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**tubeswell** · 07-01-2007, 10:12 AM

Well from my meagre understanding of fiddling with caps in my own amp over the last 12 months I'll venture an opinion.

From what I can gather, the ultimate type of small value caps (i.e. anything from .001 UF down to 10pF) are silver mica, because of their high tolerances and ability to handle high volts without compromising sound quality. They also reportedly are quite reliable, but I've only got very limited experience with them (so I can't vouch for this). They are more difficult to come by in this part of the world. I have to order mine from overseas, and that's a faggin' hassle. High voltage polystyrene caps of similar values (which I do have more experience of) tend to be dull-sounding for some reason when I tried them in the tone stack in my amp, but they work fine as coupling caps. Disc ceramics of suitable voltage ratings make my amp sound alot sound brighter than polystyrene caps (esp. in the tone stack), however they are tarnished with the reputation of being least reliable and most prone to harmonics (esp when used in some applications) but I prefer the tone they give in th etone stack (over polystyrene caps).

For values over .001uF, in my amp I've used polyester film caps of suitably high voltage ratings, esp for coupling, and even in the tone stack.

I understand that electrolytics are better for the low-leak jobs in the cathode bypass role (and although I do remember reading why, I can't remember why right now), and for filter caps and decoupling caps, although I have read somewhere that automotive style run caps used in car ignition systems make good filter caps.

How's that then?

**Ptron** · 07-01-2007, 05:01 PM

David, A cap job usually refers to just replacing the electrolytics as these are the ones that go bad over time. Plastic and ceramic caps aren't usually replaced unless you suspect a problem with one. Sounds like you want to change a few values though so my 2 cents (and mine only): Don't grow old worrying about what kind of caps you use AFA non-electrolytic ones. Different values due to tolerence are going to have a bigger effect than anything on tone, and even that is tiny potatoes compared to stuff that matters like circuit design and speakers. Not to mention what your guitar sounds like (which is more important than anything IMO) Again IMO, talk about which kind of cap sounds best where is...well lest just say I'll believe it when I see real, scientific, double blind tests, controlled for component tolerence, etc, that show that people can hear these things.

Disc ceramics of suitable voltage ratings make my amp sound alot sound brighter than polystyrene caps (esp. in the tone stack), however they are tarnished with the reputation of being least reliable and most prone to harmonics (esp when used in some applications) but I prefer the tone they give in th etone stack (over polystyrene caps).

Tubeswell, I think you mean microphonics, not harmonics, right?

For values over .001uF, in my amp I've used polyester film caps of suitably high voltage ratings, esp for coupling, and even in the tone stack.

me too

I understand that electrolytics are better for the low-leak jobs in the cathode bypass role (and although I do remember reading why, I can't remember why right now), and for filter caps and decoupling caps,

Electrolytics are used for these things because of the large values of capacitance usually called for.

although I have read somewhere that automotive style run caps used in car ignition systems make good filter caps.

I think I read that here on the forum somewhere. At least about motor start caps if that is the same thing. The idea is that they come in large values and high voltage ratings like electrolytics but don't wear out like them. They are also HUGE

**tubeswell** · 07-01-2007, 08:59 PM

Originally posted by Ptron View Post

Tubeswell, I think you mean microphonics, not harmonics, right?

Yeah microphonics is what I meant to say - why the eff did i write 'harmonics'. It was like 2 am Sunday morning over here and I just got back on a high from a fantastic gig and I should've been asleep. Not trying to blog...

**hasserl** · 07-02-2007, 05:46 AM

David, A cap job usually refers to just replacing the electrolytics as these are the ones that go bad over time. Plastic and ceramic caps aren't usually replaced unless you suspect a problem with one. Sounds like you want to change a few values though so my 2 cents (and mine only): Don't grow old worrying about what kind of caps you use AFA non-electrolytic ones. Different values due to tolerence are going to have a bigger effect than anything on tone, and even that is tiny potatoes compared to stuff that matters like circuit design and speakers. Not to mention what your guitar sounds like (which is more important than anything IMO) Again IMO, talk about which kind of cap sounds best where is...well lest just say I'll believe it when I see real, scientific, double blind tests, controlled for component tolerence, etc, that show that people can hear these things.

What he said. Don't fret about what kind of cap to use, and don't buy special caps at a premium price. Get what you can that are of the correct values, both in capacitance and voltage. Maybe get a few different types and experiment, it's fun.

**David Vinson** · 07-02-2007, 06:17 AM

Thanks

Seems wierd, but OK, I'll try it. I appreciate your input!

**hasserl** · 07-02-2007, 05:07 PM

Originally posted by David Vinson View Post

Seems wierd, but OK, I'll try it. I appreciate your input!

There has been a lot of misinformation spread around the net regarding particular caps, this kind is really good for this type of tone, this type is better for that type of tone; one guy prefers one type, another prefers another type. Orange Drops, Mallory's, Sozo's, paper in oil, $15, $20, $25 caps. How much do you want to spend?

