers outside of the official system. We accept trade-ins of equal or lesser value under certain conditions. Please visit our website to submit your gear for full consideration. We will only consider high-end equipment from mainstream manufacturers such as McIntosh, Mark Levinson, Audio Research, Krell, etc. And will typically pass on displays, projectors, receivers, dated surround processors, and mid-fi equipment of any type. We will offer a fair value for your equipment, but keep in mind we’re running a business and will need to be able to resell the equipment at a profit after investing a great deal of time and resources in testing, certifying, repairing, cleaning, and packaging the incoming equipment. SELL US YOUR GEAR (Working or Broken). Simply visit our website to submit your gear for full consideration. We are currently operating from our shop inside our dedicated building in Glen Rock, NJ. We have several well-equipped and dedicated listening areas, plus a dedicated listening studio with tons of equipment of all makes and models. 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. 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. This item is in the category “Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Amplifiers & Tube Amps”. The seller is “skyfiaudio” and is located in this country: US. This item can be shipped to United States, Canada.

• Brand: Audio Research
• Type: Tube Amplifier
• Model: D-76A
• MPN: D-76A

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. 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. Super cool and rare upgraded Dynakit ST-70 tube amplifier modified by Audio Research. What could be better than a well regarded ST-70 with a bit of love and magic from our favorite tube amp maker Audio Research. They made 3 versions of this unit over the years and this is the latest and greatest 3C version. Best of all it’s fitted with vintage GE tubes that tested really well on our modern and professional tube tester. Not sure how many pieces were actually modified, but I have not found many examples of this amp online. So it’s relatively rare. This one looks great and sounds amazing. It was tested in our lab and listening room and is working perfectly. Test Notes: Uses (3) 12AX7, (4) 6CG7, and (4) 6L6GC. 40W into 8 ohms with both channels driven. Set Bias to. 410V across 7.5ohm resistors as suggested in schematic. We have too many items for sale and it’s nearly impossible to keep track of offers outside of the official system. We accept trade-ins of equal or lesser value under certain conditions. Please visit our website to submit your gear for full consideration. We will only consider high-end equipment from mainstream manufacturers such as McIntosh, Mark Levinson, Audio Research, Krell, etc. And will typically pass on displays, projectors, receivers, dated surround processors, and mid-fi equipment of any type. We will offer a fair value for your equipment, but keep in mind we’re running a business and will need to be able to resell the equipment at a profit after investing a great deal of time and resources in testing, certifying, repairing, cleaning, and packaging the incoming equipment. SELL US YOUR GEAR (Working or Broken). Simply visit our website to submit your gear for full consideration. We are currently operating from our shop inside our dedicated building in Glen Rock, NJ. We have several well-equipped and dedicated listening areas, plus a dedicated listening studio with tons of equipment of all makes and models. 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. 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. Yes – Power Only. This item is in the category “Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Amplifiers & Tube Amps”. The seller is “skyfiaudio” and is located in this country: US. This item can be shipped to United States, Canada.

• Brand: Audio Research
• Type: Tube Amplifier
• MPN: ST-70
• Model: ST-70
• Country/Region of Manufacture: United States

Audio Innovations Series 200 MKII Valve / Tube Vintage Stereo Power Amplifier. + A UK Mains Lead. As you can clearly see this Vintage Tube – Valve Power Amplifier is in Wonderful Used Condition Throughout. It is of course in full working condition throughout. Sound Quality is Fantastic!!!!!! A copy of its Original Instruction Manual should be Available for you to Download from the Internet if Required. A UK Mains Lead will of Course be Supplied with it for you. It will be VERY well wrapped & packed, it will arrive with you as shown on these pictures. Below Is A Question & Answer Section, This Will Hopefully Answer Most Customer Questions. A: We Are Dealers Of Quality & Vintage Hi-Fi Equipment & Similar Items. Q: Where Did You Get It From? Q: Has It Been Fully Tested? A: All Items That We List For Sale Have Been Fully Tested By Us. We Test Fully & Not Just Powering Items Up. Q: Will We Take A Offer On A Item. A: All Item Are Very Competitively Priced. We Normally Sell Under The Current Market Value. Will My Item Be Packed Well? Yes It Will, Please Check Our Feedback, You Can See That Our Customers Are Very Happy With Our Packing Etc. Q: How Long Will I Have To Wait For My Order To Arrive? A: We send Most Items On A 48hr Service. (Except On Bank Holiday Mondays). Q: Do You Provide Tracking Details? Q: My Tracking Details Do Not Work, Why? A: Once Your Order Has Been Collected Your Tracking Details Will Work. Normally After 7pm Onwards On The Day Of Collection From Us. A: No, This Is Not Possible. PLEASE DO NOT ASK! Q: Will You Send By A Cheap Non Signed For Courier? A: No, All Items Are Always Send Fully Signed For & Fully Trackable. Q: Will You Send Overseas? The item “Audio Innovations Series 200 MKII Valve / Tube Vintage Stereo Power Amplifier” is in sale since Thursday, July 8, 2021. This item is in the category “Sound & Vision\Home Audio & HiFi Separates\Amplifiers & Pre-Amps”. The seller is “theworldismyoyster11″ and is located in Great Yarmouth. This item can be shipped to United Kingdom, Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Australia, United States, Bahrain, Canada, Japan, New Zealand, China, Israel, Hong Kong, Norway, Indonesia, Malaysia, Mexico, Singapore, South Korea, Switzerland, Taiwan, Thailand, Bangladesh, Bermuda, Bolivia, Barbados, Brunei darussalam, Cayman islands, Egypt, Guernsey, Gibraltar, Guadeloupe, French guiana, Iceland, Jersey, Jordan, Cambodia, Liechtenstein, Sri lanka, Macao, Monaco, Maldives, Martinique, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Saudi arabia, South africa, United arab emirates, Ukraine, Chile, Bahamas, Colombia, Costa rica, Guatemala, Honduras, Jamaica, Kuwait, Panama, Philippines, Qatar, Trinidad and tobago, Uruguay.

