Background
In about 1990, when Joseph Grado was designing his HMP-1 Holographic Scalera Scanner (perfectly-matched pair of microphones for recording), he needed some detailed, neutral headphones to diagnose the HMP-1 performance, so he developed the Joseph Grado Signature Products HP-1000 headphone (three versions- HP-1, HP-2, and HP-3). His headphones came with instructions for building a resistive divider to properly drive them from speaker terminals.
But he then saw the need for a true headphone amplifier. He engaged Sidney Stockton Smith, designer of several renown Marantz amplifiers, to design an amp, the HPA-1, that was perfect for his HP1000 and portable for use wherever needed in recording studios. Then he and Sam Cadawas, former quality engineer for Marantz, built about 150 of these at Mr. Grado's kitchen table, selling them for $795, plus a hefty wall-wart power supply, the P/S-1, for another $120. Even at that price, they lost money and soon stopped making them.
More recently, elements of HPA-1 are captured in the current RA1 amplifier now sold by Grado Labs in a wooden case. Here are both amps, along with the headphones for which each was originallly designed.
Grado Labs RA1 portable amp and RS1 headphones (left) and Joseph Grado Signature Products HPA-1 portable amp and HP1000 headphones (right).
Construction
Construction inside the HPA-1 consists of a hand-soldered prototype board of circuitry, covered on the top (component) side by a black metal shield which is glued into place. All wiring is point-to-point, and two black stubs of wire shown here function in a mysterious way (capacitors?).
Hand-built circuit board of HPA-1, covered by black metal shield. Four 9V batteries (two in use and two spare) are shown at the right.
Large capacitors (330 uF) and additional metal shielding sit just behind the front panel, and the potentiometer is the RK-40 of ALPS, the best potentiometer of the time.
Top capacitor (330 uF) filters +V and -V to ground; metal shield hangs over front panel components.
The wire used in the HPA-1 is most unusual. It consists of an outer colored insulating tube, then a mesh of copper wire braided around a central core of clear polyethylene.
Performance Tests
What can I say? The HPA-1 sounds fabulous with any of the Grado headphones. I have compared it with two less-expensive amps said to share the same circuitry, though realized out of lesser components. The HPA-1 "children" I used for comparison are the Grado Labs RA1, packaged in a carved wooden box, and the JDS Labs C-MOY BB 2.03, sold in an Altoids mint tin.
I used four songs, all encoded in Apple Lossless Format at CD quality (I actually bought the CDs and ripped them... no internet download involved) and played by my Apple iPod Touch 5th Gen. Because each of the 10 acoustic tests used a limited segment of music (2 - 10 sec), an infinite loop was used to repeat the appropriate segment of each song while headphones were switched in and out.
The 10 tests were as follows:
These tests generally emphasize what I find most pleasing in a headphone, namely high-frequency-related features including transparency, upper harmonics of sounds from drum-head, brass, organ pipe, and string bass, and high-resolution effects such as fine detail of each shaker sound and the finger on the bass string.
Performance Results
Here is how the HPA-1 compared to the RA1 and the CMOY BB 2.03. For each of the 10 acoustic features mentioned above, I ranked each amp, as heard through the Grado Labs RS2i headphones. I awarded the best performer of the three amps a first prize (blue, 3 points) for each feature, with second place (red, 2 points) and third place (yellow, 1 point) for the other amps as appropriate. I allowed for ties (2.5 points, purple, for tie for first; 1.5 points, orange, for ties for second place).
Comparison of the Joseph Grado HPA-1 to the Grado Labs RA1 and JDS CMOY BB 2.03 shows HPA-1 with overall top score, excelling on bass and soundstage width (all used the Grado RS2i headphone).
Score differences of less than three are not likely significant. Best performance was given by the Joseph Grado Signature Products HPA-1 (also the most expensive, at $1,000, though out of production). The Grado Labs RA1 scored second, with a bit less soundstage and less subbass. The CMOY was third, but was a very good amp. However, the CMOY had one significant problem -- for the subbass test (Song #4 above), the subbass tone was very distorted. This held at any volume level, and the batteries were fresh. The bass boost was turned off on the amp.
But aside from this subbass problem with the CMOY (which is a rare occurence), the differences were small enough that if I were just presented with one amp to hear, I would not likely be able to tell which it was.
I also explored the ability of the HPA-1 to drive another headphone, the HiFiMAN HE1000 that has just been released. The HE1000 is a planar magnetic headphone retailing for $2,999, stated to have an input impedance of 35 ohms +/- 5 ohms, not too different than the 32 ohms of the Grados. However, the HE1000is of less efficiency than the Grados, advertised at 90 dB per mW but measured by some as even lower (the Grados are generally 97 db - 100 dB / mW). I performed two three-way comparisons - to the CEntrance HiFi M8 portable DAC/amp and Sennheiser HDVD 800 DAC/amp (first table), the HiFiMAN EF6 and EF5 (second table),and to the Schiit Lyr 2 and HiFiMAN EF-6 amps (third table).
