Afternoon
I have just had one in the workshop for repair. I am sure that there are those with so much room a monster of this size is all but invisible but us folk in the UK are probably mostly going to stay away of this size of product that only really does a quarter of what is necessary for your music. Faults with these which will become more and more common is due entirely to simple physics. Place a 85C capacitor next to a regulator heat sink and watch how quickly it fails. The 4700uf smoothing caps for the 15volt regulator supplies are far too close to the heat sinks to make any sense for such a big box. If they had been an inch further away this thing would likely never break down. Second thing is use capacitors of 105C temperature rating! Long life caps of this type are peanuts so please fit the right thing. Going to the trouble of having a toroidal transformer wound for you is great but to pick a voltage that is going to give a 10volt drop across a regulator when you could have had your transformer wound for lower secondary voltage would have reduced the heat in the regulators and lengthened their lives. I am sure people don't expect a pre amp to get hot but because this is wrong it will do. Bigger heat sinks are really needed too as they need to get that heat away from the circuit board better. Oh and on the regs it would still have been better to fit 7815 and 7915 regs as they are much closer tolerance than using LM317, 337 types and then setting the voltage with resistors which because of the heat means that the imbalance between those rails is 600-800mV compared to 20mV with the 78** types. You could then of course spread out multiple 78** regs so that the dissipation is more even across the chassis and only used the standby circuitry to switch that toroidal transformer via another relay. Just a thought!
So a new set of four IN4007 rectifier diodes, two new main smoothing capacitors, a pair of LM317, 337 regs, a pair of safety resistors replaced because they had been burnt off the circuit board and this was back in service. I would always advise that you turn this off at the back as the standby switch at the front is nothing like it as all the main power supply is on and keeping things warm. Without any circuit diagrams it looks like the 5 volt logic supply that runs the front panel only switches the other supplies on and off well downstream of the power supply at a relay on the main board and just the front panel lights. Definitely not a green solution!
Oh and while I am at it, there are many other pre amps that sound no worse than this at half the price. It is not really AV as most of the key interface circuitry is missing so at best it is compromised. The headphone socket is a joke especially for such a big box. There is no digital IO. So whether it suits your needs or not I think depends very much on where you live. It would not meet the requirements for the UK market which probably tells you why this is the only one I know of here! If you own one in the UK let me know!