VTLMB-125 Monoblock AmplifiersusedFor sale: my pair of beautiful VTL MB-125 monoblock tube amplifiers (serial numbers 99183219 and 99183220) which have received a recent factory checkup and factory upgrades as described below. The ...2150.00

VTL MB-125 Monoblock Amplifiers with Factory Upgrades and Extra Tubes

Listing ID: LIS4J5EG Classified 
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Condition
7/10
Payment methods
Ships fromWilsonville, OR, 97070
Ships toUnited States
Package dimensions22.0" × 17.0" × 12.0" (110.0 lbs.)
Shipping carrierunspecified
Shipping costSpecified after purchase
Original accessoriesBox, Manual
AverageResearch Pricing

For sale: my pair of beautiful VTL MB-125 monoblock tube amplifiers (serial numbers 99183219 and 99183220) which have received a recent factory checkup and factory upgrades as described below. The VTLs are switchable between tetrode mode (125 watts into a 5-ohm load) and triode mode (60 watts into a 5-ohm load). The VTLs have RCA inputs and speaker binding posts that accept spades, banana plugs, and bare wire. Each amplifier uses two 12AT7 small signal tubes (one input and one driver) and four EL34 power tubes with an individual bias pot for each power tube. (Rectification is solid state for good bass.) Bias adjustment of the power tubes is easily accomplished with a small screwdriver and inexpensive digital multimeter as described in detail in the owner’s manual. The owner’s manual recommends adjusting the bias every 1,000 hours of listening or once a year. I am the original owner of the VTLs, having purchased them in November 1999 from The Audio Gallery, an authorized VTL dealer located in Lake Oswego, Oregon. I’m replacing the VTLs and my tube preamplifier with a solid-state integrated amplifier as the next step in downsizing my stereo (and life) due to my recent retirement and changing living circumstances. The VTLs are in exceptional operating and cosmetic condition and are conservatively rated 7/10 due to age and scratches on the bottom plates from metal footers. Otherwise, I can find no marks of any kind on the VTLs. The VTLs were used in a smoke-free, pet-free, and child-free dedicated music/home theater room. The VTLs have been very reliable tube amplifiers, requiring only two minor repairs. One year after purchasing the VTLs, the on/off power switch on one of the amplifiers broke. The VTL factory sent me two power switches at no cost. I replaced the broken power switch (as easy job) and kept the second replacement switch as a backup. In the summer of 2012, I noticed that one of the VTLs was playing at a lower volume level than its mate. I shipped both amplifiers to the VTL factory for a thorough checkup, repair, and upgrades. VTL found an open resistor in one of the amplifiers and replaced the resistors at that position in both amplifiers. In addition, VTL upgraded all the coupling caps, resistors, and diodes associated with the tubes and installed upgraded speaker wire binding post nuts. After the upgrades, VTL tested the amplifiers, burned in the new parts, and did a final quality control check including new low and high power frequency response and noise level graphs. The work that VTL did is documented in the sales order and graphs included with the amplifiers. The factory upgrades significantly improved the VTLs’ resolution of detail, speed, and natural musicality compared to the stock amplifiers. In addition to the upgrades performed by VTL, I replaced the primary mains and B+ fuses with HiFi Tuning fuses. Along with triode/tetrode switching, one of the most versatile features of the VTLs is the very high input impedance of 130,000 ohms. I’m not an electrical engineer, but my understanding is that the input impedance of an amplifier should be at least 20 times the output impedance of the partnered preamplifier to prevent rolloff of bass frequencies. The VTL’s high input impedance will allow you to use virtually any tube or solid-state preamplifier without incurring bass rolloff due to an impedance mismatch. Another versatile feature is that the VTLs are rated for a speaker load as low as 2 ohms. The VTLs come with eight Shuguang Treasure “Black Bottle” 6CA7-Z power tubes and four Psvane Reference Series 12AT7-T small signal tubes, all Premium Grade A tested and matched tubes purchased from Grant Fidelity. A review of the Shuguang Treasure “Black Bottle” 6CA7-Z power tubes can be found online on page 170, issue 31, of Tone Audio magazine. The magazine summarized the “Black Bottle” 6CA7-Z power tubes as “the pinnacle of EL-34 sound, in terms of current production tubes.” The “Black Bottle” power tubes were installed in January 2011. The Psvane Reference Series input tubes were installed in November 2010 and the Psvane Reference Series driver tubes are new (installed in November 2013). The VTLs also come with the following backup tubes: • Six tested and matched Shuguang Treasure “Black Bottle” 6CA7-Z Premium Grade A power tubes from Grant Fidelity. The backup “Black Bottle” tubes have approximately 300 hours of use. • Eight tested and matched Genalex Gold Lion KT77 reissue power tubes purchased from Jim McShane. The Gold Lion tubes have just over two years of use. • Eight tested and matched SED Winged “C” EL34 power tubes purchased from Kevin Deal at Upscale Audio. The Winged “C” tubes have approximately three years of use. • Two tested and matched pairs (four tubes total) of NOS Siemens 12AT7/ECC81 tubes purchased from Andy at Vintage Tube Services. The Siemens tubes have approximately two years of use. • Four JAN Philips 12AT7 tubes purchased from VTL. The JAN Philips tubes have approximately one year of use. The included tube inventory will allow you to compare the sound of a number of different power and small signal tubes in the VTLs, and you shouldn’t have to purchase new tubes for years. In addition to the factory upgrades, VTL sales order and graphs for the upgrades, tubes, fuses, and extra power switch described above, the VTLs come in their original shipping cartons complete with all packing materials, owner’s manuals, original frequency response and noise level graphs, original AC power cords, original ceramic fuses, and advertising brochure. Here are the VTL MB-125 specifications from the owner's manual: • Vacuum tube complement: four EL34 and two 12AT7 per monoblock • Output power, 20 Hz – 20 kHz into 5 ohm load: tetrode = 125 watts, triode = 60 watts • T.H.D. 20 Hz – 20 kHz at 125 watts: tetrode

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