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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”

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