Buying used - Arcam Delta 290 or Alpha 9

 

Expect to pay?  -  pricing for both models tend to range from £150 to £250 for what are described as fully working examples and this varies by condition and whether private or dealer selling (but always view 'fully working'  with a pinch of salt unless serviced).

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The original Delta 290 integrated amplifier was launched in the early 1990's and compared with other similar priced offerings from competing manufacturers it really does stand out for it's exceptionally  high quality of construction throughout.  Versions with S.N prior to D29002675 used what is now a long obsolete Mosfet output device and these were eventually replaced along with a PA circuit redesign to use a pair of more modern Mosfets instead. The very early production runs also had an error in the PCB design rectified by addition of a small daughter board under the PCB between input and record selectors (makes it a real pain to desolder the input selector!)   The Alpha 9 superseded the Delta just after the mid 90's and was pretty much identical internally to the late model Delta 290's largely benefiting from a cosmetic restyle. This included a far less robust plastic fascia instead of the D290's sturdy aluminium one which causes shipping challenges when not carefully packed easily resulting in cracked fascia's and tone/balance pots are easily ripped off the PCB if the front is knocked in transit.
Both models will happily put out a little over 80 watts into 8 ohm loads with 5 to 6  line inputs plus the optional MM/MC phono stage and when working properly are a superb sounding amplifier.  A power amplifier version of both was also available called the Delta 290P or Alpha 9P. These use the same PCB as the integrated but simply have only the power amplifier circuitry fitted with empty space where the preamplifier should be along with a blank fascia. 

However with most versions around 30 years old now most if not all will be suffering a common list of problems to a greater or lesser degree. The real achilles heel of the D290/Alpha 9 is the numerous  switches placed right throughout the audio chain. This was fine when these were new but with time all switches especially those that are rarely if ever moved become intermittent. Starting with the worst of all is the motorised Alps input selector (marked listen on fascia) . The silver plated wafers simply develop a surface layer of sulphation which interrupts audio intermittently and once it starts will only get worse and can only be remedied by removal and refurbishment (a can of magic spray is just money wasted as you cannot access anything with the switch in situ). These switches are fully overhauled here at ARS with gold plated contact surfaces instead which removes the above problem completely. The speaker output relays can be prone to going high resistance across contacts causing varying output levels. Similarly the 'direct', 'processor tape 2', internal power amp mode switch, phono MM/MC switch, and AV mode will all produce similar degradation to a failing input selector but the latter when severe will always mask degradation generated by the others.

Throughout all versions of the D290 and very early serial numbers of the Alpha 9 a very high quality volume potentiometer was used with excellent channel balance and rarely becomes noisy. Unfortunately most versions of the Alpha 9 were fitted with a fairly basic Alps component instead inferior to the original which in many cases has a very poor channel balance for very low volumes. If you only ever listen at medium to high volumes you'll be unaware of this deficiency but it's annoying when low volumes result in one channel almost absent.  
It's not unusual for output Mosfets to fail short circuit on these especially if you accidentally short the speaker output even briefly. Some unexplained Mosfet failures might be caused by instability however as almost all when their output is connected to a resistive test load in the workshop and viewed on an oscilloscope  show slight signs of instability at max power. This is in the form of brief HF parasitic oscillations on positive peaks and no other amplifier seen here ever does that no matter how pushed. Customers occasionally using these in a 'party' environment especially if the top vents are covered complain that after some time they switch off. This is quite normal and due to a protective circuit detecting the heatsink to be too high a temperature and 'tripping'. These were never designed to cope with such a hard high duty cycle for long periods and really are for domestic listening rather a home made night club environment at ear splitting volumes. 

The pcb design in general was well thought out particularly in terms of minimising placement of electrolytic capacitors close to hot areas and the quality of soldering is very high with dry joints even after 30 years being a rarity. The only exception is a small number of electrolytics clustered around heatsinks in the regulated PSU which are the first to fail especially if owners like to leave these powered 24/7 (which is largely pointless). The RCA sockets on the D290  rear easily fall apart if you don't remove tight fitting leads with a slight rotation whilst pulling out. If you don't then the outer ground ring is often ripped straight out and will be in the end of your lead instead.

The best example to go for is a late serial number (suggest 10000+) Delta 290 which if it has been fully serviced is even better. This model is just an overall better build quality than the Alpha 9 and I wouldn't be surprised if it was  a little more expensive to produce originally! However if you prefer the styling of the Alpha 9 then don't be put off as there are very good examples out there and both versions make what is an excellent almost vintage amplifier!