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Grado PS1000 Headphones & Graham Slee Solo Super Ultra Linear Amp Review

Rating: 10.0.

After our review of the GS1000i headphones we were inundated with emails, asking if we could review Grado's most expensive headphones, the elusive ‘Professional Series 1000' (PS1000). With a staggering retail price around £1,700 these are a serious purchase, for a very serious music lover.

Grado headphones split opinion, some love the retro styling and others just feel they look dated. At the end of the day however you don't buy a set of headphones to look at them, the sound quality is the all important aspect of a buying design.

Grado are a well known company who produce some of the finest headphones on the market. They hold 48 patents and Joseph Grado is credited as the inventor of the stereo moving coil phono cartridge and he is responsible for more innovations in phono cartridge design than any other person. He has been inducted into the Audio Hall of Fame. His nephew John Grado has taken control of the company and this is at heart a relatively small, family run business.

Their headphones are all a vented diaphragm design that incorporates a large air chamber. This design concept lowers the frequency reasonance (distortion) of the diaphragm and extends bass response. The diaphragm is made of a low mass polymer, carefully formed to broaden resonant modes to reduce their amplitude.

The PS1000 is their range topping headphone, and the only member of their ‘Professional Series'. It is a hybrid design which uses a specially selected series of hand crafted mahogany made using an intricate curing process. The outer coating is made of metal and is machined from a special non resonant, hard metal alloy which utilises a special processing and casting method to increase the porosity of the alloy. The combination of wood and metal is design to stop any ‘ringing' which can obscure fine detail and colour the audio. After much research and development Grado achieved a design which moves air without sound vibrations being affected by transient distortions.

The PS1000 also has a eight conductor cable design which incorpoates ultra high purity, long crystal copper to improve control and stability of the total range of the frequency spectrum. With the proprietary cushion design and reconfigured voice coil the headphones are said to produce the ultimate speed and accuracy response, while creating a musicality to make listening to music a pleasure.


  • Vented diaphragm
  • Hybrid air chamber
  • UHPLC copper voice coil wire
  • UHPLC copper connecting cord
Tranducer type dynamic
Operating principle open air
Frequency response 5-50
SPL 1mW 98
Normal impedance 32ohms
Driver matched db .0

Having an expensive set of headphones is pointless if the rest of the system build is incapable of delivering the quality of signal we need. This is where Graham Slee comes into the equation.

I have been using Graham Slee amplifiers for many years now, and when we reviewed the Grado GS1000i headphones, we used his excellent ‘Solo SRGII' headphone amplifier with upgraded ‘PSU1' power supply. His new flagship headphone amplifier is called the ‘Solo Ultra-Linear' and it has been designed by Graham himself to take all the good aspects of valves/tubes into the modern age. This amplifier is causing quite a stir among audiophile circles as Graham has created a completely unique design to mimic a warm valve sound.

“It's been my intention to recreate the (original) valve sound for years simply because I liked the valve sound of yesteryear, but as I didn't fancy high tension voltages up my arm developing the circuits, I wanted to do it in solid state. Most people would think that's impossible but it isn't as I'll explain, but first I'll tell you why it was worth the effort…

Those who can recall the valve sound, or who listen using what I term a real valve amp, will be able to relate to this…

Valves sounded warmer but not over-warm – they rendered the bass much more naturally in a much less restricted way than solid state.

The valve scored in the presence band (what's now called midrange) communicating the feel of the music so you didn't have to try to get into it.

The highs sounded much clearer – not edgy – so you could easily discern between similarly sounding instruments

But mainly they made music something everyone enjoyed – families would gather round the valve set, listen, hear and enjoy, but I never saw that with solid state. The main thing I recall is being drawn into the music and being able to picture the images being painted in my mind. The valve always “told the story” better!

Good valve amps are pricey but solid state can be made much more affordable – wouldn't it be great if we could make it work?

