PS Audio GCPH Phono Preamp - Modified by Parts Connexion

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General:
The GCPH phono preamp from PS Audio is very compact and features a passive RIAA equalization along with balanced outputs for the lowest amount of signal noise.

This preamp is compatible with both MM and MC, cartridges and settings such as gain and input loading are easily accessible as knobs on the back panel.

This particular preamp was also modified by "Parts Connexion" and contains upgrades such as audio-grade capacitors and shielding.

Tested and working perfectly. Will include its original manual and a power cord.

From PS-Audio
The GCPH is a high-end standalone phono preamplifier, designed for the highest quality phono reproduction possible.

It is based on PS Audio’s unique Gain Cell Technology and over 30 years of designing state-of-the-art phono stages.

PS Audio built its first phono stage in 1973 and has been responsible for some of the most loved vinyl amplification electronics the Audio world has ever known.

Passive RIAA Curve
The GCPH is built around the same design philosophy all PS phono preamplifiers have enjoyed over the last 30 years: a passive RIAA curve.

History of the curve
The RIAA curve is a specification for the correct playback of vinyl records, established by the Recording Industry Association of America (RIAA).

The purpose of the equalization curve is to permit greater playback times, improve sound quality, and to limit the physical extremes that would otherwise arise from recording analog records without such equalization. The RIAA curve has operated as a de facto global industry standard for the recording and playback of vinyl records since 1954.

Prior to that time - mainly between 1940 and 1954 - each record company applied its own equalization; there were over 100 combinations of turnover and rolloff frequencies in use, the main ones being AES, LP, NAB and FFRR. The RIAA standardized the EQ curve for records and hence the majority of vinyl LP’s are recorded to this standard. Before 1940, most records were cut flat. This included broadcast recordings and motion picture recordings before sound-on-film.

If you play a pre-WWII 78rpm record through a modern preamp, you will effectively be playing it with a scratch filter whose cutoff begins at 2200Hz, giving lack of high frequencies and muffled voices.

RIAA equalization is a form of pre-emphasis on recording, and de-emphasis on playback. A record is cut with the low frequencies reduced and the high frequencies boosted, and on playback the opposite occurs. The result is a flat frequency response, but with noise such as hiss and clicks arising from the vinyl surface attenuated. The other main benefit of the system is that low frequencies, which would otherwise cause the record cutter to make large excursions when cutting a groove, are reduced so grooves are smaller and more can be fitted in a given surface area, yielding longer playback times (hence the term “LP” or Long Play records).

RIAA equalization is not a simple low-pass filter. It carefully defines roll-off points in three places, 2122 Hz, 500 Hz and 50 Hz. There are multiple means of achieving this curve in a phono preamplifier, but the two main implementations are active and passive. Active means the RIAA curve is in the feedback loop of the preamplifier and passive means it is outside any feedback loop. PS Audio has always believed the best performance will be achieved when the curve is outside the feedback loop of the internal amplifier because the amplifiers’ performance will change with frequency. This is because at high frequencies the negative feedback of the phono preamplifier will be very high and at low frequencies, relatively low.

Our design philosophy of preamplification has always revolved around the notion of keeping negative feedback low and uniform at all frequencies. Thus, a passive RIAA curve is “just what the doctor ordered".

Accuracy is critical
Whatever method is employed, it is absolutely critical the curve be as exact as possible. Deviations of more than a tenth of a dB are unacceptable. The GCPH is flat to the RIAA standard by less than 0.1dB.

A unique feature of the GCPH is the multiple gain setting adjustment methods. The coarse gain settings are available on the rear of the unit, the fine gain setting available via a volume control like knob on the front panel. The front panel gain adjustment also allows the GCPH to be used as a standalone phono preamplifier, feeding the purest phono signal possible directly into your power amplifier.

Enjoy!
You should expect unrivaled sonic qualities, with low noise, high performance audio being delivered to your system through this unique and ground breaking phono preamplifier.

SkyFi Cosmetic Notes:
There is also a small blemish near the top left corner of the faceplate. Overall very good condition.

SkyFi Technical Notes:
This unit was modified by Parts Connexion in 2012. As far was we can tell the modification included the following. 1. Addition of a metal mesh shield between the power transformer and main PCB, new rectifier diodes, select audio grade capacitors, and WBT RCA and ground jacks.

Ownership:
Second Owner

Connections:
RCA, Ground, XLR, IEC power

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.Reviews:
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Specs:
- Type: Solid-state MM/MC phono preamplifier
- Cartridge Type: Accommodates both moving-coil (MC) and moving-magnet (MM) cartridges
- RIAA Accuracy: ±0.1dB
Voltage Gain:
- Unbalanced: 42/48/54/60dB
- Balanced: 48/54/60/66dB
- Input Impedance: 100/500/1k/47k ohms
- Output Impedance: 100 ohms
Features:
- Runs in fully differential mode
- Front-panel volume control
- Rear controls for cartridge resistance loading and input amplifier gain
- Switches for mono/stereo and phase reversal

Recommended Cables:
Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Phono Interconnects

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Kimber Kable - Power Cords - Better

Kimber Kable - Power Cords - Best

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.