Do Polypropylene caps break in?

[leadfootdriver]

I just got some Panasonic caps for Triode bypassing, and am wondering if the sound will change over time. Same with the OD's in there.

[img2448]http://home.comcast.net/~leadfootdriver/bias.JPG[/img]

[Cliff Schecht]

Not really. The manufacturers datasheet will specify if a capacitor has a break-in period, which almost none do to speak of. Most manufacturers aim to eliminate something like this. Who wants to use a part in a circuit that takes dozens of hours before it is working "properly"? Us tube guys are too patient sometimes .

[dave g]

Honestly, if a film capacitor needs any sort of "break-in", it's poorly constructed and should be avoided.

[leadfootdriver]

Cool then.

[angelodp]

But speaker break in is an acceptable reality? I have read about entire amps needing to break in. What parts of an amp do require break in.

[Cliff Schecht]

Speakers are different. They have physically moving parts whose materials must loosen up a bit for the optimum reproduction of sonics. The only other parts that really require break-in are large electrolytics, the plates of the capacitor will deform over time and giving it a few repetitions of high voltage through a large resistance will allow the plates to "reset" into their proper place.

[angelodp]

Cliff, I have read numerous times that builders have suggested waiting to evaluate an amp until it burns in or has considerable time on. Is it purely the speaker issue that is being considered.

[JamesHealey]

imo.. a good 10 hours of loud playing does the majority of any break in, the rest is pretty subtle.


I think speakers definitely require some break in!

Caps? well i'm dubious about this although I can vouch for my builds using MKT1813 coupling caps.. sounding a tad less sterile after a week or so of burn in.

If it's the caps i'll never know or care.

[Cliff Schecht]

Cliff, I have read numerous times that builders have suggested waiting to evaluate an amp until it burns in or has considerable time on. Is it purely the speaker issue that is being considered.

Well then there's the tubes that drift over time as well as things like the e-caps settling in and any other weird stuff that I guess happens to amps with use. But I try to aim for amp builds that sound consistent from use to use. Trainwreck's are great about this, all of my builds sound consistent if anything. What you hear is what you get, live or in the studio. But unless you are using older parts in your builds that do drift over time (carbon comp resistors, certain cap technologies, old pots), you should not be dealing with a big change in sound even after 1000 hours (remember to keep those tubes fresh!).

I can't immediately think of any new manufacture parts that change dramatically with applied voltage/current (assuming you stay within the limits) as again this is something that manufacturers try to stay away from. In the aim to miniaturize everything component values have to be more accurate to keep circuits within tolerance. This is especially true for newer amps with lots of SS circuitry. Think of the bias networks in op amps, they have to stay within tolerance over a huge temperature range. Having your external components change dramatically with use will kill the performance of a circuit in most all cases.

I could go on a whole new rant about how many manufacturers cheat the public by using the absolute cheapest (read: not safest!) methods of manufacture for their products (*looks at PCB Fender's, Marshall's, Vox's, etc*) and very sheisty circuit design methods. When I do repairs I tend to study the schematic at least for a second to see not only where a part failed but why. Usually it's because the manufacturer used a part that was BARELY rated high enough for it's application and these are always the parts that fail. This is why manufacturers recommend you only run their amps for a few hours at a time. It's so you can give their badly built amp a moment to cool off so it doesn't drip solder everywhere. Very pathetic practice IMO...

[rooster]

OK, let me sign in here about the coupling cap break in time.

I think some types 'break in' faster than others, but I think all of them need some break in time, whether its minutes, hours, or days.

The Sozo site has a little ditty describing their thinking on the break in time of their caps. Read it, I think they make a good point. They say that a path is being traveled within the material that the cap is made of as the signal is passed. As the path is traveled more often, the path becomes more established - and the tone will change.

Well, whether you buy into this story or not, I will say this, the Express amp is a great test bed for the testing of coupling caps and this potential transformation. The signal path is so straight and simple you would be hard pressed to miss it. I hear it as I try different caps, and then I hear those caps change after 8-20 hours of operation. Well, my .02.

Also I will add that - as far as my ear is concerned - it is not always the case that the particular cap 'smooths out' with break in. It is my experience that sometimes the signal actually becomes brighter given the particualr cap type and build. Yeah, remember that 'breaking in' something like a coupling cap doesn't necessarily mean 'breaking it down'. As that path is traveled more often remember that the signal also has the potential to travel throught the cap FASTER - and this can translate as a brighter amp.

Further, remember that amp the KF built with the two caps @ V2 totalling .002 uf? One was ceramic, the other polyester. It may well be that the amp was 'adjusted' with this coupling pair. The ceramic cap is harsher/brighter because it is 'faster'. KF may have heard that the amp was 'dull' or lacking in sparkle and made the decision to make this change. Eh, we may never know, but you can try this pair yourself and I am pretty sure - after 8 hours of break in - that you will hear something different than if you used a single PVC .002 OD. Try it for yourself, that's what this is all about sometimes.

[leadfootdriver]

Thanks for all' the insight!

On a side note, I'm digging the Panasonic caps. I had some Mylars in there that I got from the corner store. But the 'Sonics are pretty quiet, as my amp seems to have a pretty low noise floor.

[VacuumVoodoo]

I think you shouldn't worry about capacitor break-in or burn-in rationale but pay more attention to soldering. Solder shouldn't be used like glue (the diode rectifier bridge), also, first mica cap to the right of the bridge looks like its upper lead is only inserted into the turret hole and not soldered. At least it looks like that in the photo. This may have several orders of magnitude stronger impact on tone than 100 hrs vs none of capacitor burn-in.

[leadfootdriver]

Noted!

[Gibsonman63]

I think some of the subtleties can be attributed to adjustments is playing and settings. All rooms sound different. I usually play a few riffs after I get everything hooked up, set the level on the amp and then tweak the tone on the amp and the tone on my tube screamer just a bit. Over time, there are too many other variables to know for sure unless the amp is in the same room under very controlled conditions. In my opinion, if you play a lot, you get better at exploiting the capabilities of the amp and the amp starts to work better for you.

I have noticed that my amp sounds best after I have been playing it loud for a room full of drunk people for a couple of hours.

[greekie]

I like to be honest, but here goes: I always tell my customers to expect 24-48 hrs burn in time. For most people that corresponds to a week or two of playing the amplifier. And by then, they've become acustomed to the sound.

That way we both win.