pass ® XA200.5 Owner’s Manual October, 2007Manual XA200.
Nelson Pass has been designing audio electronics since about 1971, first with ESS (remember Heil transformers?), and then forming a new company, Threshold in 1975. Threshold pioneered the design of high power Class A power amplifiers and later, high power amplifiers using only local feedback (the Stasis series). Pass sold Threshold and created Pass Laboratories in 1991, where he concentrated first on elevating single-ended Class A power amplifiers to new power levels and performance, the Aleph series.
We start with simple FET circuits already having low distortion and noise, and arrange them in two symmetrical halves. The two halves of the amplifier channel are closely matched, eliminating a large portion of distortion and noise without feedback. A small amount of feedback is also applied, not so much for the purpose of reducing distortion but to make the distortion as identical as possible on both polarities of the balanced output.
All the usual performance metrics - power, distortion, noise, input impedance, damping factor and bandwidth have all been improved in this latest generation. The power supplies are larger, with fast rectifiers gating to larger capacitor banks. The increases in AC line noise worldwide have been addressed with heavier EMI filtering and dramatically quieter power transformers.
SET UP X amplifiers run at about the same power as their output rating, and XA amplifier run more than twice that. The heat sinks on the side of the amplifier run hot to the touch – about 25 to 30 degrees C. above ambient, so you can expect 50 to 55 degrees C. temperatures on the heat sinks. It is very important to the long life of the amplifier that they get good ventilation. You can put this amplifier anywhere you want, but it must have good ventilation.
The amplifier’s voltage and current rating are indicated on the rear panel. It will be either 240 volts, 230 volts, 220 volts, 120 volts or 100 volts. The larger amplifiers have a circuit breaker of the appropriate capacity. The smaller power amplifiers use a slowblow 3AG type fuse. The frequency rating of the AC line source is 50 to 60 Hz. Please verify that the amplifiers indicated voltage requirements are consistent with the supplied voltage and current at your location.
So the amplifier is sitting there unconnected. Make sure that the rear panel power switch/breaker is off (down). Plug the AC cord into the back of the amplifier, and then into the wall. Then turn the power switch/breaker on (up). The lights in your house will dim for a moment as the power supply charges the capacitors. If your amplifier uses a circuit breaker and not a fuse, please note that this circuit breaker is not a “safety device” or “emergency disconnect” for this product.
pin 3 is inverted (negative) input. Pin numbers are marked on the XLR. If you re-install the jumper incorrectly or leave it lying about, the amplifier will not work properly, and you will be able to tell. Choose either XLR or RCA inputs. If you run both at once from different components, the sound is not likely to be optimal, but it shouldn’t cause damage anywhere. Now that the source component is connected, turn the volume all the way down.
the temperature exceeds 75 degrees Centigrade. This thermal cutout should never occur in real life. This is a very rare occurrence, and would indicate a serious problem. Interconnects and Speaker Cables We have a general recommendation about interconnects, and speaker cables: They should cost less than the amplifier, and contain at least some conductive material. We have tried a lot of products and most work well, but as a practical matter we cannot make blanket recommendations.
After that, the longevity will depend upon the number of operating thermal cycles, but we can say that we have had amplifiers operating in the field in excess of 20 years with no particular mortality, and we don’t have good information beyond that. More to the point, you should not worry about it. This is a conservatively built industrial design, not a frail tube circuit run on the brink of catastrophic failure. If it breaks, we will simply get it fixed, so sleep well.
Warranty Information All Pass Laboratories products purchased new from an authorized Pass Laboratories dealer in North America are covered by a transferable, limited 3-year warranty. This warranty includes parts and labor charges incurred at the repair facility. Consequential damages are specifically not covered and damage due to modification or physical abuse is also not covered. The customer assumes responsibility for shipping and insurance to and from the factory, or a factory specified repair facility.
For your protection please read the following: Water and moisture: Electrical devices should not be used near water ( as per example, near a bathtub, washbasin, kitchen sink, laundry tub, wet basement or swimming pool ). Care should be taken such that objects do not have the opportunity to fall, and that liquid is never spilled onto or into the device enclosure through openings.