Santak 500va online dating
The NAP 200 is broadly similar but has much better output devices and can drive more current into 4R loads for 100WPC.The supply voltage can also be predicted from the choice of current source resistors which should maintain a similar bias current in the LTP and VAS stages, for all models.
As for the Plitron transformers I used a lot of their products in the past, and have one right now on my bench, for a big Class-A amp.I'm not sure where this 28V AC requirement has come from other than the input voltage shown on the e Bay listing for the clone kit.Stepping out on a limb here, but presumably this was the measured no-load voltage on a real NAP 200 by the kit designer?Chris I'm not sure where this 28V AC requirement has come from other than the input voltage shown on the e Bay listing for the clone kit.The mains supply voltage here in the UK is closer to 240V due to allowed supply tolerances, so my reasoning leads me to believe that a 25-0-25V transformer will be better suited than one with 28-0-28V windings which may output too high a voltage, all things considered. Well, perhaps because you hadn't posted in all that time?Note that the NAP140 is only a 45W/8R rated amplifier with lower rail voltages of /-34V, the current source resistors being different, to suit this. No matter, there are several good reasons to accept that 28VAC is the correct transformer rating.
The maximum 8 ohm power rating, of course, is dictated by the supply rail voltages so it doesn't take much to see by reversing a power calculation, just what each model requires as a minimum supply, assuming other circuit losses are much the same. Actually, it's the implied nominal 40V DC rail voltages that need to be correct within the limits of the permitted Mains supply(s).
I think I may have rushed in and bought the transformers without considering all factors.
A custom-wound transformer may well be the better option then, however 40V DC rails may just about be achievable when the mains over-voltage and the regulation is included in the calculation: Assume all voltages are RMS unless stated: (240V / 230V) * 25V = 26.09V 8% regulation: 26.09V * 1.08 = 28.18V 28.18V * sqrt(2) = 39.85V DC Seems close enough, however this is under no load.
He especially thought valve amplifiers avoided it by choices forced onto the designer. At this supply voltage the toroidals are giving an output of 27.5V AC with no load, that equates to 38.9V DC.
As Algar_emi has expressed, I'm also using 225VA transformers which will be barely loaded so I'd expect the supply to be practically 39V DC most of the time.
He thought it very unfortunate to have the mains at 50 or 60 Hz. If you look at TR1 and TR2 there are two bass time constants there.