It had to happen eventually... capacitor upgrade question for the Mainline

[Strikkflypilot]

When replacing the 10uF caps, do the inner foil leads connect to 15 and 25?

From studying the schematics, I am sure they do.

 

[PassionForSound]

When replacing the 10uF caps, do the inner foil leads connect to 15 and 25?

From studying the schematics, I am sure they do.

Sorry for the slow response! I've hardly been on this forum (or any lately). Did you get it all wired up yet?

 

[Strikkflypilot]

No worries.
I am building very slowly.
Just about to finish input wiring.
Will post some work in progress images
if I get around to it.

Edit : Just did
http://bottlehead.com/smf/index.php?topic=7463.0

 

[PassionForSound]

Nice one!

By the way, I checked my build (and discovered I got one of the Auricaps the wrong way around), and you're spot on about the red leads connecting to 15 and 25 - the same terminals where the red leads from the output transformers are connected

 

[Strikkflypilot]

Thanks Loquah, means a lot!

Was happy to see the transformer working to specs, and the attenuators are finally in there.
Today I received a black XLR connector so all parts are "in house".
I like the way the manual is chaptered so I can really think through the process before actually building. I believe it makes a good looking build. Will post as I progress.

 

[NightFlight]

The 10uF caps are the coupling caps.  They can be 10-20uF, and probably should carry at least a 200V rating.  (160V might work, but would really be pushing it)

The tiny yellow caps on the sockets are out of the signal path and implemented for silent operation.  There's a good chance that if you swapped them for something else, that alternate cap would not perform as well, and you would likely end up with a dysfunctional Mainline. 

The 0.1uF 400V capacitors on the center PC board can be swapped out as well.  They won't have nearly the influence that the 10uF caps have, and the available space on the PC board is somewhat limited.  You can help yourself out by using a 250V capacitor here, which will see more than 250V at start-up, but will operate at 225V otherwise, which I would consider acceptable.

-PB

Speaking of which, I'm seeing that initial startup voltage hit ~320-325V on the 10uF Caps for around 5 seconds or so.  Its a little disconcerting to watch. However I'm getting the impression that the rating for poly caps in general have a high margin. For example Auricap posts their stress and life tests here: http://www.audience-av.com/capacitors/PDF/Auricap_Specifications.pdf

Would it suffice to say that poly caps in general reflect this sort of rating/life margin?  I'm sure you haven't seen or plan to see any of these Dayton caps explode  ;D

 

[Grainger49]

It is not unusual for the full B+ to appear on the output caps at startup.  After all, the tube is not conducting and it has nowhere to go.

Caps have AC ratings, DC ratings and surge ratings.  You are seeing the surge at startup.  Sadly most film manufacturers don't give surge ratings.

 

[Paul Birkeland]

Speaking of which, I'm seeing that initial startup voltage hit ~320-325V on the 10uF Caps for around 5 seconds or so. 

Capacitors are able to tolerate a voltage surge for some time at startup, which can be significantly above their rated operating voltage.  In the case of the Mainline, the 12AU7 will pull the B+ rail to +225V and the 6C45PI plate will pull down to ~150V.  Each tube will do this without the other in the socket.

 

[NightFlight]

I was about to drop on the April sale at pCX and grab a pair of 10uF flat packed Jupiter caps... I still may - this is a sickness after all. I've read great things about them. Plus, they look so cool.

Then while I'm mulling this over... suddenly my Mundorf Mcap EVO - Silver / Gold & Oil  decided to open up and let their presence be known. After a year of installation no less! I've never thought a cap could take this long to come into its own, but there  it is.  Or I could just be nuts. 

http://www.partsconnexion.com/prod_pdf/evo.pdf

Well not generally revered as a top flight cap, the idea behind Mundorfs EVO winding tech intrigued me.  Their not hideously expensive either. (Actually, Mundorf must have recently fixed that by releasing an EVO 'supreme' version - ha ha ha). So while not totally impressed with these EVO SGO and gearing up to do something about it - a year of listening goes by and a couple days ago I realize they must have just 'clicked' in to place. They'd been holding back the full picture this whole time (IMHO).

