different type caps sound different?

[Hardtailed]

It's a 500pf. whats the point? i measured both with a meter and they were way too close to make a difference. in the context i used them in you could triple the size b4 you'd hear anything. Come on guys, trust me. just because a few people think i'm getting hot here doesn't mean i'm lying, stupid, or oblivious to such simple things. you guys are just a step away from questioning what size soldering tip i use and how that could be the issue.

As we said, it might test the same but react different once you apply much higher voltage (the DMM won't apply enough voltage to provoke the leakage problem). I know that because that's the exact behavior I encountered with the exact same part.

Where exactly in the circuit is it?

[daz]

It's a cap in parallel with the series resistor in a voltage divider at the 3rd stage grid.

[raiken]

Try putting a 0.022uF or some other large value film cap in series with it and see if the problem goes away. That will tell you if it is DC leakage causing your problem.

Silver mica caps are notorious for being defective, and I've seen entire batches bad from the factory. In fact, the only amp ever returned to me for a passive component failure was due to a 470pF silver mica cap in the tone stack treble position. Many manufacturers put a largish 0.1uF or so cap ahead of the tone stack to prevent just such a problem.

Randall Aiken

[daz]

Funny you should mention that because last nite i actually DID put a .022uf there ! Not to test as you suggest, but because someone elsewhere suggested i try bigger caps in place of the 470pf to get the midrange i was after. I found using a .022 there and the 470pf in the same context but earlier in the circuit (pre gain pot) that i'm getting a really nice full tone with the mids i wanted w/o getting woofy. that said, and back to the issue, i tied all my 470-500 pf caps there included a pair of 270pf's in parallel and they all caused the same harsh tone. Only that one brand was did not pass harsh treble, and like i said before, if there is a defective batch here it's the one that ISN'T harsh because all the others i tried, even a pair of 270's in parallel were harsh because it's the circuit that was to blame. The harshness was normal because there was too many areas where i was building highs and at that point it was over the top. So the harshness was normal. The *defective* cap brand, or whatecer it was about them that caused it, was smoothing that harshness, or in other words not passing the highs like that type and value of cap should have.

[guitician]

Is there any way to export the parts of this thread relating to daz's experience to a new independent thread? It is kind of taking on a life on it's own.

You should have known that a "CAPS" thread was going to be controversial


Next topic should be "What caps are made with the highest quality?"

[tedmich]

ALL CAPS THREADS are controversial

thats why its shouting

if these magic bean caps are to be distributed for analysis can I send along some of my recently procured NOS 470pF/630vdc polystyrenes so you can have a control deity?


seriously...


and daz is still cool in my book, just more prickly

[daz]

just more prickly

Well, i can live with that.

[daz]

By the way, at the risk of getting this thread on another roll which i really don't want to do, i stuck one of those uber smooth/un-bright 470pf's in the tone stack of my 18 watter with the same high gain pre in place of the "normal" 500pf i got from antique or one of those places. the amp's tone changed drastically. It hit me whet it sounds like....it sounds like it's 50pf instead of 470. Thats not the case because i measured it and my meter's cap function has proven to be very accurate. But i've always noticed that when you put a cap smaller than a 500 in the treble position in the stack you lose a lot of the harshness in the high end because you are cutting out a lot of it and getting just the very top which is silkier than say the 2-4k range. (just a guess) I have noticed that effect using a 270pf in place of the 500, but it seems to me that sound this cap gives there is the same sort of effect but more so, as tho i've gone even smaller than the 270. Like maybe 100 or even 50pf. so while it measures close to it's stated value, maybe under load it changes or some such thing ? I think someone might have mentioned that, only i believe in the context of the cap being destroyed and causing that which shouldn't be the case in the places i used them before the tone stack experiment. This is the second time i tried this by the way, and on the other amp it did the same thing in the stack. It makes a bright in your face tone go to that ultra smooth tone full tone that would just mush out in a mix when you replace a regular 470 or 500pf in a tone stack with one. I'm talking not even close to subtle. Might actually be nice on a switch for a certain recording tone thats very different.

[hasserl]

No, as I said before, if I got another one of the same type, and it made shitty distortion too, I'd suspect the whole batch of being bad.

Based on what Hardtailed said, I could easily take the cap into the lab and stick a DC voltage across it to see if I could reproduce his symptoms.

Yeah, and what Hardtailed and I said is that you heard this huge difference because you had a batch of silver mica caps that were breaking down under signal voltage, causing a lot of harsh, nasty distortion in the treble.

