Pioneer SPEC-1 Vintage Preamp with Two Phono Inputs - Serviced in 2023

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General:
Pioneer made some incredible HiFi gear in the 1970's and this Spec-1 is absolutely no exception - it's an amazing preamp.

We love the LARGE looks - in particular the size of the knobs and the brushed aluminum faceplate. 

This is a feature-rich preamp packing functions not commonly found on othesrs. There are two tone controls for bass and treble, and a switch to defeat them completely. There are a total of five inputs, with an additional gain control for the 2nd turntable input, plus two tape inputs. 

That's right - two phono inputs while some preamps don't even offer one.

There's also a handy attenuator switch that adjusts the overall gain allowing you to get the most resolution from the volume control. The independent low and high pass filters allow you to tailor your specific setup to protect your amplifier and speakers.

Lastly, this preamp features a unique setting giving you the option to feed amplifier speaker outputs through this preamp - then controlling them via the front panel selector. 

This preamp was carefully reviewed and fully tested in 2023 by our in house technician. Every function, switch, knob, and connector works as it should. All controls were cleaned and lubricated, and the knobs were removed for a thorough cleaning.  

On our test bench this preamp passed with flying colors and is super quiet. Included will be a reprint of its owners manual.

SkyFi Cosmetic Notes:
Very light wear is present on the side panels and covers. The included manual is a reprinted copy. Overall, excellent.

SkyFi Technical Notes:
This unit was serviced here at SkyFi in March 2023. It passed repeat bench testing with flying colors.

Brand Background:
Link to Pioneer Home Audio History
https://global.pioneer/en/corp/info/history/chronology/archives/1968

Ownership:
Second Owner

Connections:
RCA, Speaker Binding posts, Ground, Captive power cord

General Sound:
Smooth, uncolored, undistorted natural and clean

Cosmetic Condition:
8/10 = Very Good. Excellent front faceplate, one minor flaw on chassis side or top. See our detailed rating description here.

Working Condition:
Working perfectly and tested in our lab and listening room.

Included:
Unit, manual, and power cord.

Packing:
Will be packed using our highly developed in-house process and custom packing materials.Specs:
Frequency Response:
10 Hz to 70,000 Hz

THD:
0.03%

Input Sensitivity:
2.5mV (mic)
2.5mV (MM)
150mV (line)

Signal to Noise Ratio:
70dB (MM)
90dB (line)

Output:
150mV (line)

2V (Pre out)
Approximate Year:
1976

Dimensions:
18.90" x 7.34" x 14.37"

Weight:
25 lbs.

Approximate Age:
1976

Link to Manual:
Click Here

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects

Testing Process:
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 the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface.

The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1 KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope.

We then switch to a 1 KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment.

Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.

We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected.

If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.