What effect on sound do old caps have?

[Canetoad]

I was just curious what sort of effect aging capacitors have on the sound produced from an amplifier. :scratch:

I have an old L2 Luxman amplifier that sounds pretty muddy to listen to and was wondering if it would sound any better with new caps fitted. The reason I ask is because my brother had one in the early 80s and I always liked the way it sounded back then.

[sq225917]

It depends on the type of cap, how it has aged and where/how it is used in the circuit.

As a general rule any film cap, PET, PP or styrene should be fine. The same broadly goes fro silver/mica caps as long as they haven't been burnt alive. Various paper oil types can go noisy, tantalums tend just to rise in ESR and then go open circuit. Large PSU caps tend to drift in capacitance and rise sharply in ESR limiting the amps ability to 'deliver' on demand.

It depends on how they are used and where.

[synsei]

I was just curious what sort of effect aging capacitors have on the sound produced from an amplifier. :scratch:

I have an old L2 Luxman amplifier that sounds pretty muddy to listen to and was wondering if it would sound any better with new caps fitted. The reason I ask is because my brother had one in the early 80s and I always liked the way it sounded back then.

Before new caps were installed in the Hafler it hummed a merry choon and yes, it did sound a bit muddy. After the recap it was livelier and bass weight was a revelation... :)

[Canetoad]

Interesting Dave. The reason I asked the question is because I always thought the amp sounded great through a set of AR28 speakers back in the early 80s.

I think I'll make a project of it and have a bit of a tinker when I get round to it. At the very least it will improve my soldering skills. :eyebrows:

[DSJR]

Old Luxmans always were a bit muddy. We called it "warmth" back in the day.....

Before you start stripping out a possibly perfectly working amp, it may be worth having a professional look over it, checking any voltages etc for correct setup.

Remember, it was certain UK amps from Quad and Naim, together with many TV's of yore using cheapo caps which failed after a few years of eight hours a day which started all this. So many amps, including premium Japanese made products, used rather better specified components to start with and after thirty years, may just still be within spec for all I know ;)

[UV101]

It's also worth checking electrolytic caps for bulging.

I've just completely overhauled a quad 405 for a friend and it changed from a muddy ploddy fuzzy his sky noisy thing into something that very much surprised me. Fast, tight, clear, dynamic......admittedly I did a few other mods while I was in there but it's known that 1 of the caps causes an increasing level of hiss as it looses its tolerances. Most of what I did was a total recap of all electrolytics with a mix of F&T large value smoother and Rubycon ZA and Elna SilmicII on the amp modules. I also changed some cheap old film caps (which I suspect would have been fine) with silvered mica.

It's not just failing caps that change the sound, the type of cap will also effect it. Difference caps in different locations will make changes from subtle to quite dramatic......now there's a can of worms!!

http://i497.photobucket.com/albums/rr332/Trunky1812/Quad%2044%20405/IMG_2507.jpg

Before and after
http://i497.photobucket.com/albums/rr332/Trunky1812/Quad%2044%20405/20121017_181958.jpg
http://i497.photobucket.com/albums/rr332/Trunky1812/Quad%2044%20405/20121017_180619.jpg

http://i497.photobucket.com/albums/rr332/Trunky1812/Quad%2044%20405/20121017_190034.jpg

[DSJR]

For some reason, jap amps from the 70's and early 80's lasted far longer before needing service. The 405 caps only seemed to last twelve years or so for original fitment and the first one I had exhibited little mountains of leaked goo on top of the supply caps, not just bulging.

[Rare Bird]

+1 for recapping, it's the best thing i ever did to both my amp & speakers.

[UV101]

Indeed, and don't be afraid to "adjust" some values on PSU caps.

There can be significant gains increasing the amount of smoothing in amps.
In that quad, I went from 10,000uF per rail to 15,000uF. I've also taken my Restek from 40,000uF to 80,000uF.
The jungson has 160,000uF as std.....I've not changed that!! I'd recommend F&T caps here. I believe they make the High end SI caps for several other companies including Mundorf.

Also, local decoupling caps can be increased with good effect. I normally don't go about 470uF but I've seen up to 1000uF used in Meridian kit. I believe the original values are often chosen for price and size. You do need to be careful though. I only normally change the value on electrolytic power supply caps. As long as they are not critical filter components (arguable in PSU application) the increase is usually fine. I often also add a small 0.1uF PPS bypass cap as close to the device being supplied by the psu as this helps to filter out noise on the rail.

[icehockeyboy]

I find that ageing caps fit more snugly on my head, keeping it a bit warmer in these winter months.

Oh.......not that sort of cap.......ill get me coat! :rolleyes:

[goraman]

Sonicly, the speed and impact suffers,worst case it will distort or just crap out.
You may not even notice how bad it is till you replace them then Wow!

[Rare Bird]

Thats right Jeff the amount of people ive seen that buy a 40 year old amp to expect it to sound even half decent. :mental: