The Surprising Truth About Old Capacitors

Congrats on the dynaco procurement. I used to have a pair of st70’s back in the 80,s. They can keep you war on a cold winter night too.
By 1971, most of the bypass caps were being made to withstand moisture getting in , and were generally manufactured better. The sprauge black beauties have been known to be a problem. Test them with a high voltage tester for leakage. Definitely change the electrolytics. Don’t forget the resistors, they will fall out of spec too. Try to match pair your output tubes as closely as possible watch your bias pots make sure they are clean. Enjoy.

Thank you

I assume you mean polypropylene when you say mylar? I was under the general impression that they were more stable or something appropriately vague like that.

I mean in pro audio old gear quite often is waaaaaay out of spec and thats what give its own character. Especially when it comes to microphones. And as such it can make it much more expensive as same thing but new ;p

my concern would be those crappy carbon comp resistors

That intro is creepy asf

"if 2 caps measure the same they will sound the same" i've heard similar statements to this and plenty opposing it, wouldnt it be to

I completely agree with you. As you well know, there is a mentality in the audiophile world that every time a tech takes the bottom of of the amplifier and looks at the capacitors , they need replacing. Maybe those horrible carbon composition resistors too... As for sound of the ultra expensive capacitors... I have come to the conclusion that we have basically decided, with few exceptions, how equipment is going to sound even before we hear it. Reality from test equipment and our brain often times do not agree. All I can say is if a fellow spends $300 on new fancy capacitors, it Will sound better. Same for tubes with gold lettering.

Mr. Carlson wouldn't like this!

Liked your video. I have a Carver M500t Power amplifier. Its from 1980 with all the original parts. So that makes it 40 years old. I asked a buddy and resident expert from the Carver club I belong to at The CarverSite to give my Carver amp a "check-up". He checked all the original caps throughout the amplifier and they all checked within spec. He also checked all the performance specs of the amp and all was in spec or better. The tech advised no need to change caps. The only thing he changed was the speaker binding posts which he upgraded to newer modern type.

Thanks for another great video. I too have a complete Dynaco system, ST70, PAS3, FM3, A25 as well as several SS components. I've restored my ST70 and PAS3 but would love to see your work on the FM3.

not all black cats are mylar but i have found alot of older film caps that are very good. I have found some that actually test better than new one vitamin q caps and old good all film caps that test amazing i have found pyramid caps that are film and very good and even black beautys with red or orange writting are great caps they too are film i have never found a bumblebee cap worth a crap

So all capacitors that measure the same sound the same ? lol. Balloney Kid. just balloney.

test caps before replacing them? that's a pretty novel concept!

Hmmmm. The PAS-3X doesn't look that different (inside or out) than the PAS-3; which I bought & built in 1963.

The smart thing to do is #1 test a sample of some of the caps in question......... then make the decision as to whether or not to replace them. 70's era, and some 60's era stuff does indeed have mylar types that look "questionable"...... and one going BANG in the circuit isn't much fun either. My current project is a 1969 Jukebox, and there's lots of film caps in there. I'm just going after the electrolytic ones.

I'll give a thunbs up.
However, NOT ALL capacitors sound the same.
It has nothing to do whether they measure the same or not.
It's a mystery.

Example, why will my car engine have higher oil pressure if i only fill it with 4 quarts of oil vs 5 quarts?
No one knows

Great video, thanks for sharing it. Black Cats have always been somewhat enigmatic to me. I've worked on scores of Stereo 70 (and other Dynaco) driver boards. In some instances a board would be loaded with out of spec leaky black cats, in other cases all of them would be relatively okay. That said, the older the amp, the more likely the Black Cats would be bad. I'm don't think repopulating your PAS3 board with the original caps was the best move though. Even with extreme care, those old phenolic boards will only tolerate so many reworks before the traces give out. And at 50 years old it's just a matter of time before those old black cats begin to fail. Decent coupling caps are fairly inexpensive. You don't need to spend ridiculous amounts of money on the audiophile grade caps some companies are selling. I've found Sprague Orange drops deliver a very good bang for the buck and they last a very long time.

Some 1950's caps are still fine. Yet some early 90's 'lytics are all bad (mother boards, dvd players etc. ) If a tube amp has glowing red plates, you can be assured you need to blanket through and change out coupling caps.

"If two capacitors measure the same they'll sound the same."

What utter bullshit.

So this NOS 1964 Heathkit AA-21D I am about to assemble has silver mica, ceramic disk and electrolytic caps in the kit. I assume I should just replace the electrolytic caps outright. What do you think about the ceramic disk and silver mica? Should I keep those? Or maybe replace those with a different type of cap like poly? LOL - I am a complete noob with this! Thanks for any guidance you can offer.

I have a Dynaco factory assembled PAS-3 that was stamped tested 501 APR - 7 1966. I had all the Dynaco catalogs, I scanned them, then sold them on eBay 10 years ago. I am not sure of the production dates, nor am I familiar with what the "X" stands for. I used to have the early PAS-2 back in the 70's, that is the same with different knobs and facia. All the label on the back says is "Dyna PAS", and a factory assembled sticker with serial number.

