I'm no expert but I've heard that with time capacitors tend to dry out.
14 responses Add your response
I am no expert either, but I heard that the sound changes for the worse - if you like what you are hearing, I would say don't worry about it. Depending on how the amp was used, it might be still ok - the temperature it was subjected to, and how much it was used.
I have even older stuff I still use without changing caps - 30 years old marantz 2270 receiver, and 20 years old Quad 405-2 amp.
I owned a Nakamichi PA5A MkII. This stock version had 150wpc with large heat sinks and never got hot. The earlier version had 100wpc w/no heat sinks and did get hot. Perhaps, Nakamichi changed the bias between the two versions. I was very happy with the MkII driving my speakers w/ribbon drivers. But, when I switched to electrostatics, the amp was unable power them. So, if you purchase this model Nak, be sure that your speakers aren't too demanding. I don't have any experience with the PA 7. You can find out more at AudioReview.com.
If the amp works when you get it perfectly, it will continue to work. Buy a pristine example and it will last you a lifetime as long as it has room to breathe. There are a few people online if you search forums online that will be of assistance if your amp has trouble, but based on the amps design, nothing will go wrong provided you have a 20A outlet and sufficient ventilation and you arent driving anything like electrostats. It will even drive maggies, however I wouldnt try to power any large monsters with the amp.
Nelson Pass designed those amps , so there's nothing wrong and much right with the design. Having the caps upgraded is not hugely expensive (if they need replacement). I think the pa7 was 200 or 225 wpc. All in all , very nice amps for the money now. They show up on fleabay now and then. You can almost always sell them for about what you pay for them. They are probably worth a shot if the price isn't bad. Good luck!
The first series of the Nakamichi PA7 in my opinion is the best. It is a Threshold in a Nakamichi box. Nakamichi got sued by Threshold because Nak did not change anything inside of the amp. Nak just dublicated the Threshold. Hence, the second model MKII amp. MKII sounds a little dry in the middle sections.
Hope this helps,
Well... regarding the last posting, that's not entirely true. There are some differences between for example the Nak PA 7 and the similarly specced Threshold S/300. Both use the STASIS-design made by Nelson Pass, but due to a different lay-out and different components, for example the power-transistors, there is a difference in sound. To my ears, the Threshold sounds better, but the Nak is a great sounding amp.
As for the capacitors: a very rough comparison is that they act as batteries, only faster responding. They separate the electronics from slight changes in the incoming elektricity by storing energy, releasing this energy as the music/volume demands more power form the amp. When caps get older, they lose the ability to store and release energy. I had my Threshold revised a couple of months ago. The technician measured all components, and they were still on, or even over spec. Changing the big capacitors will cost around 250 dollars. So it's up to you to decide if you think the amp is worth it. Also, caps tend to get older quicker when the amp gets hotter, so caps in a Class A amp wil lose their capacity quicker.
PER TONE PUBLICATIONS - Introduced in 1988, the PA-7 retailed for $1,595, a bargain compared to the Threshold S-350e that cost twice as much and sported a rated power output of only 150 watts per channel. Nakamichis scale of manufacturing made it easy to grab one of Pass best designs at a very reasonable price. Today, clean PA-7s can be found on the used market for $600-$700. According to Pass, the original PA-7 (not the PA-7 series II) is the one you want. (continued) If you troll the Internet in search of a unit, insist on seeing pictures and deduct heavily for cosmetic dam- age. Replacements are unavailable and greatly diminish the resale price should you decide to resell at a future date. Run away screaming from an amplifier that has been modified.
Last year i took in on trade a system containing 5 pa5 amps.
I tested and sold them all fairly quickly. One of them came back with an intermittent channel issue wich ended up being a cold solder joint possibly opened in the shipping process. I fixed it and have been using it to drive a pair of BW nautilus 804 quite happily. It runs slightly warm to the touch but shows no signs of stress. Im very hapy with it.
Its a series one and does in fact have heatsinks so im a bit confused regarding and earlier post. Ive seen some that have handles and thought that was the identifier btween series one and two.