QUAD PA-ONE+ Owner's Manual

Contents

QUAD PA-ONE+ Owner's Manual Manual pdf 7 page image

4TECHNICAL FEATURESQUAD PA-ONE+ uses 6SL7 valves, with 6SN7 valves as the enhanced drive of ‘triode mode’, properly matched to the loadthrough alternative impedance taps of a high-performance audio transformer, selected by the rear panel switch, to deliver nearly1W of high quality, low distortion power into high or low impedance headphones.It can also be used as pre-voltage amplifier due to its pre output function. The circuits use cathode feedback instead of anegative feedback loop, contributing to very low distortion and excellent dynamic performance.With the versatility of the digital USB, coaxial and optical inputs, the amplifier can be connected to sources from computers orother devices.All components in the amplifier have been carefully selected to give consistent high performance over a long period.FURTHER ADVICEBurn In New EquipmentBurn in is very important. Valve components work at high voltages and temperatures and when new they should spend anextended period at those temperatures to bed in. We recommend you burn in the amplifier for at least four or preferably twelvehours before first using it for serious listening. If you run in your equipment for this extended period, make doubly sure that all thesafety conditions covered in this manual are fully met. Supervise the equipment for the first hour or so and if you have to leavethe unit unattended thereafter, look in occasionally to make sure all is well.Warming Up Before UseIdeally allow at least fifteen minutes for the amplifier to fully 'warm up’, or at least 1 minute before use. If you play loud musicwhile the system is cold the output valves will not be fully operational and the amplifier will be starved of voltage and current.The resulting distortion is unpleasant and may lead to potential damage to the amplifier's valves and your headphones. Intensiveuse of the equipment before it has warmed up will shorten the valve's life.Valve LifetimesValves contain a heating element. This heats up the valve's cathode which is coated to give off a steady stream of electrons. Aftera few years this coating will begin to wear out and performance will gradually deteriorate. The 6SL7 output valves are likely todeteriorate first but the driver valves 6SN7 will also eventually wear out.As the valves start to wear out the sound will become less well defined and a lack of dynamics and power will become evident.Replacing the valves with a new set will fully restore the audio performance of the amplifier. When replacing valves it is essentialto use the highest quality available. Poor quality valves will adversely affect the sound quality and may in extreme cases damagethe amplifier. When replacing the output valves, use matched sets for best results.Do not leave the amplifier permanently switched on or you will seriously shorten the lifespan of your valves!Output TransformerAfter installing or changing the connection to your headphones, keep the volume control at zero, let the amplifier warm up andturn up the main volume gradually. If you don't hear sound, switch off immediately and investigate.The output transformer is designed to match the high voltage, low current conditions in which the output valves operate to thelow voltage, high current requirements of headphones. Although robust, an output transformer can be damaged and in extremecases wrecked, by careless use. If you play a valve amplifier into a short circuit, the output transformer will soak up a lot ofenergy before failing, but if the short persists the transformer could be damaged. Operating a valve amplifier at high output levelwith headphones disconnected can also damage an output transformer.The amplifier must be used with the correct load conditions, otherwise it may cause damage to the output transformer.