Audio Research SP-3, VINTAGE ALL TUBE PREAMPLIFIER, COLLECTOR RESTORATION

Description

Audio Research SP-3, VINTAGE ALL TUBE PREAMPLIFIER, COLLECTOR RESTORATION
WHO WE ARE
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.
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This is a collector grade restoration of a classic and well regarded preamp from Audio Research. The exact model designation is SP3 and this is an example of the very first production run for this piece.
An excellent match for any vintage system using speakers that might require a bit of boost from the built-in tone controls.
You're not going to find a finer electrical restoration.
Check out our Audio Research SP3 Series video on our SkyFi YouTube channel to understand the differences between the different SP3 iterations.
All upgrades were aimed at improving reliability and long term performance, while maintaining every last bit of the original sonic signature.
Restoration Notes:
This preamp underwent a restoration focuséd on preserving the original character of the unit, while making it safe to operate at today’s AC mains voltages.
The power supply was completely recapped with modern discrete equivalent components, with increased voltage handling. An NTC thermistor was also added to limit initial inrush current. Any heat stressed resistors on the power supply board were replaced. The Zener reference diodes for the power supply voltage regulator were replaced and elevated off of the PCB. These diodes were hand selected for proper performance at operating temperatures. The thermal transfer compound for the series pass transistor was also refreshed to ensure proper heat dissipation.
The main preamp PCB was left untouched aside from a pair of low value axial electrolytic capacitors, which were replaced with modern equivalents.
All controls were fully cleaned and tested. The original volume control showed signs of out of spec channel balance, so it was replaced with an ARC approved, Japanese Manufactured, Alps Control.
**Note this has two front faceplate red lamps rather than a green and a red. We were unable to source a green one from ARC direct or other official sources.
All tubes are Orange Globe Amperex 12AX7A's which were arranged for optimal channel balance in both the phono and line stages.
Technical Specifications:
Frequency response:
15Hz-30kHz, ±1dB
Distortion (THD):
0.005% at 5V out
Maximum output:
25V at 1kHz
S/N Ratio:
90dB (Aux input, no ref. level given)
Dimensions:
15 5/8" W by 5" H x 12½ D
The SkyFi Testing Process for Preamplifiers:
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 transistors are checked for signs of stress or damage. Special attention is paid to the power supply which is the most common source of failure for preamps. We then power up the unit and run a simple 1k sine wave while monitoring the low voltage output on an oscilloscope for signs of distortion or noise to get a baseline.
At this point we will lubricate and clean all switches and potentiometers (that are not sealed) with a high quality contact cleaner, and then re-test all functions for any signs of noise or scratching.
Final testing involves putting actual music through the preamplifier We have learned over time that some issues are only noticeable to a trained ear while listening to a familiar source material. Our test bench has reference vintage KEF speakers that we are super familiar with which will quickly reveal any discrepancies. Some preamps will then move into the listening room where they will be tested with our in-house reference system.
Item
Included
Original Box
No
Manual
Yes
Remote
N/A
Cables
Yes - Power
Physical Condition
7
Working Condition
10
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PURCHASING GUIDELINES:
We do not accept or review any offers that do not go through the official eBay system. We have too many items for sale and it’s nearly impossible to keep track of offers outside of the official system. Please don’t message, email, or text any offers.
All listings are eligible for eBay’s 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 can accept bank wire transfers for international payments. And we frequently ship worldwide with UPS.
And please ensure your shipping address is correct within eBay as we ONLY ship to the eBay/PayPal Confirmed Shipping Address.
No exceptions.
TRADE IN POLICY:
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. If you’re looking for top dollar, we suggest selling direct on your own.
SELL US YOUR GEAR (Working or Broken):
We’ll also purchase your uséd or broken gear and arrange pickup if you’re in our local market. Simply visit our website to submit your gear for full consideration.
SCHEDULING AN APPOINTMENT:
We are currently operating from our shop inside our dedicated building in Glen Rock, NJ.
You’re welcome to make an appointment if there’s a piece of equipment you’d like to see in operation before or after purchase. 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.
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.
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