Comparison of HPA-1 to CEntrance HiFiM8 and Sennheiser HDVD 800 DAC/amps driving the HiFiMAN HE1000 headphone shows that the HPA-1 ties the HDVD 800.
Surprisingly, the HiFi M8 performed overall more poorly than the other two amps. It was never first place for any of the 10 acoustic characteristics. The HDVD 800 won on transparency, while the HPA1 provided the largest sound stage. In fact, the larger sound stage of the HPA1 was apparent within the first few seconds of listening. All of the amps sounded excellent with the HE1000.
Comparison of two HiFiMAN amps, the EF5 and EF6, to the Joseph Grado HPA1 place the HPA1 performance between that of the EF5 and E6.
Surprisingly (at least to me), the Grado amp performed significantly better than the EF5 amp. The EF6 amp performed best of all. Both the EF5 and the Grado amp required volume turned up to 90% -100% of full, while the EF6 kept the volume around 50%. I conclude from this comparison that a ~$500 amp (such as the Schiit Lyr 2, a hybrid tube/op-amp amp that I had been considering), at least to the extent of its similarity to the EF5 hybrid amp, would not perform as well as the Joseph Grado HPA1 that I already have (though the Lyr2 puts 6W, not 1-2 W, into 32 ohms, so there is a difference with the EF5).
When compared to the Schiit Lyr 2 and the HiFiMAN EF-6 amp, the HPA-1 performs less well in driving the HE1000. Both the Lyr 2 and the EF-6 can put 5 - 6 watts of power into 35 ohms, far more than the HPA-1.
As shown above, the HE6 outshone the Lyr 2 (and the Grado HPA1) for driving the HE1000, having better soundstage, more transparency, and better bass impact. The volume control on both the Lyr 2 and the HPA1 was at about 90% of full; the volume knob on the EF-6 was at about 50%. However, differences in sound between first and second place, and second and third place, were very small for these amps -- even the HPA1 sounded very, very good with the HE1000.
Conclusion
What can I say? The HPA-1 sounds fabulous with any of the Grado headphones, and it does a great job of driving a lower-efficiency headphone, the HiFiMAN HE1000. Additionally, there is the mental vision of the late Joseph Grado, perhaps wearing his huarachi suspenders, hunched over his kitchen table, soldering iron in hand, building My amp, for ME!
In about 1990, when Joseph Grado was designing his HMP-1 Holographic Scalera Scanner (perfectly-matched pair of microphones for recording), he needed some detailed, neutral headphones to diagnose the HMP-1 performance, so he developed the Joseph Grado Signature Products HP-1000 headphone (three versions- HP-1, HP-2, and HP-3). His headphones came with instructions for building a resistive divider to properly drive them from speaker terminals.
But he then saw the need for a true headphone amplifier. He engaged Sidney Stockton Smith, designer of several renown Marantz amplifiers, to design an amp, the HPA-1, that was perfect for his HP1000 and portable for use wherever needed in recording studios. Then he and Sam Cadawas, former quality engineer for Marantz, built about 150 of these at Mr. Grado's kitchen table, selling them for $795, plus a hefty wall-wart power supply, the P/S-1, for another $120. Even at that price, they lost money and soon stopped making them.
More recently, elements of HPA-1 are captured in the current RA1 amplifier now sold by Grado Labs in a wooden case. Here are both amps, along with the headphones for which each was originallly designed.
Grado Labs RA1 portable amp and RS1 headphones (left) and Joseph Grado Signature Products HPA-1 portable amp and HP1000 headphones (right).
Construction
Construction inside the HPA-1 consists of a hand-soldered prototype board of circuitry, covered on the top (component) side by a black metal shield which is glued into place. All wiring is point-to-point, and two black stubs of wire shown here function in a mysterious way (capacitors?).
Hand-built circuit board of HPA-1, covered by black metal shield. Four 9V batteries (two in use and two spare) are shown at the right.
Large capacitors (330 uF) and additional metal shielding sit just behind the front panel, and the potentiometer is the RK-40 of ALPS, the best potentiometer of the time.
Top capacitor (330 uF) filters +V and -V to ground; metal shield hangs over front panel components.
The wire used in the HPA-1 is most unusual. It consists of an outer colored insulating tube, then a mesh of copper wire braided around a central core of clear polyethylene.
Performance Tests
What can I say? The HPA-1 sounds fabulous with any of the Grado headphones. I have compared it with two less-expensive amps said to share the same circuitry, though realized out of lesser components. The HPA-1 "children" I used for comparison are the Grado Labs RA1, packaged in a carved wooden box, and the JDS Labs C-MOY BB 2.03, sold in an Altoids mint tin.
