This is a rare, collectible Audio Research tube amplifier.
The Audio Research (AR) V70 tube-hybrid stereo power amplifier was introduced in 1992, a period when Audio Research committed to Fully-Balanced operation, Input-to-Output, and almost went bankrupt as a result (Balanced-Input-Only tube amplifiers were generally Not well received by the tube audio community, hence they sold in very low numbers.)
PLEASE NOTE > Balanced Inputs Only!
The AUDIO RESEARCH V70:
The Audio Research V70 represents a significant, evolutionary refinement of the circuit topology first established in the legendary AR "Classic 60” amplifier that preceded it. It sold new for $4,000 ($800 more than the Classic 60).
STEREOPHILE REVIEW > AR CLASSIC 60:
While continuing to use Triode operation and Audio Research's patented, cross-coupled circuit, the V70 amplifier improves on the "Classic 60" design with a Fully-Balanced circuit topology, Input-to-Output, to increase channel separation, reduce extraneous noise and minimize distortion products that otherwise degrade the musical resolution and dynamic impact of the output stage.
The input stage uses select J-FET transistors with MOSFET followers to provide ultra-quiet, low-impedance drive to the 6FQ7 dual Triodes, which directly drive the output tubes (currently KT88s). Partial cathode coupling and highly advanced output transformer design yield an effective power bandwidth of 10 Hz to 80 kHz.
Audio Research's patented DEC (Decoupled Electrolytic Capacitor) circuit and the latest coaxial coupling capacitors are used to further enhance the performance of this remarkable amplifier.
The AR V70 design incorporates unique "soft" start-up and shutoff modes to help prevent life-shortening current "spikes" from reaching the output tubes (correcting a design limitation of the Classic 60).
• (At turn-on, a 30-second delay allows the output tube heaters to rise to proper operating voltage and lets bias supply voltage stabilize: This sequence is then followed by a two-second ramp-up of B+ supply voltage to enable normal operation. Similarly. at turn-off the B+ supply voltage is ramped down to prevent abrupt loss of operating bias — again preventing undue stress to the output tubes.)
Personal Note: This makes a Huge difference in tube life, and long-term on-spec tube performance.
The V70 also utilizes 2 ultra-quiet internal fans to ensure optimal thermal operating stability and extended life for the output tubes.
In short, the AR V70 is an elegant, logical, Fully-Balanced refinement of the iconic "Classic 60" circuit design, with an astonishing ability to resolve meaningful musical detail. Providing sufficient power to drive a wide variety of today's highest quality loudspeakers, the V70 is both versatile and virtuoso: It will produce highly satisfying results from dynamic, electrostatic or planar loudspeaker types.
Personal Note: This is the Only tube amp I have ever owned (my main amp was a Krell FPB-300c). It is also the only tube amp I’ve ever heard (anywhere in my budget range) that will drive Apogee ribbons and Martin-Logan electrostatics with authority and grace…
SEE SPECIFICATIONS IN THE ATTACHED IMAGE...
THIS PARTICULAR AUDIO RESEARCH V70 - Recapped + Two Full Sets of Tubes (KT88s, and 6550s)
VERY GOOD-EXCELLENT CONDITION:
• 8/10 for one plastic divider tab broken off at back on speaker cable binding posts (see pic for detailed closeup).
• Otherwise 9/10 overall excellent operating and cosmetic condition.
FRESHLY SERVICED - October 2017:
4 Main Caps (all older amps should be recapped), 8 Resistors (one was faulty), and Biased.
- 4 Cap ALUM 1000UF 450V SCREW
- 8 RES 100 OHM 3W 1% AXIAL
- 1 CAP ALUM 1000UF 20% 100V SNAP
- 1 CAP ALUM 1000UF 20% 35V AXIAL
• $400 – Receipt provided with purchase.
CURRENT TUBES (Fresh - Replaced by me):
• Valve Art KT88s - 8 – China - Cryogenically frozen > Matched Octet!
• GE 6FQ7/6CG7 - 4 – NOS Brazil - Cryogenically frozen > Matched Quartet.
• 75-100 hours on tubes, at most!, was never used as my “main amp”.
Personal Note: Couldn't help myself experimenting, previous tubes were working fine! My only adventure with tube “rolling”… Spent a small fortune buying cryo-frozen tubes, in matched Octet/Quartets ($700). Relatively small (for the investment) but clearly discernible improvement - somewhat lower noise-floor, more open "effortless" dynamic range, and more “natural” harmonic texture-bloom. Would I do it again, no..., but it means you get fresh, matched, really good tubes! Plus...
FULL SET OF SPARE TUBES:
• Svetlana 6550 – 8 – Russia.
• GE 6FQ7/6CG7 – 4.
• These came with the amp when I purchased it. Unknown origin and hours of use. Tubes test fine. Can be “rolled” into amp, but it will need to be re-biased.
• These are included with the amp, and I will package and ship separately. Shipping for the spare tubes is included in the purchase price.
• I am selling because I have moved from a
house to a condo and all my hoarded good audio stuff is no longer appropriate.
Almost no amp use since recapped in 2017 (moved to condo).
• Comes with original AR double-box
packaging, copy of manual, and service receipt (as specified above).
• NOTE: I LIVE IN CANADA, so please ensure you have confirmed shipping
costs. The amp is obviously US-Made so no duty payable on return to US.
• Shipping Size/Weight:
25" x 25" x 14" / 77 lbs.
• Message me with any questions. - Thank you for your time and interest!