Grado PH-1 phono preamp.
Source: Manufacturer loan
High Gain: 1.2 mv
Low Gain: 7 mv
Signal to Noise Ratio: 85 dB
Distortion (THD): Less than 0.1%
Separation: Greater than 50 dB
Frequency Response: 0.1 dB (20-400 KHz)
Output Impedance: 50K ohms
For all those music lovers who still enjoy LP records, there's a very capable phono preamp that can add both sonic and visual appeal to your system. Grado Labs is well known for its headphones, headphone amplifier and phono cartridges. Now they also have the Grado PH-1 phono preamp, which is a solid-state unit in an enclosure machined from a rectangular block of mahogany. All edges are chamfered, for a touch of class. The PH-1 is 1-1/2-inches tall x 5-1/8 -inches wide x 5-1/2-inches deep and stands on 5/16-inch tall elastomer feet. Centered on the front panel is a red LED that is lit when the unit has incoming power from the supplied 12-volt DC output transformer. On the bottom of the PH-1 is a switch to select between hi and low output cartridges. However, the instructions must be read carefully, as "H" means that the preamp output is high (56 dB for 0.4 to 1.5 mV LOW output cartridges)--and "L" means a lower preamp output of 40 dB boost for 1.5 to 4.5 mV HIGH output cartridges).
The back of the PH-1 has, from left to right, right and left output jacks, grounding post, right and left input jacks, and a BNC connector for the power. The jacks are gold-plated. The component parts appear to be high quality and Grado Labs provides a one-year warranty against defects.
Direct comparisons in this review are with my Parasound P/PH-100 phono preamp. Although the Parasound was in the slightly under $150 price range when new, it has served me well for a number of years and is the only other separate preamp I had on hand for comparisons. Other system components included a Bryston BP25 preamp and SST 4B power amplifier with Thiel CS 2.4 speakers. Sources were a Thorens TD320 Mk III turntable with Grado Reference Platinum and ClearAudio Aurum Beta phono cartridges. Speaker connections were via Kimber 8TC cables. Interconnect cables by Vampire and WireWorld
The function of a phono preamplifier is two-fold. First, it must boost the output of the small signal generated by the phonograph cartridge to a level sufficient to be properly utilized by the system preamplifier. Second, it must accurately reverse the frequency response of the RIAA curve used during recording of a record. The RIAA curve boosts high frequencies and decreases low frequencies during record cutting to make the record groove widths more constant and preclude unreasonable stylus excursions at low frequencies. During record playback, the low frequencies are electronically boosted while the high frequencies are attenuated in the reciprocal of the curves used during record cutting. This restores the bass and provides an improved signal-to-noise ratio at the higher frequencies, as well as extending playing time by decreasing the space taken up for lower frequencies.
For many years, Grado Labs has been manufacturing phono cartridges of high sonic quality. The PH-1 phono preamp is a relatively new addition to their list of products. The company's stated design goal was a high quality phono preamp that worked for both high and low output phono cartridges. Among their criteria were low noise, wide bandpass, high overload capacity, accurate RIAA amplitude and phase coherency, and low output impedance. Grado Labs states that both passive and active equalization circuits have problems. To ensure accuracy, I am quoting the information provided by Grado Labs verbatim in the following paragraph:
"The passive approach is characterized by problems of first stage headroom and second stage noise, due to the 40 dB high frequency insertion-loss of the passive network. Phono stage gain is frequency dependent with the result of too little feedback at low end and too much at high end. Both extremes are sonically non-optimum. The more commonly used active equalization stage provides solutions to the classic passive circuit problems, but comes with a whole set of its own problems arising out of classic negative feedback theory. The RIAA characteristic requires the amplifier's closed-loop gain to change by a hundred to one ration (40 db) over the audio range. This simply means too little feedback-closure at low frequency and too much at high frequency. Too little causes inadequate suppression of simple distortions, too much causes generation of complex (high order) distortions. Grado's new circuit has all the advantages of both old methods and disadvantages of neither. The processing problem has been split in to two parts, a forward propagating signal current and a back propagating error voltage, thus eliminating the limitations of all past methods. This phono equalization technique is a derivative of the principle used in the highly regarded Grado headphone amplifier (RA-1). In this design, feedback closure ratio does not change with frequency but total output gain does, virtually all latter-stage noise disappears. Output impedance is very low, with EQ stage open-loop and closed-loop gain being the same."
To make comparisons between the Grado and the Parasound phono preamps, the two phono preamp outputs were connected to adjacent inputs on my Bryston preamplifier, to enable switching easily between them. A sound level meter at the listening position and a test record with pink noise were used to identify the volume level differences between the two preamps and mark the two settings on the Bryston's volume control. I was then able to make quick and accurate comparisons between the two phono preamps at the same volume level.
The PH-1 worked very well with my system using both the Grado and ClearAudio phono cartridges. I monitored the direct electrical outputs by frequency using my ADC SS-525X analyzer and the Soundcraftsmen ITR-3292 test record band "Continuous All Band Pink Noise for General EQ Use". Aside from the Grado having 4 dB more overall output and than the Parasound, output was close to being the same at all frequencies. The exceptions were the Grado's 2 dB flatter output at 25 Hz and the Parasound's 2 dB boost at 250 and 500 Hz.
I used a variety of records and types of music for auditioning the Grado PH-1. Among them were: First Time--The Count Meets The Duke, Duke Ellington and Count Basie--Recorded 7/6/61 in NY City (Columbia CJ40586), The Best of Ray Charles (Atlantic Jazz Anthology SD 1543), J.S. Bach, The Unaccompanied Cello Suites, Yo-Yo Ma (CBS Masterworks IM39345), Sara Vaughan Sings George Gershwin, Vol. 2 (Mercury MG20311), and Hip Hug-Herby Booker T. and the MGs (STAX 717). On all of these and a wide variety of other records, the PH-1 performed very well. Tonality, spaciousness, depth, male and female vocals, and all sound qualities were as they should be. Bass was deeper and the soundstage a bit wider and slightly more dimensional with the PH-1 when that information was on the record. There was no apparent unnatural emphasis of any characteristics of the recordings.
Of course, there are many variables possible, from the quality of the recording and the record, to the cartridge used, the turntable, tonearm, speakers, room and the listener's ears. I was very pleased with the performance of the Grado Labs PH-1 phono preamp. As today's phono preamp prices go (some costing thousands of dollars), the PH-1 is as good a value monetarily as it is sonically. In addition, its high quality of components and elegant visual appeal are additional pluses. Record lovers would do themselves a favor by auditioning the Grado Labs PH-1 before purchasing another phono preamp.--JTF
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|Author:||Frane, James T.|
|Date:||Apr 1, 2006|
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