I used four songs, all encoded in Apple Lossless Format at CD quality (I actually bought the CDs and ripped them... no internet download involved) and played by my Apple iPod Touch 5th Gen. Because each of the 10 acoustic tests used a limited segment of music (2 - 10 sec), an infinite loop was used to repeat the appropriate segment of each song while headphones were switched in and out.
- "You're Going To Miss Me When I'm Gone," by Band of Heathens, from their album One Foot In The Ether (used for fidelity of drum sound, positional resolution of two vocalists, and ability to discern pitch of string bass passages);
- "Spanish Harlem," by Rebecca Pidgeon, on The Ultimate Demonstration Disc of Chesky records (used to assess female vocals, transparency, the attack of finger on bass string, and high resolution discrimination of differences in shaker shakes);
- "Symphony No. 3 in C Minor Op. 78 (Organ Symphony) - IV" by Camille Saint Saens played by Lorin Maazel and the Pittsburgh Symph
ony Orchestra (used to assess the "ripping" sound of well-rendered lower brass and organ reed pipes, and the ability to hear a very small entrance amidst a bombastic chord of orchestra and organ at full tilt); - "Throwback" by B.o.B. on Underground Luxury (used to assess ability of a bass tone, specifically lowest C on piano at about 32 Hz, to pick me up by the throat and shake me!)
The 10 tests were as follows:
- Transparency: What is between me and the music? A felt cloth? A "Sennheiser veil?" A frosted window? Dirty window? Clear Saran wrap? or nothing? At its best, makes me forget I am listening on headphones and am in room with musicians. [I use the 12-second segment 0:00 - 0:12 of "You're Going To Miss Me," which is kick drum, guitar, piano, and cymbal for this test]
- Width of sound stage: How far to the left and to the right, (yes, AND up and down in best cases) does it seem the musical sources are arranged? [I use the same 0:00 - 0:12 segment of "You're Going To Miss Me," which starts with kick drum center, guitar #1 right of center piano far right, guitar #2 far left, to see 1) to what extent am I among rather than in front of the musicians, and 2) how wide an angle do those positional extremes of instruments form?]
- Positional resolution: Can I distinguish a difference in position of two singers in Song 1? [I use 0:30 to 0:38 of "You're Going To Miss Me," where one vocalist ends a verse and a second vocalist, standing next to him, takes up the next.]
- Bass visceral: Does the bass in third verse of Song 4 actually shake me? Or do I just hear it? [This test uses 0:31 through 0:33 of "Throwback, " where the bass drops to the lowest C on the piano.]
- Drum "twang": At start of Song 1, do the bass and tom tom drumhead have a tone and a pitch, rather than just a thump? ["You're Going to Miss Me" 0:00 - 0:12]
- Bass pitch perception: For the complicated bass runs in Song 1, do I hear a pitch with sufficient accuracy to sing or transcribe the part? ["You're Going to Miss Me," 1:02 - 1:23 to see if I can hear the pitch of not only the bass glides and accented notes, but also the grace notes]
- Bass finger pluck: Do I hear the actual impact of fingers on the bass string just before hearing its sound on Song 2? ["Spanish Harlem," 0:00 - 0:04, listening most carefully to the repeated 3-note pattern to see if I not only hear an initial attack but some structure immediately following, before the finger leaves the string and the sound just rings)
- Shaker variation: In Song 2, verse 3, do the various shaker shakes sound a bit different from each other, as they should? ["Spanish Harlem," 1:40 - 1:47: there are clearly loud and soft shakes, but how many more volume levels of shakes can I distinguish, and can I hear structure within each shake as the seeds hit the shaker wall?]
- "Ripping" of organ / brass: In Song 3, is there the sensation of hearing each vibration of the French horn and low organ reed tones (sort of the tonal counterpart to hearing a "pitch" from a drumhead in Test 5); ["Organ Symphony," initial chord from 0:00 - 0:04 and French horn passage 0:06 - 0:12]
- Discern added chord: About 1:38 into Song 3, after the full orchestra and organ hold a chord at the top of a passage, can I hear a small number of orchestra instruments join in, as sort of an echo, in the second measure of that chord? ["Organ Symphony," in the passage starting at 1:08, how well can I hear the small additional chord added at 1:16 on top of the full strength organ/orchestra chord in progress? Clearly enough to have noticed it if I weren't already listening for it?]
These tests generally emphasize what I find most pleasing in a headphone, namely high-frequency-related features including transparency, upper harmonics of sounds from drum-head, brass, organ pipe, and string bass, and high-resolution effects such as fine detail of each shaker sound and the finger on the bass string.