Various arguments have been put forth as to why solid state cannot do the valve trick and the internet carries numerous points of view – some quite forceful, but still no solution. However, we touched on it to varying degrees with our earlier phono preamps but didn't fully understand how. In a way the Era Gold V and early Reflex phono preamps were almost there, with customers and reviewers suggesting they had valve-like qualities.

The Ultra-Linear technology is the result of two years almost solid research, exhaustive development and testing. We researched how to mimic all the valve’s characteristics to improve our products. What we found was that a number of op-amps (integrated circuits) could be made to perform just like valves – discrete transistor circuits being far less predictable. Graham Slee's products with Ultra-Linear technology feature significantly wider bandwidth (they go to higher frequencies) before negative feedback is applied – just like the best valve amps. What a breakthrough – valve sound at less than high-end prices!

We call this innovation Ultra-Linear because that was the tag used to describe the great performance of the best sounding valve amps that first made their appearance in the mid 1940's. These techniques vastly reduce the phase modulation distortion and linearity distortions that are hard for solid-state audio designers to perceive let alone measure. Ultra-Linear technology will feature in our top of the line products like the Solo Ultra-Linear headphone amplifier. More products will benefit from this new technology including the Reflex, Revelation and Gram Amp 3 Fanfare phono preamps plus the Elevator EXP MC step-up amplifier.

Natural like a valve: solid as a rock!

Graham Slee”

When you purchase a set of headphones at £1,700, you need partnering equipment which is going to present the music in a detailed, yet musical manner. Compact Disc technology while very convenient has always proven to be rather harsh and clinical, which is why many audiophiles have chosen to remain with their vinyl collections and expensive, high end equipment.

I believe there is nothing worse than reading an audio review and not knowing the rest of the system selected for the build. Some dedicated hi-fi magazines frequently fail to even mention the other components during reviews making it difficult to duplicate and possibly get a demo build of a similar system for yourself.

I have quite a few headphone amplifiers at home, as well as CD players and cabling, but my choice today has been selected carefully after months of fine tuning and trying to achieve audio nirvana.

As I mentioned on the last page, we are using the latest reference design from Graham Slee, the Solo ‘Ultra Linear' Headphone amplifier which retails for just over £600 inc vat in the UK.

While both units above look identical from the outside, there are significant changes under the hood.

Graham Slee has been very secretive of his ‘ultra linear module' and even when he was showing it in the early stages of design he had it coated in epoxy dip to protect the design concept. He said on his forums ‘The reason for dip coating is to protect our “intellectual property” – I'm sure if we left them uncoated our secret would be all over the world within hours. There are a few other mods over the SRGII needed to accommodate it as the module works best at a different (more) gain to the SRGII, and therefore there is also some input attenuation and other component changes to counter this.'

Graham's has also said on his public forums “If you swap from a high impedance phone to low impedance phone without swinging the volume down to where it should be, you will hear noise… This is very reminiscent of valve noise… So I guess the Solo Ultra-Linear does the valve job here too… Great!

Unfortunately, the one thing I or anybody else couldn't do all those years ago, is make valves noiseless (and still can't), but hey, it didn't matter because the sources then were not noiseless neither.

Since then we have noiseless CD and all sorts of other digital “music”. If you read up on how digital “music” works you'll see how the noise floor is cheated by “bit shifting”… you can't shift bits if you don't have any bits, and you don't have bits in analogue…

The Solo Ultra-Linear is a purely analogue amp that does not use great lashings of negative feedback to achieve ultra low noise, so, as the transducers (phones) are strapped in close proximity to your eardrums – when you wind up the “wick” – you will hear hiss and hum (like valves…!)