I am trying to replace old ceramic disc caps that have values like .005ufd but I can't figure out what "ufd" equates to in today's nomenclature. Would that be the same as 5pf, 50pf, 500pf, 5000pf?

I have found that capacitors sound different. The idea that "if they test the same they sound the same" would mean that tubes, regardless of brand, sound the same as long as they test the same. I assume you believe that's false, but maybe not. Regardless, in my experience, anything that has audio signal passing through it has the potential to change the sound characteristics. Tubes, wire, caps, whatever. It might be to a small, or meaningless degree, but the human ear is an amazing device.

Maybe this is true for components, but in speakers, capacitors can and do make a huge difference. I've done it and heard it many times over. You do need to be working with higher quality drivers for best results but to imply that a 3.3uF electrolytic will sound the same as 3.3uF Duellend is just a ridiculous statement.

Interesting how vintage electronics components had interesting names, and an exotic look, especially since they would go unseen for most of their useful life.

This intro got my left sock lost, but that's alright because then it tickled my ear.

Thanks for the vid. I recently demanded 6 caps back from a tech after learning he was selling them for $37 a piece on Reverb. Somewhat chagrined, he tested all the caps in front of me. They tested almost perfectly. One of the new caps he had blanket replaced was 9% "off." To be fair, there was no sonic difference between the replaced old caps and the new-- It just ticked me off that someone would replace good caps apparently because people are dumb enough to shell out 40 bucks to "improve" their Gibsons.

Great video, but I have to call you out on the sound characteristics of capacitors. Quality and manufacturing play a big part, if you don't believe me just swap out the caps in your crossover (even of the same value) and then convince me there is no audible difference.

If you are listening to your amp with knackered old paper caps and swap them for polypropylene caps then the amp will sound different, it will sound how it is supposed to sound. And you will no longer be able to warm your hands on the red-plating output tubes.

"If two capacitors measure the same, they'll sound the same. Don't be fooled into buying new old stock capacitors" BOOM, tell it to them!

So I had no idea that "black beauty" capacitors were actually officially called black beauty. I thought that was just what people called them.

I wondered are those black ones negative on the side with that stripe?

I look for leaks in the black caps etc.., i have seen oil leak out of them.

You do get less distortion between a film and a Electrolytic and it's noticeable you don't need expensive either it matters on material not brand name

You don't need fancy or brand name you need good material The change in capacitance with applied voltage is known as the capacitor's voltage coefficient, and it can be the dominant source of distortion in the low-frequency spectrum where capacitor impedance is relatively high. Furthermore, as the signal amplitude increases, greater distortion occurs.

“If two capacitors measure the same, they’ll sound the same.” You really shouldn’t throw out an absolute statement like that which negates and even insults many audiophiles’ experiences. But I’ll play that game with you. All those Mylar caps should be replaced with polypropylene caps. Measure the same? Maybe on the instruments you have on hand, but with lab grade equipment polypropylene measures better in terms of dielectric absorption (as well as a couple of other parameters) which causes subtle smearing in the sound. You don’t hear it? Fine. Doesn’t mean that others can’t. You don’t have to spend big bucks on polypropylene though, in my opinion. Use CDE Orange Drop 716P or Illinois polypropylene caps.

Capacitors change the sound.Not much,but they change it for sure!

What will a bad cap sound like? I have an Dynaco ST-35 that’s been sounding like it’s clipping and full of distortion. Cheers

As someone who has been restoring tube-based equipment for about 40 years, I would recommend replacing all of them. Why? Because the average person doesn't have a decent capacitor checker, and they're not going to know the difference between paper and mylar capacitors just by looking at them. Not only that, but capacitors are cheap. Nobody needs silly $40 caps, orange drops will work just fine

have you tried to make a tube amp with paper wax capacitors and compare the sound? The sound is different and there's no capacitor that sound better than those old paper ones. Try it before making conclusion, and give it to listen to someone who has ears. It can be that ppl who used to listen to modern crap lost their ability to hear. Like making an analogy you won't hear and distinguish any difference in Chinese tones, but for someone who grew up hearing tones the difference is so dramatic that different tones means absolutely different words. But if you listen to them you wouldn't notice any difference until you got familiar with those sounds a lot

My brother and I purchased new Pioneer receivers at the same time back in the 70's. I got an SX-950 and my brother went for the big SX-1250. Five years ago I got mine rebuilt and he left his alone. We are both in agreement that the rebuilt 950 now sounds much, much better than his 1250. I feel more confident than he does that mine will last another 30-40 years.

Fascinating........❤

I pulled some of those 'black cat pkm' out of something recently that, while i dont have a setup to measure hv leakage, measured way off for capacitance according to my fluke meter. something like .60+ instead of .47