Buying used - Cyrus One/Two

Expect to pay :  £100  to £150 for a working Cyrus One and £125 to £175 for the Cyrus Two (higher price for boxed, mint  examples and £100 to £175 for a PSX Power Supply)

 

With over 700 examples of this amplifier having passed through the workshop as of October 2022 this amplifier is by far the most popular overhauled here!

 

Avoid - overpriced supposedly 'serviced' examples by well meaning 'Ebay amateurs' - they are rarely if ever properly serviced and often end up in this workshop eventually!

 

With a production lifetime spanning 1984 to 1992  tens of thousands of these bargain priced unusual little amplifiers were produced and they certainly made a sizeable dent in the world of overpriced high end audio out of all proportion to their diminuitive footprint and modest budget appearance and continue to do so even today.  Compared to a warm valve-like Musical Fidelity of the same era the Cyrus is a much more detailed, lively, crisp and precise sound which many users say will easily show up a below par source! Both One and Two models share exactly the same printed circuit boards. The major differences being the 50W Two model having a bigger 40V 200VA PSU (28V 100VA in the 25W per channel One) and either double the number of output transistors or the more robust BUV48 transistors used over the One. The Two also has a lower noise LM394CH MC input stage for the phono amplifier over the simpler switched gain Op amp design used in the One with the MM stage being identical in both. FInally a socket for the PSX external 40V supply is  also provided . Cyrus did produce an upgraded 'Signature' edition of the Cyrus Two which was supplied together with a PSX.  In 1990 this cost £900 which was a £360 premiium over the standard Cyrus 2 and PSX (£330 and £230 respectively.  

 

Despite many proclaiming differences in sound with some saying this one or that one is better in reality there is little if any audible difference between any of the models despite the differing output power as they are all excellent. WIth only very minor changes to the overall circuit over it's 8 year lifespan there really is no engineering reason why one should sound any different to another unless it's faulty! Even the addition of a PSX with it's 500VA capability doesn't make as much of a difference as your now lighter wallet may be kidding your brain to tell yourself you can hear!  You may detect a perceptable improvement in the upper half of the volume scale but it won't make a jot of difference at normal listening levels. As long as you don't expect to be 'blown away by earth shattering bass' then you won't be disappointed with your PSX purchase. The other problem with the PSX is the short power lead to the Cyrus Two allowing you to place it only on one side of your amp. This can be extended quite easily though to any custom length if you know what you are doing.

 

The very first models were known as Issue 06 and sported a plastic cover and fascia with a pressed steel chassis. With only 3 line inputs plus the phono stage it's easy to quickly run out of inputs with these. By 1987 the virtually identical circuit was to be found in a much heavier diecast chassis and fascia with thin and rather brittle diecast cover (the plastic 06 one is the strongest ironically). Known as the 07 version it now had an extra line input (labelled 'Video') and a balance control combined with the volume potentiometer (these components are obsolete and unreplaceable)  The final change in 1989 finally rid the range of the over complicated and unreliable plastic on/off mechanism to the offset power switch replacing the whole assembly with a single fascia mounted toggle switch.  Earlier models also had a headphone socket but this was of limited use as it didn't disconnect the speakers when used.  A Cyrus One with these sockets does make a fine compact stand alone headphone amplifier incidentally and far better value for money than an overpriced glitzy box with little more than a couple of 50 pence Op Amps in that seem to be all the fashion these days.

 

Overall the better value for money is the Cyrus One (06 or 07) as they sound the same as the Two, are much cheaper and there are plenty more of them. Also the phono stage supply regulators run cooler with the lower input voltage used in the One and don't 'slow cook' everything adjacent to them.  If you don't covet remote controls,  LCD displays and DAC's then a good one of these will serve you well for years to come. The 07 model does have a far better heatsink over the simple piece of bent aluminium in the 06 One models so if your amplifier is likely to spend a long time at high volumes this will probably survive a little longer before it's output transistors expire (NXT make an excellent modern and more robust upgrade to the long obsolete BUV28A transistors)

 

What goes wrong?:

With an age of between 30 and almost 40 years old the vast majority of Cyrus One/Two models will be suffering from at least one of the ailments listed below if not several.  Many private sellers will often dig one of these out from a damp dusty loft, quickly test it on one line input only into a set of speakers for a few minutes and then advertise for sale proclaiming it in perfect working order. In reality the phono stage will probably suffer excessive hum and most inputs will drop out on at least one channel in addition to a crackling volume/balance control. A normally functioning phono stage should 'hiss' slightly as you approach full volume (same but higher for MC setting in Cyrus One, slightly less noise in a Cyrus Two). If you are having one of these shipped to you without the original box do make sure that the seller provides plenty of cushioning to the knobs on the front as any impact damage here even slight will smash both the fascia and volume potentiometer off the pcb particularly on those models which didn't have a proper bracket for the potentiometer. If this happens on the 07 model then there is no direct spare for this and the only solution is to lose the balance facility and modify the board to take a standard dual gang potentiometer instead. Likewise the delicate diecast cover easily suffers damage in transit which is increased due to the much higher weight of these models especially if they can move unchecked inside their box.

One common issue with modern sources is that they all have a very much higher level compared to those that Cyrus expected you would use 25 years ago. The result is that often when listening at normal volumes you are only using the first 3 to 5 clicks of the volume. The tracking of pretty much all potentiometers that low is also usually very poor even from new which can result in what appears to be poor balance at low volumes (the first few degrees of rotation). The only way you can solve this is to use an external line attenuator between your source and input so that the volume is operating more at a 9 -11 o'clock position. Such devices are available commercially but can be  rather expensive for what is just a resistor network inside a connector so it's best to shop around.