F&T wierdness

[12AX7]

I recently rebuilt my 6V6 JCM style build to clean up all the slop and swap out all the components that have been reused a zillion times with all fresh new caps and resistors. I bought most of the parts from one place and the F&T 22uf's elsewhere due to the fact they were on backorder where i got the other parts. So i did the job the other day and played it with the old F&T caps still in  it to see how it was sounding. Barely any different if at all. I couldn't really tell. Then today the F&T's arrived. Same exact 22uf/500v F&T as the old ones.  I put them in and now the amp sounds a hell of a lot different, and not to the good. The old ones were maybe 5-6 years old. What could account for this? I can see how the older caps might sound a tiny bit different, but not this much ! Is it possible these will break in?         

[drew]

Did you buy them from a reputable source?

[12AX7]

Yes

[pompeiisneaks]

I know I've heard that caps have a 'forming' stage, but I think that's a bit pseudo-science, but I'm not sure.  Ultimately, though, it is possible you got some bad caps?  But really, the caps should only add horrible noise if they're not working, as those are not part of the 'audio chain' but just power filtering.  Therefore the 'sound' of the amp, if the caps are not 'right' is usually really clearly bad in a major way.  (120 cycle hum from the rectification being only so good.)

[12AX7]

Theres no noise over the old ones. If anything maybe a tad less, tho probably the same.  But the tone is just much harder sounding. No give in the attack like before and thats never happens with filters unless they are about double the value, so i know it's not that. I haven't measured them but it takes double their 22uf value before i notice that, and it's usually not like this till i get to about 80uf. Theres no way they are off even by a fraction of that. So i have no idea what it could be but this is a real drag. I think i'll be putting the old haggard caps back in. Maybe F&T has been slacking in thier production quality lately. This isn't the first time i have renewed a amp and put in new F&T's and it's never happened before. I guess i'll remove them and check the them and see if any of them read oddly somehow.

[John]

measure the capacitance of both the old and new, see how far apart it is.

[12AX7]

I did that last night and they're the same. I did it out of desperation because i know theres no way they are going to be far enough apart to account for the difference in sound because as i said earlier, i have to double or half the filter values before i even notice a difference, and the difference then isn't s much as i'm getting now. I'm going to assume they need to form or break in or whatever and leave the amp on for the day and see if that changes it.

[shooter]

they're the same

did you by chance measure the B+ rail while playing with the old ones, possible they "sagged" enough to give you something like "the brown tone"

[Willabe]

From the way you describe the difference in sound it seems like the new caps are better/stronger then the old caps. 

[12AX7]

From the way you describe the difference in sound it seems like the new caps are better/stronger then the old caps.

Yeah, i thought about that but note that my description is weak at best. I really couldn't describe it exactly, but at this point i can better describe it as brighter with a stronger low mid and less give in the mids. However, after leaving it on for hours and some more playing it's changed quite a bit. It's still sounds/feels the same but much much less so. At first it sounded like the low mids were overpowering everything else and the top was much harsher and i was hearing what sounded like some weird harmonic content like maybe odd harmonics that clouded the sound to where notes lost articulation/clarity.  It was really messed up at first. Now it sounds close to how it did before but still retains some of that extra low mid content and the highs are still harder and more present than before. But to a lesser degree and the rest of what i described has disappeared. At this point the harder attack and more present high end is the issue, but it's much closer to how it was and i can tame it with the controls. I just feel it will now be overbearing and hard to dial out in a band context at stage volume. But given how much it has changed at this point i'm hoping it gradually end up back where it was as they break in more or whatever it is thats changing.