Preferred Tone Stack Treble Cap?

ajeffcote

Silver Supporting Member
Messages
481
I have always used silver mica caps in the tone stack for the treble frequencies. The old black or brown cheap ones.
Now Sozo has a $9 silver mica cap.
I am trying it now and like what I hear. But in some ofvthe build threads on here I see a different cap used. I think its polystyrene. How do they compare?
 

Jeff Gehring

Gold Supporting Member
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7,426
Not going to get into subjectives about the caps, but some things to keep in mind:
  • Polystyrene caps (at least the ones I use) feel very fragile (thin thin leads). I would not "point-to-point" one.
  • I never use sub 1kV rated silver micas anymore. Had a couple of the 500V rated brown ones fail in the treble cap spot.
 

gldtp99

Member
Messages
4,379
Cool............ another cap thread

(although this is a specific Treble Cap thread)

My favorite Brownface Fenders, Blackface Fenders, and JMP Marshalls all used Ceramic Disc caps as Treble Caps

I've built amps with Ceramic Discs (many types), Silver Micas, and Polystyreres as Treble caps

Personally, I don't have a clear favorite --- I believe I've built wonderful sounding amps with all types of treble Caps i've tried

But I do like to reinforce the thin leads of the Polystyrenes with thin heat shrink tubing when I use them
 

ajeffcote

Silver Supporting Member
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481
Do you hear a difference in the big caps vs the smaller( voltage ratings I mean)?
I think I do but it could be the power of suggestion.
 

gldtp99

Member
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4,379
I really don't hear a difference

But my ears are pretty beat up by age and by years of playing powerful high wattage guitar amps

So subtle differences that others could pick out might be lost to me

I hear a difference when I change the value of a cap ---- but not when I change a 500V Silver Mica for a 1000V Silver Mica of the same value (for instance)
 

ItsTonyB

Member
Messages
211
I use vishay ceramite 1kv ceramics.

Not for any particular reason other than I got a load cheap.

To be honest I built two slo clone boards with different types of caps throughout and swapped them out and did reamps after measuring the pots etc and they're was no difference.

Running both samples through a frequency analyser also confirmed the same other than tiny variations that could be explained purely by tolerance.
 

SoPhx

Member
Messages
714
I use ceramics and SM, depending on the amp and the value. I can hear a little difference between types.
 

HotBluePlates

Member
Messages
14,074
Polystyrene caps (at least the ones I use) feel very fragile (thin thin leads). I would not "point-to-point" one.
... I do like to reinforce the thin leads of the Polystyrenes with thin heat shrink tubing when I use them

For polystyrene caps, it is critical to know that the heat of soldering can melt the polystyrene, which then changes the cap's value. In a worst-case, the heat can cause the cap to fail/short.

Don't be scared to use polystyrene (they're the small-value cap I use most), just be sure you're using good soldering technique. The iron wattage/Temp should be high enough and the tip size large enough to heat the connection & complete the solder joint quickly.
 

Mr. Fret

Silver Supporting Member
Messages
344
Ok I'll dive in here. I used Cornier Dublier SM's 500v in my JTM45 & JTM50 builds. Nice tone at low volume, but the distortion "collapsed" when cranking.

I switched to the big Sozo SM's & the distortion holds together well. My .02..
 

Mr. Fret

Silver Supporting Member
Messages
344
Fender used good quality ceramic caps in their BF SF amps. Current production sounds raspy & brittle to my dog ears. The best I found are Arco Electronics ("AE" on the cap), but they are barely passable.

Wish there was a NOS supply of those old 250pf caps.
 

Cirrus

Member
Messages
2,488
Polystyrene or high voltage ceramics for me. You can't always hear a difference, but at least in AC30s where I have lots of experience and intimately know the sound, when I've heard a difference I've preferred those over silver mica.
 

gldtp99

Member
Messages
4,379
Fender used good quality ceramic caps in their BF SF amps. Current production sounds raspy & brittle to my dog ears. The best I found are Arco Electronics ("AE" on the cap), but they are barely passable.

Wish there was a NOS supply of those old 250pf caps.

I've used these 220pF/2kV Iskra's with very good results:


And these 470pF/2kV ones, too (for other amp designs):

 

aynirar27

All that, and a bag of chips
Platinum Supporting Member
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33,509
I think those “dog bone” ones look cool so that’s what I use
 

Mr. Fret

Silver Supporting Member
Messages
344
I've used these 220pF/2kV Iskra's with very good results:
Thanks for those links. I don't think the higher voltage matters as much as the physical size. Wider & bigger seems to give a more robust response with less grain & rasp.

I've seen chassis pics of Metropoulos builds where he uses really wide ceramic disc caps. The old rectangular Lemcos were really wide. I think he's tapped into something there.

The old fender blonde ceramics were of a good size diameter compared to what came later.
 
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SkydogFan81

Silver Supporting Member
Messages
2,246
I've tried the polystyrene, cheap SM, Sozo SM, metallized polyester and pp, foil pp and polyester, and vintage axial SM "domino" caps. They all work, I am currently favoring the vintage dominos and the ps ones. I see the domino caps in fender tweeds and other vintage electronics (PA heads etc.)

I have read about different grades of ceramics - some for audio and others "bad" for audio. Then when you look in a BF fender, they all have the wrong caps! So it must be fine.
 

HotBluePlates

Member
Messages
14,074
... I have read about different grades of ceramics - some for audio and others "bad" for audio. Then when you look in a BF fender, they all have the wrong caps! So it must be fine.

True. The "bad ones" are mostly "bad" for having a capacitance that is not-stable with changing temperature. And because they can be microphonic (so can a lot of caps).

Some folks who like the ceramics in vintage amps like the small bit of grit/grain they can add. If you think "Fender clean" doesn't have grit/grain, then you haven't heard a "truly clean tube amp." I know I hadn't until I built my 25L15-style amp, and then noticed the little bit of fur of Fender clean tones.
 




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