Performance Results
Here is how the HPA-1 compared to the RA1 and the CMOY BB 2.03. For each of the 10 acoustic features mentioned above, I ranked each amp, as heard through the Grado Labs RS2i headphones. I awarded the best performer of the three amps a first prize (blue, 3 points) for each feature, with second place (red, 2 points) and third place (yellow, 1 point) for the other amps as appropriate. I allowed for ties (2.5 points, purple, for tie for first; 1.5 points, orange, for ties for second place).
Comparison of the Joseph Grado HPA-1 to the Grado Labs RA1 and JDS CMOY BB 2.03 shows HPA-1 with overall top score, excelling on bass and soundstage width (all used the Grado RS2i headphone).
Score differences of less than three are not likely significant. Best performance was given by the Joseph Grado Signature Products HPA-1 (also the most expensive, at $1,000, though out of production). The Grado Labs RA1 scored second, with a bit less soundstage and less subbass. The CMOY was third, but was a very good amp. However, the CMOY had one significant problem -- for the subbass test (Song #4 above), the subbass tone was very distorted. This held at any volume level, and the batteries were fresh. The bass boost was turned off on the amp.
But aside from this subbass problem with the CMOY (which is a rare occurence), the differences were small enough that if I were just presented with one amp to hear, I would not likely be able to tell which it was.
I also explored the ability of the HPA-1 to drive another headphone, the HiFiMAN HE1000 that has just been released. The HE1000 is a planar magnetic headphone retailing for $2,999, stated to have an input impedance of 35 ohms +/- 5 ohms, not too different than the 32 ohms of the Grados. However, the HE1000is of less efficiency than the Grados, advertised at 90 dB per mW but measured by some as even lower (the Grados are generally 97 db - 100 dB / mW). I performed two three-way comparisons - to the CEntrance HiFi M8 portable DAC/amp and Sennheiser HDVD 800 DAC/amp (first table), the HiFiMAN EF6 and EF5 (second table),and to the Schiit Lyr 2 and HiFiMAN EF-6 amps (third table).
Comparison of HPA-1 to CEntrance HiFiM8 and Sennheiser HDVD 800 DAC/amps driving the HiFiMAN HE1000 headphone shows that the HPA-1 ties the HDVD 800.
Surprisingly, the HiFi M8 performed overall more poorly than the other two amps. It was never first place for any of the 10 acoustic characteristics. The HDVD 800 won on transparency, while the HPA1 provided the largest sound stage. In fact, the larger sound stage of the HPA1 was apparent within the first few seconds of listening. All of the amps sounded excellent with the HE1000.
Comparison of two HiFiMAN amps, the EF5 and EF6, to the Joseph Grado HPA1 place the HPA1 performance between that of the EF5 and E6.
Surprisingly (at least to me), the Grado amp performed significantly better than the EF5 amp. The EF6 amp performed best of all. Both the EF5 and the Grado amp required volume turned up to 90% -100% of full, while the EF6 kept the volume around 50%. I conclude from this comparison that a ~$500 amp (such as the Schiit Lyr 2, a hybrid tube/op-amp amp that I had been considering), at least to the extent of its similarity to the EF5 hybrid amp, would not perform as well as the Joseph Grado HPA1 that I already have (though the Lyr2 puts 6W, not 1-2 W, into 32 ohms, so there is a difference with the EF5).
When compared to the Schiit Lyr 2 and the HiFiMAN EF-6 amp, the HPA-1 performs less well in driving the HE1000. Both the Lyr 2 and the EF-6 can put 5 - 6 watts of power into 35 ohms, far more than the HPA-1.
As shown above, the HE6 outshone the Lyr 2 (and the Grado HPA1) for driving the HE1000, having better soundstage, more transparency, and better bass impact. The volume control on both the Lyr 2 and the HPA1 was at about 90% of full; the volume knob on the EF-6 was at about 50%. However, differences in sound between first and second place, and second and third place, were very small for these amps -- even the HPA1 sounded very, very good with the HE1000.
Conclusion
What can I say? The HPA-1 sounds fabulous with any of the Grado headphones, and it does a great job of driving a lower-efficiency headphone, the HiFiMAN HE1000. Additionally, there is the mental vision of the late Joseph Grado, perhaps wearing his huarachi suspenders, hunched over his kitchen table, soldering iron in hand, building My amp, for ME!
- All the internal wiring is made with Joseph Grado UWBRC. It has an polyethylene core with braided copper around. The Joseph Grado Standard Audio Cable has a classic copper core.
-While testing the HPA amp Joe has also found that minor frequency response differences between the left and right channels, even if they're in the 150 kHz to 200 kHz region, affect the performance of the amplifier. So, compensation capacitors made of two pieces of parallel "Grado wire" are handtrimmed during the assembly process to insure a precise match between the two channels.