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Owner’s Reference
GCPH Phono Preamplifier
4826 Sterling Drive, Boulder, CO 80301
Introduction
PH: 720.406.8946 [email protected] www.psaudio.com
15-044-11-1
Rev B
®
©2005 PS Audio Inc. All rights reserved.
Introduction
Thank you for your purchase of the PS Audio GCPH Phono Preamplifier.
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.
The GCPH is built around the same design philosophy all PS phono preamplifiers have enjoyed over
the last 30 years: a passive RIAA 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”.
What Will It Do?
History of The
Curve
Passive RIAA
Curve
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