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PRODUCT DESCRIPTION:
Our new
Grado Phono
Preamp, model
PH-1, represents the
most successful solution to one of the most complex technical challenges in the field of audio
that Grado Labs has ever tackled. It can be compared to
the undertaking of designing our highly acclaimed phono cartridges, headphones and our
world renowned RA-1 headphone amplifier over the past several years. Our design goals were for a truly
superb sounding phono
preamp to work equally well with both low and high output cartridges with negligible noise. We wanted a phono preamp with
ultra wide band pass, high overload, virtually perfect RIAA amplitude and phase
coherency, and very low output impedance.
This was the challenge set forth! This we have accomplished!
We realized immediately that a challenge like this was not going to be met by using either of the time-honored methods of passive or
active equalization circuits. The relative advantages and disadvantages of these old methods are very well known: the
passive preamp approach is characterized by problems of first stage headroom and second stage noise. This is due to the 40dB
high frequency insertion-loss of the passive network itself. Phono stage gain is frequency dependent with the result of too little
feedback at the low end and too much at the high end. Of course, both extremes are sonically non-optimum and unacceptable.
The more commonly used active equalization stage provides solutions to the classic
passive circuit problems, but it also comes with a whole new set of its own problems. These
difficulties arise out of the subtle ramifications of the classic negative feedback theory. The
RIAA characteristic requires that the amplifier's closed-loop gain needs to change by a hundred to one (40dB) over the entire audio
range. This means too little feedback-closure at low frequencies and too
much at high frequencies. Too little causes inadequate suppression of simple distortions, and too much causes the
generation of complex distortions (high-order).
The new Grado Phono
Preamp circuit design now has all of the
advantages of the old methods, yet none of its antiquated disadvantages! The challenge was met! The processing problem
has been split into two separate parts: a forward propagating signal current and a back propagating error voltage. We have
indeed eliminated all of the past methods. Our new phono equalization technique is a derivative of the principals that we used
in our highly regarded RA-1 headphone amplifier. In this design, feedback closure ratio does not change with frequency, but the
total output gain does. Virtually all latter stage noise disappears! The
output impedance is very low, with the EQ stage opened-loop and the closed-loop gain being the same. The best of both worlds!
What is so significant about these new innovations is the fact that the technical superiority claims absolutely correlate to an
unprecedented improvement in openness, greater depth of field and increased definition to the sound of each musical instrument.
The PH-1 offers a true freedom from past sonic problems along
with
Grado's
usual warm, smooth, full bodied, non-fatiguing and rich sound qualities that everyone has embraced.
If your turntable is driven with a Grado cartridge then you deserve to go the final step with the new
PH-1 phono
preamp.
Happy Listening!
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