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In Reply to: How does the sound deterioate on well used SS amp? NT posted by jensw on April 29, 2007 at 00:57:32:
supply capacitors over time. These can and do break down.
Henry
Follow Ups:
I used a pair of Kenwood L-07M monoblock for about a year or so, late 70's vintage, all stock including the large PS resevior caps, sounded fantastic.Wonder how long they'll be out there making many modern amplifiers sound like junk before they decide to break down?
Like many months or even years.
Henry
I can understand that if an amp hasn't been used for some months/years, it takes a period of "running in" playing music, before it sounds its best ... but I wouldn't have thought that the period of non-use actually degraded it?IE. after this "running in" period, the component would sound just the same as it would've, the day after it was turned off (if it hadn't been turned off!!)??
Regards,
is hard on the power supply caps. That is, once charged, allowing the unit to sit for extended periods is harder on it than regular routine use.
I can only relate one example of this. I had an Eico tubed integrated amp that I used a bit, then stuck in a closet where it sat for several years. I brought it back out and the second time I turned it on it popped loudly after 10 minutes or so. Scared the bejeebers out of me.
This was repeated several times, the last time before a tech friend of mine who immediately said it sounded like one of the PS cans arcing between sections. Having no way to determine which cap, I replaced all four as they were not expensive. That cured the popping.The tech said that these big caps lasted longer when properly "exercised."
Henry
While it is possible for a capacitor to hold a charge for a long time, I would think that a well designed circuit would provide a discharge path for the power supply filter caps when shut off. In fact, there was at one time a FCC regulation that required televisions to utilize a bleeder resistor for this purpose.
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nt
the way to loud pops if big electrolytics start to really break down.
Henry
To add to HenryH's suggestions:1. Along with the pops Henry mentioned, supply caps drying out can be heard as "hum" through the speakers. Henry is right, if they are to the popping stage, do not walk, RUN to have someone replace them, or run to get the caps yourself if you know how.
2. Any other electrolytics in the circuit, especially any that perform coupling duties, once they start drying out and losing capacitance, you will hear a general "dulling" of the sound, and perhaps more noises that sound "static-y".
3. Resistor value drift. Resistor noise is a MUCH bigger factor in the way an amp sounds than a lot of people think, especially signal path resistors. The ones that will drift the most though, are the ones that have to carry heavy current. The worst case, however, of resistor value drift that will occur over time is in the trimpots that adjust DC offset and bias current for the output transistors. The cheaper the construction of the trimpot, the worse it can be. DC offset will probably be a much more audible effect than bad bias, depending on how far off one or the other may be.
If you check DC offset or bias, and try to adjust a really old, really cheap trimpot, my advice would be to verify that either needs adjustment, then turn the amp OFF, and try turning the pot, and cleaning it if possible, checking for smooth travel before turning the map back on to adjust. Also, mark you starting point before doing anything with a permanent marker, and reset the pot to that point before firing it up and adjusting. Yes, I learned that one the hard way. I was lucky in this instance though. I was going to correct the DC offset in an old NAD 3020, had it powered up, went to turn the pot, it resisted just a tiny bit, then it completely crumbled! And I mean completely!. The wiper came up out of the amp on my screwdriver tip, and the remainder cracked.
Thanks, to both of you.
I think that is what I got (Yamaha M60) but also less resolution, if that is not the same. I will change the "signal" lyt caps, in L and do nothing in R. As it well could be that the amp just that sounds like that, I will then find out by changing things in only L.
well, because it's not far behind.
Henry
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