Restoration Information
Audio Specifications Database
Audio Picture Gallery
Our Testing Procedures
FAQ
Nakamichi PA-7 Gallery
The PA-7 is often described as a class-A amplifier, but is isn't. It uses a Stasis output configuration. For those who don't already know, the class of an amplifier does not refer to it's quality, but rather the configuration of the amplifier circuitry, particularly the output configuration. It is a class, not a grade.
It may not be class-A, but the idle current of the PA-7 is very liberal, which explains the very large heatsinks.
The PA-7 has separate power supplies for the left and right channels all the way back to the single toroidal power transformer (which has separate secondary windings for the left and right channels). The power supply has tremendous filter capacitors: four big 33000 uF cans, for 66000 uF per channel and a total of 132000 uF!
It may have very large heatsinks and power supply filter capacitors, but the specification sheet in the service manual states that the PA-7 has a 700 Watt power transformer. Transformers are most often rated in Volt-Amps (VA), not Watts, so I'm not sure what to make of that. In any case, a "700 Watt" transformer is just about the bare minimum I would expect to see in a 200 Watt per channel amplifier. That's my opinion, anyway.
In the past, Nakamichi produced audiophile-quality stereo components. However, Nakamichi's best days appear to be behind it.
The spec sheet for the PA-7 claims an output current capability of 14 amperes continuous. I don't know whether that means 14 A per channel, or 14 A total. In any case, to dissipate 200 Watts in an 8 Ω load requires only 5 amperes (Power = I2R). The more current capability the merrier, of course. However 14 amperes continuous per channel @ 8 Ω is 1568 Watts per channel. That would require an output voltage of 112 VRMS, and power supply rail voltages of (very roughly) ± 165 VDC. The PA-7 power supply doesn't even come close to that! In fact, I have not personally seen a [solid-state] amplifier that comes close to that rail voltage.
I'm not picking on the PA-7; it's a very powerful, well-built amplifier. My point is merely this: unless output current specifications are meticulously detailed, you may as well ignore them, since the numbers can not be applied to produce any meaningful results.
D 'n A Electronics is a Father & Son business located in Kitchener, Ontario, Canada. We specialize in restoring hi-fidelity audio power amplifiers, integrated amplifiers, preamplifiers, receivers, and tuners. We've been repairing vintage audio equipment since long before it was considered vintage! It is our goal, and pleasure, to reliably restore hi-fi audio equipment to original operating condition (or better!). We accept shipments from across Canada, and many customers from Kitchener, Waterloo, Cambridge, Guelph, Hamilton, London, Toronto and surrounding areas find us to be within convenient driving distance. Thank-you for visiting our website, we look forward to serving you!
A Nakamichi PA-7 power amplifier. You can look at it's specs here.
The Nakamichi PA-7 is a high-end power amplifier coveted by audiophiles. It uses a Stasis output configuration, originally developed by Nelson Pass and introduced in Threshold amplifiers, which are, perhaps not coincidentally, also highly regarded by audiophiles.