Then things change, all of a sudden those caps that everyone said sounded like ass, people start saying they don't sound so bad, in fact, some guys even like them, then somebody else says hey I like em too, and so does somebody else. WTF?? You mean I shouldn't automatically pull them out of every Fender amp that has them and replace them with big fat orange caps? Everyone else does, shouldn't I?

Then someone else says those big fat orange caps don't sound so good to me, they're too hifi sounding. Yeah, someone else agrees, and now those big fat orange caps aren't all they were cracked up to be. WTF again???

And ceramic disc caps, they all sound like ass, right? Hmmmm, how come certain vintage amps sound so freakin great, then when you look inside you see ceramic disc caps in there? How can that be? Everyone knows ceramic discs sound like ass.

Unless the stock coupling caps are leaking DC, or unless you want to change the value of the caps to tweak the amp's response, leave em alone, they don't need to be changed. If there is a change in tone from changing the type of cap, not the value, it is next to impossible to show in a blind evaluation. By the time you tear an amp down and replace the caps and fire it back up you really can't be sure if the changes you think you hear are real or imagined. Or if something has changed in the meantime, i.e. the line voltage has gone down or up.

But I don't deny there could be a difference, it's just going to be very difficult to consistently prove. And whether a perceived change is any better or not is mostly subjective anyway. But like I said, if you're going to change some out, go ahead and buy some orange ones, buy some yellow ones, and some red or green ones, if you stay away from the real expensive ones this won't cost too much (personally, I'd go to Weber VST's site and buy some polyester, some polypropylene and some silver mica caps, forget the name brand thing), and experiment with it, have some fun with it. Let us know what you find.

**Ptron** · 07-02-2007, 07:21 PM

Nice post, hasserl. I agree on every point. You can see, David, how you can end up chasing your tail if you start trying to find the "best" cap for this or that based on what others say.

by the time you tear an amp down and replace the caps and fire it back up you really can't be sure if the changes you think you hear are real or imagined. Or if something has changed in the meantime, i.e. the line voltage has gone down or up.

Absolutely. This is what I think a lot of very smart and well-meaning folks are ignoring, don't get, or in denial of.

By all means, expeiment but keep that in mind. I won't deny that there could be differences either. Just that everyone's opinions about them seem to be formed in the above manor, and has to be taken with about ten pounds of salt.

**David Vinson** · 07-03-2007, 08:00 AM

Very Good Points, hadn't thought of those

Originally posted by hasserl View Post

how come certain vintage amps sound so freakin great, then when you look inside you see ceramic disc caps in there? How can that be? Everyone knows ceramic discs sound like ass.

Now THAT is an *excellent* point. Thanks for the thoughts, guys.

OK, I'm going to follow your advice, and leave components as-is except for four situations:
- Clean up defective sound (plate resistors for hiss, filter caps for hum)
- Improve reliability (larger wattage metal resistors on 6V6 screens)
- Specific mods (Experiment with BlackFace/SilverFace).
- Experimenting on my own

I've found assertions out there about types and brands making a difference. Having very little foundation, I'm looking to the decades of experience out there so I don't have to spend years reinventing the wheel.

I had a fundamental assumption that the physics involved with different *types* of cap mattered, because a) so many different cap types are used in the original, and b) I thought physical differences would affect tonal differences. I've no baseline to compare against.

So your position is that statements like "replace the discs - they hum" or "always replace all the chocolate drops" or "replace all the cathode bypass electrolytics - it will sound better" can't be supported by reproducible data.

I've ordered parts today (FINALLY!!) and I'm gonna get the amp to a clean working condition first, then maybe try some of the mods I've been reading about. I'm toying with the idea of recording mp3's of before and after, just to see if there actually is any discernable differences.

I'll get back to you with what I find. Thanks again for all the input!

**Enzo** · 07-04-2007, 12:54 AM

Here is a typical - though made up - report on a amp overhaul.

" replaced all the coupling caps with orange drops, I changed values in the tone stack, I altered the cathode bypass caps, I added a post PI MV, I incresed the plate load resistors on the preamp stages, and I changed values in several couplers.

Boy do those orange drops make the amp sound better."

Point being, how could he possibly say the orange drops made the difference while all those other changes were made at the same time? He can't. SO watch for that sort of thing when researching.

And keep in mind it is YOUR ears you need to please, not MINE. What I like might not be what you like. SO asking what caps to use is like asking someone what to order at a restaurant. I like crabs, but my sister hates seafood. Neither of us is wrong.

**David Vinson** · 07-04-2007, 09:06 AM

We have a winner

So sounds like consensus in this thread is choice of cap type won't change things at a detectable level, and there isn't a body of info for guidance - just play around to find what sounds good. Good enough for me, thx everyone.

I'm curious though: why did Fender use different types in different circuit positions (for non-electrolytics) ?

Was it pure economics - e.g., a buyer found a big batch of ceramic disc at the cheapest price at one point, and then later maybe used some chocolate drops for the same position in the circuit? Or was it driven by layout on the circuit board, or some other issue?

