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

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.

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