As you probably realize, the 4004MkII is rated at 200W and 400W into 8 and 4 ohms respectively. At the time it was introduced, FTC requirements for amplifier power ratings specified a "pre-conditioning" prior to the measurements, comprised of 1 hour of operation driving a 1kHz signal into an 8 ohm or 4 ohm resistive load, at 1/3 of rated power. I believe that about 10 years ago the pre-conditioning requirements were revised to something less stringent. I would question the tech as to how he did the pre-conditioning. If it was for longer than 1 hour, or at more than 1/3 of rated power, that might account for the 4 ohm measurement being less than 400W. Also, I would ask him what the temperature conditions of the room were at the time. In a hot, non-air conditioned environment it is also conceivable that the measurement would be reduced. Regards, -- Al |
Dude, Be glad that thing still works! It's like almost 20 years old! I keep a standard rule to only trust electronics for ~10 years, your almost twice that! Be glad it still tolerates 4 Ohm loads at all and didn't fry the power supply in the bench test! Great amp BTW, old Dan D'Agostino design. One of my first true high end amplifiers. Thing was built like a tank and my brother still has mine to this day and AFAIK it still works, but when it dies I wouldn't advocate repair unless it was very cheap...... |
Does electronics degrade and changes the quality/sound of the amp?Yes. Capacitors tend to be the most common culprits, aside from tubes in tubed equipment. Electrolytic capacitors in the power supply circuits could affect power capability, as well as sound quality. Smaller capacitors elsewhere in the circuitry, especially if they are directly in the signal path, could affect sound quality. However, if the only indication of a problem is the max power measurements you were provided with, I would not take any action until the tech answers the questions that I and Eldartford stated. If you and the tech do conclude that the electrolytic capacitors are probably causing a reduction in power capability, and you decide to have them replaced, it would probably make sense to have as many other capacitors as practicable replaced at the same time. More generally, concerning the ability of older equipment to work well, the following threads will make for interesting reading. The upshot is that the performance of older equipment is very hit or miss, with little predictability, but in the better cases older equipment can continue to work well for MUCH longer than might be expected. http://forum.audiogon.com/cgi-bin/fr.pl?htech&1267845685 http://forum.audiogon.com/cgi-bin/fr.pl?ymisc&1274033569 Regards, -- Al |
Thanks, everyone, especially Al. I had suspected about the power Caps to my Aragon amp. They are the direct voltage supply to both channel boards. I will try to locate the caps. You can treasure a product and still keep it going unless something major breaks. I will certainly try to keep my Aragon in good working order. |
400W is only 1.5% louder than 380W - don't worry. I would recap this amp for better bass control. I changed power supply caps once and that is what I noticed. Bass became shorter more dynamic and cleaner. Older caps have higher ESR (internal resistance) because they dry out. This internal resistance will keep increasing progressively because of increased self heating (but it will take many years). Eventually it will become so high that full power test, that you did, might trigger thermal runaway (temperature increases ESR that increases temperature by self heating even further and so on) and cap might blow up its mechanical fuse (rubber plug) or explode. Electrolytic caps are the only components that age and are worth replacing if you like the amp. There is a good chance that you might be able to find today much better capacitors (lower ESR) than original. |
First of all, are you certain the power rating has decreased over time? Have you had the same measurement when you first had the amp? Like someone else mentioned, it's within 5% of the rating. Maybe your amp was assembled that way. Power rating is not like the maximum speed of the car where you measure the speed with full throttle. Power rating is measured *as relative to the distortion*. As the power goes up the distortion goes up after certain point. Are you sure you are using the same distortion percentage for clipping as published spec? |
If I have to replace these 4 power supply caps, Can somebody know an electronic supplier who carries 19,000uf, 80v screw type Electrolytic caps. These are hard to search even in the net. Your help will be appreciated. I located some electronic parts supplier but a minimum is required to order ie 100. |
You can use 22000uF/80V (more common value). You can find it in digikey.com Example here: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=E32D800HPC223MD80M-ND Another good source is mouser.com example here: http://mouser.com/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/Aluminum-Electrolytic-Capacitors-Screw-Terminal/_/N-75hqz/ I'm not sure if you want chassis mount with one large nut or one that has two screws (digikey example). Check catalog picture before you buy. |