Goose-pimples showed up. Angels wept. Etc. ;D

Maybe I'm nuts. Maybe the little bastards picked up on the threat of replacement...
But at this point I can't help but recommend them if you have to patience to break them in. A year! OY!

 

[ALL212]

Has anyone compared 10uf caps to something larger?  I think I read you can go up to 20uf.  I'm just talking value, not physical size or brand.

I'd like a bit more bass and if I go larger than 10uf in the quality of cap I'd like to use we're talking an investment. 

I'm not opposed to tacking on an 8uf or so but real estate under that hood is premium so I'm asking before I do something not so smart... 

 

[Alonzo]

I went thru a number of comparisons from 10 to 30 and settled on 15uF Jupiters.  I found these to be the best bass without losing any sparkle for my setup (HD800's - Mainline -fed by BiFrost MB).  It took about 2 weeks of back and forth to settle on these or Mundorf Supremes.  But my experience is limited to Mundorf, Jupiter and Obligatto oilers, there may be better caps for bass and more affordable ones out there. 

 

[Doc B]

I would caution folks that sometimes the perception of more bass is more about the overall tonal balance that the cap delivers than the effect of more capacitance. That is to say, with two different 10uF caps you might perceive different bass presentation just because one of them sounds softer in the highs.

If you really want to know what's going on with the bass, you need to run response curves of the amp with each type of cap installed into a load that best represents the headphones you will be using. The idea is that the cap is part of a resonant system. As the cap value changes the resonance frequency shifts - bigger uF = lower frequency. The ideal cap value positions the resonance just below the amp's "normal" rolloff, mostly determined by the plate load inductance. This gives the bass a little more extension by creating a sharper knee to the LF rolloff. If you go too big with the cap you might get a dip at the rolloff frequency and a resonance bump somewhere below the dip. Too small and you will probably hear the classic small box speaker type of midbass hump as the resonance dominates at some frequencies above the normal LF rolloff.

I know that objective measurement seems like too much work to a lot of people. It's worth learning how these parts work if you're going to mess with them in a useful manner.

 

[ALL212]

Thanks Doc! 

I think you've a point.  I shouldn't say the bass is lacking and the balance is excellent.  I'm probably just a bass junky and am looking for my fix.  :

What I probably should do is expand my listening experience with headphones to see if I really need "more bass" or if the headphones I'm using are lacking a bit.  That, over chopping up my Mainline anyday...

 

[deserat]

So my Mundorf Supremes in the coupling position have settled in delightfully.  Now I'm wonder what to mess with next. Am thinking of replacing the Daytons on the c4s board or possibly doing a bypass on the coupling caps.  Anybody done this? Thoughts on effectiveness or values for doing a bypass?

 

[Paul Birkeland]

I haven't ever heard a coupling capacitor bypass that I thought did anything positive. 

The Mainline isn't one of those kits where there are really any parts to upgrade other than the coupling caps.

 

[deserat]

Thanks .  Wasn't sure there would be anything meaningful from other mods. What I hear now is so astounding. But then, I didn't think there could be anything meaningful before I put the "better" caps in in so I thought it would be worth checking.  On to the Crack-a-twoa

 

[JamieMcC]

Not been any posts here for a while

Been trying out a new secret sauce recipe in the Mainline 10uf RTI Teflons topped off with a dash of of Duelund Cast Copper the results have been pretty yummy...

 

[Mordicai]

I'm installing some auricap and would appreciate a check on the installation. The short lead is the black lead and goes to 20u and 30U ?  The leads are beautiful but very long. Should I trim them or just let them be?  Another question: is it possible to remove one spring and ball bearing from the Attenuator after it has been built?

 

[Paul Birkeland]

The black lead is the outer foil, and generally goes toward the source side, not the load.  The source side is the side that connects to the 9 pin socket, which is 20 and 30.  It's a very good idea to provide extra mounting support for heavy caps.  Even using something like blu-tack to stick each cap to the chassis plate will be really helpful.

Yes, you can pull out a spring and ball from each switch after they are built. 

 

[Mordicai]

Thanks Paul.