Thx

**dai h.** · 07-04-2007, 11:01 AM

I think it can but it also depends on things like the overall amount of high freq. response avail. In general it seems the more extended, the easier it is to detect differences.

A good test might be putting a bunch of different brands/types, whatever measured to be the same value on a switch so you can switch between them quickly ("quickly" since it's easy to forget the sound), plus try not to remember where which cap was, plus maybe have someone else switch for you. Plus, a mic'ed amp through headphones listening at the same level (to account for differences of your head/ears relative to the exact spot in the room and speakers and the same level since louder can have the tendency to sound better). Some of the "tests" people do don't seem to have a lot of validity since they can be using a different source (different performance), or they don't measure the caps, had a lot of time between listening, etc. etc. Or they might be doing something which negates or invalidates the exercise such as "breaking in" the caps with the tubes in (tubes wear out with use, so was it the cap "breaking in" or slightly more worn tubes that someone heard?). Or maybe you spend 10x more for a set of caps and you do get a slight improvement, but is it worth it? For some of course it is, for others no (then there will be that tendency to think the more expensive or rare caps you just spent a bunch of time putting in "must be" better, etc.). You see trends and fads (as hasserl mentions above). Orange Drops hot, now today they're not... etc (plus someone making the "Orange Drop bad" assessment might not even consider that there are different types of ODs avail. such as polyester, polypropylene). Vitamin Qs, Sozos, Audio Note Pure Copper Foil, Tone Factory oil caps, NOS mustards, etc. etc. There are lots to choose and some are pretty expensive. Other factors exist as well I think such as conditioning, training, aging, hearing damage, maybe cultural that can affect perception.

**David Vinson** · 07-05-2007, 08:45 PM

Good ideas

Excellent idea about using a single, same audio source to standardize the evaluation. Good idea about a switch , but might introduce hum. hmmm.

But the basic goal of the trhead was to find out if one type of cap can be replaced with another. This seems to have been answered, so I just need to try this out.

Thanks again,

**tubeswell** · 07-11-2007, 12:16 PM

My comment about polystyrene caps being duller than disc ceramic ones in the tone stack was based on what my ears heard when I tried both sorts in my amp. And to me there was a distinctly audible difference, with the caps I changed. (i.e. the treble and boost caps). The values on the different types on caps were the 'same' (i.e. it said '390' on the polystyrene cap and '390' on the disc ceramic one etc). I'm no amp expert, but I have played a variety of styles of music on a variety of instruments for 38 years, and I daresay after all that time my hearing has adapted to being able to detect a variety of distinctions in music, than if I had been a motorbike mechanic or whatever (nothin' aginst bike mechanics mind you - they're good for fixing bikes). Other people might not hear a difference. So be it. I swear its what I heard and its all part of the subjectivity anyway. People don't all hear the same.

On the other hand, I might be inclined to agree why other comments about other tyes of caps. What difference did changing the type of Bass and Mid caps in my amp have (i.e. film caps as opposed to disc ceramics in the tone stack for the mid and bass caps? Apart from the fact that I did change the bass cap value as well, as Mr Menzo points out, with all the other changes I did it was hard to tell, but since I had the amp open, and since the Blue Guitar website mods I was doing recommended changing them anyway, I did. For a few cents and seconds more, who cares whether the difference in those changes was audible above the differences in actual values? - It made me feel happier for some perverse reason to think that I was putting more robust caps in, and I personally do prefer the tone my amp has now anyway (to what it used to be stock).

However, the experiments I did with the polystyrene versus disc ceramics in the tone stack were entirely confined to just swapping different types of the same value caps on a separate occasion, and I swear I could tell a difference. To tell you the truth I was execting the polystyrene ones to somehow sound better than the disc ceramic ones (because disc ceramics get pooh-poohed all the time), but I preferred the disc ceramics. I actually initially put disc ceramics of different values to the stock ones in, then later, once I'd gone to the trouble of finding some polystyrene ones of the same values, went and changed them for a week and yuck, so I put the disc ceramics back in. IMHO they are brighter and have more high-end sparkle to my ear. I'd been keen to find out why this is so, because I'm sure there's some science behind it.

Now having said that, and purely because I'm a pathetic masochist, I've managed to lay my hands on some silver micas of the same values again and I'm going to try some more experimenting.

**dai h.** · 07-11-2007, 02:00 PM

sorry for blathering on and on lol. I just wanted to mention some things I've experienced and noticed since I've used a lot of different types and there has been a lot of discussion about this sort of thing before. Personally I do think different types can sound different (not always), but I think it should be noted that the way that people can arrive at conclusions can invalidate results, so you need to be careful when comparing or seeing other people's results. Another example is some people when looking at the rectangular caps in old Marshalls think they are ceramic, when they are an old style mica. Someone not aware might think, (since this particular Marshall sounds great), "ceramics are the way to go" and repeat that elsewhere. But then, Marshall did also use ceramics plus there could be differences in the temp. stability of the type which apparently can make a difference to the audio, and so on.

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