Now please don't play music whilst the volume's right up there or you'll probably kill your hearing, but turn it down to your usual listening level, then listen again for the noise… …did it go much quieter? Thought so… -79dB is the level below the actual musical signal where the noise appears. If you park the volume control up full when it needs to be at say 12 o'clock to blow your eardrums out, then the noise will be heard. But if you turn it to a comfortable (rockin') level then listen to the noise it will be sufficiently back (79dB back, or 10,000 approx. times back) that although you will be able to detect it, it will be of no worry to you.

A speaker amp is designed for 8 Ohms. It will have enough latitude to drive 4 or 16 Ohms and that's a ratio of 2:1 or 1:2. With the Solo, the latitude is much more (much more). It spans 25 Ohms to 300 Ohms going on the sort of headphones in use today. That's a ratio of 12:1 or 6:1 and 1:6.

Therefore that's 3 times more latitude than a speaker amp obtainable on the Solo volume control. In fact it's more than that because the Solo is designed to do 8 Ohms to 2000 Ohms giving a ratio 125:1 or 1:125.

Now I hope it can be seen that with signal to noise being a relative thing (relative to the music) that the Solo has a much bigger job to do, impedance wise, than a speaker amp?”

Cabling is also extremely important, and for this review we turned to the Graham Slee Cusat50. This is a 6.5mm diameter cable with a 1mm diameter inner conductor which is based around solid soft annealed copper, it offers a DC resistance of 0.026 ohms per metre. The Dielectric is 5 cell semi air spaced and it has an annealed copper braid over 100% copper foil wrap. The jacket is a PVC design.

This cable is one of my favourite on the market and with the Grado headphones I have found it helps to smooth out the treble while still delivering bags of fine detail. It is an expensive cable however, costing £105 in a short 0.6m length. Graham Slee also sells the cable in 1m, 1.5m, 2m and 4.5m lengths. John, who works with Graham, designs these cables for the enthusiast audio community, and his knowledge of cabling is second to none, the guy handled similar duties for the BBC for a good portion of his working life.

Our CD player of choice, is again the Roksan Kandy K2 player, which has recently been reduced in price from £1,000 to £750 inc vat. Many people would suggest that a more expensive CD player would be needed, but we have always been stunned by the quality of sound produced from this player. Many have argued with me that the Cyrus CD 6 SE is a better player, however I personally find it a little fatiguing when partnered with Grado headphones, due to slight ‘over brightness'. It works well with my Sennheiser HD800's however.

The Kandy K2 is an unusual looking player but internally it is cutting no corners. Roksan changed the CD mechanism and they improved the power supply stages and noise isolation and revamped the master clock circuitry for even more stability. In real world terms the player is easily capable of resolving huge amounts of detail especially with complex, well recorded source material, such as classical music. It is extremely refined, emotive and enoyable over many hours of listening. It won't make a poor or compressed recording sound great, but nothing does.

It will be a shock to many that a pair of £1,700 headphones arrive in such a shoddy white box. It is plain cardboard with foam inserts.

Grado are a relatively small family run business, so the presentation is sadly lacking as they put all their time and effort into the design and creation of the headphones themselves. It may bother people used to Sennheiser packaging, but we can live with it.

When the headphones are removed, there is an extension cable and a 6.35mm to 3.5 mm converter cable.

The PS1000 headphones are really very heavy, especially when compared to the wooden GS1000i's. They do however look absolutely stunning. Like the GS1000i set, the phones have an 8 conductor cable design with high quality dynamic transducers. Grado claim that the control and stability of these phones is unsurpassed throughout the range of the frequency spectrum.

The cable is reassuringly thick and is held in place with a substantial support. It ends in a 6.35mm gold plated plug. This is an extremely high quality cable as we would expect at the price.

The PS1000 is a dynamic transducer design which works on an open air principle, with a frequency response of 5hz to 50khz.

The GS1000i by comparison have a frequency response of 8hz to 35khz. Both phones have a 32 ohm impedance rating with a matched driver db rating of 0.05.

Both sets of phones are supplied with the oversized cushion design implemented by Grado many years ago for this range.

