Levinson 20.5 monos - Time for a Refurb?

"if it's not broke don't fix" will only take you so far. What about preventative maintenance.? Your car runs fine but you change the oil every so often.

Electrolytic capacitors lose capacitance, start to leak DC, and have an increase in ESR as they get older. At some point they will begin to fail. The big question is when.

There is no definitive answer to your question but after 16 years it is reasonable to consider replacing them. Pretty much any competent tech can do the job. The hard part might be finding caps that are the same capacitance, rated voltage, and physically close to the same size.

Common thinking, (old wives tale?) is that caps are good for about 20 years.

What does that mean? Do you think they don't last that long or that they last longer.

For all naysayers, if you do a little research you will find there is indisputable proof backed by numerous studies that electrolytic capacitors deteriorate over their lifetime losing both capacitance and suffering an increase in effective series resistance. It is also true that the rate of deterioration is directly proportional to how hot they get. There are also other components that can shift in value after operating in a hot environment for so many years.

The fact that this deterioration happens very slowly means that it is very difficult to discern how it affects the performance of the amps, but I guarantee they are not performing as they did 16 years ago. I have rebuilt many vintage guitar tube amps which mostly consists of replacing all the bypass and power supply electrolytic caps along with any carbon composition resistors that are out of spec. The resistors tend to increase in value. The owners, who though their amps sounded pretty good before the service, are consistently amazed at the transformation.

Given the fact these caps have been operating for at least 16 years in a hot environment, and the owner places great value on the amps, it seems reasonable to have them serviced.

Zaikesman, you say the caps "lasted about twice Unsound's 20 years."

What that really means is they lasted that long without a catastrophic failure, either shorting out or losing so much capacitance that your amp started to hum. The amp works but it is impossible for it to be working as well as it did when it was new. The situation in tubes amps is also worse because the caps have much higher voltage sitting across them than a solid state amp, and the amount of capacitance even when new is much lower than a solid state amp.

I used to hear all of the time that a player didn't want to replace his caps because the amp would no longer be original. That is equivalent to saying that you don't want to replace the original tires on a vintage car. Things wear out and need to be replaced. If you don't do it the object (amp, car, etc) will eventually become worthless for its intended function.

What amps do you have?

The last time I rebuilt a Super Reverb the guy kissed me after he played it. At least it wasn't on the lips. (I'll probably have one of those giant beer cans fall on me now) Find somebody who knows what they are doing and you will be happy with the results.

What do you believe the life expectancy of a cap to be?

That's the $64,000 question. I don't have a strong conviction either because it is impossible to put a number on it for any given capacitor. Naim recommends 10 years. Cynics say that is just to generate revenue, Naim devotees say it is essential for maximum performance.

I would agree that in many applications they can be "reasonably serviceable" for 20 years, but most audiophiles are not going to settle for anything reasonable.

If I intended to keep my $35,000 amps and they had 16 year old electrolytics I would have them replaced

They don't wear out but can lose capacitance sitting idle. However, once you start to use them again the capacitance builds back up.

A cap that has been sitting with no charge for too long can short out if you apply full voltage all at once. This is especially true for old caps in tube amps because they have a relatively high voltage across them. This is why you see the recommendation to form these capacitors by slowly bringing up the voltage across them when turned on for the first time after a long period of being off.

http://www.quadesl.com/pdf/cit2_capboard.pdf

If you stick with the old caps it is best to bring the voltage up slowly. You'll need a variac (variable AC) transformer to do this but unless you get a used one at a good price it will cost more than the amp is worth. http://www.iseincstore.com/index.asp?PageAction=VIEWPRODGROUP&ID=20

You could take a chance and just turn it on.

oops, I had no idea it was worth that. A new variac is a few hundred. I would recap it if I was going to use it.

I'm glad you found something you like, but you have to ask yourself; Would the Levinson sound better than the Lamm if it were refurbed and didn't have those tired, old capacitors in it?

Why do you say the the Lamm's "should be" better?

Sorry, just playing the devil's advocate. I envy the fact you even have a dealer.

I would hold on to the Levinsons for a while and do a long term comparison. What is initially intoxicating can become less so over time.