I remember the thread you started saying that you rebuilt your amp and it sounded terrible with a nasty high end, and the bad capacitor kind of fits those symptoms.

So yes, you heard a real difference, I don't think anyone should doubt that, but I say that it's the difference between a bad capacitor and a good one.

Try putting a 0.022uF or some other large value film cap in series with it and see if the problem goes away. That will tell you if it is DC leakage causing your problem.

Silver mica caps are notorious for being defective, and I've seen entire batches bad from the factory. In fact, the only amp ever returned to me for a passive component failure was due to a 470pF silver mica cap in the tone stack treble position. Many manufacturers put a largish 0.1uF or so cap ahead of the tone stack to prevent just such a problem.

Randall Aiken

You guys are missing an important detail here, it is the failed caps that sound fine, it is the good caps that cause the problem.

i.e. "the ones that were making it harsh would be the ones that are fine. Those i have used in the entire amp since day one including the tone stack, and they are the same ones you get from antique, turretboards.com, and other online sources. The are fine ! It's the place in the circuit thats to blame for the harshness. It's that simple. The DEFECTIVE caps are the ones i got locally and have waaaaaaay less effect in adding high end."

[daz]

Exactly, and as i have said before it's the place in the circuit that caused the harshness, not the cap. heres the timeline of what went down clearly so all can understand. We'll call the normal 500 or 470pf caps you get online cap A, and those ones i got locally that everyone says are defective cap B.

1-did some tweaks that made the amp sound great and decided that was the final version and that i would now clean up all the sloppy solder joints and all that. At this point i was oblivious to the fact the cap i had in it was cap B. all i knew was it's a 470pf and had no idea it was different in any way

2-fired it up after i was done cleaning up and the tone was horribly trebly.

3-it hit me that when the final tweaks were done and i was happy with the tone that cap B was in it and that I now had put cap A in it instead during cleanup

4-in attempt to put everything back as was when it sounded right, I removed cap A and swapped in cap B and tone was again smooth and no harshness

5-tried other caps of both kinds to be sure it wasn't a bad cap, and also metered every cap to find they were the correct value as stated on the cap or from the place i got them from. Every one of the "special' caps sounded much less bright and all the 'normal" ones caused a very harsh sound in that particular location in the circuit.


All that said, look at my 2nd to last post about testing them in the tone stack. It makes things even more clear.

[Groover]

And just to be totally anally clear about all this, by the "special caps" you mean caps of the same brand and sourcing as cap B, and by "normal caps" you mean caps of the same brand and sourcing as cap A, correct?

[daz]

yes.

[raiken]

You guys are missing an important detail here, it is the failed caps that sound fine, it is the good caps that cause the problem.

Yes, I missed that part entirely.

My guess would have been the old trick - where "470J" is silkscreened on the silver mica cap, leading the unwary user to think it was a 470pF, when that actually means "47pF", and "471" means 470pF, but he said he measured them on a cap meter...

RA

[daz]

thats basically what i said a few posts ago......in the tone stack it sounds like it might be 47pf, but i did measure it. i could have made a mistake tho so i'll measure it again when i have access. i'm not home at the moment.

EDIT: checked 3 of them and i got extremely different readings. But i think it's the meter. The first one slowly went up to around 440pf and kept going and i just quit because i was sick of holding it on the probes. (don't have any clip leads) The other two measured 127pf and 50 something ! But the thing is, they all had the same script on them, which as randall said could mean 47pf. But then that doesn't account for the one reading close to 470 or why the shop has had these in a box labeled 470pf for at least a year that i know of if not two. i suppose i could put each one one at a time in the amp and listen for differences, but i really don't care at this point, as i just got my first shipment to build the new amp yesterday and i'm going to be busy on that. This has been a waste of time and energy anyways over a freakin' cap !

[Bruce / Mission Amps]

Yes, I missed that part entirely.

My guess would have been the old trick - where "470J" is silkscreened on the silver mica cap, leading the unwary user to think it was a 470pF, when that actually means "47pF", and "471" means 470pF, but he said he measured them on a cap meter...

RA

I was going to mention this right from the start Randall but he was VERY firm about his measurements and the thread started taking on an angry tone which I am never interested in participating in....

And by the way Daz, when measuring small caps like this, you won't get an accurate measurement when holding on to the leads or the body of the capacitor.