• Number of Channels: 2
• Audio Outputs: See The Close Up Pictures
• Model: Series 200 MKII
• Colour: As Shown
• Country/Region of Manufacture: United Kingdom
• Audio Inputs: See The Close Up Pictures
• Type: Power Amplifier
• Features: Analog
• Number of Outputs: See The Close Up Pictures
• MPN: Does Not Apply
• Number of Inputs: See The Close Up Pictures
• Brand: Audio Innovations
• Surround Sound Formats: Stereo
• Manufacturer Warranty: None

Audio Innovations Series 200 MKII Valve / Tube Vintage Stereo Power Amplifier. + A UK Mains Lead. As you can clearly see this Vintage Tube – Valve Power Amplifier is in Wonderful Used Condition Throughout. It is of course in full working condition throughout. Sound Quality is Fantastic!!!!!! A copy of its Original Instruction Manual should be Available for you to Download from the Internet if Required. A UK Mains Lead will of Course be Supplied with it for you. It will be VERY well wrapped & packed, it will arrive with you as shown on these pictures. Below Is A Question & Answer Section, This Will Hopefully Answer Most Customer Questions. A: We Are Dealers Of Quality & Vintage Hi-Fi Equipment & Similar Items. Q: Where Did You Get It From? Q: Has It Been Fully Tested? A: All Items That We List For Sale Have Been Fully Tested By Us. We Test Fully & Not Just Powering Items Up. Q: Will We Take A Offer On A Item. A: All Item Are Very Competitively Priced. We Normally Sell Under The Current Market Value. Will My Item Be Packed Well? Yes It Will, Please Check Our Feedback, You Can See That Our Customers Are Very Happy With Our Packing Etc. Q: How Long Will I Have To Wait For My Order To Arrive? A: We send Most Items On A 48hr Service. (Except On Bank Holiday Mondays). Q: Do You Provide Tracking Details? Q: My Tracking Details Do Not Work, Why? A: Once Your Order Has Been Collected Your Tracking Details Will Work. Normally After 7pm Onwards On The Day Of Collection From Us. A: No, This Is Not Possible. PLEASE DO NOT ASK! Q: Will You Send By A Cheap Non Signed For Courier? A: No, All Items Are Always Send Fully Signed For & Fully Trackable. Q: Will You Send Overseas? The item “Audio Innovations Series 200 MKII Valve / Tube Vintage Stereo Power Amplifier” is in sale since Friday, June 25, 2021. This item is in the category “Sound & Vision\Home Audio & HiFi Separates\Amplifiers & Pre-Amps”. The seller is “theworldismyoyster11″ and is located in Great Yarmouth. This item can be shipped to United Kingdom, Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Australia, United States, Bahrain, Canada, Japan, New Zealand, China, Israel, Hong Kong, Norway, Indonesia, Malaysia, Mexico, Singapore, South Korea, Switzerland, Taiwan, Thailand, Bangladesh, Bermuda, Bolivia, Barbados, Brunei darussalam, Cayman islands, Egypt, Guernsey, Gibraltar, Guadeloupe, French guiana, Iceland, Jersey, Jordan, Cambodia, Liechtenstein, Sri lanka, Macao, Monaco, Maldives, Martinique, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Saudi arabia, South africa, United arab emirates, Ukraine, Chile, Bahamas, Colombia, Costa rica, Guatemala, Honduras, Jamaica, Kuwait, Panama, Philippines, Qatar, Trinidad and tobago, Uruguay.

• Number of Channels: 2
• Audio Outputs: See The Close Up Pictures
• Model: Series 200 MKII
• Colour: As Shown
• Country/Region of Manufacture: United Kingdom
• Audio Inputs: See The Close Up Pictures
• Type: Power Amplifier
• Features: Analog
• Number of Outputs: See The Close Up Pictures
• MPN: Does Not Apply
• Number of Inputs: See The Close Up Pictures
• Brand: Audio Innovations
• Surround Sound Formats: Stereo
• Manufacturer Warranty: None