The idea is to create a ‘room’ for the ears to sit inside, which in effect creates a larger soundstage and greater spatial awareness. Grado spent many years working on fine tuning the balance between the driver and the housing to create the desired end result. Finding the sweet spot was painstaking, but they claim to have found it.

The Grado PS1000 headphones are extremely comfortable, thanks to the design the company have implemented. The ear pieces dont make contact with the ear directly due to the shape of the foam pads. Like the GS1000's headphone, they leak a lot of sound, and everyone in the vicinity will hear what you are listening to. Not ideal phones for commuting, thats for sure.

The PS1000 headphones are substantially heavier than the GS1000i, which makes them slightly less comfortable for long term use. The GS1000i become almost transparent when they are worn and you would be hard pressed to know if they are on or off. The PS1000 are heavy enough to make their presence known. I wouldn't say they were uncomfortable, but with a 500g weight, they may prove hard to handle for some of the prospective audience.

The GS1000i's are one of the finest phones I have heard to date, and while many audiophile users will argue that the Sennheiser HD800's are a better all round product I really couldn't disagree more. Music fidelity, beyond a certain point will be a very personal decision and there really is something incredibly special about Grado headphones. For me, anyway.

Initially, I found the PS1000 to be harsh and somewhat forceful, however having used many Grado headphones over the years, I knew that a long ‘bedding in' period lay in front of me. Several weeks later the drivers were starting to relax and settle into their rhythm, which I have to say is extremely moving.

They excel with timing and delivering the essense of a great recording. Dynamically they are even better than the GS1000i's which until recently I didn't think was possible.

Once fully bedded in, the transparency is bewitching, they reveal subtle nuances in recordings which you might not even be aware are there in the first place. They have a sublime ability to resolve fine detail and present it perfectly within the overall soundstage. Bass impact is more pronounced than the GS1000i, and we thoroughly enjoyed Enigma‘s MCMXC a.d. from 1990. This recording is one of the better mainstream ‘pop' releases and contains some of the most powerful low end bass frequencies we have experienced.

While a lesser headphone will distort and even skim across the surface of the bass line, the PS1000's were able to resolve an almost infinite layer of impact from ‘Principles Of Lust'. At anything even approaching half volume on the Graham Slee Ultra Linear Amplifier we could feel every one of the bass lines rammed down into the cochlea … volume misuse could cause serious ear damage. Staggering presentation would be an understatement.

Shifting quickly to the GS1000i proved that the PS1000 phones were actually resolving more detail and impact from the lowest bass frequencies. We don't often believe everything we read, so it is nice when you can experience the technical data in real world, musical terms.

Jeff Wayne's remastered musical ‘War Of The Worlds' was an extremely pleasurable experience, the presence of Richard Burton in the soundstage was incredible, his voice richly toned and delivered with all the necessary dramatic impact. Switching amplifiers to the excellent, yet budget Creek OBH11 was a good indication that the Ultra Linear was in fact doing a stellar job. The harshness of the recording was exposed, making it sound more ‘digital' and much less' vinyl'. Graham Slee has really worked wonders with this amplifier, of that I have no doubt. The treble is dynamic, yet smooth as silk, and not overly exposed as to dominate the frequencies, as is almost always the case with digital recordings.

Just as impressively, Mike Oldfield's deluxe, remastered Tubular Bells, Hergest Ridge and Ommadawn were ultimately so impressive that I could imagine myself back in time to my teenage years, listening to the vinyl recordings on my valve amplifier. Abeit, without the annoying analogue hiss and cracklings from my slightly abused collection. The Grado PS1000's are seemingly an almost perfect match for the Super Ultra Linear amplifier and I found myself actually enjoying the music, rather than tweaking the settings every 30 seconds.

