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Thread: Filter caps

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    Filter caps

    I have an '82 Marshall amp, with original power supply filter capacitors.
    Everybody says I have to change them but I have no problems of hum on the clean channel, or ghost notes, and there are no visible damages on the caps.
    Do you think that changing them I would hear any difference?
    Switching power off (leaving standby switch on) you hear the amp playing for a little, it's filter caps discharging. Shouldn't this time be a measure of the condition of filter caps? How much seconds should be in a Marshall?

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    Lifetime Member Enzo's Avatar
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    How many seconds? WHo knows? How much does the air in your car tires weigh? These are not specs the amp companies measure.

    If the amp works, don't "fix" it.

    If the amp has no performance problems bothering you, don't "fix" it.

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    Quote Originally Posted by Enzo View Post
    How many seconds? WHo knows? How much does the air in your car tires weigh? These are not specs the amp companies measure.
    Sure. Only a question to know if anybody has observed this. In my case it's 1 or 2 seconds.

    Quote Originally Posted by Enzo View Post
    If the amp has no performance problems bothering you, don't "fix" it.
    Yes, it's my opinion too, but I don't know if it could sound better ... any similar experience?

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    Any time I change caps in an amp that are around 10 years old (I change them in my own amps after about 8 years) I notice a big difference in the response and attack,particularly in the bass,everything tightens up a lot.You usually wont notice that the amps sound has suffered till you actually change the caps.If I have a customer who is skeptical about changing caps that otherwise seem fine,I make them this offer,if we change the caps and he doesnt see a marked improvement I put the old caps back in-no charge.I have yet to put the old caps back in an amp.I view filter caps as part of regular preventive maintenance.When I learned about it,I was taught that filter caps have a life of about 10 years,if the amp sits for long periods without being used it will be even shorter.After that they could fail suddenly,and that makes a real mess.And like I said I have never changed old caps and not see a big improvement.I am not saying you have to change them after a certain time frame,there are many who feel it is not necessary until a cap actually goes south,but sometimes they go south and take something else with them and the mess they make if they spew their guts,to me it just makes sense to do it as a preventive measure if nothing else.

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    Lifetime Member Enzo's Avatar
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    To each his own. I agree that when a cap fails it can be a mess, but there is usually a wide space between like-new, and blowing out its guts. usually they just slowly dry out over time.

    I tend not to like rules of thumb like caps last 10 years. They caps they make now are FAR superior to the caps they made 30-40-50 years ago like you find in old Fenders. They are made better with better materials, are more consistent, and last a lot longer. So how I might treat an amp made in 1967 versus 2007 is very different. Even the caps made in the mid 1980s are better by a good amount than once from 10-15 years earlier.

    And while I don't doubt a 20 year old cap is aging away, I also suspect that part of the equation is that a new modern cap would probably sound better than a 30 year old cap sounded when it was new.

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    HI, I am still fixing up my Peavey Classic 212 and now want to change the filter caps. Can I do this myself or is it a techie job? Also, very important, where to you find out which ones you need and where do you buy them? I know someone knows, please direct or redirect me, thanks for assisting, psingman

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    To work on a tube amp you must be sure that there is no voltage left in the caps because it could kill you. Measure it with a tester before touching anything. Keep attention.
    Said this replacing the caps is easy. You dissold the old ones and put the new ones on their place. You must have a soldering iron of course.
    You can find them in internet, depending on your country.
    For example see www.tubes.it
    The filter caps are the ones you see by the tubes without opening the amp. Read on them the specifications. Maybe they are of the multiple type, i.e. 2 in 1 each.

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    H;lo, thanks for info about replacing the filter caps. I believe there are some techs around where I live in upstate NY that would do this for me, if I had the caps, so will look around. I say this, because I don't want to get electrocuted, ouch, or anything like that. I guess they must hold a lot of voltage in there, even if turned off for a long time.

    I have had fun fixing up my Peavey Classic 212 but am realizing, for my pursuits, it would be better to buy a newer amp that had all those vintage sounds, esp. for recording, which I do a lot more of these days. I mean, the sound of a tube amp for a lot of purists can be what they want to dial in to, but older units do need TLC. I do believe though, that my amp sounds quite good now and for the right person, would be their sound investment.

    If you can keep the cards and letters coming in about where to obtain the filter caps, that would be much appreciated. Or, where there is a tech who could do this for me. I live near Oneonta and Binghamton in New York State. Appreciate the assistance, Derrick

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    For the caps try here:

    http://www.tubeampdoctor.com

    but I think you can find a lot of sellers there in USA

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    Supporting Member Dave Curtis, dB AudioTech's Avatar
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    Quote Originally Posted by psingman View Post
    I do believe though, that my amp sounds quite good now and for the right person, would be their sound investment.

    If you can keep the cards and letters coming in about where to obtain the filter caps, that would be much appreciated.
    If the amp sounds quite good, why change the caps?

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