Schubert‘s magical Piano Sonatas, beautifully played by Marta Deyanova again transported me to another time, when music meant something, rather than the modern day age of compressed, disposable digital downloads. The clarity and definition resolved from the system was breathtaking, yet I experienced none of the long term treble sibilance so normally associated with the medium. A warm, yet detailed undercurrent was carrying the music through the headphones, and I could feel the emotional impact of the recording in all its glory. Several hours of unadulterated enjoyment later I was finally able to move onto another of my favourite recordings.

Comparisons were able to be made with clear distinction between recordings of Bach's Sonatas & Partitas for Solo Violin, by both Pavlo Beznosiuk and John Holloway. The baroque violin that is Holloway's favoured instrument has a subtly different tone, and somewhat shows the traditional limitations of the conventional violin in repertiore. The dynamic impact and emotional tie of the passages were held firmly in place, and a full range of tones was able to transcend the normal limitations of a headphone environment.

Oxygene 7-13 by Jean Michel Jarre, the 20 bit mastered version was resolved with incredible detail, with Parts 8 and 10 exhibiting such control over the bass frequencies that I had to share the experiences with several friends. My excitement was heightened by the responses of the people who all couldn't literally believe that dynamic delivery this passionate was possible from a simple compact disc.

With the Graham Slee Super Ultra Linear amplifier in the chain, the dynamics and musicality were presented with such a rich tapestry that it was often difficult to believe that a valve based amplifier was not somehow in the chain. Sure, we could distinguish a little more background noise from this specific amplifier, but it is a part of the charm and lends itself perfectly to recapturing a warmer presentation of the music. Even when I switched to my Beyerdynamic A1 headphone amplifier, I felt somewhat disappointed and this cost me £1,000 a few years ago.

During the course of this review over many weeks, I have adjusted the components and cabling to keep improving the sound quality. What we have today, is what I would class as a ‘perfect' headphone based audiophile system.

While many people will argue about component selection, we all have a very individual view on what we expect from the reproduction of music. Those people for instance with slight hearing problems may very well aim for a sharper sound, and change cabling or amplifier to suit. What I have built for the review today has been carefully selected to give the finest sound quality from the Grado Professional Series 1000 headphones, but with a sweet, well rounded, fully bodied range of textures.

This would have been impossible without the Graham Slee Solo Super Ultra Linear Amplifier. This amplifier is a work of art, which significantly outclasses what we would assume possible from the very modest asking price. I am absolutely stunned that a large corporation hasn't offered to give Graham an extraordinary amount of money for his amplifier configurations. An engineer from South Yorkshire in England is managing to outperform organisations with infinitely more cash for research and development. While I don't know the man on a personal level it certainly appears to me that he is not in this for the money, but to push the digital audio platform into a warmer, more enlightening and enjoyable era. For those of you who yearn for a warmer sound from your collection, then this amplifier could very well be the miracle cure.

When this amplifier is combined with a high quality CD player and interconnect, the PS 1000 headphones literally have blown me away. The GS1000i is a marvellous headphone, which I thought was impossible to outperform. I was wrong, because once the PS1000 headphones are fully bedded in, they have more bass depth and a slightly more focused midrange, without a little ‘dip' in the frequency range. It would have been impossible for me to pick up on this slight weakness until fully experiencing the PS1000's.

I find it somewhat appealing that such an elusive and emotionally charged listening experience can come from the pairing of several family run businesses, rather than the merging of billion dollar corporations. Many say that true genius comes from an ultimate passion for the product, rather than trying to brainwash the public with an expensive marketing plan.

I have driven a Carl Fogarty Ducati 996 replica around the Nurburgring, I have dated many pretty ladies and I have travelled the world. I can also now add ‘ultimate musical experience' to the list of things I have achieved.

This setup I reviewed today can be bought online from various dealers for around £3,000. As a long term investment it is worth every penny.

Visit the websites of the companies involved – Grado // Graham Slee // Roksan.

KitGuru says: Astonishing sound quality, and it won't cause you to remortgage the house either.

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